On finite size corrections to the dispersion relations of giant magnon and single spike on \gamma -deformed T^{1,1}

In this paper we consider the finite size effects for the strings in \beta -deformed AdS_{5}\times T^{1,1} background. We analyze the finite size corrections for the cases of giant magnon and single spike string solution. The finite size corrections for the undeformed case are straightforwardly obtained sending the deformation parameter to zero.Comment: 13 page

Magnetic Catalysis of Chiral Symmetry Breaking. A Holographic Prospective

We review a recent investigation of the effect of magnetic catalysis of mass generation in holographic Yang-Mills theories. We aim at a self-contained and pedagogical form of the review. We provide a brief field theory background and review the basics of holographic flavordynamics. The main part of the review investigates the influence of external magnetic field on holographic gauge theories dual to the D3/D5-- and D3/D7-- brane intersections. Among the observed phenomena are the spontaneous breaking of a global internal symmetry, Zeeman splitting of the energy levels and the existence of pseudo Goldstone modes. An analytic derivation of the Gell-Mann--Oaks--Renner relation for the D3/D7 set up is reviewed. In the D3/D5 case the pseudo Goldstone modes satisfy non-relativistic dispersion relation. The studies reviewed confirm the universal nature of the magnetic catalysis of mass generation.Comment: 49 pages, 11 figures, a review articl

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.Comment: 20 pages, 1 figure; v2: new section added highlighting the appearance of higher-derivative oscillators in holographic systems; v3: an additional example of holographic system added and title change

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, Canad

Semiclassical Strings, Dipole Deformations of N=1 SYM and Decoupling of KK Modes

In this paper we investigate the recently found $\gamma$-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 (hep-th/0505100) 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 $\gamma$, these strings are interpreted as corresponding to pure gauge theory effects.Comment: 31 pages, references added, new solutions in Section 7 presented, an appendix added, to appear in JHE

Flavoured Large N Gauge Theory in an External Magnetic Field

We consider a D7-brane probe of AdS$_{5}\times S^5$ in the presence of pure gauge $B$-field. In the dual gauge theory, the $B$-field couples to the fundamental matter introduced by the D7-brane and acts as an external magnetic field. The $B$-field supports a 6-form Ramond-Ramond potential on the D7-branes world volume that breaks the supersymmetry and enables the dual gauge theory to develop a non-zero fermionic condensate. We explore the dependence of the fermionic condensate on the bare quark mass $m_{q}$ and show that at zero bare quark mass a chiral symmetry is spontaneously broken. A study of the meson spectrum reveals a coupling between the vector and scalar modes, and in the limit of weak magnetic field we observe Zeeman splitting of the states. We also observe the characteristic $\sqrt{m_{q}}$ dependence of the ground state corresponding to the Goldstone boson of spontaneously broken chiral symmetry.Comment: 22 pages, 7 figures, references added, few typos correcte