We derive a general relation between the ground state entanglement Hamiltonian and the physical stress tensor within the path integral formalism. For spherical entangling surfaces in a CFT, we reproduce the local ground state entanglement Hamiltonian derived by Casini, Huerta and Myers. The resulting reduced density matrix can be characterized by a spatially varying "entanglement temperature." Using the entanglement Hamiltonian, we calculate the first order change in the entanglement entropy due to changes in conserved charges of the ground state, and find a local first law-like relation for the entanglement entropy. Our approach provides a field theory derivation and generalization of recent results obtained by holographic techniques. However, we note a discrepancy between our field theoretically derived results for the entanglement entropy of excited states with a non-uniform energy density and current holographic results in the literature. Finally, we give a CFT derivation of a set of constraint equations obeyed by the entanglement entropy of excited states in any dimension. Previously, these equations were derived in the context of holography.

The world volume theory on N regular and M fractional D3-branes at the conifold singularity is a non-conformal N = 1 supersymmetric SU (N + M ) × SU (N ) gauge theory. In previous work the extremal Type IIB supergravity dual of this theory at zero temperature was constructed. Regularity of the solution requires a deformation of the conifold: this is a reflection of the chiral symmetry breaking. To study the non-zero temperature generalizations non-extremal solutions have to be considered, and in the high temperature phase the chiral symmetry is expected to be restored. Such a solution is expected to have a regular Schwarzschild horizon. We construct an ansatz necessary to study such nonextremal solutions and show that the simplest possible solution has a singular horizon. We derive the system of second order equations in the radial variable whose solutions may have regular horizons. 02/01

We consider Penrose limits of the Klebanov-Strassler and Maldacena-Núñez holographic duals to N = 1 supersymmetric Yang-Mills. By focusing in on the IR region we obtain exactly solvable string theory models. These represent the nonrelativistic motion and low-lying excitations of heavy hadrons with mass proportional to a large global charge. We argue that these hadrons, both physically and mathematically, take the form of heavy nonrelativistic strings; we term them "annulons." A simple toy model of a string boosted along a compact circle allows us considerable insight into their properties. We also calculate the Wilson loop carrying large global charge and show the effect of confinement is quadratic, not linear, in the string tension.

We study supergravity solutions representing D3-branes with transverse 6-space having RϫS 2 ϫS 3 topology. We consider regular and fractional D3-branes on a natural one-parameter extension of the standard Calabi-Yau metrics on singular and resolved conifolds. After imposing a Z 2 identification on an angular coordinate these generalized ''6D conifolds'' are nonsingular spaces. The back reaction of D3-branes creates a curvature singularity that coincides with a horizon. In the presence of fractional D3-branes the solutions are similar to the original ones by Klebanov and Tseytlin and Pando Zayas and Tseytlin: the metric has a naked repulson-type singularity located behind the radius where the 5-form flux vanishes. The semiclassical behavior of the Wilson loop suggests that the corresponding gauge theory duals are confining.

We discuss Regge trajectories of dynamical mesons in large-N c QCD, using the supergravity background describing N c D4-branes compactified on a thermal circle. The flavor degrees of freedom arise from the addition of N f N c D6 probe branes. Our work provides a string theoretical derivation, via the gauge/string correspondence, of a phenomenological model describing the meson as rotating point-like massive particles connected by a flux string. The massive endpoints induce nonlinearities for the Regge trajectory. For light quarks the Regge trajectories of mesons are essentially linear. For massive quarks our trajectories qualitatively capture the nonlinearity detected in lattice calculations.

We present a large class of new backgrounds that are solutions of type IIB supergravity with a warped AdS 5 factor, non-trivial axion-dilaton, B-field and three-form Ramond-Ramond flux but yet have no five-form flux. We obtain these solutions and many of their variations by judiciously applying non-Abelian and Abelian T-dualities, as well as coordinate shifts to AdS 5 × X 5 IIB supergravity solutions with X 5 = S 5 , T 1,1 , Y p,q . We address a number of issues pertaining to charge quantization in the context of non-Abelian T-duality. We comment on some properties of the expected dual super conformal field theories by studying their CFT central charge holographically. We also use the structure of the supergravity Page charges, central charges and some probe branes to infer aspects of the dual super conformal field theories.

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Using analytic techniques developed for Hamiltonian dynamical systems we show that a certain classical string configurations in AdS5 × X5 with X5 in a large class of Einstein spaces, is nonintegrable. This answers the question of integrability of string on such backgrounds in the negative. We consider a string localized in the center of AdS5 that winds around two circles in the manifold X5.PACS numbers: 11.25. Tq, 11.30.Na Introduction. -Chaotic motion has been one of the most studied aspects of nonlinear dynamical systems as its application extend to many areas [1]. Although its mathematical roots date back to Poincarè and the threebody problem, it was really during the last part of the XX century when its study flourished largely thanks to new advances in computing power. Naturally, under the shadow of quantum mechanics it is logical to try to understand the quantum properties in systems whose classical limit is chaotic, this area has become known as quantum chaos [2]. In the context of the AdS/CFT correspondence [3], there is a particularly special chance to understand some of these questions as we have a setting in which the classical regime of a theory is dual to the highly quantum regime of another. Understanding classical chaos and the corresponding quantization in the context of string theory provides a new framework with enhanced interpretational opportunities.The simplest version of the AdS/CFT correspondence In general the question of integrability is settled through a numerical analysis of the system [1]. Over the last decades an analytical approach has been developed to determine whether a system in integrable. Some powerful results due to Ziglin [7,8] and further refined by Morales-Ruiz and Ramis [9] turn the question of integrability of some simple systems into an algorithmic process. In this paper we study a large class of systems that appear in string theory. We generalize some of our