Gaugegravity duality

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1Gauge/gravity duality GARY T.HOROWITZ University of California at Santa Barbara JOSEPH POLCHINSKI KITP,University of California at Santa Barbara Abstract We review the emergence of gravity from gauge theory in the context of AdS/CFT duality.We discuss the evidence for the duality,its lessons for gravitational physics,generalizations,and open questions.1.1Introduction Assertion:Hidden within every non-Abelian gauge theory,even within the weak and strong nuclear interactions,is a theory of quantum gravity.This is one implication of AdS/CFT duality.It was discovered by a circuitous route,involving in particular the relation between black branes and D-branes in string theory.It is an interesting exercise,how-ever,to ?rst try to ?nd a path from gauge theory to gravity as directly as possible.Thus let us imagine that we know a bit about gauge theory and a bit about gravity but nothing about string theory,and ask,how are we to make sense of the assertion?One possibility that comes to mind is that the spin-two graviton might

arise as a composite of two spin-one gauge bosons.This interesting idea would seem to be rigorously excluded by a no-go theorem of Weinberg &Witten (1980).The Weinberg-Witten theorem appears to assume noth-ing more than the existence of a Lorentz-covariant energy momentum tensor,which indeed holds in gauge theory.The theorem does forbid a wide range of possibilities,but (as with several other beautiful and pow-erful no-go theorems)it has at least one hidden assumption that seems so trivial as to escape notice,but which later developments show to be unnecessary.The crucial assumption here is that the graviton moves in the same spacetime as the gauge bosons of which it is made!

1

2Gary T.Horowitz and Joseph Polchinski

The clue to relax this assumption comes from the holographic prin-ciple(’t Hooft,1993,and Susskind,1995),which suggests that a grav-itational theory should be related to a non-gravitational theory in one fewer dimension.In other words,we must?nd within the gauge theory not just the graviton,but a?fth dimension as well:the physics must be local with respect to some additional hidden parameter.Several hints suggest that the role of this?fth dimension is played by the energy scale of the gauge theory.For example,the renormalization group equation is local with respect to energy:it is a nonlinear evolution equation for the coupling constants as measured at a given energy scale.?

In order to make this precise,it is useful to go to certain limits in which the?ve-dimensional picture becomes manifest;we will later return to the more general case.Thus we consider four-dimensional gauge theories with the following additional properties:

?Large N c.While the holographic principle implies a certain equiva-lence between four-and?ve-dimensional theories,it is also true that in many senses a higher dimensional theory has more degrees of free-dom;for example,the one-particle states are labeled by an additional momentum parameter.Thus,in order to?nd a?fth dimension of macroscopic size,we need to consider gauge theories with many de-grees of freedom.A natural limit of this kind was identi?ed by’t Hooft(1974):if we consider SU(N c)gauge theories,then there is a smooth limit in which N c is taken large with the combination g2YM N c held?xed.

?Strong coupling.Classical Yang-Mills theory is certainly not the same as classical general relativity.If gravity is to emerge from gauge theory, we should expect that it will be in the limit where the gauge?elds are strongly quantum mechanical,and the gravitational degrees of freedom arise as e?ective classical?elds.Thus we must consider the theory with large t Hooft parameter g2YM N c.?Supersymmetry.This is a more technical assumption,but it is a natural corollary to the previous one.Quantum?eld theories at strong coupling are prone to severe instabilities;for example,particle-antiparticle pairs can appear spontaneously,and their negative poten-tial energy would exceed their positive rest and kinetic energies.Thus, QED with?ne structure constant much greater than1does not exist, even as an e?ective theory,because it immediately runs into an in-stability in the ultraviolet(known as the Landau pole).The Thirring ?This locality was emphasized to us by Shenker,who credits it to Wilson.

Gauge/gravity duality3 model provides a simple solvable illustration of the problem:it exists

only below a certain critical coupling(Coleman,1975).Supersym-

metric theories however have a natural stability property,because the

Hamiltonian is the square of a Hermitean supercharge and so bounded

below.Thus it is not surprising that most examples of?eld theories

with interesting strong coupling behavior(i.e.dualities)are super-

symmetric.We will therefore start by assuming supersymmetry,but

after understanding this case we can work back to the nonsupersym-

metric case.

We begin with the most supersymmetric possibility,N=4SU(N c)

gauge theory,meaning that there are four copies of the minimal D=4

supersymmetry algebra.The assumption of N=4supersymmetry has

a useful bonus in that the beta function vanishes,the coupling does not

run.Most gauge theories have running couplings,so that the strong

coupling required by the previous argument persists only in a very nar-

row range of energies,becoming weak on one side and blowing up on

the other.In the N=4gauge theory the coupling remains strong and

constant over an arbitrarily large range,and so we can have a large?fth

dimension.

The vanishing beta function implies that the classical conformal in-

variance of the Yang-Mills theory survives quantization:it is a conformal

?eld theory(CFT).In particular,the theory is invariant under rigid scale

transformations xμ→λxμforμ=0,1,2,3.Since we are associating the?fth coordinate r with energy scale,it must tranform inversely to

the length scale,r→r/λ.The most general metric invariant under this

scale invariance and the ordinary Poincar′e symmetries is

ds2=r2

r2

dr2(1.1)

for some constants?and?′;by a multiplicative rede?nition of r we can set?′=?.Thus our attempt to make sense of the assertion at the beginning has led us(with liberal use of hindsight)to the following conjecture:D=4,N=4,SU(N c)gauge theory is equivalent to a grav-itational theory in?ve-dimensional anti-de Sitter(AdS)space.Indeed, this appears to be true.In the next section we will make this statement more precise,and discuss the evidence for it.In the?nal section we will discuss various lessons for quantum gravity,generalizations,and open questions.

4Gary T.Horowitz and Joseph Polchinski

1.2AdS/CFT duality

Let us de?ne more fully the two sides of the duality.?The gauge theory can be written in a compact way by starting with the D=10Lagrangian density for an SU(N c)gauge?eld and a16component Majorana-Weyl spinor,both in the adjoint(N c×N c matrix)representation:

L=1

Gauge/gravity duality5 completely crazy comes from comparing the symmetries.The D=4, N=4,SU(N c)super-Yang-Mills theory has an SO(4,2)symmetry

coming from conformal invariance and an SO(6)symmetry coming from rotation of the scalars.This agrees with the geometric symmetries of AdS5×S5.On both sides there are also32supersymmetries.Again on the gravitational side these are geometric,arising as Killing spinors on the AdS5×S5spacetime.On the gauge theory side they include the 16‘ordinary’supersymmetries of the N=4algebra,and16additional supersymmetries as required by the conformal algebra.

The precise(though still not fully complete)statement is that the IIB supergravity theory in a space whose geometry is asymptotically AdS5×S5is dual to the D=4,N=4,SU(N c)gauge theory.The metric(1.1) describes only a Poincar′e patch of AdS spacetime,and the gauge theory lives on R4.It is generally more natural to consider the fully extended global AdS space,in which case the dual gauge theory lives on S3×R. In each case the gauge theory lives on the conformal boundary of the gravitational spacetime(r→∞in the Poincar′e coordinates),which will give us a natural dictionary for the observables.

The initial checks of this duality concerned perturbations of AdS5×S5. It was shown that all linearized supergravity states have corresponding states in the gauge theory(Witten,1998a).In particular,the global time translation in the bulk is identi?ed with time translation in the ?eld theory,and the energies of states in the?eld theory and string theory agree.For perturbations of AdS5×S5,one can reconstruct the background spacetime from the gauge theory as follows.Fields on S5 can be decomposed into spherical harmonics,which can be described as symmetric traceless tensors on R6:T i···j X i···X j.Restricted to the unit sphere one gets a basis of functions.Recall that the gauge theory has six scalars and the SO(6)symmetry of rotating the?i.So the operators T i···j?i···?j give information about position on S5.Four of the remaining directions are explicitly present in the gauge theory,and the radial direction corresponds to the energy scale in the gauge theory. In the gauge theory the expectation values of local operators(gauge invariant products of the N=4?elds and their covariant derivatives) provide one natural set of observables.It is convenient to work with the generating functional for these expectation values by shifting the Lagrangian density

L(x)→L(x)+ I J I(x)O I(x),(1.3) where O I is some basis of local operators and J I(x)are arbitrary func-

6Gary T.Horowitz and Joseph Polchinski

tions.Since we are taking products of operators at a point,we are perturbing the theory in the ultraviolet,which according to the energy-radius relation maps to the AdS boundary.Thus the duality dictionary relates the gauge theory generating functional to a gravitational theory in which the boundary conditions at in?nity are perturbed in a speci?ed way(Gubser et al.,1998,and Witten,1998a).As a further check on the duality,all three-point interactions were shown to agree(Lee et al., 1998).

