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星体
宇宙中很可能存在黑洞，它
不辐射电磁波，因此无法直接观测，但是它的巨大质量和极小的体积使其附近产生极强的引力场，引力透镜是探索黑洞的途径之一．
无
法
黑
星体
观
洞
测
32
时间间隔与引力场有关
引力场的存在使得空间不同位置的时间进程出现差别．
对于高速转动的圆盘，除了转动轴的位置外，各点都在做加速运动，越是靠近边缘，加速度越大，方向指向盘心．
3、时间和空间相互独立、互不相关。
4
相对论简黑介体辐两射朵乌云
光速问
19世纪后半叶，关于电磁场的研究不题断深入，
人们认识到了光的电磁本质．我们已经知道，电
磁波是以巨大且有限的速度传播的，因此在电磁
场的研究中不断遇到一些矛盾，这些矛盾导致了
相对论的出现．
量子力学
相对论
相对论不仅给出了物体在高速运动时所遵循的规
15
狭义相对论的其他三个结论下面，我们学习狭义相对论的三个重要结论…
相对论的速度叠加公式相对论质量质能方程
16
相对论的速度叠加公式
v
u
车外的人看到车上人
相对地面的速度为：
u v
u

1
uv c2
17
相对论质量
物体的运动速度不能无限增加，那么物体的质量是否随着速度而变化？
严格的论证表明，物体高速（与光速相比）运动时的质量与它静止时的质量之间有下面的关系：
地面上看到：越是靠近边缘，速度越大．根据狭义相对论，靠近边缘部位的时间进程较慢．
圆盘上的人认为：盘上存在引力场，方向由盘心指向边缘，引力势较低，得出：引力势较低的位置，时间进程比较慢． 33

Vorton Formation

a rXiv:h ep-ph/984378v123Apr1998Vorton FormationC.J.A.P.Martins ∗and E.P.S.Shellard †Department of Applied Mathematics and Theoretical Physics University of Cambridge Silver Street,Cambridge CB39EW,U.K.In this paper we present the ﬁrst analytic model for vorton forma-tion.We start by deriving the microscopic string equations of motion in Witten’s superconducting model,and show that in the relevant chiral limit these coincide with the ones obtained from the supersonic elastic models of Carter and Peter.We then numerically study a number of solutions of these equations of motion and thereby suggest criteria for deciding whether a given superconducting loop conﬁguration can form a vorton.Finally,using a recently developed model for the evolution of currents in superconducting strings we conjecture,by comparison with these criteria,that string networks formed at the GUT phase transition should produce no vortons.On the other hand,a network formed at the electroweak scale can produce vortons accounting for up to 6%of the critical density.Some consequences of our results are discussed.I.INTRODUCTION As ﬁrst pointed out by Witten [1],cosmic strings can in some circumstances (typically when the electromagnetic gauge invariance is broken inside the string)behave as ‘superconducting wires’carrying large currents and charges—up to the order of the string mass scale in appropriate units.The charge carriers can be either bosons or fermions (see [2]for a review).The former type occurs when it becomes energetically favourable for a charged Higgs ﬁeld to have a non-zero vacuum expectation value in the string core;the latter happens when fermions couple to the string ﬁelds creating fermion zero modes.It is well known that arbitrarily large currents are not allowed—there is a criticalvalue beyond which the current saturates.In other words,for large enough wind-ing number per unit length,the superconducting condensate is quenched down,suppressing the current ﬂow.Also,the current can decay by magnetic ﬂux-line tun-nelling;this can be used to impose constraints on allowed particle physics models.If superconducting strings carry currents,they must also carry charges of similar magnitude.This includes not only charges trapped at formation by the Kibble mechanism but also the ones due to string inter-commuting between regions of the string network with diﬀerent currents.Just like with currents,charge densities cannot have arbitrarily large magnitude—there is a limit beyond which there will no longer be an energy barrier preventing the charge carriers from leaving the string.A rather important point is that the presence of charges on the string tends to counteract the current quenching eﬀect discussed above.In fact,numerical simula-tions of contracting string loops at ﬁxed charge and winding number have shown [3]that a‘chiral’state with equal charge and current densities is approached as the loop contracts.In this limiting chiral case,quenching is in fact eliminated completely. This has several important consequences.Strings that have trapped charges as a consequence of a phase transition can become superconducting even if the formation of a condensate was otherwise energetically unfavoured.More importantly,a string with both a charge and a current density will have a non-zero angular momentum. In the cosmological context,these strings would of course interact with the cosmic plasma,originating a number of interesting consequences.The most remarkable of these,however,has to do with the evolution of string loops.If a superconducting string loop has an angular momentum,it is semi-classically conserved,and it tries to resist the loop’s tension.This will at least increase the loop’s lifetime.If the current is too large,charge carriers will leave the string accompanied by a burst of electromagnetic radiation,but otherwise it is possible that dynamically stable loops form.These are called vortons[4]—they are stationary rings that do not ra-diate classically,and at large distances they look like point particles with quantised charge and angular momentum.Their cosmological signiﬁcance comes from the fact that they provide very strong constraints on allowed particle physics models, since they behave like non-relativistic particles.According to current belief[4,5], if they are formed at high enough energy scales they are as dangerous as magnetic monopoles,producing an over-density of matter in disagreement with observations. On the other hand,low-mass vortons could be a very interesting dark matter can-didate.Understanding the mechanisms behind formation and evolution is therefore an essential cosmological task.The overwhelming majority of the work done on cosmic strings so far was con-cerned with the structureless Goto-Nambu strings(but see[6]and references therein for some exceptions).In the case of work on vortons,this means that somewhat ad-hoc estimates had to be made for some properties of the cosmic string network—notably for microscopic quantities such as current and charge densities.This is de-spite the fact it has been recognised a long time ago that,even though they might be computationally very useful[7–9],Goto-Nambu models cannot realistically be expected to account for a number of cosmologically relevant phenomena,due to the very limited number of degrees of freedom available.Two such phenomena are the build-up of small-scale structure and charge and current densities.In this paper weﬁll this important gap by discussing the problem of vorton formation in the context of the superconducting string models of Witten[1]and of Carter and Peter[10](sections II and III).Strangely enough,the issue of the conditions for vorton formation has been so far neglected with respect to those of their stability and cosmological consequences.We will start by introducing these models and determining the microscopic string equations of motion in each case.It will be shown that in the relevant chiral limit these equations coincide—this also provides theﬁrst conclusive evidence of the validity of the supersonic elastic models of Carter and Peter[10].We then proceed to study the evolution of a number of loop solutions of these equations numerically(sections IV and V),and from the results of this analysis parameters will be introduced which characterise the loop’s ability to evolve into a vorton state(section VI).Finally,we discuss a very simple phenomenological model for the evolution of the superconducting currents on the long cosmic string network [11],based on the dynamics of a‘superconducting correlation length’(sections VII–VIII).Using this model we can therefore estimate the currents carried by string loops formed at all relevant times,and thus(in principle)decide if these can become vortons(section IX)and calculate the corresponding density(section X).Based on our results,we don’t expect any GUT vortons to form at all.This is essentially because the friction-dominated epoch is very short for GUT-scale strings [7],so their currents and charges are never large enough to prevent them frombecoming relativistic—and therefore liable to losses.Even if they did form,they wouldn’t be in conﬂict with the standard cosmological scenario if they decayed soon after the end of the friction-domination epoch.Hence we conclude that,in contrast with previously existing estimates[4,5], one cannot at the moment rule out GUT superconducting string models.We should point out at the outset that there are essentially three improvements in the present work which justify the diﬀerent end result for GUT-scale strings.Firstly,by analysing simple(but physically relevant)loop solutions of the microscopic string equations of motion for the Witten model,we can get a much improved idea of how superconducting loops evolve and of how(and under which conditions)they reach a vorton state.Secondly,by using a simple model for the evolution of the currents on the long strings[11]we can accurately determine the typical currents on each string loop at the epoch of its formation.Finally,the use of the analytic formalism previously introduced by the present authors[7,9]allows us to use a quantitative description throughout the paper,and in particular to determine the loop sizes at formation.As will become clear below,when taken together these allow a detailed analysis of the process of vorton formation to be carried out,either in the Witten model(as is done in this paper)or any other that one considers relevant.In contrast,note that Davis&Shellard[4]restrict themselves to the particular case of the initial Brownian Vachaspati-Vilenkin loops with Kibble currents,and do not consider the subsequent evolution of the network.On the other hand,Brandenberger et al.[5] make rather optimistic order-of-magnitude estimates about the process of relaxation into a vorton state.As it turns out,for high energy GUT scales,all these loops be-come relativistic before reaching a vorton state.Finally,neither of these treatments has the beneﬁt of a quantitative model for the evolution of the long-string network [7]which allows one to accurately describe the process of loop production.On the other hand,as we lower the string-forming energy scale we expect more and more eﬃcient vorton production,and the’old’scenario still holds.Therefore intermediate-scale superconducting strings are still ruled out,since they would lead to a universe becoming matter-dominated earlier than observationally allowed.Fi-nally,at low enough energy scales,vortons will be a dark matter candidate.For example,for a string network formed around T∼102GeV(typical of the elec-troweak phase transition)they can provide up to6%of the critical density.A more detailed discussion of these issues is left to a forthcoming publication[12]. Throughout this paper we will use fundamental units in which¯h=c=k B= Gm2P l=1.II.WITTEN’S MICROSCOPIC MODELAsﬁrst pointed out by Witten[1],a low-energy eﬀective action for a supercon-ducting string can be derived in a way that is fairly similar to what is done in the Goto-Nambu case(see for example[2]).One has to adopt the additional as-sumptions that the current is much smaller than the critical current and that the electromagnetic vector potential Aµis slowly varying on the scale of the condensate thickness.The derivation then proceeds as in the neutral case,except for the use of the well-known fact that in two dimensions a conserved current can be written as the derivative of a scalarﬁeld.One obtainsS= √2γabφ,aφ,b−qAµxµ,aǫab−γφ,b d2σ(2.1)−1−gFµνFµν;(2.2) the four terms are respectively the usual Goto-Nambu term,the inertia of the charge carriers,the current coupling to the electromagnetic potential and the external electromagneticﬁeld(ǫab is the alternating tensor);note that this applies to both the bosonic and the fermionic case[2].Recalling the usual deﬁnitionsA a=xµ,a Aµ,(2.3)F ab=Fµνxµ,a xν,b=A b,a−A a,b,(2.4) and deﬁningΥab to be the stress-energy tensor of the scalarﬁeldφΥab=φ,aφ,b−1√−γγabφ,b +1−γ˜ǫab F ab=0,(2.8) and∂a √µ0Υab xα,b +√µ0Υab Γασρxσ,a xρ,b=(2.9)√=gαλ(gαµ,ν+gνα,µ−gµν,α),(2.11)2and Fαis the Lorentz force1Fα=ℓf uα−xα,a xσ,a uσ ,(2.13) using the same procedure as described in[13,7].As shown in[11],plasma eﬀects are subdominant,except possibly in the presence of background magneticﬁelds—either of‘primordial’origin or generated(typically by a dynamo mechanism)onceproto-galaxies have formed.Hence one expectsAharonov-Bohm scattering [14]to be the dominant eﬀect,and consequently we have [7]ℓf =µµ0γ00,(2.17)and choosing the standard gauge conditionsσ0=τ,˙x ·x ′=0,(2.18)(with dots and primes respectively denoting derivatives with respect to the time-like and space-like coordinates on the worldsheet as usual)the string equations of motion in an FRW background with the line element ds 2=a 2 dτ2−dx 2 (2.19)(which implies that γ00=a 2(1−˙x 2))have the form[ǫ(1+Φ)]˙+ǫa ǫΦ,(2.20)andǫ(1+Φ)¨x +ǫǫ ′+ ˙Φ+2˙a ℓd =a 2H +1ǫ.(2.24)Note that the Witten action is ‘microscopic’in the sense of being built using only the properties of the underlying particle physics model [1].In the next section we will analyse the equations of motion obtained form the action for the elastic supersonic models of Carter and Peter [10],which is is this sense ‘macroscopic’.III.SUPERSONIC ELASTIC MODELSIn order to account for phenomena such as the build-up of charge and current densities on cosmic strings,one must introduce additional degrees of freedom on the string worldsheet.One such class of models,originally introduced by Carter and co-workers is usually referred to as elastic models(see[6]and references therein,on which the following two subsections are based).A.Basics of elastic modelsIn general,elastic string models can be described by a Lagrangian density de-pending on the spacetime metric gµν,backgroundﬁelds such as a Maxwellian-type gauge potential Aµor a Kalb-Ramond gaugeﬁeld Bµν(but not their gradients) and any relevant internalﬁelds(that will be discussed in detail below).Note that the Goto-Nambu model has a constant Lagrangian density,namelyL GN=−µ0.(3.1) Upon inﬁnitesimal variations in the backgroundﬁelds,and provided that indepen-dent internalﬁelds are keptﬁxed(or alternatively that their dynamic equations of motion are satisﬁed),the action will change byδS=−1−γd2σ,(3.2)whereTµν=2δLδAµ(3.4) is the worldsheet electromagnetic current density,andWµν=2δLNote that U and T are simply constants for a Goto-Nambu string,U=T=µ0,(3.8) but they are variable in general—hence the name‘elastic strings’.In particular, one should expect that the string tension in an elastic model will be reduced with respect to the Goto-Nambu case due to the mechanical eﬀect of the current. Since elastic string models necessarily possess conserved currents,it is convenient to deﬁne a‘stream function’ψon the worldsheet that will be constant along the current’sﬂow lines.The part of the Lagrangian density L containing the internal ﬁelds is usually called the‘master function’,and can be deﬁned as a function of the magnitude of the gradient of this stream function,Λ=Λ(χ),such thatχ=γabψ;aψ;b,(3.9) where the gauge covariant derivative is deﬁned asψ;a=∂aψ−eAµxµ,a.(3.10) Note that the deﬁnition ofχdiﬀers by a minus sign from that of Carter[6];the reason for this will become clear below.This‘dynamic’term contains charge cou-plings,whose relevance will be further discussed below.Nevertheless,whether or not these or other background gaugeﬁelds are present,it is always the form of the master function which determines the equation—or equations—of state.There is also a dual[15]potential˜ψ,whose gradient is orthogonal to that ofψ, and the corresponding dual master function˜Λ=˜Λ(˜χ)such that˜χ=γab˜ψ;a˜ψ;b,(3.11) with the obvious deﬁnition for˜ψ;a.The duality between these descriptions means that theﬁeld equations for the stream functionψobtained with the master function Λare the same as those for the dual potential˜ψobtained with the dual master function˜Λ.However,there will in general be two diﬀerent equation of state relating the energy density U and the tension T;these correspond to what is known as the ‘magnetic’and‘electric’regimes,respectively corresponding to the cases˜χmg<0<χmg(3.12) andχel<0<˜χel,(3.13) that are respectively characterised by space-like and time-like currents.In the degenerate null state limit,however,there will be a single equation,U=T=µ0.(3.14) Note that the distinction between a given model and its dual disappears in the absence of charge couplings;such models are then called‘self-dual’for obvious reasons.In each case the equation of state provides the expressionsc2E=TdU =νdν,(3.16)for the extrinsic(that is transverse,or‘wiggle’)and for the sound-type(longitudinal or‘woggle’)perturbations of the worldsheet.Both of these must obey c2≥0(a requirement for local stability)and c2≤1(a requirement for local causality).These two speeds can be used to characterise the elastic model in question;in particular there is a straightforward but quite meaningful division of the models into supersonic (that is,those obeying c E>c L),transonic(c E=c L;only in the null limit is this common speed unity)and subsonic(c E<c L).B.Supersonic(superconducting)modelsCarter and Peter[10]have recently proposed two supersonic elastic models to describe the behaviour of current-carrying cosmic strings.The Lagrangian density in the magnetic regime is˜Λmg =−m2+˜χ2k0m2σ −1,(3.17)mσbeing the current carrier mass(which is at most of the order of the relevant Higgs mass);this is valid in the range−1k0m2σ<1−k0m2σm2=1+k0m2σk02mσm2−1+k0m2σ2ln 1−˜χk0m2σ<1−e−2m2/k0m2σ,(3.21)and the corresponding equation of state isUm2+k0m2σk0m2σ/m2 −1.(3.22)These models are supersonic for all space-like,and weak time-like currents,with the exception that in the null limit˜χ=0one has c L=c E=1.C.Equations of motionWe now derive the microscopic equations of motion for elastic cosmic string mod-els.It is convenient to start by deﬁning the quantityΘab≡˜Λγab−2∂˜Λthen recalling the deﬁnition of ˜χ,(3.11),onecanﬁnd the free string equations of motion in the usual (variational)way,obtaining(√−γΘab Γαµνx µ,a x ν,b =0.(3.24)Also in a similar way to what was done in section II,the eﬀect of the frictional forces is accounted for by introducing a term√βT 3b (3.26)(note that ˜Λis negative).Of course we now have a further equation for the scalar ﬁeld ˜ψ,namely ∂a √∂˜χγab ˜ψ;b =0.(3.27)Furthermore,the spacetime energy-momentum tensor and electromagnetic cur-rent will be given by√−γΘab x µ,a x ν,b δ(x −x (σ,τ))d 2σ(3.28)and√−γγab ∂˜Λ−(3)gT 00=a−˜Λ+2∂˜Λ−(3)gJ 0=−2ea∂˜Λ∂˜χ√∂˜χǫ˜ψ;0,(3.33)j≡−j1=−2e ∂˜Λǫ.(3.34)Again,for the reasons explained above,a particularly relevant situation will be that of a chiral current,that is one in whichγab j a j b=0.(3.35) This is equivalent to˜ψ′2=ǫ2˙˜ψ2,(3.36) and therefore it implies that∂ρ∂σ(3.37)and that the total(spacetime)charge and current are also equal.Note that in the chiral case one also has˜χ=0,2∂˜Λ−γ∂˜Λ−γ∂˜ΛD.The chiral limitWe now consider the(common)chiral limit of the two supersonic elastic models of Carter and Peter[10],deﬁned by the Lagrangian densities(3.17)and(3.20), respectively for the magnetic and electric regimes.Also,as we did in section II for the Witten model,we will interpret the charge coupling and the scalarﬁeld as being renormalised and neglect the coupling to external electromagneticﬁelds.Then,with our usual gauge choices and deﬁnitions of the damping and friction length-scales,the microscopic string equations of motion(3.24)simplify to[ǫ(1+Ψ)]˙+ǫaǫΨ,(3.44)andǫ(1+Ψ)¨x+ǫǫ ′+˙Ψ+2˙aµ0γ00.(3.46)That is,these are exactly the same equations of motion as those of Witten’s model(2.20–2.21)if one identiﬁes the corresponding scalarﬁelds,φ≡˜ψ.(3.47) Then,the worldsheet charge and current densities also coincide,ρw=qǫ˙˜ψ,(3.48)j w=q˜ψ′x(τ)=r(τ)(sinθ,cosθ,0);(4.1)we also need an ansatz for the scalarﬁeld˜ψ(orφ),which we will take to be˜ψ=√r2 =1,(4.4)¨r+ 1−n4t4c2.(4.6)Note that opposite signs of n correspond to left and right moving currents;naturally it always appears as n2in any relevant equation,and we will therefore be taking n to be positive.Inﬁgure1we plotted some relevant evolutionary properties of chiral supercon-ducting loops with diﬀerent n’s inﬂat spacetime.Note that these loops never collapse to zero size,and that their microscopic velocity is always less than unity (unlike in the Goto-Nambu case).Furthermore,there is a static solution withn=1t c˙r=0;(4.7)in this case the energy is equally divided between the string and the current.It should also be noted that energy is transferred back and forth between the string and the current as the loop oscillates.We can easily determine the following quantities(the averages are over one oscillation period)r22−n2,(4.8)t2c n2,(4.9)˙r2 =1E total =1−n,(4.11)12E2string2n;(4.12) note that the energy of these loops is E total/t c=2πµ.Finally,two other points that will have further relevance below.Firstly,a loops with a given conserved number n will reach a maximum microscopic velocity(and corresponding Lorentz factor)given by1˙r2max=1−4n2,γmax=µ0(F(τ)+nσ)t c.(5.1) The winding number per unitσand the function F are also constrained as before. In terms of these quantities the total energy of the loop can be written asE total=µ0ℓtotal=µ0a 1+n2t2c˙r a2r2 1a2r2 ¨r+(1−˙r2)4πnt cn=n is a variable parameter obeying0≤n=0corresponds to the Goto-Nambu case,while thev t2,ℓstring√n,namelyℓtotal1−n goes from zeroto unity we go from the Goto-Nambu case to the static case where the energy is split equally between the string and the current;the positive sign corresponds to the current branch,where the ratio of the energies in the string and in the current decreases until it vanishes whenn=2ℓstringℓstring−11/2.(5.9)In practice,it is not easily conceivable that in cosmological contexts loops can be formed with more energy in the current than in the string itself.Therefore, although for the sake of completeness we will be discussing the current branch in the remainder of this section,we will neglect it afterwards.Thus from(5.3)one obtains the evolution equation forℓ(ℓi,t i,n i,t) and other relevant quantities.As we will see below,a crucial quantity will be the the maximum velocity reached by each loop conﬁguration during it evolution, v max(ℓi,t i,n i).Inﬁgures3–5we plot the cosmological evolution of some relevant GUT-scale chiral circular loops.We should mention that in order to save space,only one out of every forty points resulting from the numerical integrations is plotted,and this is the reason why some plots show irregularities.Figure3shows some relevant properties of the evolution of chiral circular GUT-scale loops formed at t=t c;all have an initial total energy E total/2πµt c=10,but the distribution of the energy between the string and the current varies. Obviously,loops with higher currents will have smaller physical radii,and hence they will be less stretched by expansion and enter the horizon earlier,at which point they start oscillating—as can be conﬁrmed in3(a-b).Regarding the velocities,note the signiﬁcant diﬀerences between loops in the‘string branch’(which still reach fairly high microscopic velocities,but never v=1)and in the‘current branch’(which quickly become non-relativistic).Therefore the latter ones should deﬁnitely become vortons,and so it is perhaps fortunate that,as we pointed out above,we do not expect loops with such high currents to be produced in the early universe (at least,for GUT-scale networks).Note that in one of the cases shown the initial current is so high that the loop‘overshoots’and acquires a fairly large velocity,but friction quickly slows it down again.On the other hand,in the string branch the velocity is reduced with respect to the Goto-Nambu case,and a more detailed investigation will be needed to set14up some criterion deﬁning which velocities will allow vorton formation—recall that relativistic velocities will imply charge losses and it will therefore be unrealistic to make any deﬁnite claims or predictions about such cases.The evolution of the fraction of the loop’s energy in the current is particularly il-luminating(see3(c)).This will obviously decrease while the loop is being stretched, and it will start oscillating when the loop falls in side the horizon.The oscillations are around the state with equipartition of the energy between the string and the current,which as we saw corresponds to a static solution inﬂat spacetime.Note that the eﬀect of the friction force is to reduce the amplitude of these oscillations, so one can see that friction is in fact crucial for vorton formation.Naturally,loops with smaller velocities will undergo oscillations with smaller amplitudes,so again we conﬁrm that these are the strongest vorton candidates.Finally,we have plotted the parametern once the loop is‘free’—that is,much smaller than the damping length deﬁned in(2.22). On the other hand,radiative backreaction also tends to damp these energy os-cillations,and consequently increasen becomes a constant in this limit—hence its usefulness)˙r2 =1n2),(5.10)E string2E2total=1−3n;(5.12) the variance of the fraction of the energy in string is therefore∆E string4n).(5.13)Inﬁgure4we show chiral loops with the same initial conditions as3,but starting to evolve at the epoch t⋆when when friction becomes negligible[7].The diﬀerences are self-evident.Now,after aﬁrst period of growth of the total radius due to expansion,there is no mechanism forcing the loops to return this extra energy back to the medium when they fall inside the horizon.Consequently there is also no velocity damping(all loops will have microscopic velocities larger than0.5) and the energy oscillations between the string and the current always have a large amplitude—so thatthe region of the space of initial conditions that will originate them—because as we said the eﬀect of friction is to increasen∼1,in which case velocity is so small that friction does not signiﬁcantly aﬀect the loop.Note that asn and v needs to be looked at in more detail,and we shall do that in the next section.VI.CRITERIA FOR VORTON FORMATIONIn the previous section we saw that the evolution of chiral superconducting cosmic string loops depends sensitively on the conditions at formation.In particular,one would need to know in which cases one ends up with a vorton.Clearly,since we are not including radiative mechanisms at this stage,our crite-rion should be that loops whose velocity is always small(in a sense that will need to be made more precise)will become vortons,while those who are relativistic at some stage will suﬀer signiﬁcant charge losses,so that their fate cannot be clearly asserted until a rigourous quantum-mechanical treatment of these processes is available. Thus we will explore in more detail the phase space of possible initial condi-tions in order to determine relevant properties of these loops.Figure6shows the maximum microscopic velocity v max(ℓi,t i,n and to the base-ten logarithm of the initial string radius relative to the horizon;recall that we only consider loops having initially most of their energy in the string(in other words,loops in the string branch).Note that the friction length-scale corresponds to about−1.5in the vertical axis on theﬁrst plot,and to0on the last(where it is equal to the horizon, by deﬁnition).It can be seen that any loop initially larger than the horizon will inevitably become relativistic.This is essentially because expansion will(temporarily,at least) decrease the fraction of the loop’s energy in the current(and hencen(neglecting radiation),so we will need fairly high initial currents in order to get non-relativistic velocities.Finally,for the case of loops being produced with sizes between the friction length-scale and the horizon,which is of course the cosmologically relevant case during the16。

