arXiv subjects

Soudabe Nasirimoghadam

Publications and source records attributed to Soudabe Nasirimoghadam.

7 recordsLinked to original sources

arXiv2026

Wormholes in $f(Q,T)$ gravity with different matter Lagrangian density

This study explores asymptotically flat wormhole solutions in $f(Q,T)=αQ+ βT$ gravity, expanding upon our prior work (arXiv:2602.00527v1) with matter Lagrangian density, $L_m=-P$ . Here, we examine the implications of employing $Lm=-T$ and $L_m=ρ$. The field equations, derived via action variation, share a common general structure but are fundamentally dictated by the parameters $α$ and $β$ through the coefficients $A_i$. Solutions with linear and asymptotically linear equation of state are explored. We conclude that non-exotic asymptotically flat wormhole solutions exist for all considered matter Lagrangian densities. A key outcome is the demonstration that different $L_m$ choices enable the same shape function to be supported by varied fluid configurations, or vice versa, identical fluids to yield different geometries. The energy conditions and physical characteristics of these solutions are shown to be distinct and critically dependent on the selected $L_m$.

gr-qc↗

arXiv2026

Non-exotic asymptotically flat wormholes in $f(Q,T)$ gravity

In this study, we investigate the possible existence of static and spherically symmetric wormhole solutions within the context of the newly formulated extended $f(Q,T)$ gravity. We analyze a linear model, $f(Q,T)=αQ+ βT$, and focus on traversable wormholes. By applying the variational method, we derive modified versions of the field equations that are influenced by an anisotropic matter source for a zero redshift function. It has been observed that the violation of energy conditions is influenced by the parameters $α$ and $β$. We reach the conclusion that solutions which violate the radial and lateral null energy condition in the context of general relativity may still adhere to the energy conditions within the realm of $f(Q,T)$ gravity. To begin with, by utilizing a linear equation of state for radial pressure, we obtain a power-law shape function. Additionally, we investigate solutions defined by a variable equation of state parameter. A broad spectrum of non-exotic wormhole solutions has been identified, contingent upon the particular parameters of the model.

gr-qc↗

arXiv2023

Nonlinear Yang-Mills black holes

This paper is devoted to investigating the nonlinear non-abelian Yang-Mills black holes. We consider three Born-Infeld, exponential, and logarithmic nonlinear Yang-Mills theories with $SO(n-1)$ and $SO(n-2,1)$ semi-simple groups, which n is the dimension of spacetime, and obtain a new class of nonlinear Yang-Mills (NYM) black hole solutions. Depending on the values of dimension $n$, Yang-Mills charge $e$ and the mass $m$ and nonlinear parameters $β$, our solutions can lead to a naked singularity, a black hole with two horizons, an extreme or a Schwarzschild-type black hole. We also investigate the thermodynamic behaviors of the NYM black holes. For small charge values, the NYM solutions may be thermally stable in the canonical ensemble, if we consider an AdS spacetime with spherical $k=+1$ and hyperbolic $k=-1$ coordinates or a flat one with $k=+1$. However, there are no stable regions in the grand canonical ensemble in higher dimensions. For the NYM black hole, we observe a reentrant phase transition between large and small black holes in the BI-branch with small $β$, which cannot be visible for the nonlinear Reissner-Nordstrom AdS black hole in the higher dimension. For the limit $β\rightarrow\infty$, the critical ratio $\frac{P_{c} v_{c}}{T_{c}}$ tends to the constant value $3/8$ for each dimension $n$, while it depends on the dimension for the case of nonlinear electrodynamics black holes.

gr-qc↗

arXiv2022

Capillary-driven biaxial planar and homeotropic nematization of hard cylinders

We use the Parsons Lee modification of Onsagers second virial theory within the restricted orientation approximation to analyse the phase behaviour of hard cylindrical rods confined in narrow pores Depending on the wall to wall separation we predict a number of distinctly different surface generated nematic phases including a biaxial planar nematic with variable number of layers a monolayer homeotropic and a hybrid T type structure For narrow pores we find evidence of two types of second order uniaxial biaxial transitions depending on the aspect ratio of the particles More specifically we observe a continuous cross over from n to layers each with a distinct planar anchoring symmetry as well as first order transitions from planar to homeotropic surface anchoring Contrary to the previously studied case of parallelepipeds we find that the surface anchoring transition from planar to homeotropic symmetry occurs at much lower overall rod packing fractions

cond-mat.soft↗

arXiv2021

Lifshitz and hyperscaling violated Yang-Mills-dilaton black holes

We obtain two types of Yang-Mills-dilaton black hole solutions in both Lifshitz and hyperscaling violation spacetimes. We must consider at least three Yang-Mills gauge fields that interact with a scalar field and either $SO(n)$ or $SO(n-1,1)$ gauge symmetry groups, where $n+1$ denotes the dimension of the spacetime. They lead to the spherical and hyperbolic solutions. The obtained solutions in the hyperscaling violation spacetime fall into two categories for $z\neq n-3-\frac{n-5}{n-1}θ$ and $z= n-3-\frac{n-5}{n-1}θ$, where $θ=0$ represents the Lifshitz spacetime. In order to have a real asymptotic behavior for the hyperscaling violated black hole solutions, we should consider a negative value for the hyperscaling violation parameter as $θ<0$. We also evaluate the thermodynamic quantities of the mentioned black holes and probe their thermal stability in the grand canonical ensemble. For $z\geq2$, the hyperscaling violated solutions are not thermally stable for $z\leq n-3-\frac{n-5}{n-1}θ$, while they are stable for large $r_{+}$ with $z>n-3-\frac{n-5}{n-1}θ$. We also check out the critical behavior of the obtained black holes and obtain a Smarr relation for the solutions. The results also announce of a first-order small-large phase transition for both black holes in the case $T>T_{C}$.

hep-th↗

arXiv2017

Behavior of light polarization in photon-scalar interaction

Quantum theories of gravity help us to improve our insight into the gravitational interactions. Motivated by the interesting effect of gravity on the photon trajectory, we treat a quantum recipe concluding a classical interaction of light and a massive object such as the sun. We use the linear quantum gravity to compute the classical potential of a photon interacting with a massive scalar. The leading terms have a traditional $1/r$ subordinate and demonstrate a polarization-dependent behavior. This result challenges the equivalence principle; attractive and/or repulsive interactions are admissible.

hep-th↗

arXiv2016

Shear viscosity of p-wave superfluid Fermi gas with weak interaction at low temperatures

The shear viscosity tensor of the superfluid Fermi gas in p-wave state with weak interaction is calculated at low temperatures, by using the Boltzmann equation approach. We consider the transition probabilities for the binary, decay and coalescence processes. We show that only the binary processes are dominated at low temperatures and the components of shear viscosity η_xy, η_xx, η_yy are proportional to (1/T)^2, and η_xz, η_yz and η_zz are proportional to (1/T)^4 and (1/T)^6, respectively.

cond-mat.quant-gas↗