The linearized supergravity excitations map to gauge invariant states of the gauge bosons,scalars,and fermions,but in fact only to a small subset of these;in particular,all the supergravity states live in special small multiplets of the superconformal symmetry algebra.Thus the dual to the gauge theory contains much more than supergravity.The identity of the additional degrees of freedom becomes particularly clear if one looks at highly boosted states,those having large angular momentum on S5and/or AdS5(Berenstein et al.,2002,and Gubser et al.,2002).The ?elds of the gauge theory then organize naturally into one-dimensional structures,coming from the Yang-Mills large-N c trace:they correspond to the excited states of strings.In some cases,one can even construct a two dimensional sigma model directly from the gauge theory and show that it agrees(at large boost)with the sigma model describing strings moving in AdS5×S5(Kruczenski,2004).

Thus,by trying to make sense of the assertion at the beginning,we are forced to‘discover’string theory.We can now state the duality in its full form(Maldacena,1998a):

Four-dimensional N=4supersymmetric SU(N c)gauge theory is equivalent to IIB string theory with AdS5×S5boundary conditions. The need for strings(though not the presence of gravity!)was already anticipated by’t Hooft(1974),based on the planar structure of the large-N c Yang-Mills perturbation theory;the AdS/CFT duality puts this into a precise form.It also?ts with the existence of another important set of gauge theory observables,the one-dimensional Wilson loops.The Wilson loop can be thought of as creating a string at the AdS5boundary, whose world-sheet then extends into the interior(Maldacena,1998b,and Rey&Yee,2001).See also Polyakov(1987,1999)for other perspectives on gauge/string duality and the role of the?fth dimension.

We now drop the pretense of not knowing string theory,and outline the original argument for the duality in Maldacena(1998a).He con-sidered a stack of N c parallel D3-branes on top of each other.Each

Gauge/gravity duality7 D3-brane couples to gravity with a strength proportional to the dimen-

sionless string coupling g s,so the distortion of the metric by the branes

is proportional to g s N c.When g s N c?1the spacetime is nearly?at and there are two types of string excitations.There are open strings on the

brane whose low energy modes are described by a U(N c)gauge theory.

There are also closed strings away from the brane.When g s N c?1,the backreaction is important and the metric describes an extremal black 3-brane.This is a generalization of a black hole appropriate for a three dimensional extended object.It is extremal with respect to the charge carried by the3-branes,which sources the?ve form F5.Near the hori-zon,the spacetime becomes a product of S5and AdS5.(This is directly analogous to the fact that near the horizon of an extremal Reissner-Nordstrom black hole,the spacetime is AdS2×S2.)String states near the horizon are strongly redshifted and have very low energy as seen asymptotically.In a certain low energy limit,one can decouple these strings from the strings in the asymptotically?at region.At weak cou-pling,g s N c?1,this same limit decouples the excitations of the3-branes from the closed strings.Thus the low energy decoupled physics is de-scribed by the gauge theory at small g s and by the AdS5×S5closed string theory at large g s,and the simplest conjecture is that these are the same theory as seen at di?erent values of the coupling.?This con-jecture resolved a puzzle,the fact that very di?erent gauge theory and gravity calculations were found to give the same answers for a variety of string-brane interactions.

In the context of string theory we can relate the parameters on the

two sides of the duality.In the gauge theory we have g2YM and N c.The

known D3-brane Lagrangian determines the relation of couplings,g2YM=

4πg s.Further,each D3-brane is a source for the?ve-form?eld strength,

so on the string side N c is determined by S5F5;this integrated?ux is quantized by a generalization of Dirac’s argument for quantization of the ?ux S2F2of a magnetic monopole.The supergravity?eld equations give a relation between this?ux and the radii of curvature of the AdS5 and S5spaces,both being given by

?=(4πg s N c)1/4?s.(1.4) Here?s is the fundamental length scale of string theory,related to the string tensionμbyμ?1=2π?2s.Notice that the spacetime radii are large in string units(and so the curvature is small)precisely when the’t Hooft ?The U(1)factor in U(N c)=SU(N c)×U(1)also decouples:it is Abelian and does not feel the strong gauge interactions.

8Gary T.Horowitz and Joseph Polchinski

coupling4πg s N c=g2YM N c is large,in keeping with the heuristic argu-ments that we made in the introduction.It is also instructive to express the AdS radius entirely in gravitational variables.The ten-dimensional gravitational coupling is G～g2s?8s,up to a numerical constant.Thus

?～N1/4

c G1/8,G～

?8

?2+1?

r20

?2

+1?

r20

Gauge/gravity duality9 is

S BH=A

g2s?8s～

T3H?11

4

S YM

(Gubser et al.,1996).The numerical disagreement is not surprising,as the Yang-Mills calculation is for an ideal gas,and at large g s the Yang-Mills degrees of freedom are interacting.Thus one expects a relation of the form S BH=f(g s N c)S YM,ideal,where f(0)=1;the above calculation implies that f(∞)=3

4,but the?rst correction has been calculated both at weak

and strong coupling and is consistent with f(g s N c)interpolating in a rather smooth way.

Hawking&Page(1983)showed that for thermal AdS boundary con-ditions there is a phase transition:below a transition temperature of order1/?the dominant con?guration is not the black hole but a gas of particles in AdS space.The low temperature geometry has no horizon and so its entropy comes only from the ordinary statistical mechanics of the gas.The same transition occurs in the gauge theory(Witten, 1998b).The N=4gauge theory on S3has an analog of a con?nement transition.At low temperature one has a thermal ensemble of gauge-invariant degrees of freedom,whose entropy therefore scales as N0c,and at high temperature one has the N2c behavior found above—the same scalings as on the gravitational side.

There is another test one can perform with the gauge theory at?-nite temperature.At long wavelengths,one can use a hydrodynamic approximation and think of this as a?uid(for a recent overview see Kovtun et al.,2003).It is then natural to ask:What is the speed of sound waves?Conformal invariance implies that the stress energy ten-sor is traceless,so p=ρ/3which implies that v=1/

√

10Gary T.Horowitz and Joseph Polchinski

seem to be di?cult since the bulk does not seem to have any preferred speed other than the speed of light.But recent work has shown that the answer is yes.

The AdS/CFT duality also gives an interesting perspective on the black hole membrane paradigm(Thorne et al.,1986).The black hole horizon is known to have many of the properties of a dissipative sys-tem.On the dual side it is a dissipative system,the hot gauge theory. One can thus compute such hydrodynamic quantities such as the shear viscosity.These are hard to check since they are di?cult to calculate directly in the strongly coupled thermal gauge theory,but,rather re-markably,the numerical agreement with the observed properties of the real quark-gluon plasma at RHIC is better than for conventional?eld theory calculations(for a discussion see Blau,2005).

There is also a?eld theory interpretation of black hole quasinormal modes(Horowitz&Hubeny2000).A perturbation of the black hole decays with a characteristic time set by the imaginary part of the low-est quasinormal mode.This should correspond to the timescale for the gauge theory to return to thermal equilibrium.One can show that the quasinormal mode frequencies are poles in the retarded Green’s func-tion of a certain operator in the gauge theory.The particular operator depends on the type of?eld used to perturb the black hole(Kovtun& Starinets,2005).