2.1狭义相对论基本原理.pdf

速应该各向不等，因而可看到干涉条纹。再使整个仪器转过 900，就应该发现条纹的
移到，由条纹移动的总数，就可算出地球运动的速度 v。迈克尔孙—莫来实验的装置
如图 2-1-2 所示，使一束由光源 S 射来的平行光，到达对光线倾斜 450 角的半镀银镜
面 M 上，被分成两束互相垂直的相干光。其中透射部分沿 MM 2 方向前进，被镜 M 2 反射回来，到 M 上，再部分地反射后沿 MT 进行；反射部分沿 MM1 方行进行，被镜反射
c 动，选 s ' 系固定在介质上，在 s ' 上观察，介质中的光速各方向都是 n ，所以光相对实
验室的速度 u 为
c +v c +v
u=
n
c v
=n 1+
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c +v
c −v
传播速度为 n ，逆水为 n ；若水完全不带动以太，光对装置的速度顺逆水均为
c
c + kv
c − kv
n ；若部分被带动，令带动系数（曳引系数）为 k，则顺水为 n ，逆水为 n ，
k 多少由实验测定，这时两束光到达目镜 T 的时差为
t = 2l − 2l 4lkv
c − kv n
系数了。
迈克尔孙—莫来实验迈克尔孙—莫来于 1887 年利用灵敏的
S
M1 M2
M T
图 2-1-2

相对论原文（网摘）

相对论原文（网摘）论动体的电动力学大家知道，麦克斯韦电动力学 -- 像现在通常为人们所理解的那样 -- 应用到运动的物体上时，就要引起一些不对称，而这种不对称似乎不是现象所固有的。

比如设想一个磁体同一个导体之间的电动力的相互作用。

在这里，可观察到的现象只同导体和磁体的相对运动有关，可是按照通常的看法，这两个物体之中，究竟是这个在运动，还是那个在运动，却是截然不同的两回事。

如果是磁体在运动，导体静止着，那么在磁体附近就会出现一个具有一定能量的电场，它在导体各部分所在的地方产生一股电流。

但是如果磁体是静止的，而导体在运动，那么磁体附近就没有电场，可是在导体中却有一电动势，这种电动势本身虽然并不相当于能量，但是它 -- 假定这里所考虑的两种情况中的相对运动是相等的 -- 却会引起电流，这种电流的大小和路线都同前一情况中由电力所产生的一样。

诸如此类的例子，以及企图证实地球相对于“光媒质”运动的实验的失败，引起了这样一种猜想：绝对静止这概念，不仅在力学中，而且在电动力学中也不符合现象的特性，倒是应当认为，凡是对力学方程适用的一切坐标系，对于上述电动力学和光学的定律也一样适用，对于第一级微量来说，这时已经证明了的。

我们要把这个猜想（它的内容以后就称之为“相对性原理”①）提升为公设，并且还要引进另一条在表上看来同它不相容的公设：光在空虚空间里总是以一确定的速度V传播着，这速度同发射体的运动状态无关。

由这两条公设，根据静体的麦克斯韦理论，就足以得到一个简单而又不自相矛盾的动体电动力学。

“光以太”的引入将被证明是多余的，因为按照这里所要阐明的见解，既不需要引进一个具有特殊性质的“绝对静止的空间”，也不需要给发生电磁过程的空虚空间中的每个点规定一个速度矢量。

