Nemani V. Suryanarayana

Aspects of semiclassical strings in AdS5

Abstract We find an infinite number of conserved currents and charges in the semiclassical limit λ →∞ of string theory in AdS 5 × S 5 and remark on their relevance to conserved charges in the dual gauge theory. We establish a general procedure of exploring the semiclassical limit by viewing the classical motion as collective motion in the relevant part of the configuration space. We illustrate the procedure for semiclassical expansion around solutions of string theory on AdS 5 ×( S 5 / Z M ).

Counting 1/8-BPS dual-giants

We count 1/8-BPS states in type IIB string theory on AdS5 × S 5 background which carry three independent angular momenta on S 5 . These states can be counted by considering configurations of multiple dual-giant gravitons up to N in number which share at least four supersymmetries. We map this counting problem to that of counting the energy eigenstates of a system of N bosons in a 3-dimensional harmonic oscillator. We also count 1/8-BPS states with two independent non-zero spins in AdS5 and one non-zero angular momentum on S 5 by considering configurations of arbitrary number of giant gravitons that share at least four supersymmetries.

Gauge-Invariant Couplings of Noncommutative Branes to Ramond-Ramond Backgrounds

We derive the couplings of noncommutative D-branes to spatially varying Ramond-Ramond fields, extending our earlier results in hep-th/0009101. These couplings are expressed in terms of *n products of operators involving open Wilson lines. Equivalence of the noncommutative to the commutative couplings implies interesting identities as well as an expression for the Seiberg-Witten map that was previously conjectured. We generalise our couplings to include transverse scalars, thereby obtaining a Seiberg-Witten map relating commutative and noncommutative descriptions of these scalars. RR couplings for unstable non-BPS branes are also proposed.

Extremal single-charge small black holes: entropy function analysis

We study stretched horizons of the type AdS2 × S8 for certain spherically symmetric extremal small black holes in type IIA carrying only D0-brane charge making use of Sens entropy function formalism for higher derivative gravity. A scaling argument is given to show that the entropy of this class of black holes for large charge behaves as , where q is the electric charge. The leading order result arises from IIA string loop corrections. We find that for solutions to exist the force on a probe D0-brane has to vanish and we prove that this feature persists to all higher derivative orders. We comment on the nature of the extremum of these solutions and on the sub-leading corrections to the entropy. The entropy of other small black holes related by dualities to our case is also discussed.

Chern-Simons terms on noncommutative branes

We write down couplings of the fields on a single BPS Dp-brane with noncommutative world-volume coordinates to the RR-forms in type II theories, in a manifestly background independent way. This generalises the usual Chern-Simons action for a commutative Dp-brane. We show that the noncommutative Chern-Simons terms can be mapped to Myers terms on a collection of infinitely many D-instantons. We also propose Chern-Simons couplings for unstable non-BPS branes, and show that condensation of noncommutative tachyons on these branes leads to the correct Myers terms on the decay products.

Exact operator bosonization of finite number of fermions in one space dimension

We derive an exact operator bosonization of a finite number of fermions in one space dimension. The fermions can be interacting or noninteracting and can have an arbitrary hamiltonian, as long as there is a countable basis of states in the Hilbert space. In the bosonized theory the finiteness of the number of fermions appears as an ultraviolet cut-off. We discuss implications of this for the bosonized theory. We also discuss applications of our bosonization to one-dimensional fermion systems dual to (sectors of) string theory such as LLM geometries and c = 1 matrix model.

An sl(2, \mathbb{R} ) current algebra from AdS3 gravity

A bstractWe provide a set of chiral boundary conditions for three-dimensional gravity that allow for asymptotic symmetries identical to those of two-dimensional induced gravity in light-cone gauge considered by Polyakov. These are the most general boundary conditions consistent with the boundary terms introduced by Compère, Song and Strominger recently. We show that the asymptotic symmetry algebra of our boundary conditions is a Virasoro algebra with Brown-Henneaux central charge c and an sl(2,

A deformation of AdS5 × S5

\mathbb{R}

Brane-antibrane constructions

) current algebra with level given by c/6. The fully non-linear solution in Fefferman-Graham coordinates is also provided along with its charges.

Two-charge small black hole entropy: string-loops and multi-strings

We analyse a one parameter family of supersymmetric solutions of type IIB supergravity that includes AdS_5 x S^5. For small values of the parameter the solutions are causally well-behaved, but beyond a critical value closed timelike curves (CTCs) appear. The solutions are holographically dual to N=4 supersymmetric Yang-Mills theory on a non-conformally flat background with non-vanishing R-currents. We compute the holographic energy-momentum tensor for the spacetime and show that it remains finite even when the CTCs appear. The solutions, as well as the uplift of some recently discovered AdS_5 black hole solutions, are shown to preserve precisely two supersymmetries.