Finally,consider the formation and evaporation of a small black hole in a spacetime which is asymptotically AdS5×S5.By the AdS/CFT correspondence,this process is described by ordinary unitary evolution in the gauge theory.So black hole evaporation does not violate quan-tum mechanics:information is preserved.This also provides an indirect argument against the existence of a‘bounce’at the black hole singular-ity,because the resulting disconnected universe would presumably carry away information.

1.3.2Background independence and emergence

The AdS/CFT system is entirely embedded in the framework of quan-tum mechanics.On the gauge theory side we have an explicit Hamil-tonian,and states which we can think of as gauge invariant functionals of the?elds.Thus the gravitational theory on the other side is quan-tum mechanical as well.In particular the metric?uctuates freely except at the AdS boundary.One is not restricted to perturbations about a particular background.

Gauge/gravity duality11 This is clearly illustrated by a rich set of examples which provide a detailed map between a class of nontrivial asymptotically AdS5×S5

supergravity solutions and a class of states in the gauge theory(Lin et al.,2004).These states and geometries both preserve half of the supersymmetry of AdS5×S5itself.On the?eld theory side,one restricts to?elds that are independent of S3and hence reduce to N c×N c matrices. In fact,all the states are created by a single complex matrix,so can be described by a one-matrix model.This theory can be quantized exactly in terms of free fermions,and the states can be labeled by a arbitrary closed curve(the Fermi surface)on a plane.On the gravity side,one considers solutions to ten dimensional supergravity involving just the metric and self-dual?ve form F5.The?eld equations are simply dF5=0 and

R MN=F MP QRS F N P QRS(1.9) There exists a large class of stationary solutions to(1.9),which have an SO(4)×SO(4)symmetry and can be obtained by solving a linear equation.These solutions are nonsingular,have no event horizons,but can have complicated topology.They are also labeled by arbitrary closed curves on a plane.This provides a precise way to map states in the?eld theory into bulk geometries.Only for some“semi-classical”states is the curvature below the Planck scale everywhere,but the matrix/free fermion description readily describes all the states,of all topologies, within a single Hilbert space.

Thus the gauge theory gives a representation of quantum gravity that is background independent almost everywhere—-that is,everywhere ex-cept the boundary.Conventional string perturbation theory constructs string amplitudes as an asymptotic expansion around a given spacetime geometry;here we have an exact quantum mechanical construction for which the conventional expansion generates the asymptotics.All lo-cal phenomena of quantum gravity,such as formation and evaporation of black holes,the interaction of quanta with Planckian energies,and even transitions that change topology,are described by the gauge the-ory.However,the boundary conditions do have the important limitation that most cosmological situations,and most compacti?cations of string theory,cannot be described;we will return to these points later.

To summarize,AdS/CFT duality is an example of emergent gravity, emergent spacetime,and emergent general coordinate invariance.But it is also an example of emergent strings!We should note that the terms‘gauge/gravity duality’and‘gauge/string duality’are often used,

12Gary T.Horowitz and Joseph Polchinski

both to re?ect these emergent properties and also the fact that(as we

are about the see)the duality generalizes to gravitational theories with

certain other boundary conditions,and to?eld theories that are not

conformally invariant.

Let us expand somewhat on the emergence of general coordinate in-

variance.The AdS/CFT duality is a close analog to the phenomenon

of emergent gauge symmetry(e.g.D’Adda et al.,1978,and Baskaran

&Anderson,1988).For example,in some condensed matter systems in

which the starting point has only electrons with short-ranged interac-

tions,there are phases where the electron separates into a new fermion

and boson,

e(x)=b(x)f?(x).(1.10) However,the new?elds are redundant:there is a gauge transformation

b(x)→e iλ(x)b(x),f(x)→e iλ(x)f(x),which leaves the physical elec-

tron?eld invariant.This new gauge invariance is clearly emergent:it is

completely invisible in terms of the electron?eld appearing in the orig-

inal description of the theory.?Similarly,the gauge theory variables of

AdS/CFT are trivially invariant under the bulk di?eomorphisms,which

are entirely invisible in the gauge theory(the gauge theory?elds do

transform under the asymptotic symmetries of AdS5×S5,but these are ADM symmetries,not gauge redundancies).Of course we can always

in general relativity introduce a set of gauge-invariant observables by

setting up e?ectively a system of rods and clocks,so to this extent the

notion of emergence is imprecise,but it carries the connotation that the

dynamics can be expressed in a simple way in terms of the invariant

variables,as the case in AdS/CFT.?

1.3.3Generalizations

Thus far we have considered only the most well-studied example of

gauge/gravity duality:D=4,N=4,Yang-Mills?string theory

with AdS5×S5boundary conditions.Let us now ask how much more general this phenomenon is(again,for details see the review by Aharony et al.,2000).

?This‘statistical’gauge invariance is not to be confused with the ordinary electro-magnetic gauge invariance,which does act on the electron.

?Note that on the gauge theory side there is still the ordinary Yang-Mills gauge redundancy,which is more tractable than general coordinate invariance(it does not act on spacetime).In fact in most examples of duality there are gauge symmetries on both sides and these are unrelated to each other:the duality pertains only to the physical quantities.

Gauge/gravity duality13 First,we imagine perturbing the theory we have already studied, adding additional terms(such as masses for some of the?elds)to the gauge theory action.This is just a special case of the modi?cation(1.3), such that the functions J I(x)=g I are independent of position.Thus we already have the dictionary,that the the dual theory is given by IIB string theory in a spacetime with some perturbation of the AdS5×S5 boundary conditions.

In general,the perturbation of the gauge theory will break conformal invariance,so that the physics depends on energy scale.In quantum ?eld theory there is a standard procedure for integrating out high en-ergy degrees of freedom and obtaining an e?ective theory at low energy. This is known as renormalization group(RG)?ow.If one starts with a conformal?eld theory at high energy,the RG?ow is trivial.The low energy theory looks the same as the high energy theory.This is because there is no intrinsic scale.But if we perturb the theory,the RG?ow is nontrivial and we obtain a di?erent theory at low energies.There are two broad possibilities:either some degrees of freedom remain massless and we approach a new conformal theory at low energy,or all?elds become massive and the low energy limit is trivial.

Since the energy scale corresponds to the radius,this RG?ow in the boundary?eld theory should correspond to radial dependence in the bulk.Let us expand a bit on the relation between radial coordinate and energy(we will make this argument in Poincar′e coordinates,since the perturbed gauge theories are usually studied on R4).The AdS geom-etry(1.1)is warped:in Poincare coordinates,the four?at dimensions experience a gravitational redshift that depends on?fth coordinate,just as in Randall-Sundrum compacti?cation.Consequently the conserved Killing momentum pμ(Noether momentum in the gauge theory)is re-lated to the local inertial momentum?pμby

r

pμ=

14Gary T.Horowitz and Joseph Polchinski

o?in such a way that the warp factor(which is r/?in AdS spacetime) has a lower bound.The former clearly corresponds to a new conformal theory,while the latter would imply a mass gap,by the argument fol-lowing eq.(1.11).In the various examples,one?nds that the nature of the solution correctly re?ects the low energy physics as expected from gauge theory arguments;there is also more detailed numerical agree-ment(Freedman et al.,1999).So the classical Einstein equation knows a lot about RG?ows in quantum?eld theory.

A notable example is the case where one gives mass to all the scalars and fermions,leaving only the gauge?elds massless in the Lagrangian. One then expects the gauge theory to?ow to strong coupling and pro-duce a mass gap,and this is what is found in the supergravity solution. Further,the gauge theory should con?ne,and indeed in the deformed geometry a con?ning area law is found for the Wilson loop(but still a perimeter law for the’t Hooft loop,again as expected).In other ex-amples one also?nds chiral symmetry breaking,as expected in strongly coupled gauge theories(Klebanov&Strassler,2000).

