Akikazu Hashimoto

Large branes in AdS and their field theory dual

Recently it was suggested that a graviton in AdS5 ? S5 with a large momentum along the sphere can blow up into a spherical D-brane in S5. In this paper we show that the same graviton can also blow up into a spherical D-brane in AdS5 with exactly the same quantum numbers (angular momentum and energy). These branes are BPS, preserving 16 of the 32 supersymmetries. We show that there is a BPS classical solution for SYM on S3 ? R with exactly the same quantum numbers. The solution has non-vanishing Higgs expectation values and hence is dual to the large brane in AdS.

FLUCTUATION SPECTRA OF TILTED AND INTERSECTING D-BRANES FROM THE BORN-INFELD ACTION

Abstract We consider the spectra of excitations around diagonal and intersecting D-brane configurations on tori. These configurations are described by constant curvature connections in a dual gauge theory description. The low-energy string fluctuation spectrum is reproduced exactly by the gauge theory in the case of vanishing field strength; however, this correspondence breaks down for fixed non-zero field strength. We show that in many cases the full Born-Infeld action correctly captures the low-energy spectrum in the case of non-vanishing field strength. This gives a field theory description of the low-energy physics of systems of diagonally wound branes and branes at angles as considered by Berkooz, Douglas and Leigh. This description extends naturally to non-supersymmetric configurations, where the tachyonic instability associated with brane-antibrane systems appears as an instability around a saddle point solution of the corresponding Yang-Mills/Born-Infeld theory. In some cases, the field theory description requires a non-abelian generalization of the Born-Infeld action. We follow Tseytlins recent proposal for formulating such an action. In the case of intersecting branes, the non-abelian Bom-Infeld theory produces a transcendental relation which comes tantalizingly close to reproducing the correct spectrum; however, a discrepancy remains which indicates that a further clarification of the non-abelian Born-Infeld action may be necessary.

Scattering of strings from D-branes

We review a number of perturbative calculations describing the interactions of D-branes with massless elementary string states. The form factors for the scattering of closed strings off D-branes are closely related to the Veneziano amplitude. They show that, in interactions with strings, D-branes acquire many of their physical features: the effective size of D-branes is of order the string scale and expands with the energy of the probe, while the fixed angle scattering amplitudes fall off exponentially. We also calculate the leading process responsible for the absorption of closed strings: the amplitude for a closed string to turn into a pair of open strings attached to the D-brane. The inverse of this process describes the Hawking radiation by an excited D-brane.

Decay of Excited D-branes

Abstract We calculate the leading order interactions of massless D-brane excitations. Their 4-point functions are found to be identical to those found in type I theory. The amplitude for two massless D-brane fluctuations to produce a massless closed string is found to possess interesting new structure. As a function of its single kinematic invariant, it displays an infinite sequence of alternating zeros and poles. At high transverse momenta, this amplitude decays exponentially, indicating a growing effective thickness of the D-brane. This amplitude is the leading process by which non-extremal D-branes produce Hawking radiation.

Gravitational lensing by p-branes

The scattering of R-R gauge bosons off of Dirichlet p-branes is computed to leading order in the string coupling. The results are qualitatively similar to those found in the scattering of massless NS-NS bosons: all p-branes with p ≥ 0 exhibit stringy properties, in particular the Regge behavior. Both the R-R and NS-NS scattering amplitudes agree in the limit of small momentum transfer with scattering off the extremal R-R charged p-brane solutions found in the low-energy supergravities. We interpret this as evidence that Dirichlet-branes are an exact worldsheet description of the extremal p-branes. The −1-brane (D-instanton) is a special object which, unlike all other Dirichlet-branes, exhibits point-like behavior. We show that the field theoretic scattering off of the R-R charged instanton solution to type IIB supergravity exactly reproduces the full stringy calculation. As an aside, we include a discussion of the entropy of nonextremal black holes in ten dimensions, produced by exciting the 0-brane.

Scalar absorption and the breaking of the world volume conformal invariance

Abstract We investigate a version of fixed scalars for nondilatonic branes which correspond to dilatations of the brane world-volume. We obtain a cross section whose world-volume interpretation falls out naturally from an investigation of the breaking of conformal invariance by the irrelevant Born-Infeld corrections to Yang-Mills theory. From the same irrelevant world-volume operator we obtain the leading correction to the cross sections of minimal scalars. This correction can be obtained in supergravity via an improved matching of inner and outer solutions to the minimal wave equation.

Holography and string dynamics in time-dependent backgrounds.

We study the dynamics of D-branes in a smooth time-dependent background. The theory on the branes is a time-dependent noncommutative field theory. We find the metric and fluxes that determine the dual holographic closed string theory. This provides a concrete example of holography in a cosmological setting.

Supergravity solution of intersecting branes and AdS/CFT with flavor

We construct the supergravity solution for fully localized D2/D6 intersection. The near horizon limit of this solution is the supergravity dual of supersymmetric Yang-Mills theory in 2+1 dimensions with flavor. We use this solution to formulate mirror symmetry of 2+1 dimensional gauge theories in the language of AdS/CFT correspondence. We also construct the supergravity dual of a non-commutative gauge theory with fundamental matter.

D-brane charges in gravitational duals of 2 + 1 dimensional gauge theories and duality cascades

We perform a systematic analysis of the D-brane charges associated with string theory realizations of d = 3 gauge theories, focusing on the examples of the

Black strings in asymptotically plane wave geometries

\mathcal{N} = 4