arXiv subjects

H. Mohammadzadeh

Publications and source records attributed to H. Mohammadzadeh.

11 recordsLinked to original sources

arXiv2026

Foundations of Many-Body Theory of Quantum Unified Statistics: Green functions and Linear Response Theory

We develop a comprehensive many-body theory for systems of particles obeying quantum unified statistics, or quons. After exploring the properties of the Fock space of this system, we formulate a systematic S-matrix expansion and a generalized Wick's theorem. A consistent Green-function formalism is constructed at both zero and finite temperatures, accompanied by a generalized Wick's theorem appropriate for infinite-statistics operator algebras. Within this framework, we establish diagrammatic rules for interacting quon systems. Employing the random phase approximation, we derive the dielectric function and reveal the emergence of anomalous plasmon modes that have no direct counterpart in conventional Bose or Fermi systems. We further analyze the ground-state energy, energy-loss function, generalized Thomas-Fermi screening wave vectors, and Friedel oscillations, elucidating how infinite statistics qualitatively modifies collective behavior and screening properties.

cond-mat.stat-mech↗

arXiv2022

Manifestly $SL(2,R)$ Duality-Symmetric Forms in ModMax Theory

In this paper, we will investigate a manifestly $SL(2,R)$-invariant structure for the energy-momentum tensor of ModMax theory as a nonlinear modification of Maxwell electrodynamics which includes conformal invariance as well. In the context of this theory, we show that the energy-momentum tensor of the generalized Born-Infeld theory can also be written in the same invariant form. We will find manifestly self-dual invariant actions corresponding to the invariant couplings $λ$ and $γ$ in these theories. It can be shown that the resultant actions correspond to the irrelevant and marginal $T\bar{T}$-like deformations, respectively.

hep-th↗

arXiv2022

Emergence of non-linear electrodynamic theories from $T\bar{T}$-like deformations

In this letter, we investigate the deformation of the ModMax theory, as a unique Lagrangian of non-linear electrodynamics preserving both conformal and electromagnetic-duality invariance, under $T\bar{T}$-like flows. We will show that the deformed theory is the generalized non-linear Born-Infeld electrodynamics. Being inspired by the invariance under the flow equation for Born-Infeld theories, we propose another $T\bar{T}$-like operator generating the ModMax and generalized Born-Infeld non-linear electrodynamic theories from the usual Maxwell and Born-Infeld theories, respectively.

hep-th↗

arXiv2022

Complexity growth in Gubser-Rocha models with momentum relaxation

The Einstein-Maxwell-Axion-Dilaton (EMAD) theories, based on the Gubser-Rocha (GR) model, are very interesting in holographic calculations of strongly correlated systems in the condensed matter physics. Due to the presence of spatially dependent massless axionic scalar fields, the momentum is relaxed and we have no translational invariance at finite charge density. It would be of interest to study some aspects of quantum information theory for such systems in the context of $AdS/CFT$ where EMAD theory is a holographic dual theory. For instance, in this paper we investigate the complexity and its time dependence for charged $AdS$ black holes of EMAD theories in diverse dimensions via the complexity equals action (CA) conjecture. We will show that the growth rate of the holographic complexity violates the Lloyd's bound at finite times. However, as shown at late times, it depends on the strength of momentum relaxation and saturates the bound for these black holes.

hep-th↗

arXiv2021

Holographic complexity for black branes with momentum relaxation

We employ the "complexity equals action" conjecture to investigate the action growth rate for the charged and neutral AdS black branes of a holographic toy model consisting of Einstein-Maxwell theory in $d + 1$-dimensional bulk spacetime with $d - 1$ massless scalar fields which is called Einstein-Maxwell-Axion (EMA) theory. From the holographic point of view, the scalar fields source a spatially dependent field theory with momentum relaxation on the boundary, which is dual to the homogeneous and isotropic black branes. We find that the growth rate of the holographic complexity within the Wheeler-DeWitt (WDW) patch saturates the corresponding Lloyd's bound at the late time limit. Especially for the neutral AdS black branes, it will be shown that the complexity growth rate at late time vanishes for a particular value of relaxation parameter $β_{max}$ where the temperature of the black hole is minimal. Then, we investigate the transport properties of the holographic dual theory in the minimum temperature. A non-linear contribution of the axion field kinetic term in the context of k-essence model in the four-dimensional spacetime is considered as well. We also study the time evolution of the holographic complexity for the dyonic AdS black branes in this model.

hep-th↗

arXiv2021

$T\bar{T}$-like Flows in Non-linear Electrodynamic Theories and S-duality

We investigate the $T\bar{T}$-like flows for non-linear electrodynamic theories in $D(=\!\!2n)$-dimensional spacetime. Our analysis is restricted to the deformation problem of the classical free action by employing the proposed $T\bar{T}$ operator from a simple integration technique. We show that this flow equation is compatible with $T\bar{T}$ deformation of a scalar field theory in $D\!=\!2$ and of a non-linear Born-Infeld type theory in $D\!=\!4$ dimensions. However, our computation discloses that this kind of $T\bar{T}$ flow in higher dimensions is essentially different from deformation that has been derived from the AdS/CFT interpretations. Indeed, the gravity that may be exist as a holographic dual theory of this kind of effective Born-Infeld action is not necessarily an AdS space. As an illustrative investigation in $D\!=\!4$, we shall also show that our construction for the $T\bar{T}$ operator preserves the original $SL(2,R)$ symmetry of a non-supersymmetric Born-Infeld theory, as well as $\mathcal{N}=2$ supersymmetric model. It is shown that the corresponding $SL(2,R)$ invariant action fixes the relationship between the $T\bar{T}$ operator and quadratic form of the energy-momentum tensor in $D\!=\!4$.