As a second generalization,rather than a deformation of the geometry we can make a big change,replacing S5with any other Einstein space; the simplest examples would be S5identi?ed by some discrete subgroup of its SO(6)symmetry.The product of the Einstein space with AdS5 still solves the?eld equations(at least classically),so there should be a conformally invariant dual.These duals are known in a very large class of examples;characteristically they are quiver gauge theories,a product of SU(N1)×...×SU(N k)with matter?elds transforming as adjoints and bifundamentals(one can also get orthogonal and symplectic factors). As a third generalization,we can start with D p-branes for other val-ues of p,or combinations of branes of di?erent dimensions.These lead to other examples of gauge-gravity duality for?eld theories in various dimensions,many of which are nonconformal.The case p=0is the BFSS matrix model,although the focus in that case is on a di?erent set of observables,the scattering amplitudes for the D0-branes themselves.

A particularly interesting system is D1-branes plus D5-branes,leading to the near-horizon geometry AdS3×S3×T4.This case has at least one advantage over AdS5×S5.The entropy of large black holes can now be reproduced exactly,including the numerical coe?cient.This is related to the fact that a black hole in AdS3is a BTZ black hole which is locally AdS3everywhere.Thus when one extrapolates to small coupling,one does not modify the geometry with higher curvature corrections.

We have discussed modi?cations of the gauge theory’s Hamiltonian,

Gauge/gravity duality15 its spectrum,and even its dimensionality.Many of these break the the-ory’s conformal symmetry and some or all of its supersymmetry(with all of it broken the stability is delicate,but possible).Thus we can relax the assumption of supersymmetry,as promised earlier.If we start with a nonsupersymmetric gauge theory,do we get a gravitational theory with-out supergravity(and maybe without strings)?Apparently not.When we change the dynamics of the gauge theory,we do not change the local dynamics of the gravitational theory,i.e.its equation of motion,but only its boundary conditions at AdS in?nity.In all known examples where a macroscopic spacetime and gravitational physics emerge from gauge the-ory,the local dynamics is given by string theory.This is consistent with the lore that string theory has no free parameters,the local dynamical laws are completely?xed.This was the conclusion when string theory was?rst constructed as an expansion around a?xed spacetime,and it has not been altered as the theory has been rediscovered in various dual forms;it is one of the principal reasons for the theory’s appeal.

Let us also relax the other assumptions from the introduction,large ’t Hooft coupling and large N c.The AdS radius?=(g2YM N c)1/4?s～

N1/4

c G1/8becomes small compare

d to th

e string size when the’t Hooft coupling is small,and comparable to the Planck scale when N c is not large.This is consistent with our argument that we needed strong cou-pling and large N c in order to see macroscopic gravity.However,string theory remains well-de?ned on spaces o

f large curvature,so the strin

g dual should still make sense;hence our assertion that even the strong and weak nuclear interactions can be written as string theories,thoug

h in highly curved spaces.?

In more detail,consider?rst varying the’t Hooft coupling.The string world-sheet action in AdS5×S5is proportional to?2/?2s=(g2YM N c)1/2. This is large when the’t Hooft coupling is large,so the world-sheet path integral is then nearly gaussian(i.e.weakly coupled).On the other hand when the’t Hooft coupling is small the string world-sheet theory is strongly coupled:the cost of living on a space of high curvature is strong world-sheet coupling.This limits one’s ability to calculate,though in the case of AdS5×S5there is enough symmetry that one might ultimately be able to solve the world-sheet theory completely(Berkovits,2005). Now consider varying N c.From eq.(1.5)the gauge theory expansion parameter1/N2c matches the gravitational loop expansion parameter ?There have been proposals that a?ve-dimensional picture is phenomenologically useful even for real QCD;see the recent papers Erlich et al.(2006),Brodsky&de Teramond(2006),and references therein.

16Gary T.Horowitz and Joseph Polchinski

G,so we can expect an order-by-order matching.In fact,there are various indications that the duality remains true even at?nite values of N c,and not just as an expansion in1/N2c.A striking example is the ‘string exclusion principle’(Maldacena&Strominger,1998).We have noted that the wavefunctions of the gravity states on S5arises in the gauge theory from traces of products of the?i.However,these?elds are N c×N c matrices,so the traces cease to be independent for products of more than N c?elds:there is an upper bound

J/N c≤1(1.12) for the angular momentum on S5.From the point of view of supergravity this is mysterious,because the spherical harmonics extend to arbitrary J.However,there is an elegant resolution in string theory(McGreevy et al.,2000).A graviton moving su?ciently rapidly on S5will blow up into a spherical D3-brane(this growth with energy is a characteristic property of holographic theories),and J=N c is the largest D3-brane that will?t in the spacetime.Thus the same bound is found on both sides of the duality,and this is a nonperturbative statement in N c:it would be trivial in a power series expansion around1/N c=0.

1.3.4Open questions

An obvious question is,to what extent is the AdS/CFT duality proven? We should?rst note that this duality is itself our most precise de?-nition of string theory,giving an exact construction of the theory with AdS5×S5boundary conditions or the various generalizations described above.This does not mean that the duality is a tautology,because we have a great deal of independent information about string theory,such as its spectrum,its low energy gravitational action,the weak coupling expansion of its amplitudes,and so on:the gauge theory must correctly reproduce these.Thus the duality implies a large number of precise statements,for example about the amplitudes in the strongly coupled gauge theory at each order in1/N c and1/

Gauge/gravity duality17 assumptions.The quantitative tests are largely restricted to those quan-tities that are required by supersymmetry to be independent of the cou-pling.This is not to say that the agreement follows from supersymmetry alone.For example,supersymmetry requires the states to lie in multi-plets,but the number of multiplets(as a function of their SO(6)charges) is not?xed,and the fact that it agrees for each value of the charges is a strong dynamical statement—recall in particular that the string ex-clusion principle must enter to make the range of charges match.

In many ways the more impressive tests are the more qualitative ones. The point has often been made that the claim that a ten-dimensional string theory is the same a four-dimensional?eld theory is so audacious that if it were incorrect this should be easy to show.Instead we?nd, as we look at a wide variety of situations,that the qualitative physics is exactly what we would expect.We have noted some of these situations above:the appearance of string-like states in the gauge theory at large boost,the matching of the con?ning transition with the Hawking-Page transition and with the correct N c scaling on each side,the hydrody-namic properties,the matching of the deformed geometries with the RG ?ows and the expected low energy physics be it conformal,massive,con-?ning,chiral symmetry-breaking,and so on.For the con?ning theories, with all conformal and supersymmetries broken,one can calculate the results of high energy scattering processes.The results di?er from QCD because the theory is di?erent,but the di?erences are qualitatively just those that would be expected(Polchinski&Strassler,2003). Finally,we mention a very di?erent kind of quantitative test.State-ments about strongly coupled gauge theory can be tested directly by simulation of the theory.The range of tests is limited by the computa-tional di?culty,but some positive results have been reported(Antonuc-cio et al.,1999,and Hiller et al.,2005).

In summary,we see convincing reason to place AdS/CFT duality in the category of true but not proven.Indeed,we regard it on much the same footing as such mathematical conjectures as the Riemann hypoth-esis.Both provide unexpected connections between seemingly di?erent structures(and speaking as physicists we?nd a connection between gauge theory and gravity even more fascinating than one between prime numbers and analytic functions),and each has resisted either proof or disproof in spite of concentrated attention.In either case it may be that the?nal proof will be narrow and uninstructive,but it seems more likely that the absence of a proof points to the existence of important new concepts to be found.

18Gary T.Horowitz and Joseph Polchinski

As another open question,the dictionary relating spacetime concepts in the bulk and?eld theory concepts on the boundary is very incomplete, and still being developed.For example,while we know how to translate certain states of the CFT into bulk geometries,we do not yet know the general condition on the state in order for a semiclassical spacetime to be well de?ned.

A related issue is a more precise understanding of the conservation of information in black hole decay.The AdS/CFT duality implies that we can?nd an S-matrix by passing to the gauge theory variables,but there should be some prescription directly in the gravitational theory.The black hole information problem can be understood as a con?ict between quantum mechanics and locality.In the context of emergent spacetime it is not surprising that it is locality that yields,but we would like to understand the precise manner in which it does so.

