arXiv subjects
Publications and source records attributed to Hossein Yavartanoo.
Inspired by the recently discovered holographic duality between N=2 SCFTs and half-BPS M-theory backgrounds, we study probe M5-branes. Though our main focus is supersymmetric M5-branes whose worldvolume has an AdS_n factor, we also consider some other configurations. Of special mention is the identification of AdS_5 and AdS_3 probes preserving supersymmetry, with only the latter supporting a self-dual field strength.
We find the most general solution of 11-dimensional supergravity compatible with N=2 super-Schrodinger symmetry with six supercharges and SU(2) x SU(2) x U(1) x Z_2 global symmetry. It can be viewed as a one-parameter extension of a recently constructed solution by Ooguri and Park. Our original motivation was to find the gravity dual of the non-relativistic ABJM theory. But, our analysis shows that no such solution exists within the reach of our assumptions. We discuss possible reasons for the non-existence of the desired solution. We also uplift a super-Schrodinger solution in IIB supergravity of Donos and Gauntlett to 11-dimension and comment on its properties.
We study semi-classical rotating open strings ending on a probe Dp-brane close to a stack of extremal, non-extremal Dp-branes and Dp-branes with $B$-fields. These states may be interpreted as positronium-like bound states of spinning W-bosons in an $SU(N+1) \to SU(N) \times U(1)$ theory. In each case, we describe the behaviour of the strings and examine the relation between the energy and the angular momentum of the bound state.
We extend the search for supergravity solution duals of non-relativistic $d=3$ CFTs to $d=11$ supergravity. We consider the internal space to be an $S^2$ bundle over a product base: $S^2 \times S^2$ and $S^2 \times T^2$. For purely M-theoretic $S^2 \times S^2$, we find only magnetic fluxes preserving two supersymmetries. $S^2 \times T^2$ is far richer admitting in addition to magnetic fluxes, various non-trivial electric fluxes which break all supersymmetry.
We present new families of non-supersymmetric solutions of D=11 supergravity with non-relativistic symmetry, based on six-dimensional Kaehler-Einstein manifolds. In constructing these solutions, we make use of a consistent reduction to a five-dimensional gravity theory coupled to a massive scalar and vector field. This theory admits a non-relativistic CFT dual with dynamical exponent z=4, which may be uplifted to D=11 supergravity. Finally, we generalise this solution and find new solutions with various z, including z=2.
Recently proposed Horava-Lifshitz gravity promises a UV completion of Einstein's theory by sacrificing general covariance at short distances and introducing anisotropic spacetime scaling. Here we present a dyonic solution by coupling this theory to a vector field and we discuss some properties of solution.
We analyse 1/2 BPS IIA Dp-brane supergravity solutions with $B$-fields and their Killing spinor equations. Via probe analysis, we rederive the supersymmetry conditions for D0-Dp with $B$-fields. In the case of D6 with $B$-fields, the D0-probe sees a multi-centred BPS configuration where the $B$-fields give the location of a wall of marginal stability. Finally we go beyond the probe approximation and construct a 1/8 BPS supergravity solution for a fully back-reacted D0-D6 with $B$-fields.
We investigate the symmetries of the near horizon geometry of extremal stationary black holes in four dimensional Einstein gravity coupled to abelian gauge fields and neutral scalars. Careful consideration of the equations of motion and the boundary conditions at the horizon imply that the near horizon geometry has $SO(2,1)\times U(1)$ isometry. This complements the rotating attractors proposal of hep-th/0606244 that had assumed the presence of this isometry. The extremal solutions are classified into two families differentiated by the presence or absence of an ergo-region. We also comment on the attractor mechanism of both branches.
We examine four dimensional magnetically charged extremal black holes in certain non-linear U(1) gauge theories coupled to two derivative gravity. For a given coupling, one can tune the magnetic charge (or vice versa) so that the curvature singularity at the centre of the space-time is cancelled. Since these solutions have a horizon but no singularity, they have been called regular black holes. Contrary to recent claims in the literature, we find that the entropy function formalism reproduces the near horizon geometry and gives the correct entropy for these objects.
