arXiv subjects

L. K. Duchaniya

Publications and source records attributed to L. K. Duchaniya.

11 recordsLinked to original sources

arXiv2026

Quintessence model in the late Universe

Scalar fields have shown great potential in inducing tailored modifications compared to cosmic evolution in the $Λ$CDM model. We investigate a quintessence model with five physically motivated scalar field potentials: the general power-law, quadratic, fifth-power, hyperbolic sinh, and axion-like potentials. The model parameters are constrained by using the late-time cosmological observations, including Cosmic Chronometers (CC), Pantheon$^{+}$, BAO, and DESI DR2 data. To assess the influence of the local distance-ladder calibration, we additionally perform a separate analysis using the Pantheon$^{+}$\& SH0ES compilation. Our analysis shows that the inclusion of the SH0ES calibration systematically shifts the inferred Hubble constant toward higher values, whereas the addition of BAO and DESI DR2 data prefers comparatively lower values and significantly reduces parameter degeneracies. We center the action of these models in the late Universe which leaves early $Λ$CDM cosmology unchanged. Across all five potentials, an inverse correlation between $H_0$ and $Ω_{m0}$ is consistently observed, indicating that higher values of the Hubble constant are associated with a lower present-day matter density and a stronger contribution from dark energy to the current accelerated expansion.

gr-qc↗

arXiv2025

Late-time acceleration and structure formation in interacting $α$-attractor dark energy models

We investigate the cosmological dynamics of interacting dark energy within the framework of $α$-attractor models. Specifically, we analyze the associated autonomous system, focusing on its fixed points that represent dark energy and scaling solutions, along with their stability conditions. We employ center manifold theory to address cases where some fixed points display eigenvalues with zero and negative real parts. The model reveals attractors describing dark energy, enabling a smooth transition from the radiation-dominated era to the matter-dominated era, and ultimately into the dark-energy-dominated phase. Additionally, we identify a scaling matter solution capable of modifying the growth rate of matter perturbations during the matter-dominated epoch. Consequently, we study the evolution of matter perturbations by obtaining both analytical and numerical solutions to the density contrast evolution equation. Based on these results, we compute numerical solutions for the weighted growth rate $fσ_{8}$, indicating that interacting $α$-attractor dark energy models may provide a better fit to structure formation data than the standard $Λ$CDM scenario.

gr-qc↗

arXiv2025

Late Time Phenomena in $f(T,\mathcal{T})$ Gravity Framework: Role of $H_0$ Priors

This study explored the behavior of the $f(T, \mathcal{T})$ cosmological model with the use of various data set combinations. We also compared the results for this model between the Pantheon+ (without SH0ES) and the Pantheon+\&SH0ES (with SH0ES) data sets. Additionally, we incorporated data from BAO along with $H_0$ priors. We observed that integrating SH0ES data points leads to a higher estimation of $H_0$ than Pantheon+ (without SH0ES). We perform an extensive MCMC analysis for each combination of data sets, providing constraints on the model parameters. We also computed the $χ^2_{min}$ value for each combination of data sets to evaluate the chosen model against the standard $Λ$CDM model. Our primary finding is that the various dataset combinations in the $f(T, \mathcal{T})$ model we examined relate to a range of Hubble constants, which could contribute to reducing the cosmic tension associated with this parameter. Additionally, we investigate the evolution of matter fluctuations by solving the density contrast evolution equation numerically. We calculate numerical solutions for the weighted growth rate $fσ_8$ using these findings. We plotted the cosmological background parameters to check the behavior of the $f(T, \mathcal{T})$ model in late-time. Based on the behavior of these background cosmological parameters, we conclude that our selected models reflect the late-time cosmic dynamics of the Universe.

gr-qc↗

arXiv2025

The scalar-torsion gravity corrections in the first-order inflationary models

The corrections to the cosmological models induced by non-minimal coupling between scalar field and torsion are considered. To determine these corrections in explicit form, the power-law parametrization of these corrections are proposed. The estimates of possible influence of non-minimal coupling between scalar field and torsion on cosmological parameters for inflationary models implying linear relation between tensor-to-scalar ratio and spectral index of scalar perturbations are obtained. A procedure for verifying these inflationary models due to the observational constraints on the values of cosmological perturbation parameters is also considered.

gr-qc↗

arXiv2024

Dynamical system analysis in modified Galileon cosmology

In this paper, we have investigated the phase space analysis in modified Galileon cosmology, where the Galileon term is considered a coupled scalar field, $F(ϕ)$. We focus on the exponential type function of $F(ϕ)$ and the three well-motivated potential functions $V(ϕ)$. We obtain the critical points of the autonomous system, along with their stability conditions and cosmological properties. The critical points of the autonomous system describe different phases of the Universe. In the results of our analysis, we have found the scaling solution for critical points, which determine different evolutionary eras for the Universe. The dark-energy-dominated critical points show stable behavior and indicate the Universe's late-time cosmic acceleration phase. Further, the results are examined with the cosmological data sets of the Hubble rate $H(z)$ and the Supernovae Ia.