A big open question is how to extend all this from AdS boundary conditions to spacetimes that are more relevant to nature;we did?nd some generalizations,but they all have a causal structure similar to that of AdS.Again,the goal is a precisely de?ned nonperturbative construc-tion of the theory,presumably with the same features of emergence that we have found in the AdS/CFT case.A natural next step might seem to be de Sitter space.There were some attempts along these lines,for example Strominger(2001)and Witten(2001),but there are also gen-eral arguments that this idea is problematic(Susskind,2003).In fact, this may be the wrong question,as constructions of de Sitter vacua in string theory(beginning with Silverstein,2001,and Kachru et al.,2003) always seem to produce states that are only metastable(see Giddings, 2003,for further discussion,and Banks,2005,for an alternate view). As a result,cosmology will produce a chaotic state with bubbles of all possible metastable vacua(Bousso&Polchinski,2000).The question is then the nonperturbative construction of states of this kind.The only obvious spacetime boundaries are in the in?nite future,in eternal bubbles of zero cosmological constant(and possibly similar boundaries in the in?nite past).By analogy these would be the location of the holographic dual variables(Susskind,2003).

In conclusion,the embedding of quantum gravity in ordinary gauge theory is a remarkable and unexpected property of the mathematical structures underlying theoretical physics.We?nd it di?cult to believe that nature does not make use of it,but the precise way in which it does so remains to be discovered.

Gauge/gravity duality19

Acknowledgments

This work was supported in part by NSF grants PHY99-07949,PHY02-44764,and PHY04-56556.

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修辞学在生活中的应用

修辞学在生活中的应用 文题: 人类文明的交流离不开语言,而语言的使用又离不开修辞,修辞渗透到生活的方方面面,一句话,一篇文章等。没有修辞与有修辞的语言表达效果就是大相径庭的,不同的修辞手法运用到不同的场景,产生的效果也就是不一样的。 关键词: 语言、修辞、生活 正文: 瞧到这个题目,许多人会存在这样的疑惑:什么就是修辞？语言不仅就是人类最基本的符号系统,更就是人类最重要的交际工具。交际主体根据自己的角色定位、交际意图、交际环境与对象的不同,尽可能运用合适的语言形式以实现自己的交际目的,这就就是修辞。在现代汉语中,修辞分别指“修辞行为”、“修辞规律”、“修辞理论”。(参考资料来自教材)通过教材,我们已经了解修辞学的定义,但只就是一个模糊的概念,如果通过生活的例子来解释什么就是修辞,应该会更加生动易懂。 小学的时候讲文章或诗句时,老师都会问,“这句话运用了什么修辞手法？有什么作用”所以从小学开始便对修辞手法有了一个初步的了解,但也仅仅只就是局限于“比喻、拟人、对比、借代、对偶、夸张……”等这一类的手法,未曾深入了解过。但这些修辞手法,在生活中运用得就是最普遍的。 在大学对修辞学的进一步学习中,我了解了比喻、比拟、借代、夸张、双关等修辞手法又有另外一种说法,叫修辞格。修辞格又称辞格、修辞方式,就是为了提高修辞行为的效果而运用的组织语言材料的策略性方法。

比喻在生活中的运用十分广泛,在口语中也就是经常被使用的。比如,朋友之间互相打趣,“别吃了,再吃就变成猪了”“您瞧您胖得跟猪似的”“哎呦您瞅瞅您这头发,哪烫的啊,跟方便面一样。”这就是比较口语化的运用了比喻的修辞手法的句子。比喻的手法在诗歌中更就是得到了充分的运用。比如贺知章的《咏柳》“不知细叶谁裁出,二月春风似剪刀。”李贺的《马诗》“大漠沙如雪,燕山月似钩”,这两句诗都就是运用了比喻的手法。 拟人也就是运用得很多的。“成熟的麦穗压弯了腰”“小鸟在窗外愉快地唱起了歌”,这些都就是随便一想便能想起的拟人句子。拟人能够使句子富有表现力,形象生动。 要讲的第三种修辞手法就是借代。通俗点说,借代就就是“借用”一物来“代替”所要言说之物。比如,“巾帼不让须眉”这句话中,巾帼指的就是女性,须眉指的就是男性,这就是根据男女性别的特征运用借代手法来表现的。还有杜甫的“朱门酒肉臭,路有冻死骨”以“朱门”表示富贵人家,“冻死骨”表示贫苦人民。“白衣天使救助了许许多多的人”,我们可以判断出,白衣天使指的就是医生或就是护士。 恰当地运用借代可以突出事物的本质特征,增强语言的形象性,而且可以使文笔 简洁精炼,语言富于变化与幽默感。借代的作用可以用十六字概括:以简代繁,以实代虚,以奇代凡,以事代情。 还有另外一种修辞手法也就是经常运用的——夸张。夸张在我们日常生活对话交流中被频繁地使用。“我好饿,饿得能吞下一头恐龙”“只要老师一发火,教室里安静得连根针掉下去的声音都听得见”。在古诗词中也有很多例子。比如,“瀚海阑干百丈冰,愁云惨淡万里凝”“飞流直下三千尺,疑就是银河落九天”“黄

新版简明英语语言学 Chapter 6 pragmatics 语用学

Chapter 6 pragmatics 语用学 知识点： 1.*Definition: pragmatics; context 2.*sentence meaning vs utterance meaning 3.*Austin’s model of speech act theory 4.Searle’s classification of speech acts 5.*Grice’s Cooperative Principle 考核目标： 识记：*Definition: pragmatics; context 领会：Searle’s classification of speech acts 综合应用：sentence meaning vs utterance meaning；Austin’s model of speech act theory；Grice’s Cooperative Principle 一、定义 1. Pragmatics语用学: Pragmatics: the study of how speakers of a language use sentences to effect successful communication. Pragmatic can also be regarded as a kind of meaning study.语用学研究的是语言使用者是如何使用句子成功进行交际的。语用学也可以看作是一中意义研究。(它不是孤立地去研究语义，而是把语义置于使用语境中去研究的一门学科。) 2. Context 语境：The notion of context is essential to the pragmatic study of language, it’s generally considered as constituted by the knowledge shared by the speaker and the hearer. 语境这个概念对语言的语用研究来说是必不可少的。一般认为他是由言者和听者的共享知识所构成的。 二、知识点 6.1.2 pragmatics vs. semantics语用学与语义学 二十世纪初，Saussure’s Course in General Linguistics 一书的出版标志着现代语言学研究的开始，同时也为现代语言学奠定了基础调，即语言应该作为一个独立的，内在的系统来加以研究。 语用学和语义学既有相关性又有相异性。两者都是对意义的研究。传统语义学把语义看成是抽象的，内在的，是语言本身的特性，不受语境的影响。因此传统语义学只研究语义的内在特征，不把语义研究置于语境中来考察。语用学研究的是交际过程中语言意义的表达和理解。语用学家认为不把意义放在语境中来考虑就不可能对语义进行充分的描述，因此在研究语义时是否考虑语境便成了传统语义学和语用学的根本区别所在。 Semantics 和Pragmatics的区分 Pragmatics studies how meaning is conveyed in the process of communication. The basic difference between them is that pragmatics considers meaning in context, traditional semantics studies meaning in isolation from the context of use.