这里所要阐明的理论 -- 像其他各种电动力学一样 -- 是以刚提的运动学为根据的，因为任何这种理论所讲的，都是关于刚体（坐标系）、时钟和电磁过程之间的关系。

对这种情况考虑不足，就是动体电动力学目前所必须克服的那些困难的根源。

a-Galactosylceramide as a Therapeutic Agent for

a-Galactosylceramide as a Therapeutic Agent for Pulmonary Mycobacterium tuberculosis InfectionIsabel Sada-Ovalle1,Markus Sko¨ld1,Tian Tian1,Gurdyal S.Besra2,and Samuel M.Behar11Division of Rheumatology,Immunology,and Allergy,Brigham and Women’s Hospital and Harvard Medical School,Boston,Massachusetts; and2School of Biosciences,University of Birmingham,Edgbaston,Birmingham,United KingdomRationale:Invariant natural killer T(iNKT)cells are a unique subset of Tcells that recognize lipid antigens presented by CD1d molecules.Recentstudies have shown that iNKT cells can protect mice against Mycobac-terium tuberculosis(Mtb)infection.We sought to determine whetherpharmacological activation of iNKT cells by a-galactosylceramide(a-GalCer)could be used to treat tuberculosis(TB).Objectives:We hypothesized that a-GalCer,either alone or incombination with isoniazid,could be used to treat pulmonary TB.Methods:The ability of a-GalCer–activated iNKT cells to suppressMtb replication was evaluated using an in vitro coculture system.Totest its potency in vivo,mice infected with virulent Mtb were treatedwith a-GalCer alone or in combination with isoniazid.Measurements and Main Results:Quantitative colony-forming unitcounts were compared for both experimental systems.Our resultsshow that a-GalCer plus isoniazid controls bacterial growth betterthan a-GalCer or INH alone,and single or multiple a-GalCer admin-istrations prolong the survival of the mice infected via the aerosolroute.Conclusions:Our results demonstrate that a-GalCer administrationcan improve the outcome of Mtb infection,even when transmitted by the aerosol route.However,a combination of isoniazid and a-GalCer treatment has a synergistic effect on infection control. We conclude that more efﬁcient treatment of TB will be achieved through a combination of classic chemotherapy and modulation of the host immune response.Keywords:CD1d;antibiotics;natural killer T cells;tuberculosis;lipids Tuberculosis(TB)is caused by Mycobacterium tuberculosis(Mtb) and represents an important global threat to health,especially in developing countries where new and efﬁcient therapies are urgently needed.Although current antibiotic regimens against Mtb are effective against drug-susceptible strains,patients require long-term follow-up and can suffer severe side effects.In addition, the prevalence of multidrug-and extensively drug-resistant Mtb strains is on the rise(1).Treatment of drug-resistant bacterial strains is more complicated,requiring hospital supervision(2). Recent efforts to develop new therapeutic regimens are promis-ing,but their efﬁciency remains to be tested in larger populations. In the current study,we investigated whether the speciﬁc activa-tion of iNKT cells,which we have previously shown is capable of activating macrophages(M w)to suppress intracellular Mtb rep-lication,can act therapeutically against established pulmonary TB(3).Invariant natural killer T(iNKT)cells are a sublineage of T lymphocytes that are deﬁned by their expression of a canonical V a14-J a18T-cell receptor(TCR)a-chain.The ab-TCR expressed by iNKT cells recognizes self and foreign lipid antigens presented by the antigen-presenting molecule CD1d. iNKT cells inﬂuence host immunity during infectious diseases through production of soluble mediators,such as IL-4and IFN-g,by reciprocal NKT–dendritic cell(DC)activation and by elaboration of chemokines that recruit inﬂammatory cells(4–6).The discovery that CD1d presentation of a-galactosylcer-amide(a-GalCer)rapidly activates murine and human iNKT cells has greatly increased our understanding of the potential role that iNKT cells play in host immunity(7,8).The synthetic glycosphingolipid a-GalCer is a potent iNKT cell agonist,and even though it is not a natural ligand for iNKT cells,a-GalCer and its analogs are commonly used experimentally(9).iNKT cell activation by a-GalCer in vivo induces downstream activa-tion of several lymphoid and myeloid cell populations,including B and T cells,NK cells,M w,and DCs,which in turn can modify multiple immune responses(10–13).For example,a-GalCer has been used to analyze the immunomodulatory properties of activated iNKT cells in mice and patients with malignancies (14–16).Administration of a-GalCer activates both the innate and adaptive immune system and has raised the possibility of using a-GalCer for therapeutic purposes(8,17).The number of iNKT cells in the lung is increased after infection of mice with virulent Mtb(18).CD1d,which presents antigen to iNKT cells,is up-regulated by IFN-g and is also increased in the lungs of infected mice(19).We havepreviously(Received in original form December23,2009;accepted inﬁnal form May17,2010) Supported by the National Institutes of Health grant R01HL80312(S.M.B)and a Parker B.Francis Foundation postdoctoral fellowship(I.S.O).G.S.B.was supported by a Personal Research Chair from Mr.James Badrick,Royal Society Wolfson Research Merit Award,as a former Lister Institute-Jenner Research Fellow,the Medical Council,and The Wellcome Trust(084,923/B/08/7).M.S. was supported by the Swedish Heart Lung Foundation.Present address for I.S-O.is Immunochemistry Department,National Institute of Respiratory Diseases,Me´xico.Present address for M.S.is Department of Microbiology,Tumor and Cell Biology, Karolinska Institutet,Stockholm,Sweden.Present address for T.T.is Department of Dermatology,Brigham and Women’s Hospital and Harvard Medical School,Boston,Massachusetts. Correspondence and requests for reprints should be addressed to Samuel M. Behar,M.D.,Ph.D.,Division of Rheumatology,Immunology,and Allergy, Brigham and Women’s Hospital,Smith Building Room516C,One Jimmy Fund Way,Boston,MA02115.E-mail:sbehar@Am J Respir Crit Care Med Vol182.pp841–847,2010Originally Published in Press as DOI:10.1164/rccm.200912-1921OC on May27,2010 Internet address:shown that innate iNKT cells recognize Mtb-infected M w, produce IFN-g,and kill intracellular bacteria both in vitro and in vivo(3).Although these data suggest that iNKT cells can mediate protective immunity against TB,several laboratories have found that iNKT cells are not required for optimal immunity to Mtb(20,21).One explanation is that iNKT cells make only a small and possibly redundant contribution to antimycobacterial immunity.Another possibility is that after infection,iNKT cells become anergic,as has been shown after BCG and viral infection(22).Given the potential ability of activated iNKT cells to suppress bacterial growth,we wished to determine whether administration of a-GalCer could enhance the antibacterial activity of iNKT cells and whether a-GalCer could serve a role in the treatment of established disease. METHODSMiceSix-to8-week-old female C3H/HeJ(C3H)(highly susceptible to Mtb) and C57BL/6(B6)(relatively resistant to Mtb)mice were obtained from Jackson Laboratories(Bar Harbor,ME).All mice were housed in a BSL3facility under speciﬁc pathogen–free conditions in the Animal Biohazard Containment Suite(Dana Farber Cancer Institute,Boston, MA)and used in a protocol approved by the institution.Bacteria and In Vitro Infection of Peritoneal Macrophages Macrophages were harvested by peritoneal lavage4days after intraperitoneal injection of sterile3%thioglycolate medium.M w were puriﬁed by positive selection using CD11b-microbeads accord-ing to manufacturer’s directions(Miltenyi Biotec,Auburn,CA).The puriﬁed cells were95%F4/801CD11b1,as determined byﬂow cytom-etry.Puriﬁed M w(0.53106/well)were cultured in24-well plates in RPMI1640medium(Invitrogen Life Technologies,Carlsbad,CA) supplemented with10%fetal calf serum(HyClone,Rockford,IL), penicillin/streptomycin,L-glutamine,sodium-pyruvate,2-ME,nonessen-tial amino acids,essential amino acids,and N-2-hydroxyethylpiperazine-N9-ethane sulfonic acid(all from Gibco,Carlsbad,CA).Virulent Mtb (H37Rv)was grown to mid-log phase in Middlebrook7H9medium supplemented with10%albumin/dextrose/catalase(BD Biosciences, San Jose,CA).Bacteria were opsonized for5minutes using RPMI 1640with2%human serum(Gemini Bio-Products,West Sacramento, CA),10%fetal bovine serum,and0.05%Tween80and then washed twice with complete medium without antibiotics.Bacteria were passed through a5-m m syringeﬁlter(Millipore,Billerica,MA),counted in a Petroff-Hausser chamber,and added to enriched M w for2hours before extensive washing to remove extracellular bacteria.The length of infection was2hours for all experiments.Recombinant mouse IFN-g(US Biological,Swampscott,MA),a-GalCer,and a-C-GalCer were used at the concentrations indicated.Colony-Forming Unit Determination(In Vitro Model) Bacterial growth was quantiﬁed72hours after coculture with naive splenocytes with or without IFN-g and/or a-GalCer(Day4).The cells were lysed after removing the supernatant by adding distilled water. Serial dilutions were plated on Middlebrook7H11agar plates.The number of bacteria contained in the supernatant was less than10%of the cell-associated colony-forming units(CFU),independently of whether splenocytes were added.The colonies were enumerated after 3weeks at378C.Bacteria and InfectionsVirulent M.tuberculosis(Erdman strain)were passed through mice and subsequently grown once in Middlebrook7H9supplemented with the oleic acid–albumin–dextrose complex and stored at808C.For each experiment an aliquot was thawed,sonicated twice for10seconds with a cup horn sonicator,and then diluted in0.9%NaCl20.02%Tween80. Mice were infected via the aerosol route as described previously(23). For intravenous infections,mice were injected via the lateral tail vein with0.253106to4.03106live mycobacteria.The inoculum was conﬁrmed by plating.Treatment of Mice with a-GalCera-GalCer was prepared in a vehicle of0.5%polysorbate20.The mice were injected with a low(100m gÁkg21)or high(500m gÁkg21)dose of a-GalCer,or injected with control vehicle.The following treatment regi-mens were tested:(1)intraperitoneal injection of100m gÁkg21a-GalCer on Days5,3,and1before aerosol infection;(2)intraperitoneal injection of100m gÁkg21a-GalCer on Days1,5,and9after aerosol infection;(3) intratracheal injection of100m gÁkg21a-GalCer on Day1after aerosol infection;(4)intraperitoneal injection of500m gÁkg21a-GalCer on Day1 after aerosol infection;(5)intraperitoneal injection of500m gÁkg21 a-GalCer on Day1after aerosol infection and then again every30th day;(6)intraperitoneal injection of500m gÁkg21a-GalCer on Day30 post aerosol infection and then again every30th day.a-GalCer and Antibiotic TreatmentGroups of C3H/HeJ mice were infected via the intravenous route and injected with a low dose of a-GalCer or vehicle on Day1post infection (p.i.).On Day14p.i.,isoniazid(100mg/L)was added to the drinking water.The drinking water was changed twice weekly during the treatment period and the mice had access to the water ad libitum. The isoniazid treatment was stopped on Day28p.i.and the CFU was determined in lung and spleen on Day36p.i.Measurement of IFN-g Lung ProductionBefore removal,lungs were perfused by injecting5to10ml of sterile PBS into the right ventricle of the heart after severing the inferior vena cava.The lungs were homogenized in0.9%NaCl20.02%Tween80 with a Minibeadbeater-8and centrifugation for20minutes at3,000 rpm,then supernatants were recovered and IFN-g was analyzed by a standard ELISA sandwich.CFU Determination(In Vivo Model)Three,5,or12weeks after infection,mice were killed and their left lung and spleen were aseptically removed and individually homoge-nized in0.9%NaCl–0.02%Tween80.Viable bacteria were enumer-ated by plating organ homogenates onto7H11agar plates.Colonies were counted after3weeks.StatisticsData were expressed as parisons of data among experimental groups were performed using analysis of variance with Bonferroni post test.A survival analysis was performed using Kaplan-Meier method and comparisons were done with log-rank test.Values of P,0.05were considered to be statistically signiﬁcant. RESULTSa-GalCer–Activated Splenocytes Reduce Intracellular Replication of Mtb In VitroWe have previously shown that nonimmune splenocytes have innate antimycobacterial activity that is mediated by iNKT cells,which recognize Mtb infected M w and restrict intracellular bacterial growth(3).Although CD1d expression by the infected M w is required,which implies cognate recognition(3),it is uncertain whether CD1presents a microbial antigen,or alter-natively,whether cytokine production costimulates weak rec-ognition of an endogenous(self)antigen(24).Because only1to 2%of splenocytes are iNKT cells,we wondered whether pharmacological activation of iNKT cells with a-GalCer would enhance the growth suppression of Mtb mediated by iNKT cells in vitro.Coculture of naive splenocytes with Mtb-infected M w reduced the number of viable CFU as reported previously (Figure1A)(3).Addition of a-GalCer led to a further re-duction in CFU,as did the addition of IFN-g,and adding both a-GalCer and IFN-g led to an additive,and possibly coopera-842AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE VOL1822010tive,effect on CFU control.Treatment with a-GalCer was associated with a dose-dependent increase in IFN-g production (Figure1B).Thus,although iNKT cells have the physiological potential to recognize infected M w,their pharmacological activation by the synthetic lipid a-GalCer leads to a more potent mycobactericidal effect.Systemic Therapy with a-GalCer Prolongs the Survivalof Susceptible Mice after Low-Dose Aerosol Infectionwith M.tuberculosisWe next wished to determine the potential of a-GalCer to treat mice with pulmonary TB.To observe protection,we selected C3H mice,which are a susceptible mouse strain that develops extensive lung pathology and succumbs to infection earlier than B6mice(25–27).Previously,we demonstrated that a single dose of a-GalCer(100m gÁkg21)administered intraperitoneally within5days of Mtb infection by the intravenous route was effective in prolonging the survival of susceptible C3H mice (28).However,a-GalCer administered by the intraperitoneal route did not protect mice against low-dose aerosol(LDA) infection with virulent Mtb(Figure2A).There are several important differences between the systemic and pulmonary routes of infection that may affect the efﬁcacy of a-GalCer. We hypothesized that a-GalCer–activated iNKT cells acted locally.Therefore,a-GalCer(100m gÁkg21)was administered intratracheally after LDA infection with Mtb.a-GalCer-treated mice had prolonged survival in two separate experiments (Figure2A).These data indicate that locally activated iNKT cells can provide protection against LDA Mtb infection.Ishii and colleagues reported that intraperitoneally adminis-tered a-GalCer(10m g/100m l vehicle)has a protective effect on the lung after bleomycin treatment(29).Based on these results, we analyzed whether a high dose of a-GalCer(500m gÁkg21) administered systemically protected mice challenged with LDA pared with mice treated with vehicle alone,a-GalCer administered intraperitoneally on Day1post infection pro-longed the survival of susceptible C3H/HeJ mice(Figure2B). The mean survival time(MST)of vehicle-treated mice was60 days.In contrast,the mice that received a single injection of a-GalCer(500m gÁkg21)had a MST of106days.These data show that systemic administration of high-dose a-GalCer pro-tects mice against pulmonary TB.Having established that systemic a-GalCer could protect mice against LDA Mtb infection,we next determined whether repeated administration of a-GalCer would provide longer-term protection.Mice were given a-GalCer on Day1after Mtb infection and then administered a-GalCer every30days, a treatment regimen that signiﬁcantly prolonged their survival compared with vehicle-treated control mice(MST5124d vs. 31d;P50.0009).However,repeated monthly injections with a-GalCer had only an incremental effect on the survival compared with animals injected with a single dose of a-GalCer on Day1after LDA infection(MST5124d vs.106d;P5not signiﬁcant)(Figure2C).Thus,similar to the low-dose a-GalCer treatment regimen after intravenous MtbinfectionFigure2.Treatment with a-galactosylceramide(a-GalCer)(100m gÁkg21or500m gÁkg21)signiﬁcantly prolongs the survival of mice infected bythe aerosol route.