gr-qc↗

arXiv2024

Teleparallel Gravity and Quintessence: The Role of Nonminimal Boundary Couplings

In this paper, we have outlined the development of an autonomous dynamical system within a general scalar-tensor gravity framework. This framework encompasses the overall structure of the non-minimally coupled scalar field functions for both the torsion scalar ($T$) and the boundary term ($B$). We have examined three well-motivated forms of potential functions and constrained the model parameters through dynamical system analysis. This analysis has played a crucial role in identifying cosmologically viable models. We have analysed the behaviour of dynamical parameters such as equation-of-state parameters for dark energy and the total, as well as all the standard density parameters for radiation, matter, and dark energy to assess their compatibility with current observational data. The phase space diagrams are presented to support the stability conditions of the corresponding critical points. The Universe is apparent in its late-time cosmic acceleration phase via the dark energy-dominated critical points. Additionally, we compare our findings with the most prevailing $Λ$CDM model. The outcomes are further inspected using the cosmological data sets of Supernovae Ia and the Hubble rate H(z).

gr-qc↗

arXiv2024

Attractor behaviour of $f(T)$ modified gravity and the cosmic acceleration

In this paper, we have performed the dynamical system analysis of $f(T)$ gravity cosmological models at both background and perturbation levels. We have presented three models pertaining to three distinct functional forms of $f(T)$. The first form is that of the logarithmic form of the torsion scalar $T$, the second one is in the power law form, and the third one is the combination of the first two forms. For all these three forms of $f(T)$, we have derived the corresponding cosmological parameters in terms of the dynamical variables. Subsequently, the critical points are obtained and the condition(s) of its existence has been derived. Critical points of each model have been analysed individually and the corresponding cosmology are derived. The stability behaviour of these critical points are discussed from the behaviour of the eigenvalues and the phase portraits. At least one stable node has been obtained in each of these models. Further from the evolution plots of the cosmological parameters, the accelerating behaviour of the cosmological models are also verified.

gr-qc↗

arXiv2023

Cosmological models in $f (T, \mathcal{T})$ gravity and the dynamical system analysis

The study addresses matter-coupled modified gravity, particularly $f (T, \mathcal{T})$ gravity, unveiling distinct formalism. The research further discusses stability analysis, and the dynamical system approach, exploring the dynamics of critical points to understand these models' viability better. The dynamical system analysis of the cosmological models in $f(T, \mathcal{T})$ gravity, where $T$ and $\mathcal{T}$ respectively represent the torsion scalar and trace of the energy-momentum tensor has been investigated. It demonstrates how first-order autonomous systems can be treated as cosmological equations and analyzed using standard dynamical system theory techniques. Two forms of the function $f(T,\mathcal{T})$ are considered (i) one with the product of trace and higher order torsion scalar and the other (ii) linear combination of linear trace and squared torsion. By employing this methodology, the research aims to uncover the actual behavior of the Universe. The findings emphasize the graphical representation of these insights, enriching our understanding of cosmological scenarios.

gr-qc↗

arXiv2023

Noether Symmetry Approach in Scalar-Torsion $f(T,ϕ)$ Gravity

The Noether Symmetry approach is applied to study an extended teleparallel $f(T,ϕ)$ gravity that contains the torsion scalar $T$ and the scalar field $ϕ$ in the context of an Friedmann-Lemaître-Robertson-Walker space-time. We investigate the Noether symmetry approach in $f(T,ϕ)$ gravity formalism with the specific form of $f(T,ϕ)$ and analyze how to demonstrate a nontrivial Noether vector. The Noether symmetry method is a helpful resource for generating models and finding out the exact solution of the Lagrangian. In this article, we go through how the Noether symmetry approach enables us to define the form of the function $f(T,ϕ)$ and obtain exact cosmological solutions. We also find the analytical cosmological solutions to the field equations, that is consistent with the Noether symmetry. Our results demonstrate that the obtained solutions enable an accelerated expansion of the Universe. We have also obtained the present value of the Hubble parameter, deceleration parameter, and effective equation of state parameter, which is fit in the range of current cosmological observations.

gr-qc↗

arXiv2023

Dynamical systems analysis in $f(T,ϕ)$ gravity

Teleparallel based cosmological models provide a description of gravity in which torsion is the mediator of gravitation. Several extensions have been made within the so-called Teleparallel equivalent of general relativity which is equivalent to general relativity at the level of the equations of motion where attempts are made to study the extensions of this form of gravity and to describe more general functions of the torsion scalar $T$. One of these extensions is $f(T,ϕ)$ gravity; $T$ and $ϕ$ respectively denote the torsion scalar and scalar field. In this work, the dynamical system analysis has been performed for this class of theories to obtain the cosmological behaviour of a number of models. Two models are presented here with some functional form of the torsion scalar and the critical points are obtained. For each critical point, the stability behaviour and the corresponding cosmology are shown. Through the graphical representation the equation of state parameter and the density parameters for matter-dominated, radiation-dominated and dark energy phase are also presented for both the models.

gr-qc↗

arXiv2022

Dynamical Stability Analysis of Accelerating f(T) Gravity Models

In this paper, we have emphasized the stability analysis of the accelerating cosmological models obtained in $f(T)$ gravity theory. The behavior of the models based on the evolution of the equation of state parameter shows phantom-like behavior at the present epoch. The scalar perturbation technique is used to create the perturbed evolution equations, and the stability of the models has been demonstrated. Also, we have performed the dynamical system analysis for both the models. In the two specific $f(T)$ gravity models, three critical points are obtained in each model. In each model, at least one critical point has been observed to be stable.

gr-qc↗