arXiv subjects

S. A. Kadam

Publications and source records attributed to S. A. Kadam.

At least 19 recordsLinked to original sources

arXiv2026

Bouncing Cosmology and Cosmological Dynamics in $f(Q,T)$ Gravity

We propose a reconstructed cosmological model in the framework of $f(Q,T)$ gravity, that provides a unified description of the early- and late-time evolution of the Universe. The model exhibits a non-singular asymmetric bounce, smoothly connecting an initial contracting phase to the subsequent expanding Universe and naturally evolving into a late-time dark energy-dominated epoch. Our study focuses on the progression of the Hubble parameter, energy density, pressure, and the parameter. This analysis aims to define the various stages of cosmic evolution and explore the characteristics of dark energy. The analysis of energy conditions reveals that the essential conditions for achieving a non-singular bounce are violated. Overall, the $f(Q, T)$ gravity model, once reconstructed, effectively captures the cosmic dynamics surrounding the bounce. It offers a cohesive theoretical framework that reliably explains the Universe's evolution during both its early and late stages.

gr-qc↗

arXiv2026

Probing dark energy dynamics through a new CPL-type $Om(z)$ parametrization in FLRW Universe

In this work, we investigate a CPL-type $Om(z)$ parametrization given by $Om(z)=l+m\left(\frac{z}{1+z}\right)$ to study the evolution of dark energy and possible deviations from the standard $Λ$CDM cosmology. The model reduces to the flat $Λ$CDM scenario for $m=0$, while $m\neq0$ indicates dynamical evolution. The free parameters are constrained using Pantheon+SH0ES (PPS), Cosmic Chronometer (CC), and DESI BAO DR2 observations through Markov Chain Monte Carlo analysis. The obtained constraints yield $72.48\lesssim H_0\lesssim72.97~\mathrm{km\,s^{-1}\,Mpc^{-1}}$, while the evolution parameter remains negative for all dataset combinations, leading to decreasing $Om(z)$ evolution and favoring quintessence-like behaviour. The combined PPS+CC+DR2 analysis shifts the evolution closer to the $Λ$CDM limit. The statistical analysis based on $χ^2$, AIC, and BIC indicates that the proposed model remains statistically competitive with $Λ$CDM. The deceleration parameter and total equation of state are further analyzed to examine the cosmic evolution. The transition from deceleration to acceleration occurs within $z_{tr}\approx0.66-1.01$, while the present values vary within $-0.459\lesssim q_0\lesssim-0.325$ and $-0.639\lesssimω_0\lesssim-0.550$ depending on the datasets. Overall, the proposed parametrization provides a flexible framework for studying late-time cosmic evolution.

physics.gen-ph↗

arXiv2026

Dynamical analysis of the covariant $f(Q)$ gravity models

In this study, we explore the cosmological evolution of the Universe in the framework of covariant $f(Q)$ gravity, with a coupling function that evolves dynamically in proportion to the Hubble parameter. Two specific forms of the function are examined: a power-law model and a logarithmic model. By rewriting the cosmological field equations as an autonomous dynamical system, we determine and classify the corresponding critical points and analyze their stability. Our results show that both models are able to reproduce the sequence of cosmic evolution, including radiation, matter, and dark energy-dominated eras, along with the transitions between them. The physical properties at each critical point are described using key cosmological quantities such as the total EoS parameter, density parameters, and the deceleration parameter. The stability of the non-hyperbolic critical point is analyzed through center manifold theory. In addition, we present phase space trajectories along with the stability behavior of each critical point. The evolution plots for the density parameters of radiation, matter, and dark energy, along with the EoS parameter for the total, are illustrated for further analysis. Overall, the analysis suggests that the $f(Q)$ models considered here, within the context of covariant formulation, provide a consistent description of cosmic evolution and offer a promising approach to explaining the late-time acceleration of the Universe.

gr-qc↗

arXiv2026

Bouncing Cosmological Models and Energy Conditions in $f(Q, L_m)$ gravity

This study explores the bouncing solutions within the framework of modified $f(Q, L_m)$ gravity. We examine four prominent bouncing models, the symmetric bounce, super bounce, oscillatory bounce, and matter bounce, each of which has been extensively analyzed in the context of modified gravity theories. Our investigation focuses on the behavior of the Hubble parameter, the evolution of the scale factor, and the equation of state (EoS) parameters. Notably, the dynamics of the scale factor and Hubble parameter effectively support the bouncing scenario. During the bouncing epoch, the EoS parameters fall within the phantom region, reinforcing the viability of the bounce. To further validate the bouncing scenario, we assess the energy conditions associated with each model. Our findings reveal a violation of the null energy condition at the bouncing epoch, which successfully characterizes the model's bouncing behavior.

gr-qc↗

arXiv2026

Observational tests of \texorpdfstring{$Λ(t)$}{Lambda(t)} cosmology in light of DESI DR2