(A)Survival of mice after the administration ofa-GalCer(100m gÁkg21)by the intraperitoneal or intratracheal route(n510).Mice were divided in four groups.One group(solid diamonds)received a-GalCer group by intraperitoneal administration on Days25,23,and21.A second group(solid squares)received a-GalCer groupby intraperitoneal administration on Days1,5,and9.A third group(closed circles)received a-GalCer group by the intratracheal route onDay1.Mice were infected with Mycobacterium tuberculosis(Mtb)bylow-dose aerosol(LDA)on Day0.(B)Vehicle(open circles)or a-GalCergroup(500m gÁkg21)(solid circles)was administered intraperitoneally1day after LDA infection with Mtb.(C)Survival of mice after theadministration of a-GalCer(500m gÁkg21)by the intraperitoneal route(n510).No animals died in the uninfected group treated witha-GalCer.Mice received vehicle(open circles),a-GalCer on Day1byintraperitoneal administration(solid circle),or multiple doses ofa-GalCer(solid squares)starting on Day1and then every30days.(D)Mice(solid diamonds)received multiple intraperitoneal administra-tions starting on Day30and then every30days.C and D are from thesame experiment and the data are separated for clarity.Survivalanalysis was performed using Kaplan-Meier method and comparisonswere done with log-rank test.*P,0.05,***P,0.0005.Sada-Ovalle,Sko¨ld,Tian,et al.:iNKT Cells,INH,and Tuberculosis843(28),a single dose of a-GalCer injected on Day1after LDA Mtb infection signiﬁcantly prolonged the survival of the infected mice and repeated administration did not provide any additional beneﬁt.Importantly,treatment with a-GalCer did not diminish the survival of uninfected mice and there were no deaths in mice repeatedly treated with a-GalCer,even after200days of observation(data not shown).This is consistent with Kimura and colleagues,who found that although a-GalCer treatment attenuated the development of bleomycin-induced pulmonary ﬁbrosis,it did not appear to have any adverse effects on the pulmonary architecture(29).Three weeks after a-GalCer treatment of infected mice,no histopathological changes in the lung were observed compared with vehicle-treated control mice(data not shown).However,this does not rule out other subtle changes in the number or volume of granuloma or changes at later time points(28).These results demonstrate that systemic activation of iNKT cells can provide protection to susceptible mouse strains against LDA Mtb infection.a-GalCer Treatment of Susceptible Mice with EstablishedMtb Infection Prolongs Their SurvivalThe ability of a-GalCer to protect mice against LDA Mtb infection suggests that it could be useful as an adjunct treatment against TB.A critical issue is whether a-GalCer had efﬁcacy against established TB disease.To evaluate this question,treatment of mice infected with a low dose of aero-solized Mtb was postponed until Day30post infection.At this time point,the bacterial counts in the lung are approximately 10,000-fold greater than the initial inoculum,and the immune response has controlled bacterial replication leading to the establishment of the plateau phase of the infection.Starting on Day30,mice were treated with a-GalCer(500m gÁkg21) every30days.Delayed administration resulted in a signiﬁcant increase in survival compared with vehicle control mice(MST5 56d vs.31d;P50.02)(Figure2D).This indicates that act-ivated iNKT cells can alter the course of established TB infection.a-GalCer Administration Increases Lung IFN-g Production and Controls Bacterial ReplicationInjection of a-GalCer into naive mice leads to rapid but transient activation of iNKT cells(22).Still,we observed a long-term beneﬁcial effect after a single injection of a-GalCer in Mtb aerosol-infected mice.A dose-dependent stimulation of IFN-g (Figure1B)but not IL-4(data not shown)was observed when a-GalCer is added to a coculture of splenocytes and Mtb-infected M w.We hypothesized that the beneﬁcial effect of iNKT cells is mediated in part by IFN-g production.To determine whether iNKT cell activation induces long-term IFN-g production in the lung,a-GalCer(500m gÁkg21)or vehicle was injected intraperi-toneally into resistant B6or susceptible C3H mice24hours after LDA Mtb infection.Lung CFU and IFN-g production were measured in total lung homogenates3weeks post infection. Although the data did not reach statistical signiﬁcance,the IFN-g concentration was elevated in lung homogenates3weeks after a-GalCer treatment compared with vehicle-treated control mice (Figure3A).Importantly,the bacterial burden in the lungs of mice treated with a-GalCer was signiﬁcantly reduced3weeks after aerosol infection compared with vehicle-treated control mice(B6and C3H;Figures3B and3C).In addition,treatment of B6mice with a-C-GalCer(30),an analog of a-GalCer that has greater Th1-inducing capability,led to a greater CFU reduction (Figure3B).a-GalCer Has an Additive Effect When Administeredwith IsoniazidWe have shown that a-GalCer treatment ameliorates pulmo-nary TB and prolongs survival of susceptible mice,even in those with established pulmonary TB.However,a-GalCer treatment did not eradicate the bacterium or fully cure infected mice, indicating that the use of a-GalCer as a single therapeutic agent is not feasible.Because immune modulation using a-GalCer and conventional antibiotics reduces bacterial growth by dis-tinct mechanisms,we considered whether a-GalCer could have a role as an adjunct therapy.Therefore,we determined the efﬁcacy of a-GalCer when administrated with or without the ﬁrst-line antibiotic isoniazid(INH).We were particularly in-terested in testing this combination in a different disease model, one in which there was signiﬁcant systemic disease.Therefore, we infected mice by the intravenous route to rapidly dissemi-nate the bacteria and establish a systemic infection with a high peripheral bacterial burden.Five weeks after Mtb infection,the combination of a-GalCer and INH signiﬁcantly reduced bacte-rial burden in spleen and lung tissue.Importantly,even under conditions of disseminated disease with a high bacterial burden, the combination of a-GalCer plus INH had an additive effect in controlling bacterial growth in the lungs and in the spleen (Figure4).Our results suggest that a combination of traditional chemotherapy and modulation of the immune response during pulmonary TB can be used for more efﬁcient control of Mtb replication.DISCUSSIONThe promise of immunotherapy,an approach that may have important implications for drug-resistant disease(31,32),has yet to show itself as an important part of the arsenal against TB. Although IFN-g,IL-2,IL-12,and thalidomide have been tried as immune modulators in patients with pulmonary TB,the results of experimental studies and clinical trials have been only moderately encouraging(33–37).Although many clinical stud-ies using IFN-g,IL-12,and thalidomide have demonstrated the potential of these agents to enhance immune responses to infection(38,39),a clinical response has beenﬂeeting.Obtain-ing a therapeutic effect will require unraveling the mechanism of action in addition to optimizing the timing,dose,and route of administration.The complex and myriad effects ofcytokinesmost likely explain the difﬁculty in implementing the clinical use of these different agents.Immune therapy with a-GalCer has also been suggested as a therapeutic option for human diseases,including multiple sclerosis,type1diabetes,rheumatoid arthritis,and lung cancer (16,40,41).Given the low frequency of these iNKT cells,it is remarkable that their activation could change the outcome of disease.Furthermore,given the complex interactions between Mtb and host immunity within the microenvironment of infected foci,simple activation of iNKT cells with a-GalCer in vivo is unlikely to be sufﬁcient to elicit a curative response.A more realistic strategy would be to combine a-GalCer with conventional antibiotics.Pharmacological activation of iNKT cells by a-GalCer modulates adaptive immunity to several different microorgan-isms,including Mtb,Pseudomonas aeruginosa,Cryptococcus neoformans,and several different viruses(3,42,43).However, it has also been shown that speciﬁc iNKT cell activation with a-GalCer can exacerbate disease caused by Leishmania dono-vani infection(44).Therefore,the use of synthetic glycolipids to potentiate the function of iNKT cells must be carefully studied. Weﬁnd that a-GalCer and INH have an additive effect in reducing the bacterial burden in Mtb-infected mice,and that a-GalCer prolongs the survival of infected mice with estab-lished pulmonary TB after Mtb infection via the respiratory route.How does a-GalCer modify the natural course of pulmonary TB?We have previously shown that the ability of a-GalCer to prolong the survival of Mtb-infected mice and to ameliorate disease requires CD1d(28)and is therefore dependent on the action of iNKT cells.We have recently shown,using an in vitro model of infection,that iNKT cells can kill intracellular Mtb and induce host protection after being adoptively transferred into mice infected with Mtb via the aerosol route(3).However, other actions of a-GalCer may be important.For example,Fujii and colleagues have shown that intravenous administration of a-GalCer into mice induces DC maturation.This effect is mainly mediated by TNF-a and IFN-g,and mature DCs can induce greater T-cell responses because of more efﬁcient antigen presentation than exposure to mycobacterial antigens alone(45).Recently,a-GalCer incorporation into BCG has been shown to enhance the conventional CD81T-cell response;thus,it does appear that iNKT cell activation is modulating T-cell priming(46).The ability of iNKT cells to produce IFN-g after a-GalCer stimulation is one of their most important features to mediate host protection and may have therapeutic implications(47,48). Given the importance of IFN-g in controlling Mtb growth and the fact that a-GalCer administration induces IFN-g production by iNKT cells and by NK cells after downstream activation(49), one explanation for how a-GalCer ameliorates pulmonary TB may simply be via the induction of IFN-g.However,our in vitro data show that a combination a-GalCer and IFN-g is more efﬁcient in controlling bacterial growth than a-GalCer or IFN-g treatment alone(Figure1A).This suggests that a-GalCer–activated iNKT cells reduce Mtb replication via an IFN-g independent mechanism,perhaps via direct effector functions.In this study we wanted to determine whether a-GalCer could ameliorate TB after infection via the respiratory route and if a-GalCer could ameliorate established pulmonary TB. Therefore,we infected mice via the aerosol route to mimic the natural route of Mtb infection and we used a high dose of a-GalCer(500m gÁkg21),which has been shown by others to inﬂuence the immune response in lung tissue(29).We found that a single dose of a-GalCer systemically or intratracheally signiﬁcantly prolonged the survival of LDA Mtb-infected mice. We also observed that delayed administration of a-GalCer dramatically improved the outcome of established infection as determined by survival.We have previously shown that repeated a-GalCer admin-istration does not have a greater beneﬁcial effect on survival after intravenous Mtb infection than a single a-GalCer in-jection.In the present study weﬁnd similar results using a model of LDA Mtb infection.The LDA Mtb-infected group that received multiple a-GalCer administrations30days apart lived only18.5more days compared with the infected group that received a single a-GalCer dose.Chiba and colleagues have previously shown using an in vivo model of Mycobacterium bovis bacille Calmette-Gue´rin(BCG)infection that the re-sponsiveness of NKT cells changes during the natural course of the infection,including a transient period of anergy(22).If a-GalCer activation of NKT cells also leads to a period of anergy,the timing of repeated a-GalCer administration could be a critical variable that affects the NKT cell response.At present,one of the most important approaches against TB infection is the design of new therapeutic options,including adjuvants and vaccines.Although current treatment is effective against susceptible Mtb strains,the emergence of multidrug-and extensively drug-resistant strains requires the use of new strategies that can enhance the immune response.We show that the use of a-GalCer as adjuvant therapy inﬂuences the immune response by enhancing iNKT cell production of IFN-g,which presumably activates lung M w to kill Mtb and induces DC maturation to improve antigen presentation to T cells.Similar effects have been observed in other infection models(50–52). Using a clever strategy to exploit the adjuvant properties of a-GalCer clinically,Venkataswamy and colleagues incorpo-rated a-GalCer into the cell wall of BCG.A better immune response was elicited by the modiﬁed BCG(46).New and efﬁcient antibiotics are likely to emerge on the market to help ﬁght pulmonary TB.Unfortunately,there will be an ongoing battle between any new anti-TB drug candidate and the de-velopment of drug resistance.The inclusion of immunomodu-latory agents as adjuvant therapy may prove to be beneﬁcial in the treatment of TB.Because a-GalCer treatment in people with cancer has been proven to be safe(53),we believe that further studies with a-GalCer are warranted todetermine。