hep-th↗

arXiv2020

Two temperature Ising Model

We introduce a two-temperature Ising model as a prototype of superstatistic critical phenomena. The model is described by two temperatures ($T_1,T_2$) in zero magnetic field. To predict the phase diagram and numerically estimate the exponents, we develop Metropolis and Swendsen-Wang Monte Carlo method. We observe that there is a non-trivial critical line, separating ordered and disordered phases. We propose an analytic equation for the critical line in the phase diagram. Our numerical estimation of the critical exponents illustrates that all points on the critical line belong to the ordinary Ising universality class.

cond-mat.stat-mech↗

arXiv2020

Effects of high intensity Lasers on the Entanglement fidelity of quantum plasmas

The dynamics of entanglement during the low energy scattering processes in bipartite systems at the presence of a laser field is studied, using the Kramers-Henneberger unitary transformation as the semi classical counterpart of the Block-Nordsieck transformation, in the quantizied field formalism. The Stationary-state Schrodinger equation for quantum scattering process is obtained for such systems. Then, by using partial wave analysis, we introduce new form of entanglement fidelity containing high intense laser field. Therefore, the effective potential of hot quantum plasmas including plasmon and quantum screening effect is used to show entanglement fidelity ratio as a function of the laser amplitude, plasmon parameter and the Debye length parameter for elastic electron-ion collisions. It is shown that the amplitude of laser beam or free electron oscillation play important roles in the evolution of entanglement of the system.

physics.plasm-ph↗

arXiv2018

Gaussian Free Field in the iso-height random islands tuned by percolation model

The Gaussian free field (GFF) is considered in the background of random iso-height islands which is modeled by the site percolation with the occupation probability $p$. To realize GFF, we consider the Poisson equation in the presence of normal distributed white-noise charges, as the stationary state of the Edwards-Wilkinson (EW) model. The iso-potential (metallic in the terminology of the electrostatic problem) sites are chosen over the lattice according to the percolation problem, giving rise to some metallic islands and some active (not metallic, nor surrounded by a metallic island) area. We see that the dilution of the system by incorporating metallic particles (or equivalently considering the iso-height islands) annihilates the spatial correlations and also the potential fluctuations. Some local and global critical exponents of the problem are reported in this work. The GFF, when simulated on the active area show a cross over between two regimes: small (UV) and large (IR) scales. Importantly, by analyzing the change of exponents (in and out of the critical occupation $p_c$) under changing the system size and the change of the cross-over points, we find two fixed points and propose that GFF$_{p=p_c}$ is unstable towards GFF$_{p=1}$.

cond-mat.stat-mech↗

arXiv2018

Gaussian Free Field in the background of correlated random clusters, formed by metallic nanoparticles

The effect of metallic nano-particles (MNPs) on the electrostatic potential of a disordered 2D dielectric media is considered. The disorder in the media is assumed to be white-noise Coulomb impurities with normal distribution. To realize the correlations between the MNPs we have used the Ising model with an artificial temperature $T$ that controls the number of MNPs as well as their correlations. In the $T\rightarrow 0$ limit, one retrieves the Gaussian free field (GFF), and in the finite temperature the problem is equivalent to a GFF in iso-potential islands. The problem is argued to be equivalent to a scale-invariant random surface with some critical exponents which vary with $T$ and correspondingly are correlation-dependent. Two type of observables have been considered: local and global quantities. We have observed that the MNPs soften the random potential and reduce its statistical fluctuations. This softening is observed in the local as well as the geometrical quantities. The correlation function of the electrostatic and its total variance are observed to be logarithmic just like the GFF, i.e. the roughness exponent remains zero for all temperatures, whereas the proportionality constants scale with $T-T_c$. The fractal dimension of iso-potential lines ($D_f$), the exponent of the distribution function of the gyration radius ($τ_r$), and the loop lengths ($τ_l$), and also the exponent of the loop Green function $x_l$ change in terms of $T-T_c$ in a power-law fashion, with some critical exponents reported in the text. Importantly we have observed that $D_f(T)-D_f(T_c)\sim\frac{1}{\sqrt{ξ(T)}}$, in which $ξ(T)$ is the spin correlation length in the Ising model.

cond-mat.stat-mech↗

arXiv2018

Self-Avoiding Walk on the square site-diluted Ising-correlated lattice

The self-avoiding walk on the square site-diluted correlated percolation lattice is considered. The Ising model is employed to realize the spatial correlations of the metric space. As a well-accepted result, the (generalized) Flory's mean field relation is tested to measure the effect of correlation. After exploring a perturbative Fokker-Planck-like equation, we apply an enriched Rosenbluth Monte Carlo method to study the problem. To be more precise, the winding angel analysis is also performed from which the diffusivity parameter of Schramm-Loewner evolution (SLE) theory ($κ$) is extracted. We find that at the critical Ising (host) system the exponents are in agreement with the Flory's approximation. For the off-critical Ising system we find also a new behavior for the fractal dimension of the walker trace in terms of the correlation length of the Ising system $ξ(T)$, i.e. $D_F^{\text{SAW}}(T)-D_F^{\text{SAW}}(T_c)\sim \frac{1}{\sqrt{ξ(T)}}$.

cond-mat.stat-mech↗