We investigate the attractor mechanism in Kaluza-Klein black hole solution in the presence of higher derivative terms. In particular, we discuss the attractor behavior of static black holes by using the effective potential approach as well as entropy function formalism. We consider different higher derivative terms with a general coupling to moduli field. For the $R^2$ theory, we use effective potential approach, looking for solutions which are analytic near the horizon and show that they exist and enjoy the attractor behavior. The attractor point is determined by extremization of the modified effective potential at the horizon. We study the effect of the general higher derivative corrections of $R^n$ terms. Using the entropy function we define the modified effective potential and we find the conditions to have the attractor solution. In particular for a single charged Kaluza-Klein black hole solution we show that higher derivative correction dresses the naked singularity for an appropriate coupling, and we can find the attractor solution.
We investigate the attractor mechanism in gauged supergravity in the presence of higher derivatives terms. In particular, we discuss the attractor behaviour of static black hole horizons in anti-de Sitter spacetime by using the effective potential approach as well as Sen's entropy function formalism. We use the holographic techniques to interpret the moduli flow as an RG flow towards the IR attractor horizon. We find that the holographic c-function obeys the expected properties and point out some subtleties in understanding attractors in AdS.
We study singular 1/2 BPS solutions in M-theory using 11-dimensional superstar solutions. The superstar solutions and their corresponding plane wave limits could give an insight how one may deform the boundary conditions to get singular, but still physically acceptable, solutions. Starting from M-theory solutions with an isometry, we will also study 10-dimensional solutions coming from these M-theory solutions compactified on a circle.
We study supergravity solutions of type II branes wrapping a Melvin universe. These solutions provide the gravity description of non-commutative field theories with non-constant non-commutative parameter. Typically these theories are non-supersymmetric, though they exhibit some feature of their corresponding supersymmetric theories. An interesting feature of these non-commutative theories is that there is a critical length in the theory in which for distances larger than this length the effects of non-commutativity become important and for smaller distances these effects are negligible. Therefore we would expect to see this kind of non-commutativity in large distances which might be relevant in cosmology. We also study M5-brane wrapping on 11-dimensional Melvin universe and its descendant theories upon compactifying on a circle.
We study dynamics of a D3-brane propagating in the vicinity of k coincident NS5 branes. We show that when $g_s$ is small, there exists a regime in which dynamics of the D-brane is governed by Dirac-Born-Infeld action while higher order derivative in the expansion can not be neglected. This leads to a restriction on how fast scalar field may roll. We analyze the motion of a rolling scalar field in this regime, and extend the analysis to cosmological systems obtained by coupling this type of field theory to four dimensinal gravity. It also leads to some FRW cosmologies, some of which are related to those obtained with tachyon matter.
We study semi-classical multi-spin strings in the non-supersymmetric backgrounds of $AdS$ Black Hole and Witten's confining model. We consider constant radius strings with rotations along the isometries of the backgrounds. In the $AdS$ Black Hole, solutions exist only if there is a non-zero spin in the Black Hole part. In contrast with the $AdS$ background, we find solutions which although have no rotation in the $S^5$ part, have a regular $λ$ expansion in the expression for large energy. In the near-extremal $D_3$ and $D_4$ backgrounds, we find that strings have to be located on the confining wall. We also discuss the stability of solutions by considering the fluctuation Lagrangians.
We study N=1 supersymmetric U(N) gauge theory coupled to an adjoint scalar superfiled with a cubic superpotential containing a multi trace term. We show that the field theory results can be reproduced from a matrix model which its potential is given in terms of a linearized potential obtained from the gauge theory superpotential by adding some auxiliary nondynamical field. Once we get the effective action from this matrix model we could integrate out the auxiliary field getting the correct field theory results.
We consider system of Dp-branes in the presence of a nonzero B field with one leg along brane worldvolume and the other transverse to it. We study the corresponding supergravity solutions and show that the worldvolume theories decouple from gravity for $p\leq 5$. Therefore these solutions provide dual description of large N noncommutative dipole field theories. We shall only consider those systems which preserve 8 supercharges in the branes worldvolume. We analyze the system of M5-branes and NS5-branes in the presence of nonzero C field and RR field with one leg along the transverse direction and the others along the worldvolume of the brane, respectively. This could provide a new deformation of (2,0) and little string field theories. Finally, we study the Wilson loops using the dual gravity descriptions.