05第五章相对论

第5章相对论基础5-1 相对性原理1. 伽利略相对性原理● 伽利略相对性原理：一切彼此作匀速直线运动的惯性系，对于描写机械运动的力学规律来说是完全等价的，并不存在任何一个比其它惯性系更为优越的惯性系，与之相应，一个惯性系的内部所作的任何力学的实验都不能够确定这一惯性系本身是在静止状态，还是在作匀速直线运动。

● 伽利略相对性原理解释：在一个惯性参照系K 中，质点的质量、位矢、速度、加速度和质点所受的力分别为：Fa v r m ,,,,，在另一个相对于参照系K 以速度R v 作匀速直线运动的惯性参照系K '中，该质点的质量、位矢、速度、加速度和质点所受的力分别为：F a v r m ''''' ,,,,。

伽利略相对性原理指出，无论在参照系K 中，还在在参照系K '中，描写机械运动的力学规律的牛顿定律应该具有相同的形式：在参照系K 中：a m F =在参照系K '中：a m F ''='● 伽利略相对性原理来源：在经典力学的时空观是绝对时空观，绝对时空观得到的坐标变换为伽利略坐标变换，由伽利略坐标变换得到，在参照系K 和参照系K '中的加速度相等，经典力学认为，在参照系K 和K '中，质点的质量和所受的力都相等，所以在参照系K 和K '中描写机械运动的力学规律的牛顿定律具有相同的形式，所以经典力学的概念满足伽利略相对性原理。

伽利略坐标变换：t v r r R -='，t t ='得加速度变换为：a a=' 经典力学认为：m m ='，F F ='所以由参照系K 中的牛顿定律：a m F =可以推出参照系K '中的牛顿定律：am F ''=' 两个参照系中的牛顿定律形式相同2. 洛伦兹坐标变换● 洛伦兹坐标变换的来由：根据伽利略坐标变换，电磁学方程在参照系K 和K '中具有不同的形式，电磁学方程不满足相对性原理，为了使电磁学方程满足相对性原理，洛伦兹提出了洛伦兹坐标变换。

百度_相对论吧_[原创-假说]西洋物理学错误观点大全(更新为15个)

2、正确观点：在同一星球上，无法区分静止和匀速运动；在不同的星球上，甚至无法区分匀速运动和加速运动。
3、证据：在地球和火星上分别停放俩火车，俩火车上牛顿运动定律都绝对精确成立，但俩火车之间却在做相对加速运动。
4、独创、首创。广义相对论表明无法区分加速运动和引力场，但错误地将它在同一星球上“使用”。他没有将伽利略相对性原理限制在“同一星球上”，没有将广义相对性原理限制在“星球之间”。
西洋物理学错误观点大全
一、牛顿力学中的加速度的参照物
1、西洋观点：牛顿认为其“水桶实验”证明了绝对空间的存在，认为水相对“绝对空间”加速运动时，水面不再水平。即牛顿定律中的加速度是相对“绝对空间”的。
2、正确观点：牛顿“水桶实验”并不能证明绝对空间的存在，水相对地球加速运动时，水面不再水平。
3、证据：电子围绕原子核加速运动（向心加速度），并不辐射电磁波；外力对电荷作的功正好等于电荷的动能，没有能量损失；在电磁波中，辐射的瞬时功率最大时，发射塔中电荷的加速度却是零，瞬时功率为零时，电荷的加速度却最大。
4、独创、首创
十二、电容器间的电场强度和两端的电压
3、证据：电流既有“位移电流”又有“传导电流”，与电流不同，“磁流”只有“位移磁流”没有“传导磁流”。因此人们只注意到了磁场的“磁容性”（弹性），即认为磁场强度（位移）永远和电流强度（力）成正比！而事实上“变化的磁场”就是“位移磁流”，磁场同样有“磁感性”（惯性），因此电流强度同样可以让磁场产生“加速度”（而不再是形变）。比如在电磁波中，振源的电流强度最大时，振源处的磁场强度却是零，符合“面积定律”。
4、原创但非独创，北京大学孟庆信也表示，在计算光速的过程中，让公式E=BV和B=EV/CC中的E和B同速前进是件很奇怪的事。肖军也表示，不能将公式E=BV计算出来的E再代回公式B=EV/CC中（求公式E=BV中的B）。我在与肖军的辩论时说：将公式E=BV计算出来的E再代回公式B=EV/CC中（求公式E=BV中的B），那就是找死。（当然，我和肖军辩论的具体情况与此不同，我们议题中的B=EV/CC中的E是库仑电场，B是运动电荷产生的（感生）磁场；我们议题中的E’=BV中的E’是上述（感生）磁场（再）运动时产生的（感生）电场，此E’和彼E不可比。）

MARKSCHEME M11 P1 TZ2

8
Alternative methods Candidates will sometimes use methods other than those in the markscheme. Unless the question specifies a method, other correct methods should be marked in line with the markscheme. If in doubt, contact your team leader for advice.
–3–
M11/5/MATHL/HP1/ENG/TZ2/XX/M
Instructions to Examiners
Abbreviations M (M) A (A) R N AG Marks awarded for attempting to use a correct Method; working must be seen. Marks awarded for Method; may be implied by correct subsequent working. Marks awarded for an Answer or for Accuracy; often dependent on preceding M marks. Marks awarded for an Answer or for Accuracy; may be implied by correct subsequent working. Marks awarded for clear Reasoning. Marks awarded for correct answers if no working shown. Answer given in the question and so no marks are awarded.

大学物理伽利略变换

------同时 ------不同时
不同时不同地
t
v c
2
x 时
------同时
第十四章相对论
25
结论同时性具有相对意义沿两个惯性系运动方向，在其中一个惯性系中异地同时发生的两个事件，在另一惯性系中观察则不同时；
只有同地同时发生的两个事件，在其他惯性系中观察也是同时的.
第十四章相对论
10
t 1 L （u c） /
投球手投球动作发出的光到达旁观者眼中需要的时间为：
t2 L / c
显然有：
t1 t 2 〈
表示接球手先看到球而后看到投球手投球的动作--------因果颠倒！其根本原因是我们认为所有的速度都满足伽里略速度叠加原理。
第十四章相对论
11
迈克耳孙-莫雷实验
S 系 ( 地面参考系 )
y'
1
12
v
2
12
事件 1
( x 1 , y 1 , z 1 , t1 )
事件 2
3
( x2 , y2 , z2 , t2 )
o '9
3 6
9 6
x'
Δ t t 2 t1
第十四章相对论
22
S' 系 (车厢参考系 )
( x '1 , y '1 , z '1 , t '1 )
y
y'
l
' y'
v
' l x 'x
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解
在 S' 系
' 45 , l ' 1 m

