David A. Sahakyan

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The low energy dynamics of a certain D-brane configuration in string theory is described at weak t'Hooft coupling by a nonlocal version of the Nambu-Jona-Lasinio model. We study this system at finite temperature and strong t'Hooft coupling, using the string theory dual. We show that for sufficiently low temperatures chiral symmetry is broken, while for(More)
We study the properties of a D-brane in the presence of k NS5 branes. The Dirac-Born-Infeld action describing the dynamics of this D-brane is very similar to that of a non-BPS D-brane in ten dimensions. As the D-brane approaches the fivebranes, its equation of state approaches that of a pressureless fluid. In non-BPS D-brane case this is considered as an(More)
Little String Theory (LST) is a still somewhat mysterious theory that describes the dynamics near a certain class of time-like singularities in string theory. In this paper we discuss the topological version of LST, which describes topological strings near these sin-gularities. For 5 + 1 dimensional LSTs with sixteen supercharges, the topological version(More)
We study the high energy thermodynamics of Little String Theory, using its holographic description. This leads to the entropy-energy relation S = β H E + α log E + O(1/E). We compute α and show that it is negative; as a consequence, the high energy thermodynamics is unstable. We exhibit a mode localized near the horizon of the black brane, which has winding(More)
It has been shown by Batyrev and Borisov that nef partitions of reflexive polyhedra can be used to construct mirror pairs of complete intersection Calabi–Yau manifolds in toric ambient spaces. We construct a number of such spaces and compute their cohomological data. We also discuss the relation of our results to complete intersections in weighted(More)
We study the N = 2 string theory or the N = 4 topological string on the deformed CHS background. That is, we consider the N = 2 minimal model coupled to the N = 2 Liouville theory. This model describes holographically the topological sector of Little String Theory. We use degenerate vectors of the respective N = 2 Verma modules to find the set of BRST(More)
For a given configuration space M and Lie algebra G whose action is defined on M the space V 0.0 of weakly G-invariant Lagrangians (i.e. Lagrangians whose motion equations left hand sides are G-invariant) is studied. The problem is reformulated in terms of the double complex of Lie algebra cochains with values in the complex of Lagrangians. Calculating the(More)