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Joseph Polchinski

Publications and source records attributed to Joseph Polchinski.

At least 73 records · Page 4Linked to original sources
arXiv2003

Hidden Symmetries of the AdS_5 x S^5 Superstring

Attempts to solve Yang-Mills theory must eventually face the problem of analyzing the theory at intermediate values of the coupling constant. In this regime neither perturbation theory nor the gravity dual are adequate, and one must consider the full string theory in the appropriate background. We suggest that in some nontrivial cases the world sheet theory may be exactly solvable. For the Green-Schwarz superstring on AdS_5 x S^5 we find an infinite set of nonlocal classically conserved charges, of the type that exist in integrable field theories.

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arXiv2003

AdS Holography in the Penrose Limit

We study the holographic description of string theory in a plane wave spacetime by taking the Penrose limit of the usual AdS/CFT correspondence. We consider three-point functions with two BMN operators and one non-BMN operator; the latter should go over to a perturbation of the dual CFT. On the string side we take the Penrose limit of the metric perturbation produced by the non-BMN operator, and the BMN state propagates in this perturbed background. The work of Lee, Minwalla, Rangamani, and Seiberg shows that for chiral operators the AdS three-point functions agree with those calculated in the free gauge theory. However, when this is reduced to an effective plane wave amplitude by truncating the amplitude to propagate from the AdS boundary to the Penrose geodesic, we find a puzzling mismatch. We discuss possible resolutions, and future directions.

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arXiv2003

Monopoles, Duality, and String Theory

Dirac showed that the existence of magnetic monopoles would imply quantization of electric charge. I discuss the converse, and propose two `principles of completeness' which I illustrate with various examples.

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arXiv2002

Deep Inelastic Scattering and Gauge/String Duality

We study deep inelastic scattering in gauge theories which have dual string descriptions. As a function of $gN$ we find a transition. For small $gN$, the dominant operators in the OPE are the usual ones, of approximate twist two, corresponding to scattering from weakly interacting partons. For large $gN$, double-trace operators dominate, corresponding to scattering from entire hadrons (either the original `valence' hadron or part of a hadron cloud.) At large $gN$ we calculate the structure functions. As a function of Bjorken $x$ there are three regimes: $x$ of order one, where the scattering produces only supergravity states; $x$ small, where excited strings are produced; and, $x$ exponentially small, where the excited strings are comparable in size to the AdS space. The last regime requires in principle a full string calculation in curved spacetime, but the effect of string growth can be simply obtained from the world-sheet renormalization group.

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arXiv2002

The Quantum Hall Effect on R^4

Zhang and Hu have formulated an SU(2) quantum Hall system on the four-sphere, with interesting three-dimensional boundary dynamics including gapless states of nonzero helicity. In order to understand the local physics of their model we study the U(1) and SU(2) quantum Hall systems on flat R^4, with flat boundary R^3. In the U(1) case the boundary dynamics is essentially one dimensional. The SU(2) theory can be formulated on R^4 for any isospin I, but in order to obtain a flat boundary theory we must take I \to \infty as in Zhang and Hu. The theory simplifies in the limit, the boundary becoming a collection of one-dimensional systems. We also discuss general constraints on the emergence of gravity from nongravitational field theories.

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arXiv2002

Instability of Spacelike and Null Orbifold Singularities

Time dependent orbifolds with spacelike or null singularities have recently been studied as simple models of cosmological singularities. We show that their apparent simplicity is an illusion: the introduction of a single particle causes the spacetime to collapse to a strong curvature singularity (a Big Crunch), even in regions arbitrarily far from the particle.

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arXiv2002

N=3 Warped Compactifications

Orientifolds with three-form flux provide some of the simplest string examples of warped compactification. In this paper we show that some models of this type have the unusual feature of D=4, N=3 spacetime supersymmetry. We discuss their construction and low energy physics. Although the local form of the moduli space is fully determined by supersymmetry, to find its global form requires a careful study of the BPS spectrum.

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arXiv2002

Hierarchies from Fluxes in String Compactifications

Warped compactifications with significant warping provide one of the few known mechanisms for naturally generating large hierarchies of physical scales. We demonstrate that this mechanism is realizable in string theory, and give examples involving orientifold compactifications of IIB string theory and F-theory compactifications on Calabi-Yau four-folds. In each case, the hierarchy of scales is fixed by a choice of RR and NS fluxes in the compact manifold. Our solutions involve compactifications of the Klebanov-Strassler gravity dual to a confining N=1 supersymmetric gauge theory,and the hierarchy reflects the small scale of chiral symmetry breaking in the dual gauge theory.

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arXiv2001

String Theory and the Size of Hadrons

We begin by outlining the ancient puzzle of off shell currents and infinite size particles in a string theory of hadrons. We then consider the problem from the modern AdS/CFT perspective. We argue that although hadrons should be thought of as ideal thin strings from the 5-dimensional bulk point of view, the 4-dimensional strings are a superposition of "fat" strings of different thickness. We also find that the warped nature of the target geometry provides a mechanism for taming the infinite zero point fluctuations which apparently produce a divergent result for hadronic radii. Finally a calculation of the large momentum behavior of the form factor is given in the limit of strong 't Hooft parameter where the classical gravity limit is appropriate. We find agreement with parton model expectations.

