arXiv subjects

Sara Rastgoo

Publications and source records attributed to Sara Rastgoo.

12 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

Wormhole Geometries in Extended Symmetric Teleparallel Gravity with $f(Q, T) = αQ + βT + γT^2$

In this study, we study static and spherically-symmetric wormhole configurations within the recently proposed class of extended symmetric teleparallel gravities characterised by the functional form $f(Q,T)=αQ+βT+γT^{2}$, where $Q$ is the non-metricity scalar, $T$ is the trace of the energy-momentum tensor, and ($α,β,γ$) are constant coupling parameters. By varying the action with respect to the metric, we derive the modified field equations and cast them in an effective Einstein-like form containing additional geometric contributions that depend on $Q$ and $T$. We conclude that the $f(Q,T)=αQ+βT+γT^{2}$ framework offers a viable arena for constructing physically realistic wormholes without invoking severe energy condition violations, opening new pathways for connecting modified gravity phenomenology with astrophysical signatures of non-trivial spacetime topologies.

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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.

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arXiv2025

Non-exotic wormholes in $f(R,L_m)$ gravity

In the present analysis, we examine the potential existence of generalized wormhole models within the framework of newly developed extended $f(R,L_m)$ gravity. We investigate both a linear model, $f(R,L_m)=αR+βL_m$, and a non-linear model, $f(R,L_m)=\frac{R}{2}+ L^α_m$, to analyze traversable wormholes. By employing the variational approach, we derive modified versions of the field equations under the influence of an anisotropic matter source. A power-law shape function is applied, resulting in a linear equation of state for both radial and lateral pressures. Furthermore, we explore solutions characterized by a variable equation of state parameter. It was observed that the violation of energy conditions is influenced by the parameters $α$ and $β$. A wide range of non-exotic wormhole solutions was discovered, dependent on the specific parameters of the model. We demonstrate that wormholes with power-law shape functions yield solutions that comply with the energy conditions in both linear and non-linear forms of $f(R, L_m)$. It is shown that the non-exotic wormhole solutions obtained within this framework are not isotropic.

gr-qc↗

arXiv2025

Wormholes in $f(T,\mathcal{T})$ gravity

This study aims to investigate the physical properties of wormhole geometry within the context of $f(T,\mathcal{T})$ gravity, which serves as a teleparallel formulation of general relativity. We study a linear model, $f(T,\mathcal{T})=αT+β\mathcal{T}$, to explore traversable wormholes. A linear equation of state is utilized for radial pressure, leading to a power-law shaped function. It was found that the violation of energy conditions, depends on the $α$ and $β$ parameters. A diverse array of intriguing wormhole solutions was identified, contingent upon the specific model parameters employed. It is demonstrated that isotropic wormhole solutions cannot be attained within this framework. Additionally, solutions characterized by a variable equation of state parameter are introduced. A comparative analysis of wormhole solutions in the context of $f(T,\mathcal{T})$ and curvature-based gravity, specifically $f(R,T)$, is also provided.

gr-qc↗

arXiv2024

Wormholes in $f(R,T)=R+λT+λ_1 T^2$ gravity

This study explores asymptotically flat wormhole solutions within the framework of $f(R,T)$ gravity. We analyze $f(R,T)$ expressed as $f(R,T)=R+λT+λ_1 T^2$. A linear equation of state is employed for both radial and lateral pressures, resulting in a power-law shape function. The investigation encompasses solutions characterized by both negative and positive energy densities. It has been determined that solutions with positive energy density comply with all energy conditions, specifically the null, weak, strong, and dominant energy conditions. Additionally, we identify constraints on the parameters $λ$, $λ_1$, and the parameters associated with the equation of state and shape function.