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点面结合场面描写 场面描写指的是在某一特定时间和特定地点范围内以人物活动为中心的生活画面的描写。场面描写一般由“人”、“事”、“境”构成，它是叙事性作品的基本构成单位，是刻画人物、展开情节、表现主题的主要手段。常见的有劳动场面、战斗场面、运动场面以及各种会议场面等。那么如何写好场面呢？点面结合是进行场面描写最好的选择。 所谓“点”，指的是最能显示人事景物场面的形象状态特征的详细描写；所谓“面”，指的是对人事景物场面的叙述或概括性描写。点面结合就是“点”的详细描写和“面”的叙述或概括性描写的有机结合。点面结合一般有以下三种形式： 一、视角笔触横向化，就是要把观察的视线向横的方向展开。要看到整个场面在同一个时间里所发生的事，不能只集中看一点。如下面一段场面描写： “王励勤，加油，中国队，雄起！”随着观众此起彼伏的呐喊声，中国对韩国的世界杯乒乓赛决赛被王励勤与韩国柳承敏的几个大力远拉推向高潮，场内翻滚着一股热浪，坐在电视机前的我们，也目不转睛地看着电视，我、爸爸、哥哥戴着头巾，挥舞着乒乓拍，用力捶着茶几当起场外拉拉队来，王励勤又胜一局，在加油声中一路高歌，这时，对方柳承敏奋起反击，几个短摆，直线，反手对拉，利用王励勤侧身过多，迎头赶上，观众的叫声更响亮了，震耳欲聋，把电视机前的观众的心深深地震撼了。我们一家也急得直跺脚，索性脱掉衣服

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高三语文写作指导与训练系列二编号 GS YW XZ--002 记叙文写作之细节描写篇导学案 编写：徐明生审定：张明玺时间：2014-08-26 班级：组别：组名：姓名： 知识与技能：理解细节描写的概念及分类，掌握细节描写的方法，学会运用细节描写表现人物细腻的情感，为文章增色。 过程与方法：1.创设情境，赏析富有情趣的细节描写。2.例文引导，掌握细节描写的方法。 3.写作训练，将细节描写融入作文中。 情感态度与价值观：培养观察力、想象力，引导学生发现生活中的细节之美，形成热爱生活、积极的人生态度。 教学方法：揣摩、讨论、归纳、操练 课前准备：1．了解细节描写的相关知识点； 2．回顾所学过的记叙文（小说），初步体会细节描写的作用。 课时：2课时 导学过程：一、导语众所周知，记叙文的灵魂在于细节描写。同学们在作文里缺少的不是把某件事写完整的能力，而是缺少细节捕捉、描写的能力。这些缺失细节描写的文章读来生涩呆板，缺乏感染力。而高考作文评分在发展等级项中有明确的规定，即：“材料丰富，形象丰满，意境深远”，这“形象丰满”很大程度上依赖于考生对细节的描摹与刻画。细节描写之重要，不仅可以在“生动”上“出彩”加分，而且可以使作品形象丰满，使整个文章升格。所以作文缺少感人的细节实在是一个制约记叙文成绩提高的瓶颈。 一沙一世界，一叶一菩提。其实，纷繁的生活，是由无数小的细节构成的。细节虽小，却是美的源泉，情的聚焦。生活中的细节之美，看在眼里，便是风景；握在掌心，便是花朵；拥进怀中，便是温暖；写在笔端，便是精彩。今天这节课，我们来一起用双眼发现细节，用心灵感悟细节，用文字展现细节，让我们作文中的人与事如生活中一般于细处见情，微处见妙！ 二、了解概念、分类，感受作用、魅力 （1）什么是细节描写？ 细节描写就是某些细小的能很好表现中心的环节和情节，如对人物的一个动作、一种表情、一句话等以及事物发展的具体环节、环境中的细小物体，通过准确、生动、细致的描绘，使读者“如见其人”“如睹其物”。 细节描写如电影中的特写镜头，具体渗透在对人物、景物或场面描写之中。它将我们身边

语言学知识_语用学

语用学 一．语用学（Pragmatics）的定义： 语用学是用以研究语言使用者如何使用句子成功进行交际的学问。语用学（Pragmatics）与语义学（Semantics）虽然都涉及对语言意义的研究，但是语义学（Semantics）只是将语言视作一个独立的系统来研究，而语用学（Pragmatics）则是将语言置于语境（context）之中。所以，语用学（Pragmatics）与语义学（Semantics）本质区别在于是否将语境（context）因素纳入考量范围之内。 二．句子意义与话语意义（Sentence Meaning Vs. Utterance Meaning）： 1) 句子意义（Sentence Meaning）：句子意义指的是独立于语境的句子本身所传达的字面意义。 2）话语意义（Utterance Meaning）：话语意义指的是将句子的意义置于特定语境中以表达言者某种意图的意义。 三．指示现象（Deixis）： 指示现象指的是说话人利用语言形式表达说话内容所涉及的人员、事物、时间、地点等方面。指示现象是连接语言形式及其发生语境的桥梁。指示语主要分为以下三类：1）人称指示语（person deixis）：用于表达言语交际的参与者。 2）空间指示语（spatial deixis）：用于指代言语活动中所涉及的人、物或事的相对位置。 3）时间指示语（temporal deixis）：用于表达言语交际活动中的时间点和时间段。 四．言语行为理论（Speech Act Theory）： 1) 约翰·奥斯汀（John Austin）的言语行为模式： 英国哲学家约翰·奥斯汀（John Austin）于20世纪50年代提出的言语行为模式区分了言有所述（constative）和言有所为（performative）。 随后，他又对原先的理论进行了发展，放弃了言有所述（constative）和言有所为（performative）的区分，发展出了新的言语行为模式。该模式认为，言者在说话时可同时执行三个动作：即言内行动（locutionary act），言外行动（illocutionary act）和言后行动（perlocutionary act）。 言内行动（locutionary act）：指言者发出言语，传达字面意义的行为动作。 言外行动（illocutionary act）：指言者通过话语所表达的意图。例如：某人说I promise to give you a surprise时，他是在许下诺言。 言后行动（perlocutionary act）：指言者通过言语表达的而实际实施的行为。 2）舍尔（Searle）的言语行为分类： 美国语言学家舍尔（Searle）在约翰·奥斯汀（John Austin）的言语行为模式的基础上对言外行动（illocutionary act）进行了分类：阐述性言语行为（representatives），指令性言语行为（directives），承诺性言语行为（commissives），表达性言语行为（expressives），宣告性言语行为（declaratives）。 3）直接和间接言语行为（direct and indirect speech act）： 直接言语行为：直接通过话语来实施某一行为。 间接言语行为：句子的意思不能按照其字面意义去理解，需要推导其话语的施为用意。

对比语言学

第一章绪论 1.1什么是对比语言学 比较：同类语言中亲属语言之间求共性 对比：不同语言间e.g.汉英对比求个性 1象限：同一种语言内部共时对比 2象限：同一种语言内部的历史比较，找出演变规律，以建立语言学史. 3象限：不同语言间的历史比较，一般限制亲属语言之间，目的在于谱系分类，构拟原始古语。 4象限：共时的语际之间的对比。有三种类型 A、多种语言对比找出人类语言的共性和倾向性的规律 B、多种语言对比以便找出语言的以便建立语言类型学 在A 、B 中对比的语言愈多愈好，对比的语言愈不同愈好 C、两种语言对比，目的在于找出相同点和不同点，特别是不同点， 给出解释（一般说来解释都归于民族精神和历史）

e.g. .第1象限名动形的区别 “不”—剔除n 不－桌子* “很”—剔除一般的v 很－看*/喜欢书 “加宾语”－剔除adj 很－好 e.g. 第2象限上古和近代汉语的区别比较 上古－国代－中古－近代－现代汉语 注：汉语小词类分25种 1.2对比语言学的定义 对比语言学是语言学的一个分支，它兼有理论语言学和应用语言学的性质，其任务是对两种或两种以上的语言进行共时的对比研究，描述它们之间的异同，重在其异，找出产生的原因，并将这类研究应用于其他有关领域。 注：对比研究要切割小类－小类动词－动词× 英语心理动词－汉语心理动词√ 注：汉语心理动词研究－1篇论文 英语心理动词研究－1篇论文 二者对比，发现问题－1篇论文、 注：历时是动态的过程解释答案可能要 共时是状态的过程回到历史中去 1.3对比语言学的分类 对比语言学的分类

“2”研究对比语言学的性质和任务，解释对比研究中的理论和方法 “5”运用对比语言学原理、方法已经运用其他一些语言学知识对两种或两种以上的语言进行具体的对比描述，探索不同语言之间的相同点和不同点。作用在于检索完善理论对比语言学的理论方法；加深对两种语言的认识；检索某种语言学理论的可行性；可对语言进行比较准确精细的分类，促进语言普遍现象研究。 注：理论对比是双向的对比应用对比是单项的对比 e.g. x (被动范畴) x (被动范畴) X(a) X(b) A(xa) B A语言的被动范畴在 B语言中是如何表现的 “6”探讨对比语言学应用的一般理论和方法并将研究成果应用于和对比的语言有关的语言活动中去，特别上应用于外语教学或其他语 言教学活动中去。