Saskatoon By

Game Theoretic and Machine Learning Techniques for Balancing GamesA Thesis Submitted to theCollege of Graduate Studies and Researchin Partial Fulﬁllment of the Requirementsfor the degree of Master of Sciencein the Department of Computer ScienceUniversity of SaskatchewanSaskatoonByJeﬀLongc JeﬀLong,August2006.All rights reserved.Permission to UseIn presenting this thesis in partial fulﬁlment of the requirements for a Postgrad-uate degree from the University of Saskatchewan,I agree that the Libraries of this University may make it freely available for inspection.I further agree that permission for copying of this thesis in any manner,in whole or in part,for scholarly purposes may be granted by the professor or professors who supervised my thesis work or,in their absence,by the Head of the Department or the Dean of the College in which my thesis work was done.It is understood that any copying or publication or use of this thesis or parts thereof forﬁnancial gain shall not be allowed without my written permission.It is also understood that due recognition shall be given to me and to the University of Saskatchewan in any scholarly use which may be made of any material in my thesis.Requests for permission to copy or to make other use of material in this thesis in whole or part should be addressed to:Head of the Department of Computer Science176Thorvaldson Building110Science PlaceUniversity of SaskatchewanSaskatoon,SaskatchewanCanadaS7N5C9AbstractGame balance is the problem of determining the fairness of actions or sets of actions in competitive,multiplayer games.This problem primarily arises in the context of designing board and video games.Traditionally,balance has been achieved through large amounts of play-testing and trial-and-error on the part of the designers.In this thesis,it is our intent to lay down the beginnings of a framework for a formal and analytical solution to this problem,combining techniques from game theory and machine learning.Weﬁrst develop a set of game-theoretic deﬁnitions for diﬀerent forms of balance,and then introduce the concept of a strategic abstraction.We show how machine classiﬁcation techniques can be used to identify high-level player strategy in games,using the two principal methods of sequence alignment and Naive Bayes classiﬁcation.Bioinformatics sequence alignment,when combined with a3-nearest neighbor classiﬁcation approach,can,with only3exemplars of each strategy, correctly identify the strategy used in55%of cases using all data,and77%of cases on data that experts indicated actually had a strategic class.Naive Bayes classiﬁcation achieves similar results,with65%accuracy on all data and75%accuracy on data rated to have an actual class.We then show how these game theoretic and machine learning techniques can be combined to automatically build matrices that can be used to analyze game balance properties.AcknowledgementsMany thanks to my supervisor,Michael C.Horsch,for his invaluable support, advice and for reading this so many times he must surely be bored of it by now.Thanks also to all participants in the study,and the valuable advice of my thesis committee.Thanks also to NSERC for funding the years of study that went into this work.ContentsPermission to Use i Abstract ii Acknowledgements iii Contents iv List of Tables vi List of Figures viii 1Problem Description and Motivation1 2Game Theory62.1External Balance (8)2.2Internal Balance (10)2.3Game Theory in Games (11)3Machine Learning for Constructing Game Matrices from Data133.1Machine Learning in Games (17)3.2Experimental Methods and Terminology (18)3.2.1Experimental Testbed (19)3.2.2Sequence Alignment (20)3.2.3Nearest Neighbors Methods (22)3.2.4Naive Bayes Classiﬁcation (23)3.2.5Boosting and the ADABoost Algorithm (25)4An Empirical Study of Abstract Strategy Identiﬁcation from Data284.1Pre-Data Survey (28)4.2Data Collection (29)4.3Data Classiﬁcation (32)4.3.1Structure of Data (33)4.3.2Needleman-Wunsch Alignment Methodology (34)4.3.33-nearest Neighbor Classiﬁcation (39)4.3.4Naive Bayes Classiﬁcation Methodology (40)4.3.5Naive Bayes with Boosting Methodology (46)4.4Constructing Game-Balance Matrices (48)4.5Results and Analysis (50)5Conclusion and Future Work565.1Conclusion (56)5.2Future Work (57)A The Warcraft III Ladder65B Pre-Data Survey66C Questionnaire72D Sequence Alignment Scoring Matrices78List of Tables2.1A4x4matrix game that illustrates internal imbalance,where theﬁrstrow and column represent play frequencies for each player’s optimalmixed strategy.Note that no row or column is dominated by any other.11 4.1Results of the pre-data survey issued to participance,showing thenumber of participants who agreed that the strategies proposed bythe study’s author were common and viable Warcraft III strategies..30 4.2Results of game data classiﬁcation,showing the number of times eachstrategy appeared according to human experts.Note that the totalstrategies listed will be higher than the total number of games,asparticipants were permitted to list more than one strategy per game.32 4.3Results of100test runs using Needleman-Wunsch sequence alignmentfor classiﬁcation and selecting exemplars at random (37)4.4Breakdown of Needleman-Wunsch alignment results by game strategyusing the edit-distance scoring matrix (37)4.5Breakdown of Needleman-Wunsch alignment results by game strategyusing the customized scoring matrix (38)4.6Results a test run using Needleman-Wunsch sequence alignment forclassiﬁcation and selecting a set of‘good’exemplars according to asimple heuristic (39)4.7Results of100test runs using Needleman-Wunsch sequence alignmentwith a3-nearest neighbor approach for classiﬁcation (40)4.8Breakdown of Needleman-Wunsch alignment results with3-nearestneighbor approach by game strategy (41)4.9Results of100test runs using Naive Bayes classiﬁcation,randomlyselecting half of the data as a training set for each run (43)4.10Breakdown of Naive Bayes classiﬁer results by strategy (44)4.11Results of100test runs using Naive Bayes classiﬁcation,with the en-hancement of10additional nodes representing the presence or absenceof individual unit types in the build (44)4.12Breakdown of Naive Bayes classiﬁer with enhancement of10additionalnodes results by strategy (45)4.13Results of100test runs using Naive Bayes classiﬁcation,using theADABoost boosting algorithm with M equal to5 (47)4.14Breakdown of the boosted Naive Bayes classiﬁer M equal to5for theADABoost boosting algorithm (47)4.15A game balance matrix,with rows and columns constructed usingstrictly the labelling provided by human experts over14games (50)4.16A game balance matrix,with rows and columns constructed using thelabelling provided by Needleman-Wunsch sequence alignment over14games (50)4.17A game balance matrix,with rows and columns constructed usingNaive Bayes classiﬁcation over14games (50)4.18A game balance matrix,with rows and columns constructed using thekNN Needleman-Wunsch alignment classiﬁer,run on100unlabelledOrc vs.Night Elf games (51)4.19A measurement of the diﬀerence in alignment score and posterior prob-ability between correctly and incorrectly classiﬁed samples,over100random test runs (55)D.1The character encoding key for Orc and Human military units (79)D.2The character encoding key for Undead and Night Elf military units.80 D.3The scoring matrix used for Orc strategy classiﬁcation (81)D.4The scoring matrix used for Human strategy classiﬁcation (82)D.5The scoring matrix used for Undead strategy classiﬁcation (83)D.6The scoring matrix used for Night Elf strategy classiﬁcation (84)List of Figures4.1The structure of the Naive Bayesian classiﬁer for strategy prediction.Each UnitX node represents the character at position X in the gamedescription (42)4.2The structure of the enhanced Naive Bayesian classiﬁer for strategyprediction.Each UnitX node represents the character at position Xin the game description,and each TypeX node is a boolean valuerepresenting the presence or absence of a speciﬁc unit type (46)Chapter1Problem Description and MotivationPeople who play any sort of competitive game on a regular basis have an intuitive sense of what‘game balance’means.Indeed,many a losing player will,sometimes with justiﬁcation and sometimes not,blame his impending loss not on his own lack of skill,but on imbalances present in the game.Take,for example,a game of chess.The player who is assigned to play black may feel that he has been forced to play the weaker side in the game,and thus a loss may not be due to his skill, but rather because the odds were stacked against him.Available online statistics indicate that such a complaint could be well-founded,and that black is at a signiﬁcant disadvantage over white in chess[Chessgames,2005].Similarly,players will often come to identify individual game elements with the monikers‘overpowered’or‘underpowered.’This is especially prevalent in online competitive video games.Certain elements of the game—such as a particular military unit or weapon,for example—may seem overly eﬀective,thus marginalizing other elements that they overpower.In the same manner,elements that are too weak will simply go unused by experienced players.Problems of this sort have long plagued online multiplayer games;the mutalisk unit,from the popular strategy game Starcraft [Blizzard Entertainment,1998],has been cited by designers as a prime example of a game element that was overpowered and diﬃcult to balance[Cadwell,2002].However,while players are intuitively familiar with the concepts brieftly sketched above,intuition is generally where the familiarity ends.While some classical games have been modeled from a complexity theory standpoint(chess,for instance,is EXPTIME-complete[Fraenkel and Lichtenstein,1981]),to my knowledge there has been no formal deﬁnition of these particular problems in an academic setting,espe-cially coming from the perspective of a design standpoint.Some expertise and advice on‘rules of thumb’exist in industry,of which Cadwell[Cadwell,2002]is a prime ex-ample.Carpenter[Carpenter,2003]uses risk analysis and spread-sheeting techniques to balance individual elements of multiplayer role-playing games,and Kennerly[Ken-nerly,2003]suggests the use of data mining for improving game design.A few other tips and tricks are available[Adams,1998,2002,Rouse III,2005],and usually con-sists mainly of the author’s personal advice and experiences.Furthermore,none of these articles demonstrate rigorous proof or testing of the suggested techniques,nor do they suggest a formal and general-purpose framework for discussing game-balance and its most important properties.For the purposes of this thesis,the term game is used to refer primarily to so-called parlor games-often manifested by board games such as chess,and card games such as Blackjack-and multiplayer computer games.However,many of the concepts and issues raised are applicable to an even wider variety of competitive domains,such as professional sports.We also restrict our attention to games of the two-player variety,though in general the principles discussed are intended to apply to games with numerous players.To further examine and codify the problem of balance,which at this point has only been discussed as an informal concept,we divide it into two distinct categories: external balance and internal balance.We will formalize both of these concepts in Chapter2.External balance refers to the balance between two opposing players in an asymmetric game who are assigned diﬀerent roles,or action sets,at the game’s outset.Many games exhibit this asymmetric property;the example of chess,in which white movesﬁrst,has already been mentioned.In the domain of online games,it is extremely common for players to choose a role or faction at the game’s outset that dictates their available action set for the remainder of the game.The game is said to be externally balanced if neither player has an advantage over the other due simply to the role initially assigned or chosen.Internal balance refers to the balance between diﬀerent available actions or ele-ments of an individual player.If a given action is too weak,then the optimal strategymay be to never use it.Similarly,an action that is too strong may be overused,and could in fact become the game’s only viable course of action.Unlike problems of ex-ternal balance,internal balance problems can exist even in symmetric games where both players have identical action sets available.For instance,online real-time strat-egy games are symmetric so long as both players select the same initial faction,but the players may have military units available to them that should never be built under optimal play.This is an internal balance problem.Cadwell[Cadwell,2002]contends that all forms of imbalance boil down to an elimination of choices.We see that the deﬁnitions given here agree with that claim. In the case of internal balance,it is evident that if the eﬀectiveness of available actions is too disparate,several player choices have been eliminated.In the case of external balance,if one role in the game is stronger than the other,then that role should always be selectedﬁrst,if a player is permitted to choose her own role.Again, assuming both players are trying their utmost to win the game,it seems reasonable to say that a player choice exists only if the two sides of the game,although diﬀerent, are equally likely to win the game.On the point of external balance,it should be noted that in many games a handicap is sometimes desirable so as to even the playingﬁeld between two players of disparate skill.Therefore,it might sometimes be argued that factions of diﬀerent strengths are desirable so as to provide such a handicap,so that one player can volunteer to play the‘harder’side.However,it is our opinion that a handicap should be an explicit element of a game,conﬁgurable by the players,rather than hidden away in the game’s opposing roles.A handicap is of little use,after all,if players mustﬁrst be experts at the game to even realize that the handicap exists.Both forms of imbalance are highly undesirable in a competitive game.Cadwell [Cadwell,2002]describes poor game balance as the factor that often stands in be-tween a good design and a good game;Carpenter goes so far as to call it the“holy grail”of game design[Carpenter,2003].External imbalance can create discontent and frustration among players before the game has even begun,particularly for the player who is forced into the weaker role.Internal imbalance means that the gamecontains extraneous elements,that exist only to frustrate and confuse inexperienced players.From a designer’s point of view,it makes little sense to devote resources to creating a game element that expert players will quickly come to ignore.The most formal of publicly available industry methods of which we are aware for dealing with these problems is the Risk Analysis method by Carpenter[Carpenter, 2003].This is essentially a probabilistic sampling method which simulates the pitting of game elements against one another and generates a probabilistic model of the outcome using multiple iterations.This method requires an extensive user-deﬁned description of the process being simulated,as well as a knowledge of’average’player statistics.The method provides a pair-wise comparison of game elements,but for truly complex systems,the number of iterations required to obtain a meaningful output will be signiﬁcant.Kennerly advocates the use of data mining techniques [Kennerly,2003],involving simple comparisons of statistics and rates of change. Such techniques can inform a designer that a given aggregated rate(such as the rate at which a certain character class improves in an online role-playing game,for instance)needs to be changed,although how to change the rate or by how much is left to the discretion of the designer.Beyond the above methods,it appears for the most part that game balance is achieved through extensive amounts of play-testing and trial-and-error on the part of panies such as Blizzard Entertainment run extensive beta tests that last for months and involve thousands of players,in part to obtain data on game balance issues Blizzard Entertainment[2005].Balance patches for online strategy games continue to be released for months or even years after a game goes public. Board games and card games generally do not have this option,and so it is even more imperative they be properly balanced before a commercial release.An analytical method for extracting balance problems and principles from game data,or better yet identifying and correcting game balance issues without the need for generating large amounts of data,would be a signiﬁcant contribution in both domains.The contributions of this thesis are twofold.First,we reframe and formalize the problems of game balance using the language of economic game theory.We showhow game theoretic concepts and tools can be used to analyze games in extensional form and extract properties relating to game balance.Secondly,we propose building formal game models of manageable size through the use of strategic abstractions,i.e., a high-level strategy implemented by the player.We provide and evaluate several diﬀerent machine learning techniques for automatically classifying these high-level strategies from real game data,and then show how the results can be used to build game theoretic matrices.The remainder of this thesis is organized as follows.Chapter2gives a brief overview of the game theory used in this work and presents game theoretic deﬁnitions of balance,as well as a brief overview of the general application of game theory to games.Chapter3presents a general overview of the machine learning approach used in this thesis,as well as describing all of the individual technologies used for experiments.Chapter4describes in detail the experimental work of this thesis in automatically classifying strategies from game data,and presents an analysis of the results.Finally,Chapter5suggests directions of future work and concludes the thesis.Chapter2Game TheoryIn this chapter,weﬁrst present the game theoretic notation used in this thesis and then go on to formally deﬁne the concepts of external and internal balance and show how they can be identiﬁed once a game has been reduced to a normal form matrix.As discussed in Chapter1,game balance for competitive,multi-player games is essentially ensuring that the following two broad properties hold.Theﬁrst property we call external balance.For a2-person game to be externally balanced,we require that both players have an equal chance at winning the game regardless of the game’s potential starting conditions.This means we do not want the starting conditions of the game to give an inherent advantage to one player.A symmetric game is trivially externally balanced,because the starting conditions are identical for both players. The second property we call internal balance.For a2-person game to be internally balanced,we require that for each available action or game element available to a player,it is useful in at least one circumstance.In other words,we do not want to confuse players with options that should never sensibly be taken.For the subsequent work of this thesis,it is necessary to formalize these concepts. To do so,we turn to the language of game theory,as commonly used in the economic sciences.In spite of its name,game theory has rarely been applied to actual games, especially in the context of the game balance problem studied here.We will use game theory to describe the formalisms that will be our objects of study and analysis.A game,G,consists of an n-dimensional array of payoﬀelements,where n is the number of players in the game.This matrix representation is said to be the normal form of the game.The rows and columns of the matrix represent actions or strategiesthat are available to the players.Each payoﬀelement is an n-tuple,which speciﬁes the payoﬀs to each of the n players.A payoﬀis the reward given to a player for the outcome that a particular array element ually,these payoﬀs may be any element of the set of real numbers;sometimes they can even be qualitative in nature.It is assumed that each player’s preference is to maximize this payoﬀ.In this thesis,we consider only2-player games,in which case the array is a 2-dimensional matrix M,in which the rows represent possible actions of player1 (termed the row player)and the columns represent the actions of player2(termed the column player).The element M(i,j)is a pair of payoﬀvalues,indicating the payoﬀfor each player when player1selects action i and player2selects action j.We also restrict our attention to zero-sum games;that is to say,games that require that the sum of the payoﬀs in each particular matrix cell is zero.This model is an accurate reﬂection of competitive games,since in such games one player winning requires that the other has lost.In fact,two-player,zero-sum games are often termed “strictly competitive”in game theoretic language.In this thesis,we represent the payoﬀvalue of a win as1,the value of a loss as-1,and a draw(in games where such is permitted)as0.Payoﬀtables throughout this thesis show only the payoﬀfor the row player;the column player’s payoﬀis of course the negation of these payoﬀelements.The solution concept used in this thesis is that of mixed strategy Nash equilib-rium.A set of strategies is said to be in Nash equilibrium if no player can improve her expected payoﬀby changing strategies,provided that the other players also do not change strategies.Each row in the payoﬀmatrix is said to represent a pure strat-egy for the row player(and similarly with columns for the column player).A mixed strategy for a player is a probability distribution over the set of his pure strategies, that deﬁnes the probabilistic frequency that each pure-strategy will be selected by the player.While many games will not contain a pure-strategy Nash equilibrium,at least one mixed strategy Nash equilibrium is guaranteed to exist.This mixed strat-egy will often be referred to as a player’s optimal strategy.The standard method of ﬁnding the optimal mixed strategy for a matrix game is the Simplex algorithm,agood description of which can be found in Owen[Owen,1995]or Papadimitriou and Steiglitz[Papadimitriou and Steiglitz,1998].The value of a game,v,is the expected payoﬀthat player1will receive upon playing her optimal strategy;player2will receive its negation.In the case of two-player,zero-sum games,this value will be unique.Calculating the value of a game is straightforward once the optimal strategies of the game are known;usually it can be obtained simply as a byproduct of calculating these strategies via the Simplex method.It should be noted that while probably the most common,Nash equilibrium is not the only solution concept in game theory.There are others that exist as well; Azhar,McLennan and Reif[Azhar et al.,1992]and Papadimitriou[Papadimitriou, 2005]discuss some of them,as well as some of the shortcomings of Nash equilibrium. Perhaps the most signiﬁcant short-coming is that in the general case,multiple Nash equilibria may exist,and there is no known eﬃcient means toﬁnd all equilibria points. However,two convenient properties of Nash equilibria are obtained by restricting the proposed model to two-person,zero-sum games.Theﬁrst is that while it is possible for multiple equilibrium mixed strategies to exist,they are all guaranteed to result in the same expected payoﬀ.Secondly,all equilibrium strategies are interchangeable; that is to say,if(σ1,σ2)is an equilibrium pair,that is to sayσ1is an optimal mixed strategy for player1andσ2is an optimal mixed strategy for player2,and(τ1,τ2)is also an equilibrium pair,then so are(σ1,τ2)and(τ1,σ2)[Owen,1995].2.1External BalanceTo deﬁne external balance in game theoretic terms,we relate it to the concept of the value of a two-person,zero-sum game.Deﬁnition2.1A two-player competitive game is externally balanced if neither player, given perfect skill,has a higher probability of winning the game than the other.We will now show how this deﬁnition relates to the game-theoretic value of the game through the following theorem.Theorem2.1A two-player competitive game G is externally balanced if and only if the corresponding zero-sum matrix game has a value of0.Proof2.1The following equivalences can be used to obtain both directions of the proof.Let G be an n×m zero-sum matrix game where n and m are the number of pure strategies available to players1and2respectively,and where element g ij is1if player 1wins the game when her action is i and player2’s action is j,and-1if player1 loses.A payoﬀof0indicates a draw.Let x and y be the optimal mixed strategies for players1and2respectively,where x i and y i represent the players’frequency of play for pure strategy i.G has a value of0if and only if the following sum holds:n i=1mj=1x i y j g ij=0(2.1)As previously deﬁned,g ij∈{−1,0,1},with1representing a win for player1,−1 representing a loss,or0representing a draw.We can partition this sum according to the values of g ij.i,j:g ij=1x i y j g ij+i,j:g ij=−1x i y j g ij+i,j:g ij=0x i y j g ij=0(2.2)Clearly,the terms where g ij=0can all be dropped,as they do not aﬀect the equality.Furthermore,since the g ij are constant in both the other sums(1for the ﬁrst sum,and-1for the second),they can be factored from the summation,yielding the following:i,j:g ij=1x i y j−i,j:g ij=−1x i y j=0(2.3)i,j:g ij=1x i y j=i,j:g ij=−1x i y j(2.4)Now,let p1be the probability that player1wins the game,and p2be the probability that player2wins the game,given perfect play by both sides.Since by the deﬁnition ofG,player1wins the game when g ij=1,and the x i y i deﬁne a probability distribution over these possible outcomes,we see that:x i y j(2.5)p1=i,j:g ij=1x i y j(2.6)p2=i,j:g ij=−1By equation2.4,this is true if and only if:p1=p2(2.7) 2.2Internal BalanceNext we consider the issue of internal balance in game theoretic terms.Deﬁnition2.2A two-player competitive game is said to be internally balanced if for every available action i,there exists some optimal strategy x for which x i has a non-zero frequency of play.One obvious method of determining this is simply toﬁnd a player’s optimal mixed strategy,x.If x i>0for all i,then the deﬁnition of internal balance is immediately satisﬁed.Since optimal strategies are interchangeable in a two-player, zero-sum game,we need not concern ourselves withﬁnding all possible optimal strategies;ﬁnding a single one for which this property holds is suﬃcient.However, whileﬁnding a single strategy could prove that the property does hold,we would have toﬁnd all optimal strategies to prove that it does not,and in general there is no known method for doing this[Owen,1995].Therefore,it would be convenient if an even simpler criteria could be found for determining internal imbalance.One such game-theoretic concept that seems intuitively plausible is that of domination.We say that the ith row dominates the kth row if,in a matrix game G,g ij≥g kj for all j and g ij>g kj for at least one j. The situation is similar for columns.A dominated row or column can be eliminated from the game without aﬀecting optimal strategies for either player.Table2.1:A4x4matrix game that illustrates internal imbalance,where theﬁrst row and column represent play frequencies for each player’s optimal mixed strategy. Note that no row or column is dominated by any other.//33%33%-100%-11100%01However,while it is evident that a game is not internally balanced if it contains a dominated row or column,the converse does not hold.The proof is through the following simple counter-example in Table2.1.It can be found through standard means that the optimal strategy proﬁle x for player1consists of the vector(0,0,1.0,0),whereas the proﬁle y for player2consists of(0,0.33,0.33,0.33).Both players have one or more options available that should never be played under their optimal strategies.However,an examination of the matrix reveals that no row or column is dominated by any other.This means that a lack of domination is not suﬃcient to demonstrate internal balance in a game.Therefore,for this thesis,we must resort to calculating a strategy proﬁle for each player,and ensuring that no action has a zero-frequency of play.Should weﬁnd an optimal strategy such that this property holds,we call the game internally balanced. Should weﬁnd a dominated action,we say the game is internally imbalanced.Should we fail toﬁnd either a strategy where no action has a zero-frequency of play or a dominated action,we cannot say whether or not the game is internally balanced. Therefore,the problem of determining internal balance is a semi-decidable problem.2.3Game Theory in GamesIn spite of its name,as a modelling tool game theory has more often been used to describe economic,social and political situations than actual games.However, the most basic and famous game-playing algorithm,minimax search,is based upon。

