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A. Rezaei-Aghdam

Publications and source records attributed to A. Rezaei-Aghdam.

At least 55 records · Page 3Linked to original sources
arXiv2015

Gravity and induced matter on Nearly Kahler Manifolds

We show that the conservation of energy-momentum tensor of a gravitational model with Einstein-Hilbert like action on a nearly Kahler manifold with the scalar curvature of a curvature-like tensor, is consistent with the nearly Kahler properties. In this way, the nearly Kahler structure is automatically manifested in the action as a induced matter field. As an example of nearly Kahler manifold, we consider the group manifold of R x II x S3 x S3 on which we identify a nearly Kahler structure and solve the Einstein equations to interpret the model. It is shown that the nearly Kahler structure in this example is capable of alleviating the well known fine tuning problem of the cosmological constant. Moreover, this structure may be considered as a potential candidate for dark energy.

hep-th↗
arXiv2014

2 + 1 dimensional gravity from Maxwell and semi-simple extension of the Poincare gauge symmetric models

We obtain 2 + 1 dimensional gravity with cosmological constant which is coupled to gauge fields, using Maxwell and semi-simple extension of the Poincare gauge symmetric models (i.e. Chern-Simons models with these gauge groups). Also, we obtain some Ads and BTZ type solutions for the classical equations of motion for these 2 + 1 dimensional gravities. For the semi-simple extension of the Poincare gauge group we investigate the Ads/CFT correspondence and show that the model at the boundary is equivalent to the sum of three WZW models over group SO(2,1). Then, we show that the central charge of the CFT is the same as that of CFT at the boundary of Ads spacetime related to the Chern-Simons model with gauge group SO(2,2). Finally, we show that these two 2 + 1 dimensional gravity models are dual (canonically transformed) to each other.

hep-th↗
arXiv2014

Algebraic Structures of N=(4,4) and N=(8,8) SUSY Sigma Models on Lie groups and SUSY WZW Models

Algebraic structures of N = (4; 4) and N = (8; 8) supersymmetric (SUSY) two dimensional sigma models on Lie groups (in general) and SUSY Wess-Zumino-Witten (WZW) models (as special) are obtained. For SUSY WZW models, these algebraic structures are reduced to Lie bialgebraic structures as for the N = (2; 2) SUSY WZW case; with the difference that there is a one 2-cocycle for the N = (4; 4) case and there are two 2-cocycles for the N = (8; 8) case. In general, we show that N = (8; 8) SUSY structure on Lie algebra must be constructed from two N = (4; 4) SUSY structures and in special there must be two 2-cocycles for Manin triples (one 2-cocycle for each of the N = (4; 4) structures). Some examples are investigated. In this way, a calculational method for classifying the N = (4; 4) and N = (8; 8) structures on Lie algebras and Lie groups are obtained.

hep-th↗
arXiv2014

Perturbed Wess-Zumino-Witten models and N=(2,2) supersymmetric sigma models on Lie groups with complex structure

We have perturbed Wess-Zumino-Witten (WZW) models and also N=(2,2) supersymmetric sigma models on Lie groups by adding a term containing complex structure to their actions. Then, using non-coordinate basis, we have shown that for N=(2,2) supersymmetric sigma models on Lie groups the conditions (from the algebraic point of view) for the preservation of the N=(2,2) supersymmetry impose that the complex structure must be invariant; so only the Abelian Lie algebras admit these deformations preserving the N=(2,2) supersymmetry. Also, we have shown that the perturbed WZW model with this term, using Hermitian (not necessarily invariant) condition, is an integrable model.

hep-th↗
arXiv2014

Quantum tunneling from generalized $(2+1)$ dimensional black holes having Noether symmetry

We have studied the Hawking radiation from {\it generalized} rotating and static $(2+1)$-dimensional BTZ black holes. In this regard, we have benefited the quantum tunneling approach with WKB approximation and obtained the tunneling rate of outgoing scalar and spinor particles across the horizons. We have also obtained the Hawking temperature at the horizons corresponding to the emission of these particles. It is shown that the tunneling rate and Hawking temperature of generalized $(2+1)$-dimensional BTZ black holes are different from ordinary $(2+1)$-dimensional BTZ black holes due to the Noether symmetry. In other words, the Noether symmetry can change the tunneling rate and Hawking temperature of the BTZ black holes. This symmetry may cause the BTZ black holes to avoid of evaporation and its breakdown may start the evaporation.

gr-qc↗
arXiv2013

WZW models as mutual super Poisson-Lie T-dual sigma models

A WZW model on the Lie supergroup (C3+A) is constructed. It is shown that this model contains super Poisson-Lie symmetry with the dual Lie supergroup C3 + A1,1|.i. Furthermore, we show that the dual model is also equivalent to the WZW model on isomorphic Lie supergroup (C3+A).i. In this manner, because of isomorphism of the (C3+A) with a Manin supertriple, it is shown that the N=(2,2) structure is preserved under the super Poisson-Lie T-duality transformation.

