Radoslav C. Rashkov

Generalized pulsating strings

In this paper we consider new solutions for pulsating strings. For this purpose we use the idea of the generalized ansatz for folded and circular strings in [1]. We find the solutions to the resulting Neumann-Rosochatius integralbe system and the corrections to the energy. To do that we use the approach developed by Minahan in [2] and find that the corrections are quite different from those obtained in that paper and in [3]. We conclude with comments on our solutions and the obtained corrections to the energy, expanded to the leading order in lambda.

Note on the boundary terms in AdS / CFT correspondence for Rarita-Schwinger field

In this letter the boundary problem for massless and massive Rarita–Schwinger fields in the AdS/CFT correspondence is considered. The considerations are along the lines of a paper by Henneaux24 and are based on the requirement that the solutions have to be a stationary point for the action functional. It is shown that this requirement, along with a definite asymptotic behavior of the solutions, fixes the boundary term that must be added to the initial Rarita–Schwinger action. It is also shown that the boundary term reproduce the known two-point correlation functions of certain local operators in CFT living on the boundary.In this letter the boundary problem for massless and massive Rarita-Schwinger field in the AdS/CFT correspondence is considered. The considerations are along the lines of a paper by Henneaux (hep-th/9902137) and are based on the requirement the solutions to be a stationary point for the action functional. It is shown that this requirement, along with a definite asymptotic behavior of the solutions, fixes the boundary term that must be added to the initial Rarita-Schwinger action. It is also shown that the boundary term reproduce the known two point correlation functions of certain local operators in CFT living on the boundary.

Semiclassical strings, dipole deformations of Script N = 1 SYM and decoupling of KK modes

In this paper we investigate the recently found °-deformed Maldacena-Nunez background by studying the behavior of different semiclassical string configurations. This background is conjectured to be dual to dipole deformations of N = 1 SYM. We compare our results to those in the pure Maldacena-Nunez background and show that the energies of our string configurations are higher than in the undeformed background. Thinking in the lines of (1) we argue that this is an evidence for better decoupling of the Kaluza-Klein modes from the pure SYM theory excitations. Moreover we are able to find a limit of the background in which the string energy is independent of °, these strings are interpreted as corresponding to pure gauge theory effects.

Magnon-like dispersion relation from M-theory

Abstract We investigate classical rotating membranes in two different backgrounds. First, we obtain membrane solution in AdS 4 × S 7 background, analogous to the solution obtained by Hofman and Maldacena in the case of string theory. We find a magnon type dispersion relation similar to that of Hofman and Maldacena and to the one found by Dorey for the two spin case. In the appendix of the paper, we consider membrane solutions in AdS 7 × S 4 , which give new relations between the conserved charges.

On the pulsating strings in AdS5 × T1, 1

We study the class of pulsating strings in AdS5 × T1, 1. Using a generalized ansatz for pulsating string configurations, we find new solutions of this class. Further we semiclassically quantize the theory and obtain the first correction to the energy. The latter, due to AdS/CFT correspondence, is supposed to give the anomalous dimensions of operators in the dual superconformal gauge field theory.

Gauge/String Duality

1 Dipartimento di Scienze Fisiche, Universita degli Studi di Napoli Federico II, INFN, Sezione di Napoli, Via Cintia, 80126 Napoli, Italy 2 Department of Physics, University of Wales Swansea, Singleton Park, Swansea SA2 8PP, UK 3 Michigan Center for Theoretical Physics, The University of Michigan, Ann Arbor, MI 48109-1120, USA 4 Departamento de Fisica de Particulas, Instituto Galego de Fisica de Altas Energias (IGFAE), Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain 5 Institute for Theoretical Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, 1040 Vienna, Austria 6 Department of Physics, Sofia University, 1504 Sofia, Bulgaria 7 Department of Physics, and IRMACS, Simon Fraser University, Burnaby, British Columbia, Canada

Non-abelian T-duality of Pilch-Warner background

In this work we obtain the non-abelian T-dual geometry of the well-known Pilch-Warner supergravity solution in its infrared point. We derive the dual metric and the NS two-form by gauging the isometry group of the initial theory and integrating out the introduced auxiliary gauge fields. Then we use the Fourier-Mukai transform from algebraic geometry to find the transformation rules of the R-R fields. The dual background preserves the supersymmetry of the original one due to the fact that the Killing spinor does not depend on the directions on which the N-AT-D is performed. Finally, we consider two different pp-wave limits of the T-dual geometry by performing Penrose limits for two light-like geodesics.

Strings on the deformed T 1,1 : giant magnon and single spike solutions

In this paper we have found giant magnon and single spike string solutions in a sector of the gamma-deformed conifold. We examined the dispersion relations and find a behavior analogous to the undeformed case. The transcendental functional relations between the conserved charges are shifted by a certain gamma-dependent term. The latter is proportional to the total momentum and thus qualitatively different from known cases.

Flavours in global Klebanov-Witten background

A bstractWe probe flavour branes in the Klebanov-Witten background in global coordinates. We show that supersymmetric probes correspond to massless flavours and analyse their spectrum of fluctuations. Our studies suggest that the mesons are dissociated by the Casimir energy. The spectrum is equidistant, with a ground state given by the conformal dimension of the operator dual to the fluctuations. We show that the equidistant structure of the spectrum arises from the addition of the angular momenta of the fundamental fields composing the meson operators.

Entanglement of higher-derivative oscillators in holographic systems

We study the quantum entanglement of coupled Pais–Uhlenbeck oscillators using the formalism of thermo-field dynamics. The entanglement entropy is computed for the specific cases of two and a ring of N coupled Pais–Uhlenbeck oscillators of fourth order. It is shown that the entanglement entropy depends on the temperatures, frequencies and coupling parameters of the different degrees of freedom corresponding to harmonic oscillators. We also make remarks on the appearance of instabilities of higher-derivative oscillators in the context of AdS/CFT correspondence. Finally, we advert to the information geometry theory by calculating the Fisher information metric for the considered system of coupled oscillators.