我对语言学的认识

我对语言学的认识 语言学，顾名思义，是研究语言的科学。语言是语言学的研究对象。语言现象是人类社会普遍具有的现象，是人类生活中最司空见惯的现象。语言现象在我们生活中是普遍存在的。我们日常生活中总是以言语的形式与他人交流互动。语言学就是研究我们日常生活交际中所使用的语言的发展规律以及语言所表现的结构，当然这个语言既包括声音形式的口语，也包括了我们读书看报所涉及的书面语。 语言现象是最早纳入人类研究视野的现象之一。语言学的发展也经历了漫长的发展古城。中国、印度、希腊-罗马是语言学的三大发源地，在传统语文学的研究上都取得了辉煌的成就。其中，中国传统的语言研究主要是围绕着解读文言文典籍的需要进行的。 语言本身的构造很复杂，需要从不同的角度、不同的方面进行研究。通常来说，语言系统大致可以分为语音、语法、词汇等几个子系统。正是这几个子系统才会构成纷繁复杂的语言结构。也正是因为语言结构的复杂，变化多端，所以我在学习的过程中才会困难。 由于语言用于日常交际互动，语言与社会生活也有密切的关联。语言既有自身结构的独立性和自主性，同时也与人类自身以及社会环境存在着密切的关联。语言学除了关注语言本体的结构性质和发展规律，同时也要探究语言系统与人、与社会之间错综复杂的联系。可以说，语言的发展变化是随着时代发展变化而变化的，语言的变化反应这社会生活的变迁。语言形式与内容之间的关系，是语言研究的最根本的问题。随着时代的发展和科学思想的进步，语言学和各个时代的自然科学思潮同样体现出密切的相关性。语言学是自然科学与人文社会科学联系的桥梁。在历史上，语言研究曾为解读古代经典、继承传统文化提供了基本保证。随着社会的发展和科学体系的完善，语言学的应用价值越来越广泛。语言学在科学发展中正发挥着越来越大的作用。语言学既有作为基础学科的魅力和学术价值，同时也具有广泛的应用前景，是一门既有悠久历史又具有科学前沿性的充满活力的科学。 那语言的功能有什么呢？第一功能是社会功能。语言的信息传递功能，是最基本的社会功能。同时语言还有人际互动功能。在人际互动过程中它使语言作为说话者和听话者之间交际互动的工具。语言的第二功能是思维功能。语言是社会现象，是社会的交际工具，同时也是心理现象，是人类思维的工具。思维功能是语言功能的另一重要方面。在思维功能方面，儿童语言习得与思维发展有密切的联系。儿童学习语言的过程是考察语言与思维的关系的一条很好的途径。儿童的思维和认知的发展在语法掌握方面有更明显的体现。除了儿童，聋哑人同样也有自己的思维方式。像这样的视觉符号成为聋哑人中重要的表达方式。教会聋哑人观察和模仿常人说话时的口型，是帮助他们掌握语言的另一条途径。思维能力的普遍性和思维方式的特殊性，与语言性质是密切相关的。人类语言既有全人类的普遍性，也具有不同语言结构的特殊性，二者都是语言学所要探究的是深入认识语言的本质所不能忽略的。 在学习语言学的过程当中，我认为有一个整体的框架很重要。我们应该知道语言学的分类，能在脑海里有分支图，从而使我们自己能够对每个分支图下的内容有比较深入的了解。语言学虽然听上去非常空洞让人觉得概念很大，但其中的学科分支是很细很密，非常有意思的。他不仅是文科，还与理科有密切的联系，所以学习研究语言学很锻炼人，很有意义。但是，由于语言自身的复杂性和我们对于语言的了解还不够深入，有关语言的理论非常复杂。虽然我们所学的课程只是全部语言理论的一部分，但在学习过程中我们还是为大量而抽象的理论所困扰。同时，因为语言学纲要是从概论性质阐述语言学，所以在学习的过程中会涉及到之前学过的《现代汉语》和《古代汉语》我们也要融会贯通，及时复习掌握大纲。所以，我们在学习这门课程中要注意理论性与实践性相结合。

作文技巧：围绕中心写场面

作文技巧：围绕中心写场面 场面描写，那么什么是场面呢？场面一般是指集体活动中某一段时间内，呈现在人们面前的情景。就如同我们在话剧中看到的某一场、某一幕一样。生活中，有哪些场面是我们参加过或者看到过的呢？下面举一些例子供参考。劳动场面。我们在学校经常参加校办工厂、农场或服务性劳动，劳动中大家的热、干劲以及劳动中出现的好人好事是很多的。我们也经常去工厂、农村、商店参观、问，看到叔叔阿姨们是怎样劳动的，这些就是劳动场面。游戏场面。同学们在家里或校园里经常在一起做游戏，体育活动时老师也组织大家开展各种活动。这些游戏场面常常非常活跃，非常有趣，也是同学们比较熟悉的娱乐场面。在我们丰富多彩的课余生活中，娱乐活动是一项很重要的内容。文艺演出，联欢活动，观看影视，都有许多生动的场面值得我们记叙下来。典礼场面。每学期开学时，我们都要举行开学典礼。你所在的城市、村镇、有什么新的建筑落成，也常常举行典礼仪式。这些典礼的场面有意义、有教育性，应该认真观察，记录下这一值得纪念的时刻。运动场面。运动会上，运动员你追我赶，奋力拼搏，争取创造优异成绩；观众们为运动员鼓掌加油，欢呼助兴，这些激动人心的场面是令人难忘的。生活场面。在日常生活中有许多场面也是很有特点的。例如购买货物，家人团聚，乘车坐船，求医治病，盖房修墙，；，布置居室等等，都具有浓厚的生活气息。会议场面。班会、队会、校会，；，和英雄模范人物会见，参加各种庆祝会，纪念会，那会议的场面也往往给我们留下深采刻的印象。总之，练习场面描写，可以提高苛我们

观察认识能力、记叙描写能力。我们在记叙场面时要注意以下三点．1．认真观察。比如进行会议场面的描写，要仔细观察会场的环境：主席台在哪儿，会标是怎吞样写的，台上是怎样布置的，有哪些人在台上就座，他们的神态、动作、讲话、|内容是怎样的；会场有多大，有多少人参加，会场的气氛怎样；会议的议程怎样，怎样开始，哪时达到高潮，会议是怎样结束的等等，都应如实具体观察，认真积累写作的材料。2．抓住重点3；把人和事物写具体。场面描写常常离不开人物和事物，这是场面描写的主要内；：l容。人物的外貌、神情、语言、动作、心理，事物的起因、经过、高潮和结果，以及物体的i l形状、颜色、变化、活动情况等等，都应细致具体地加以描述，使读者如身临其境，这才是成功的场面描写。当然，场面描写也应围绕一个中心，不要想到什么写什么，这样就不集中了，这也是要注意的问题。

在生活中学习语文

在生活中学习语文 摘要：得体，是语言表达的基本要求，也是最高要求，它要求我们运用语言要注意时间、场合、环境、对象等方面的得体，根据具体情况有时可委婉，有时可直白，有时可讽刺，有时可严肃，有时也可幽默。总之，要选用恰当的语句来表情达意，表达方式要适合特定的语境。 关键词：交流；语言；得体；巧说为妙 在日常生活中，我们时时处处要与人交流，而主要的交流方式是语言。同样的意思，可能有多种表达方式，不同方式的表达会让听者产生不同的心理感受。人常说：“话有三说，巧说为妙。”所以与人交流一定要注意自己用语的得体，要分清场合，注意文体，分清目的，注意对象，更要讲究礼貌，用语是否得体也是我们语言交际能力的重要体现。就拿生活中的一件事情来说：下午是两点上课，但王华在骑自行车的路上，碰倒了一个小孩子，因送他去医院上药，两点半才赶到学校。王华在教室门口喊了“报告”，老师不满地看着他，问到：“现在几点了？”王华该怎么回答呢？在这种场合下首先要明白老师表达的是责怪之意，并不是要王华答出时间，所以不宜回答几点几分；其次，尽管王华是有原因的，但毕竟迟到了很久，中途走进教室，打断了老师的讲课，因表示歉意；课堂上的时间很宝贵，不宜多说具体原因，应该等下课后找老师解释，所以答话因尽量简短，可以回答：对不起，碰到了特殊情况，我迟到了很久。