《广义相对论简介》课件

局域性
引力场在局域范围内可近似为牛顿引力，满足线性叠加原理。
引力场方程的推导与表述
80%
场方程的推导
基于爱因斯坦的场方程，通过数学推导得到引力场方程。
100%
场方程的表述
引力场方程表述了物质和能量如何弯曲时空，进而产生引力。
80%
几何意义
引力场方程是时空曲率与物质能量分布之间的联系。
引力场方程的解与意义
爱因斯坦对物理学基础问题的关注
爱因斯坦对物理学的基础问题产生了浓厚的兴趣，开始探索光速不变和相对性原理背后的更深层次原理。
爱因斯坦的科研经历与思想转变
从特殊相对论到广义相对论的过渡
爱因斯坦在提出特殊相对论后，意识到其只能解释惯性参考系下的物理现象，因此开始探索引力问题，最终发展出广义相对论。
对等效原理和最小作用量原理的应用
详细描述
1919年，爱丁顿和戴森带领的探险队在日全食期间观测到太阳附近的星光发生偏折的现象，与广义相对论的预测相符，证实了爱
因斯坦的理论。
水星轨道近日点的进动现象
总结词
水星轨道近日点的进动现象观测结果与牛顿经典力学预测不符，而与广义相对论的预测一致。
详细描述
水星是太阳系中离太阳最近的行星，其轨道近日点会发生进动现象。观测数据显示，水星轨道的进动速度比牛顿经典力学预测的要快，这一现象只有通过广义相对论才能得到
广义协变原理
总结词
该原理要求所有物理定律在任何参照系中都保持形式不变，即具有协变性。
详细描述
广义协变原理是广义相对论的另一个重要原理，它要求所有物理定律在不同的参照系中保持形式不变，即具有协变性。这意味着物理定律的形式在任何参照系中都应该是一样的，不受参照系选择的影响。这一原理进一步强调了物理定律的普遍性和相对性，是广义相对论的重要基石之一。

线索手册11

线索检查汉斯•里莫瑞特的尸体（第一次）从尸体的温度可以推出死亡时间为下午6：30。

凶手在背后开了两枪。

第一枪子弹击中了肩膀，第二枪是致命一击，子弹从后背进入，从腹部射出,应该击中了某个重要器官。

一条细微的血迹让你相信要么有人轻微地移动过尸体，要么汉斯没有马上丧命，并且试图向门外求救。

一颗子弹从尸体中被取了出来。

（1#线索）检查汉斯•里莫瑞特的尸体（第二次）更深层次的检查让你发现了比第一次检查更多地细节。

第一，你注意到汉斯的衬衫衣领沾染了血迹。

你觉得那是因为他在做手术时没有系好大褂，病人的血弄脏了衣领。

你还注意到汉斯没有带上他的结婚戒指。

此外，在他身上没有发现任何能够证明他身份的东西，很有可能是被杀手偷走了。

难道是有人想让大家相信这只是个简单的犯罪？检查汉斯•里莫瑞特的纹身你检查了一下死去的男人的右后肩，希望找到纹身。

不幸的是，一颗子弹正好击中了那个部位。

如果那里有个纹身，也被枪击带了的创伤毁坏了。

（2#线索）检查汉斯•里莫瑞特的手指在汉斯的左手中指上没有可见的戒指痕迹。

不过有许多外科医生在需要做手术时都不会带戒指。

也许汉斯只会在工作以外的时候戴戒指。

走廊线索1你注意到这是出入急诊病房唯一的一条路，走廊尽头被一个大型衣柜挡住了，被很明显是绑匪把它推到这里来阻止警察进入。

线索2在被大型衣柜挡住的急诊病房出口旁边，你找到了少量空腔外壳，随着膛线看去，一颗子弹！（3#线索）德雷克•里莫瑞特的衣帽柜线索1你发现了大量关于器官移植的复杂的医学文本，显然德雷克医生对器官移植相当感兴趣。