hep-th↗
arXiv2013

Generalized (2+1) dimensional black hole by Noether symmetry

We use the Noether symmetry approach to find $f(R)$ theory of $(2+1)$ dimensional gravity and $(2+1)$ dimensional black hole solution consistent with this $f(R)$ gravity and the associated symmetry. We obtain $f({R})=D_1 R({n}/{n+1})({R}/{K})^{1/n}+D_2 R+D_3$, where the constant term $D_3$ plays no dynamical role. Then, we find general spherically symmetric solution for this $f(R)$ gravity which is potentially capable of being as a black hole. Moreover, in the special case $D_1=0, D_2={1}$, namely $f(R)=R+D_3$, we obtain a generalized BTZ black hole which, other than common conserved charges $m$ and $J$, contains a new conserved charge Q. It is shown that this conserved charge corresponds to the freedom in the choice of the constant term $D_3$ and represents symmetry of the action under the transformation $R \rightarrow R'=R+D_3$ along the killing vector $\partial_{R}$. The ordinary BTZ black hole is obtained as the special case where $D_3$ is {\it fixed} to be proportional to the infinitesimal cosmological constant and consequently the symmetry is broken via Q=0. We study the thermodynamics of the generalized BTZ black hole and show that its entropy can be described by the Cardy-Verlinde formula.

gr-qc↗
arXiv2012

The gl(1|1) Lie superbialgebras

By direct calculations of matrix form of super Jacobi and mixed super Jacobi identities which are obtained from adjoint representation, and using the automorphism supergroup of the gl(1|1) Lie superalgebra, we determine and classify all gl(1|1) Lie superbialgebras. Then, by calculating their classical r-matrices, the gl(1j1) coboundary Lie superbialgebras and their types (triangular, quasi-triangular or factorizable) are determined, furthermore in this way super Poisson structures on the GL(1|1) Lie supergroup are obtained. Also, we classify Drinfeld superdoubles based on the gl(1|1) as a theorem. Afterwards, as a physical application of the coboundary Lie superbialgebras, we construct a new integrable system on the homogeneous superspace OSp(1|2)/U(1). Finally, we make use of the Lyakhovsky and Mudrov formalism in order to build up the deformed gl(1|1) Lie superalgebra related to all gl(1|1) coboundary Lie superbialgebras. For one case, the quantization at the supergroup level is also provided, including its quantum R-matrix.

math-ph↗
arXiv2012

Perturbed N=(2,2) supersymmetric sigma models on Lie groups

We perturbed N=(2,2) supersymmetric WZW and sigma models on Lie groups by adding a term to their actions. Then by using non-coordinate basis we obtain conditions, from the algebraic point of view, under which the N=(2,2) supersymmetry is preserved. By applying this method, we have obtained conditions on the existence of N=(2,2) supersymmetry on the Drinfeld action (master action for the Poisson-Lie T-dual sigma models).

hep-th↗
arXiv2012

Super Poisson-Lie symmetry of the GL(1|1) WZNW model and worldsheet boundary conditions

We show that the WZNW model on the Lie supergroup GL(1|1) has super Poisson-Lie symmetry with the dual Lie supergroup B + A + A1;1|.i. Then, we discuss about D-branes and worldsheet boundary conditions on supermanifolds, in general, and obtain the algebraic relations on the gluing supermatrix for the Lie supergroup case. Finally, using the supercanonical transformation description of the super Poisson-Lie T-duality transformation, we obtain formula for the description of the dual gluing supermatrix, then, we find the gluing supermatrix for the WZNW model on GL(1|1) and its dual model. We also discuss about different boundary conditions.

hep-th↗
arXiv2012

Two dimensional Nambu sigma model

We present two dimensional sigma model by using the Nambu structure on a manifold in general, and on a Lie group as a special case. Then, we consider model constructed from Nambu structure of order three and obtain conditions under which this model is equivalent to a WZW model. Furthermore, we present an example for this case on the four dimensional Heisenberg Lie group. Finally, as another example we show that the model constructed with Nambu structure of order three on the central extension of the 2D Poincare Lie group is integrable.

hep-th↗
arXiv2012

4+1 dimensional homogeneous anisotropic string cosmological models

We present exact solutions of string cosmological models characterized by five dimensional metrics (with four-dimensional real Lie groups as isometry groups), space independent dilaton and vanishing torsion. As an example we consider VII 0 \oplus R model and show that it is equivalent to the (4 +1)-dimensional cosmological model coupled to perfect fluid with negative deceleration parameters (accelerating universe).

hep-th↗
arXiv2012

String cosmology from Poisson-Lie T-dual sigma models on supermanifolds

We generalize the formulation of Poisson-Lie T-dual sigma models on manifolds to supermanifolds. In this respect, we formulate 1+1 dimensional string cosmological models on the Lie supergroup C^3 and its dual (A_1,1 + 2A)^0_(1,0,0), which are coupled to two fermionic fields. Then, we solve the equations of motion of the models and show that there is a essential singularity for the metric of the original model and its dual.

hep-th↗
arXiv2011

Poisson-Lie sigma models over low dimensional real Poisson-Lie groups

The Poisson-Lie sigma models over nonsemisimple low dimensional real Poisson-Lie groups are investigated. We find two sided models on two, three and some four dimensional Poisson-Lie groups where the Poisson-Lie sigma models over Poisson-Lie groups G and its dual $\tilde{G}$ are topological sigma models or BF gauge models.

hep-th↗
arXiv2011

Classification of four and six dimensional Drinfel'd superdoubles

Using adjoint representation we firstly classify two and three dimensional Lie super-bialgebras obtain from decomposable Lie superalgebras. In this way we complete the classification obtained by Eghbali et al., [J. Math. Phys. 51, 073503 (2010); e-print arXiv:0901.4471 [math-ph]]. Then we classify all four and six dimensional Drinfel'd superdoubles.

math-ph↗