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arXiv2024

Wormholes in $f(R,T)$ gravity with variable equation of state

In this work, we introduce a novel set of asymptotically flat wormhole solutions within the framework of $f(R,T)$ theory of gravity. Considering a linear $f(R,T)=R+ 2λT$ form, we show that a wide variety of wormhole solutions with asymptotically linear equation of state exist. Our solutions satisfy all the energy conditions, namely the null, weak, strong and dominant energy conditions. The relationship between free parameters in the shape function and boundary conditions is analyzed.

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arXiv2024

Traversable wormholes satisfying energy conditions in $f(Q)$ gravity

In this article, a new family of asymptotically flat wormhole solutions in the context of symmetric teleparallel gravity, i.e., $f(Q)$ theory of gravity, are presented. Considering a power-law shape function and some different forms for $f(Q)$ function, we show that a wide variety of wormhole solutions for which the matter fields satisfy some energy conditions, are accessible. We explore that the presence of $f(Q)$ gravity will be enough to sustain a traversable wormhole without exotic matter. The influence of free parameters in shape function and $f(Q)$ models on the energy conditions is investigated. The equation of state and boundary conditions are analyzed.

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arXiv2022

Wormhole in $f(Q)$ gravity

In this paper, exact asymptotically flat wormhole solutions in the context of symmetric teleparallel gravity, i.e., $f(Q)$ theory of gravity, are investigated. Since modified theories of gravity provide new field equations, we have analyzed some possible wormhole solutions by using modified field equations. Four different forms of the $f(Q)$ function are considered then the shape function is calculated with some different equations of state. Also we have used a power-law shape function with these models, which lead to an asymptotically barotropic equation of state. Some physical and mathematical properties of the solutions, like energy conditions and boundary conditions, are addressed .

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arXiv2021

Wormhole in f(R) gravity revisited

In this paper, exact wormhole solutions in the context of $f(R)$ theory of gravity are investigated. Since the Einstein field equations are modified in 3+1 dimensions in the $f(R)$ theory of gravity, we have studied some possible solutions with different forms of shape function and $f(R)$ function. We show that choosing $f(R)$ or metric functions arbitrarily may lead to a conflict for wormhole solutions. Some previous solutions are discussed which verify the contradiction throughout the equations. We conclude that wormhole solutions in the context of $f(R)$ gravity should be revisited.

gr-qc↗

arXiv2020

Wormhole solutions with a polynomial equation-of-state and minimal violation of the null energy condition

This paper discusses wormholes supported by general equation-of-state , resulting in a significant combination of the linear equation-of-state and some other models. Wormhole with a quadratic equation-of-state is studied as a particular example. It is shown that the violation of null energy condition is restricted to some regions in the vicinity of the throat. The combination of barotropic and polytropic equation-of-state has been studied. We consider fluid near the wormhole throat in an exotic regime which at some $r=r_{1}$, the exotic regime is connected to a distribution of asymptotically dark energy regime with $-1<ω<-1/3$. We have presented wormhole solutions with small amount of exotic matter. We have shown that using different forms of equation-of-state has a considerable effect on the minimizing violation of the null energy condition. The effect of many parameters such as redshift as detected by a distant observer and energy density at the throat on the $r_1$ is investigated. The solutions are asymptotically flat and compatible with presently available observational data at the large cosmic scale.

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arXiv2019

Asymptotically flat wormhole solutions with variable equation-of-state parameter

In this paper, we study exact wormhole solutions in the framework of general relativity with a general equation of state that reduced to a linear equation of state asymptotically. By considering a special shape function, we find classes of solutions which are asymptotically flat. We study the violation of NEC as the main ingredient in the wormhole physics. We investigate the possibility of finding wormhole solutions with asymptotically different state parameter. We show that in principle, wormhole with vanishing redshift function and the selected shape function, cannot satisfy NEC at large infinity. We present solutions which have the positive total amount of mater in the "volume integral quantifier" method. For this class of solutions, fluid near the wormhole throat is in the phantom regime and at some $r=r_{2}$, the phantom regime is connected to a dark energy regime. Thus, we need small amount of exotic matter to construct wormhole solutions.

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