线索2你发现了一张雄性激素的订单，通常是用来与其他药品配合治疗严重阳痿的。

难道德雷克这方面有问题？（4#线索）线索3你发现了一张超声波检查结果。

上面是一张非常清晰的足月的婴儿影像。

在这检查结果上面写着病人的名字是“盖尔•里莫瑞特”。

（5#线索）线索4你发现了一份保险合同，内容是如果汉斯死亡，盖尔•里莫瑞特、德雷克•里莫瑞特和布莱特医院一起将获得约六百万美元的赔偿。

科学文献

ReferencesAlexander S(2001)Scrabble FAQ.[http://www.teleport. com/ stevena/scrabble/faqtext.html.]Buro M(2000)LOGISTELLO's homepage.[http://www. /homepages/mic/log.html.] Geoffroy L(2000)Hannibal homepage.[http://www. / bigjeff/Hannibal.html.]IBM Corporation(1997)Kasparov Versus Deep Blue:The Rematch.[/deepblue/ home/html/b.html.]Kaindl H(1988)Minimaxing:theory and practice.AI Magazine,Fall,pp.69±76.Knuth D and Moore R(1975)An Analysis of alpha±beta pruning.Artificial Intelligence6:293±326.Nau D(1983)Pathology on game trees revisited,and an alternative to minimaxing.Artificial Intelligence21(1,2): 221±244.Pearl J(1984)Heuristics:Intelligent Search Strategies for Computer Problem Solving.Reading,MA:Addison Wesley.Schaeffer J(1997)One Jump Ahead:Challenging Human Supremacy in Checkers.New York,NY:Springer-Verlag. [Further information available at http://www.cs. ualberta.ca/ chinook/.]Shannon C(1950)Programming a computer for playing chess.Philosophical Magazine(Series7)41: 256±275.Tesauro G(1995)Temporal difference learning andmunications of the ACM38(3):58±68. [Also available at / massive/tdl.html.]Further ReadingAAAI(2000±2002)Games and Puzzles.http://www.aaai. org/AITopics/html/games.htmlHirsh H(ed.)(1999)Playing with AI.IEEE Intelligent Systems November/December pp.8±18.http://www. /intelligent/ex1999/pdf/x6008.pdf Nau D(1999)AI game-playing techniques:are they useful for anything other than games?AI Magazine20(1):117±118.Newborn M and Newborn M(1996)Kasparov versus Deep Blue:Computer Chess Comes of Age.New York,NY: Springer Verlag.Russell S and Norvig P(1995)Artificial Intelligence,a Modern Approach.Englewood Cliffs,NJ:Prentice-Hall. Schaeffer J(2001)A gamut of games.AI Magazine22(3): 29±46.Introductory articleSecond Language AcquisitionAlan Juffs,University of Pittsburgh,Pittsburgh,Pennsylvania,USA Robert M DeKeyser,University of Pittsburgh,Pittsburgh,Pennsylvania,USASecond language acquisition(SLA)involves the development of the knowledge of a complex system of sound,word,sentence structure,and meaning of any non-native language by children as well as adults;it also involves the acquisition of the ability to use that system appropriately in different social settings.THE RELATION OF SECOND LANGUAGE ACQUISITION TO FIRST LANGUAGE ACQUISITIONThe acquisition of first language(L1)phonology (sound structure)and morphosyntax(the rules of word formation and sentence formation)normally occurs rapidly,effortlessly,and without explicit instruction.By about age five,research suggests that acquisition of the basic linguistic system is largely complete.Many studies that are based on abstract theories of language structure have also shown that children possess knowledge of subtle properties of their first language that they could not have acquired by simply listening to the speech of their care-givers or by repeating only what they hear.Although children are sometimes told when they make mistakes with vocabulary,they rarely receive useful corrections about mistakes in word order and morphology.CONTENTSThe relation of second language acquisition to first language acquisitionThe role of first language knowledge Psycholinguistic issues Implicit and explicit learning Automatization1022Search,AdversarialThese facts about L1acquisition have led to a widely accepted theory that children's acquisition of their mother tongue is guided by innate prin-ciples,which linguists have called Universal Gram-mar(UG).It remains a matter of debate whether these innate principles are specific only to humans' capacity for language or whether they are related to more general learning mechanisms.In either case, UG can be thought of as a blueprint of±or a set of constraints on±what a possible human language is;in other words,UG is a theory of properties that all human languages share and which vary only slightly from one language to another.The task that children face in acquiring their native language is to match the language spoken around them(the `input'in acquisition)with the blueprint they have been born ing this blueprint to filter and understand the input,they construct the grammar of the specific language they are acquiring without conscious reflection.Other views of first language acquisition down-play the role of innate mechanisms and seek to account for acquisition by studying the nature of the input that children receive,as well as their abilities to derive generalizations from this input. Hence,while UG is widely accepted within the field of linguistics,in the wider field of cognitive science the existence of a UG separate from general cognition remains highly disputed.Many researchers believe that the acquisition of a second language by adults involves some of the same abilities that are involved in L1acquisition. Even those researchers who question whether UG is still available after puberty(i.e.researchers who believe in a critical period for UG)accept that some knowledge of universal constraints on human lan-guages may be accessible through knowledge of the first language.However,second language ac-quisition(SLA)is also thought to involve many other factors and processes that are not evident in the acquisition of a mother tongue.One of the most important of these factors is that most adults have some classroom instruction or at least some opportunity to reflect on the process of learning a second language(L2).(Some adults may acquire a second language simply by contact with speakers of another language,but even in this case it is unlikely that they never think about their learn-ing experiences at all.)Second,the role of affect, attitude to learning in general,and to the culture of L2speakers can have an influence on learning out-comes.Third,the role of language aptitude and general intelligence may play a more important role in SLA than in first language acquisition. Finally,one of the most important differences between L1and L2acquisition is that the learners already have a complete linguistic system in place when they begin learning a second language.THE ROLE OF FIRST LANGUAGE KNOWLEDGEBackgroundThe effects of the phonology and morphosyntax of the first language(L1)in SLA is known as`trans-fer'.Transfer can both help and hinder second lan-guage development.Positive transfer occurs when principles that apply to the L1can be readily ap-plied to the second language,whereas negative transfer occurs when a structure or principle that applies in the L1is incorrectly used as part of the L2 grammar.Transfer can affect all levels of the lin-guistic system from basic sound patterns to mor-phology,syntax,semantics,and social conventions of language use.Here we will focus on morpho-syntax,the lexicon,and phonology.Morphosyntax and the Lexicon Researchers disagree substantially on the role of transfer in the acquisition of morphosyntax and the lexicon;two major positions will be briefly dis-cussed.The first position is that the L1plays only a limited role in SLA.The basis for this claim is that speakers of different L1s sometimes show the same developmental patterns when they are learning a second language;in addition,it has been claimed that these patterns show some similarities to stages that are found in first language acquisition.For example,during the early stages of acquisition chil-dren learning English,whether as a first or a second language,omit the subjects of sentences,they ac-quire verbal agreement morphology later than other morphemes,and they learn how to ask ques-tions and negate sentences in somewhat similar developmental stages.Furthermore,learners make some errors that cannot be traced back to the first language influence at all,but to other kinds of learning`strat-egies'.These strategies include deliberate avoid-ance of a difficult structure or the use of a simple L2structure to communicate an idea that is cor-rectly expressed with a more complex structure. Finally,some learners do not use L1forms to ex-press certain meanings because they believe they are unlikely to have the same meaning or use in the L2.One example is the transfer of idiomatic meanings of words from L1to L2.For instance,inSecond Language Acquisition1023addition to its basic meaning,the word`eye'can also refer to the hole at the top of a needle or the sprout on a potato in both English and Dutch. Nevertheless,it has been reported that Dutch-speaking learners of English are reluctant to use the word`eye'to refer to these non-basic concepts when speaking English.In contrast,other researchers have claimed that L1transfer has a very important role to play in SLA.Some researchers claim that the beginning point of second language acquisition is in fact the whole of first language grammar,minus the sound representation of vocabulary items.The evidence for this claim is that at the very early stages, learners appear to attach words from the second language(L2)to what seem to be L1sentence pat-terns.Only later do they begin to adopt the syntac-tic patterns of the L2.In addition,when learners fail to learn a property of the second language the cause can often be traced to the fact that the L1allows consistently more options than the L2where that property is concerned.For example,in English one can say `John gave a book to Mary'or`John gave Mary a book';in French,the second word order is not pos-sible,and so one can say that French is a subset of English in this case.As a result of this wider range of structures,English-speaking learners of French have difficulty in learning that French does not allow the equivalent of`John gave Mary a book'. This relationship between languages has implica-tions for instruction that are discussed below.PhonologyA`foreign accent'is perhaps the most easily identi-fiable characteristic of the adult second language learner;indeed,it is sometimes possible to identify the first language of the learner based on his or her accent.It is therefore clear that the sound system of the first language has an effect on that of the de-veloping second language system.L1influence can be detected in the pronunciation of individual sounds,in syllable structure,and in intonation. However,L1phonology does not transfer whole-sale and the severity of phonological transfer may be predicted on the basis of subtle differences in the underlying sound systems,not just on the basis of whether the first language has the same sounds as the second language.For example,it is well known that Japanese-speaking learners of English as a second language have difficulty in distinguishing between the sounds[l]and[r]in English,as in the words `lock'and`rock'.It was thought that the source of this problem is that Japanese lacks the sounds/l/ and/r/,but instead has one single sound which is close to both,but not the same as either one. While this explanation may be a simple one,it may not in fact be the best or correct one.Modern theories of phonology propose that sounds can be broken down into subparts that represent the sep-arate,but coordinated and simultaneous,move-ments of the vocal cords,tongue,and other parts of the mouth.Research suggests that the source of difficulty is the construction of the abstract sound system based on these articulatory movements, rather than the presence or absence of individual sounds in different languages.For example,Eng-lish only has lip-rounding with vowels that are produced at the back of the mouth;in contrast, French allows lip-rounding to occur with front, central,and back vowels.English-speaking learners of French must therefore learn to produce and distinguish vowels that have lip-rounding in more environments than English does.It is import-ant for acquirers to incorporate the feature of`lip-rounding'as a general distinguishing feature of the whole vowel system in French,not just individual sounds.Second language learners also show influence from their L1when they combine individual speech sounds into words and sentences.For example,some languages do not allow more than one consonant at the beginning of a word.In Eng-lish the words`plate'and`floor'both begin with a sequence of two consonants([p]and[f]followed by [1]),but the Korean language does not allow such sequences.As a result,Korean-speaking learners of English make syllabification errors in words with word-initial consonant sequences;they insert a weak vowel[@]between the consonants,creating two syllables.Hence,they pronounce`floor'as `feloor'[f@lOr],and plate as`pelate'[p@lejt]).SummaryIn general,the L1grammar can be shown to influ-ence the development of the L2grammar,but it is clear that a direct relationship between a sound or syntactic structure in the L1and the sound or syn-tactic structure in the L2does not always exist.PSYCHOLINGUISTIC ISSUESInput Processing,Comprehension,and AcquisitionIn order to understand a sentence when we read or listen to language,it is necessary to put the words1024Second Language Acquisitioninto the structure of a sentence.This structure does not only reflect a strict word-by-word order,but it has a hierarchical as well as a linear organization. For example,in the sentence`The man who was running tripped over',the verb`tripped'is more important to the whole clause than the verb`run-ning'.This importance is represented in an abstract syntactic representation of the sentence.The pro-cess of putting words into a hierarchical structure is called parsing.It is important to understand parsing because it may be an essential part of the acquisition mechan-ism and it may help develop better ways of helping students understand the L2.Unfortunately,we still have a poor grasp of how learners process the form and meaning of input in real time and how they use the results of that processing in constructing the developing grammar.Methods used in first language sentence-processing research have only just begun to inform the issue of input processing in second language puters and eye-tracking devices are being used to measure where learners pause in reading;from these pauses researchers can infer what the process of comprehension might be,or at what point in the sentence the learners are having problems.From results of studies like these we can gain insights into second language processing. Results of preliminary L2research suggest that second language learners,like native speakers,con-struct the sentence structure of a sentence that they are reading one word at a time,revising the struc-ture they are building as they go along.They do not read seven or eight words and then decide on a possible structure for the group of words.It is becoming clear that the influence from first lan-guage parsing mechanisms,as well as the structure of the first language,can explain why even some advanced learners fail to process the second lan-guage efficiently.Language Production in SLASpeech production is a highly complex process that begins with conceptualization and ends with actu-ally making the muscular movements to pronounce words in a sentence.Research suggests that con-ceptualization is not specific to a given language, but that all other components of the production process have some elements unique to that lan-guage.For instance,our conceptualization of prop-erties of objects,such as`wetness'and knowledge of the world(e.g.rain is wet,the sun is hot)may be separate from the individual words in each lan-guage that represent concepts and properties.Evidence for the independence of concepts from language derives from at least two sources.Where nouns are concerned it seems that humans classify things into natural kinds,which have conceptual `prototypes'for membership.For example,when asked whether a penguin,a robin,or an ostrich are good examples of`BIRD',participants in studies tend to choose robin,even though penguins,robins, and ostriches all have wings.Hence,the word `bird'appears to be a collection of properties rather than a list of discrete definitions which can be ana-lyzed in a purely linguistic way.With verbs,all humans can presumably conceptualize the place-ment of things on a flat surface or the placement of something tightly over another item,for example a thimble on a finger,or a top on a pen.However, individual languages tend to encode these two con-cepts of placement in verbs in quite specific ways that are different from one another.Hence,linguis-tic systems are separate from conceptual systems, but they may of course influence one another.It has been proposed that language learners are subject to processing constraints in their second language production and that these processing constraints dictate different stages in the acquisi-tion of second language syntax.In this theory, language structures are available,but limited pro-cessing capacity constrains production.At the ini-tial stages,the claim is that learners have a basic word order strategy and that they are unable to reorder words during the production process.Sub-sequently,they are able to add material to the beginning or end of a sentence,and later are able to insert material into the basic sentence patterns of their second language.Current revisions of this theory propose that processing constraints limit the ability to match the syntactic properties of one part of a sentence with another part of the sentence.Sen-tences that require minimal matching of parts,with only a small number of words between the parts,will be easiest to produce.For example,the agreement between a subject and a verb is easiest when the subject is right next to the verb.As language develops,learners acquire abstract properties of words(e.g.grammatical gender,tense)and become capable of matching these abstract properties with those of another word at increasing`distances'. These distances are defined as the boundaries between phrases and clauses in a sentence.SummarySecond language processing and production re-search is still very much in its infancy.A great deal more work remains to be carried out on theSecond Language Acquisition1025interaction of memory constraints,processing,and developing grammars.IMPLICIT AND EXPLICIT LEARNING Psychological BackgroundIt was noted above that second language learners may still have access to some principles that guide first language acquisition,but that they also use conscious strategies.This distinction is relevant to the difference between implicit and explicit learn-ing.While many definitions of implicit learning (IL)exist,the one that is used most commonly in the field of SLA and in related work in cognitive psychology is the following:a process whereby complex information about a set of stimuli is ac-quired independently of the learner's awareness of either the acquisition process or the resulting knowledge.Explicit learning is the opposite:learn-ing with awareness of the learning that is taking place and of the resulting knowledge.This distinc-tion is the focus of a large,complex,and controver-sial body of research in cognitive psychology.It is also central to much contemporary thinking about SLA,because one's views on this distinction determine in large part both how one understands the psychology of SLA and how one thinks second/foreign languages should be learned and taught.The psychological research on IL that is most directly relevant to SLA deals with artificial gram-mars.In such experiments people are shown large numbers of strings of letters;these strings follow certain patterns(`rules')that constitute a system (`grammar').The participants in these experiments are never told that there is a system of rules under-lying the strings they see,yet they are able,to some extent,to classify new strings into two groups: those that follow the pattern of the previous strings and those that do not.This seems to be evidence of implicit learning:even though people have not thought about the patterns,and even though they cannot say what the patterns are,their classi-fication of new strings shows that,at some level, they have knowledge of the underlying patterns.It is controversial,however,to what extent learning can be both implicit and abstract at the same time. Many researchers claim that learning in adults can be implicit,but that it will then be limited to fairly concrete patterns.They also believe that learning can be abstract,but that it will then be explicit, involving awareness/consciousness of what is learned.Empirical Research on SLAWhile young children clearly learn virtually all of their native language implicitly,the situation in adults is less obvious.Clearly,many adult immig-rants eventually learn to communicate well in the language of their new country,without taking classes in the language or even reflecting much on its structure.On the other hand,many people have acquired much explicit knowledge about an L2in school(in the sense that they can tell you how verbs are conjugated,or how gender agreement between nouns and adjectives or articles work),but they cannot speak the language fluently at all.These two facts together clearly illustrate the big differ-ence between implicit and explicit knowledge. Some educators have concluded from these facts that successful learning of a language,even in adults,requires implicit rather than explicit learn-ing.Recent research of various kinds,however, casts doubt on that reasoning.First,research on naturalistic language acquisi-tion(outside a school context)has shown that un-tutored adult immigrants,while learning to communicate well,often do so through an ex-tremely rudimentary grammatical system,even after many years in their new country,and that even those who seem to speak perfectly grammat-ically have intuitions about grammaticality that rarely if ever match those of native speakers. Second,research in L2classrooms has shown that,at least for certain elements of grammar,stu-dents need explicit teaching of grammar and error correction.This is especially the case when the second language offers fewer options than the first language(e.g.about where in the sentence to put an adverb or about how to form a question). While it is easy to notice that the second language has forms or structures that do not exist in the L1,it is impossible to notice the absence in the L2of one of the possibilities that exist in the L1.Thus explicit teaching is required to make students aware that certain L1options do not exist in the L2. Third,research under laboratory conditions (with miniature linguistic systems or very re-stricted parts of an existing language),often through computerized instruction,has shown that explicit teaching and practising of rules is far su-perior to mere exposure to relevant examples with-out explanation of structure,even when that exposure is very extensive(thousands of examples per rule).Only when the rules are very complex or fuzzy are the rules of no help;there might even be a slight advantage for IL in such a case.1026Second Language AcquisitionIn summary,while IL of many elements of an L2 by adults is possible,and while many adults can learn the whole set of abstract grammar rules of an L2well,it is very doubtful that any adult can suc-cessfully learn the whole set of L2grammar rules implicitly.This conclusion is very reminiscent,of course,of the research in cognitive psychology which suggests that adults can learn implicitly and can learn abstract patterns,but not both at the same time.It also explains the traces of non-nativeness in the syntax of untutored immigrants, even those who are able to get their ideas across perfectly.Implications for Learning and Teaching of an L2The history of L2teaching has shown a repeated pendulum movement between emphasis on impli-cit and on explicit learning.Even over the last century alone,various teaching methods have em-bodied one extreme or the other.Many people remember foreign language classes from their high school or college days in which they spent substantial amounts of time learning gram-mar rules and vocabulary items,and translating sentences,without ever practising the language for communication(the grammar-translation method), let alone learning anything implicitly through ex-posure to spoken or written text in the language.On the other hand,in more recent decades,some lan-guage teachers have tried to largely leave out gram-mar teaching and error correction,and to make their students absorb the structure of the L2from large amounts of exposure to(usually adapted)input (the natural approach).Most teaching practice,however,is somewhere in between.Audiolingual methodology,especially popular in the1950s and1960s,while emphasizing implicit absorption through endless drills,certainly did provide a highly systematic presentation of structures for practice,and not just adapted input. In many cases,in fact,grammar rules were expli-citly presented before the extensive -municative language teaching,probably the most widespread methodology world-wide from the 1970s onwards,stresses communicative practice in comprehension and production,and varies in the extent to which rules are taught explicitly and practised systematically.Variants of all these methods are still widely used in educational settings throughout the world. To some extent this variation reflects continuing debate in the language teaching profession about the roles of implicit and explicit knowledge,but other,and often more important,factors are the training that the teacher received(sometimes decades earlier),the methodology endorsed by widely available textbooks,time constraints,and individual characteristics of the students.The last two factors deserve some further explanation.Time constraints often work against teaching methodolo-gies that make sense from the point of view of research on second language acquisition because these methodologies are only efficient in the long run.Even those educators who are strong advo-cates of explicit grammar teaching and systematic practice will admit that this approach cannot lead to full proficiency after just a couple of years of study in high school or college,and that a less rigid approach with more time for authentic mater-ials and fun communicative activities can seem more attractive under such conditions.Individual characteristics play a role in the sense that only students with a certain level of language learning aptitude(strongly related to verbal intelligence) can be expected to benefit maximally from a method that requires them to learn and use explicit rules.Therefore,in cases where all students of a certain age(are required to)take L2classes,a teach-ing approach focused on the absorption of vocabu-lary and common phrases through extensive communicative use may be more efficient than an approach based on the systematic learning of expli-citly taught rules.One should keep in mind,how-ever,that while the more implicit methodologies may be the most efficient under those circumstances, they can by no means be maximally effective in bringing about high levels of both fluency and ac-curacy in spontaneous communication.Adults do need explicit learning to reach high levels of gram-matical accuracy,as was argued above.The need for explicit learning does not automat-ically entail the need for explicit teaching.Besides taking classes,adult learners have two other options for explicit learning:formal self-study by means of textbooks,phrasebooks,grammars,and dictionaries,and informal self-study by figuring out structural patterns in the input available from interaction with native speakers,recordings,or texts.From a psycholinguistic point of view,this institutional versus naturalistic distinction does not matter;in all these cases the learning process is explicit,because the learner is aware of both the learning process and the resulting knowledge of L2 structure.Also,explicit learning does not require the use of extensive grammatical terminology or a traditional syllabus organized structure by structure.The crucial factor is whether the learner somehowSecond Language Acquisition1027。

贾斯汀站长文章吧吧刊——2011年第一期

《迪恩@贾斯汀》
——原版 1、序章爱德华· 贾斯汀在火星港上家喻户晓，谁不知道这位自学法术、深思远虑、风华绝代、乐于助人的少年啊！不过虽然名气很高，但没几个人见过他。按照道理来说，就算火星港上的人们忙得走路只会跑、睡觉只有3小时，那也总不能连这么一个大名鼎鼎的少年也见不到一面啊！不过贾斯汀有一个特殊的爱好——与精灵为伴、研究精灵战术。但是在刚刚发现精灵的火星港上，精灵可不是一眼几十只、身影遍地是。它们大多数都在郊外的晨雾森林里。晨雾森林据说是终日迷雾重重，你可不要以为“晨雾森林”就是只有清晨才会有雾，它的毒雾可是让无数擅自闯入的人丢了命。所以，能进入晨雾森林的人就已经是非常优秀的人了——更何况贾斯汀就生活在这个夺命森林里呢。 “江山自有人才出”，异常喜爱精灵的贾斯汀在晨雾森林里也并非时时孤单，因为总有形形色色的人闯入这里。而且他早已与精灵们建立了深厚的友谊，孤单个啥啊！？但在一个艳阳高照的中午，他竟在晨雾森林中遇到了一个与他同样俊美的少年…… （未完待续）
大家都很希望能看到吧刊。还好现在是寒假，多一些时间去作图，赶稿。这份吧刊是大家共同努力的结果，希望大家珍惜。
吧刊在大家的共同努力下，终于完工，于今日正式上稿贾斯汀站长文章吧。感谢所有来稿的会员们。感谢你们的支持。
最后，祝愿各位贾斯汀站长文章吧的羽翼们，新年快乐，兔年大吉，万事如意！
Happy new year 兔 every one！
（未完待续）
《迪恩@贾斯汀》
——原版 3、初战贾斯汀听后，就抛出了他的精灵胶囊，一道亮光闪过，现出了一只英卡洛斯。迪恩也把他的萨格罗斯扔了出来。两只精灵交合在一起，亮光对着闪电，瞬间爆发出了一片强烈的光源，照得两人都睁不开眼睛。两只精灵都是极品。但是它们的对战却很耗时间。不论速度、攻击力还是防御力，都不相上下。看来，是要打耗时战了。一回合，两回合，三回合……两只精灵不分胜负。迪恩的规则是自己的精灵决不能输，因此萨格罗斯见赢不了英卡洛斯，心中也是十分着急。在一旁观战的迪贾二人却似乎并不着急。迪恩抚弄着身旁的花草，而贾斯汀则站在一旁打量着迪恩。 ------------------------------耗时间的激战-----------------------------已是第二百三十六个回合了，训练有素的英卡洛斯渐占上风。萨格罗斯喘口气，忽然心中一动，把攻击目标转向了贾斯汀。萨格罗斯开始储蓄力量，发了一个大招，直扑贾斯汀。好凌厉的一招！