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M. Alishahiha

Publications and source records attributed to M. Alishahiha.

10 recordsLinked to original sources
arXiv2024

Krylov Complexity in Lifshitz-type Scalar Field Theories

We investigate various aspects of the Lanczos coefficients in a family of free Lifshitz scalar theories, characterized by their integer dynamical exponent, at finite temperature. In this non-relativistic setup, we examine the effects of mass, finite ultraviolet cutoff, and finite lattice spacing on the behavior of the Lanczos coefficients. We also investigate the effect of the dynamical exponent on the asymptotic behavior of the Lanczos coefficients, which show a universal scaling behavior. We carefully examine how these results can affect different measures in Krylov space, including Krylov complexity and entropy. Remarkably, we find that our results are similar to those previously observed in the literature for relativistic theories.

hep-th↗
arXiv2005

Semi-classical Probe Strings on Giant Gravitons Backgrounds

In the first part of this paper we study two $Z_2$ symmetries of the LLM metric, both of which exchange black and white regions. One of them which can be interpreted as the particle-hole symmetry is the symmetry of the whole supergravity solution while the second one is just the symmetry of the metric and changes the sign of the fivefrom flux. In the second part of the paper we use closed string probes and their semi-classical analysis to compare the two 1/2 BPS deformations of $AdS_5\times S^5$, the smooth LLM geometry which contains localized giant gravitons and the superstar case which is a solution with naked singularity corresponding to smeared giants. We discuss the realization of the $Z_2$ symmetry in the semi-classical closed string probes point of view.

hep-th↗
arXiv2000

On Type II NS5-branes in the presence of an RR field

In this letter we use Type II NS5-branes in the presence of an RR field at the decoupling limit to study a non-commutative version of little string theory. We shall see that the decoupling limit of NS5-branes in the presence of an RR field is completely different from the one we had in ordinary little string theory; in particular for Type IIA NS5-branes this decoupling limit can be defined only when the theory is wrapped on a circle, but nevertheless flows to the ordinary non-compact (0,2) theory at the IR limit. We also see that these theories, in the UV regime, where the non-commutative effects are important, can be described by smeared ordinary D3(D2)-branes in Type IIB(A) string theory.

hep-th↗
arXiv1998

On the Brane Configuration of $N=(4,4)$ 2D supersymmetric gauge theory

We study two dimensional $N=(4,4)$ supersymmetric gauge theories with various gauge groups and various hypermultiplets in the fundamental as well as bi-fundamental and adjoint representations. They have " mirror theories " which become equivalent to them at the strong coupling. The theory with one fundamental and one adjoint has a Higgs branch which is parametrized by the adjoint matter. We also consider theories which involve an orientifold plane. The brane realization of the Matrix theory formulation of NS 5-branes in Type II string theories is also considered.

hep-th↗
arXiv1997

N=(4,4) 2D Supersymmetric Gauge Theory and Brane Configuration

We construct type II A brane configuration of N=(4,4) supersymmetric two dimensional gauge theory with gauge group U(1) and N_f hypermultiplets in the fundamental representation. By lifting to M-theory (strong coupling), we can see the origin of the R-symmetry enhancement of the Coulomb branch. One can also find two theories which become equivalent at strong coupling.

hep-th↗
arXiv1996

On the Picard-Fuchs equations of the SW models

We obtain the closed form of the Picard-Fuchs equations for $N=2$ supersymmetric Yang-Mills theories with classical Lie gauge groups. For a gauge group of rank $r$, there are $r-1$ regular and an exceptional differential equations. We describe the series solutions of the Picard-Fuchs equations in the semi-classical regime.

hep-th↗
arXiv1996

The Moduli Space of the $N=2$ Supersymmetric $G_{2}$ Yang-Mills Theory

We present the hyper-elliptic curve describing the moduli space of the N=2 supersymmetric Yang-Mills theory with the $G_2$ gauge group. The exact monodromies and the dyon spectrum of the theory are determined. It is verified that the recently proposed solitonic equation is also satisfied by our solution.

hep-th↗
arXiv1996

Non-Commutative Geometry and Chiral Perturbation Lagrangian

Chiral perturbation lagrangian in the framework of non-commutative geometry is considered in full detail. It is found that the explicit symmetry breaking terms appear and some relations between the coupling constants of the theory come out naturally. The WZW term also turns up on the same footing as the other terms of the chiral lagrangian.

hep-th↗
arXiv1995

Generalization of the $h$-Deformation to Higher Dimensions

In this article we construct $GL_{h}(3)$ from $GL_{q}(3)$ by a singular map. We show that there exist two singular maps which map $GL_{q}(3)$ to new quantum groups. We also construct their $R$-matrices and will show although the maps are singular but their $R$-matrices are not. Then we generalize these singular maps to the case $GL(N)$ and for $C_{n}$ series.

q-alg↗