因此，在日常交际中，我们应随时随地注意语言表达得体，培养语言表达能力。新课程标准提出：注意在生活和跨学科的学习中学语文，用语文，在学习和应用过程中提高语言文字的应用能力。而近几年来的高考语文，在这一板块中的确出现了不少关注生活和社会现实的新题型，也有意识地体现和验证着这一点。尤其从2006年语言运用题上可以看出，多数语言运用题，在实用性、时尚性上最为显眼，非常贴近生活和学生的实际。因此，学习训练要以生活实际为背景材料，以综合运用为考察导向，进行针对性语文素养训练，多参与一些与实际生活相关的模拟实践活动，搭建一个提升考生接近生活实际并解决实际运用能力的展示平台，做到游刃有余。 得体是运用语言的一项重要要求，语言的运用受“语境”的制约。“语境”有“内部语境”和“外部语境”。“内部语境”主要指文章的上下文，如文体、句式、语言间的搭配和使用习惯等。“外部语境”指言语焦急时的多种情境条件，如说话的目的，说话的场合，需要表达的方式，发话者的身份、职业、处境，受话者的年龄、性别、经历、思想性格、爱好、文化水平、心理需求、职业处境等。“得体”就是语言的运用要注意并适应各种情境，注意掌握语言使用的分寸。要学会思考：在某种特定的语境中，能说什么，不能说什么；说什么好，说什么不好；怎么说有分寸，怎样说没有分寸；怎么说效果好，怎么说效果不好。既要考虑说话者自己的地位、身份、文化素养、生活阅历等方面的差异，更要考虑听话者的诸多情况，并根据不同的交际场合，不同的目的，选择不同的表达方式，

☆语言学及应用语言学与汉语言文字学的区别

语言学及应用语言学与汉语言文字学的区别语言学与应用语言学研究的是语言内部的各个方面的获得和认知情况,下设中文信息处理、应用文公文写作、语言获得方法研究等专业。文字学的话，就比较窄了~主要是各种字体，从古至今~ 但是要是从考试角度的话，考试内容应该差不多，都要考语言学概论与现代汉语，古代汉语 1.“语言学及应用语言学”更侧重于语言学和现代汉语，而“汉语言文字学”则侧重于古代汉语和文字方面，目前对外汉语教学大多设在语言学与应用语言学下面，是其一个分支。 2.对外汉语和对外汉语教学不是一句话能够说清楚的，但区别也不是特别大。如果你报考了“现代汉语”专业，日后当然可以进行外汉教学（或者你报考了“对外汉语”专业，那是肯定确定以及一定要进行现代汉语方面的研究的）一个是侧重于对语言的考察，一个侧重于对文字的专研和了解，比如篆书，甲骨等。两个方向考的书目步一样，文字学比较冷门。一个研究语言包括方言研究，普通话和方言的对比等，文字学主要研究文字，包括篆书，甲骨文等。通俗一点来讲，对外汉语主要学习怎么教外国人，汉语言文字学主要是中国人自己研究理论问题。祝您好运！语言学及应用语言学主要是学语言学的东西，主要是一些语言学的理论，分支，流派，应用语言学的内容很多，包括心理语言学，语言教学等等。主要还有就是现代汉语语法方面的东西。语言学及应用语言学下面还有些方向，现在比较火的是对外汉语。很多人考这个专业也就是冲着这个方向

去的。文字学相对于要枯燥些，他们的课程设置很多和古汉有关，一些训诂，释意，说文之类的内容。在我们学校，我们两个专业有些课是差不多的，像语音学，中古汉语，只有这两门课重合。同为二级学科。语言文字学主要修习“小学”（音韵学、训诂学、文字学）、应用语言学主要学习现代语言学，包括：修辞、应用语言学（其下还可细分，如：计算机语言学）等等......请问应用语言学与语言文字学区 2008-10-14 13:00:45 xqyrlq 中国研究生招生信息网 Wed Sep 10 10:05:32 CST 2008 由湖南的 xqyrlq 提出的问题问题：请问应用语言学与语言文字学区别内容：1 应用语言学专业与语言文字学专业的区别到底体现在哪些方面；2学校在课程设置上有怎样的区别，应该怎样选择比较好；3专业方向会影响录取吗？谢谢你好，应用语言学专业更侧重于应用，而语言文字学更注重本体研究。在课程设置上，语言文字学对古汉语有更多的偏重。在录取工作中，我们是按照专业录取，而不是方向。对外汉语专业 1.业务培养目标：本专业注重汉英(或另一种外语或少数民族语言，则以下有关用语作相应调整)双语教学，培养具有较扎实的汉语和英语基础，对中国文学、中国文化及中外文化交往有较全面了解，有进一步培养潜能的高层次对外汉语专门人才；以及能在国内外有关部门、各类学校、新闻出版、文化管理和企事业单 位从事对外汉语教学及中外文化交流相关工作的实践型语言学高级人才。业务培养要求：本专业学生主要学习语言学和第二语言教育的基本理论，

作文指导课场面描写教案

作文指导课——场面描写 平度经济开发区小学李荷英 课堂导入：我们上周刚刚举行了秋季阳光运动会，回忆一下那是一个什么样的场面（紧张、兴奋、热烈） 运动会是一个紧张、热烈的场面，那么，请列举一下你的生活中还有那些场面（赶集的拥挤热闹，球场的热烈火爆，下课的喧闹）场面的特点 看多媒体图片，看一下是什么场面，描述场面特点或者气氛 （比赛场面紧张激烈，阅兵场面宏大整齐，春运场面拥挤） 上周我们开完运动会后写了一篇日记，通过批阅，发现同学们对于场面描写有所欠缺，好多同学的日记我读完了之后看不出运动会是一个怎样的场面。今天我们一块儿来学习一下如何进行场面描写。 一，明确定义。什么是“场面描写” 场面描写，就是对一个特定的时间与地点内许多人物活动的总体 情况的描写。它是自然景色、社会环境、人物活动等描写对象的集中展现。 常见的有劳动场面、战斗场面、运动场面以及各种会议场面等。 二，场面描写的关键——写出特定气氛 场面描写的关键是什么呢我们先来看一段文字。刘成章的《安

塞腰鼓》。 个别学生读，其他学生思考：1，这是一个什么场面2、这是一个怎样的场面（场面特点、气氛）安塞腰鼓表演场面。气势壮阔，豪放火烈。 场面描写的特点——写出特定气氛 气氛是人在一定环境中看到的景象或感觉到的一种情绪或感情。无论什么场面，都会有气氛，如庆祝场面有欢乐的气氛；比赛场面有紧张的气氛；送别场面有难舍难分的气氛等等。 三,语段分析找方法 那么，如何才能写出场面氛围呢，我们来学几个小妙招。 1、以景衬情，营造氛围(板书) 例子一：春天到了，儿子种的花全都开了。春风吹来，姹紫嫣 红的花儿轻轻摇晃着，散发出阵阵芳香，引来了一只只小蜜蜂。 傍晚，彩霞染红了天空。高尔基坐在院子里，欣赏着儿子种的花，心里有说不出的高兴。瞧，那些盛开的花朵多像儿子红扑扑的脸庞啊！（高兴喜悦） 例子二：天灰蒙蒙的，又阴又冷。长安街两旁的人行道上挤满了男女老少。路那样长，人那样多，向东望不见头，向西望不见尾。人们臂上都缠着黑纱，胸前都佩着白花，眼睛都望着周总理的灵车将要开来的方向。一位满头银发的老奶奶拄着拐杖，背靠着一棵洋槐树，焦急而又耐心地等待着。一对青年夫妇，丈夫抱着小女儿，妻子领着六七岁的儿子，