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arXiv2001

Hard Scattering and Gauge/String Duality

We consider high-energy fixed-angle scattering of glueballs in confining gauge theories that have supergravity duals. Although the effective description is in terms of the scattering of strings, we find that the amplitudes are hard (power law). This is a consequence of the warped geometry of the dual theory, which has the effect that in an inertial frame the string process is never in the soft regime. At small angle we find hard and Regge behaviors in different kinematic regions.

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arXiv2000

Gauge Dual and Noncommutative Extension of an N=2 Supergravity Solution

We investigate some properties of a recent supergravity solution of Pilch and Warner, which is dual to the N=4 gauge theory softly broken to N=2. We verify that a D3-brane probe has the expected moduli space and its effective action can be brought to N=2 form. The kinetic term for the probe vanishes on an enhancon locus, as in earlier work on large-n N=2 theories, though for the Pilch-Warner solution this locus is a line rather than a ring. On the gauge theory side we find that the probe metric can be obtained from a perturbative one-loop calculation; this principle may be useful in obtaining the supergravity dual at more general points in the N=2 gauge theory moduli space. We then turn on a B-field, following earlier work on the N=4 theory, to obtain the supergravity dual to the noncommutative N=2 theory.

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arXiv2000

Quantization of Four-form Fluxes and Dynamical Neutralization of the Cosmological Constant

A four-form gauge flux makes a variable contribution to the cosmological constant. This has often been assumed to take continuous values, but we argue that it has a generalized Dirac quantization condition. For a single flux the steps are much larger than the observational limit, but we show that with multiple fluxes the allowed values can form a sufficiently dense `discretuum'. Multiple fluxes generally arise in M theory compactifications on manifolds with non-trivial three-cycles. In theories with large extra dimensions a few four-forms suffice; otherwise of order 100 are needed. Starting from generic initial conditions, the repeated nucleation of membranes dynamically generates regions with a cosmological constant in the observational range. Entropy and density perturbations can be produced.

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arXiv2000

The String Dual of a Confining Four-Dimensional Gauge Theory

We study N=1 gauge theories obtained by adding finite mass terms to N=4 Yang-Mills theory. The Maldacena dual is nonsingular: in each of the many vacua, there is an extended brane source, arising from Myers' dielectric effect. The source consists of one or more (p,q) 5-branes. In particular, the confining vacuum contains an NS5-brane; the confining flux tube is a fundamental string bound to the 5-brane. The system admits a simple quantitative description as a perturbation of a state on the N=4 Coulomb branch. Various nonperturbative phenomena, including flux tubes, baryon vertices, domain walls, condensates and instantons, have new, quantitatively precise, dual descriptions. We also briefly consider two QCD-like theories. Our method extends to the nonsupersymmetric case. As expected, the N=4 matter cannot be decoupled within the supergravity regime.

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arXiv1999

Gauge Theory and the Excision of Repulson Singularities

We study brane configurations that give rise to large-N gauge theories with eight supersymmetries and no hypermultiplets. These configurations include a variety of wrapped, fractional, and stretched branes or strings. The corresponding spacetime geometries which we study have a distinct kind of singularity known as a repulson. We find that this singularity is removed by a distinctive mechanism, leaving a smooth geometry with a core having an enhanced gauge symmetry. The spacetime geometry can be related to large-N Seiberg-Witten theory.

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arXiv1999

Negative Energy, Superluminosity and Holography

The holographic connection between large $N$ Super Yang Mills theory and gravity in anti deSitter space requires unfamiliar behavior of the SYM theory in the limit that the curvature of the AdS geometry becomes small. The paradoxical behavior includes superluminal oscillations and negative energy density. These effects typically occur in the SYM description of events which take place far from the boundary of AdS when the signal from the event arrives at the boundary. The paradoxes can be resolved by assuming a very rich collection of hidden degrees of freedom of the SYM theory which store information but give rise to no local energy density. These degrees of freedom, called precursors, are needed to make possible sudden apparently acausal energy momentum flows. Such behavior would be impossible in classical field theory as a consequence of the positivity of the energy density. However we show that these effects are not only allowed in quantum field theory but that we can model them in free quantum field theory.

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arXiv1999

M-Theory and the Light Cone

I discuss D0-brane quantum mechanics as a nonperturbative formulation of string theory, in particular the relation between the Banks-Fischler-Shenker-Susskind matrix model, the Maldacena conjecture for D0-branes, and type IIA/M-theory duality. Some features of the quantum mechanics of D0-branes are also discussed. Lecture presented at the Nishinomiya-Yukawa Memorial Symposium, Nov. 1998.

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arXiv1999

Effective Field Theory and the Fermi Surface

This is an introduction to the method of effective field theory. As an application, I derive the effective field theory of low energy excitations in a conductor, the Landau theory of Fermi liquids, and explain why the high-$T_c$ superconductors must be described by a different effective field theory.

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