In this article, we investigate two phenomenological decaying vacuum cosmological models describing the accelerated expansion of the Universe. We constrain the model parameters using a Markov Chain Monte Carlo (MCMC) technique with recent datasets, including cosmic chronometer (CC), Pantheon+SH0ES (PPS), and DESI BAO data release (DR2). Our analysis provides constraints from PPS, PPS+CC, and the joint PPS+CC+DR2 datasets for both models. All datasets favor $H_0 \simeq 72.53$--$73.01~\mathrm{Km\,s^{-1}\,Mpc^{-1}}$, while $Ω_{m0}$ is higher with PPS alone and decreases to standard paradigm estimates with the inclusion of additional data. The evolution parameter is $n \approx 0.30$ from joint analysis, indicating a mild deviation from the $Λ$CDM framework. Furthermore, the physical behavior of the models is examined through the deceleration parameter and the total equation of state, confirming a smooth transition from past deceleration expansion to the present accelerated expansion.

physics.gen-ph↗

arXiv2026

Cosmological Parameters in $f(T)$ Gravity: Theoretical and Observational Analysis

The $f(T)$ gravity is one of the extensions of teleparallel equivalent of general relativity, in which more general functions of the torsion scalar $T$ can be described. With the proposed functional form of $f(T) = αT - βu^{-n} + γu^m$, where $u = (-T/6)$, we have analyzed the cosmological parameters using dynamical system analysis and cosmological datasets. The dynamical behavior of this model is analyzed with phase-space analysis by transforming the cosmological equations into an autonomous system. Critical points are identified, and their stability conditions examined, enabling the classifications of the early and late-time evolutionary phases of the Universe. The stability conditions are further demonstrated by phase-portrait diagrams that highlight transitions between radiation, matter, and dark-energy-dominated epochs. Then we used the Markov Chain Monte Carlo statistical technique to constrain the model parameters with the recent observational dataset, such as DESI DR2 BAO, and its combination with the Hubble and Pantheon+SH0ES data. The best-fit values for the model parameters were obtained by data analysis, $m \equiv 0.91^{+0.07}_{-0.09}$ and $n \equiv 0.69^{+0.09}_{-0.08}$, and are well within the stability range obtained ($m<1\land n>-1$) through dynamical system analysis. The combined theoretical and observational analysis shows that the proposed $f(T)$ gravity model successfully reproduces the observed cosmic expansion history of the Universe.

gr-qc↗

arXiv2026

Cosmological Dynamics of Hyperbolic Evolution Models in $f(Q,L_m)$ Gravity

This paper highlights cosmologically viable sine and cosine hyperbolic evolution functions in the framework of $f(Q,\mathcal{L}_m)$ gravity. The models have been tested to check the behavior of the equation of state (EoS) parameter under the variation of parametric values. The EoS parameter experiences a quintessence phase, and is approaching to $-1$ at late time. The models are showing inclined behaviour with the $Λ$CDM model at the late time. The viability of both the models is retested using the widely accepted energy conditions in both cases. The violation of the strong energy condition admits the accelerating behaviour of the models. The same has been explained through the analysis of the profile of deceleration parameter, which concretely supports the evidence that the models explain early deceleration to late time acceleration phenomena.

gr-qc↗

arXiv2026

Cosmological Dynamics on a Novel $f(Q)$ Gravity Model with Recent DESI DR2 Observation

In this article, we investigate the cosmological viability of a modified symmetric teleparallel gravity model within the $f(Q)$ framework. We derive observational constraints on the model parameters by performing a Markov Chain Monte Carlo analysis using a combined dataset consisting of cosmic chronometers, PantheonPlus SH0ES, and DESI BAO DR2. Our analysis yields the best-fit values for the model parameters $m=-0.386 \pm 0.090$ and $n=-1.055 \pm 0.047$, along with the cosmological parameters at present: $H_0 = 73.19 \pm 0.25$, $q_0 = -0.51 \pm 0.6$, and $ω_{0} = -0.73 \pm 0.3$, at 68\% CL. Furthermore, we examine the physical behavior of the model, focusing on the effective equation of state and deceleration parameter. Our findings indicate that the model experiences a transition from the early deceleration phase to the late-time cosmic acceleration, and the transition occurs at a redshift $z_{tr} = 0.573$. We also analyse the $om(z)$ diagnostic, which reflects a positive slope, supporting the behavior of the equation of state parameter in the quintessence region.

gr-qc↗

arXiv2025

Cosmological Dynamics in $f(R,L_m,T)$ Modified Gravity

In this paper, we investigate the accelerating phase of the Universe within the context of $f(R,L_m,T)$ gravity theory, where $R$, $L_m$, and $T$ represent the Ricci scalar, matter Lagrangian, and the trace of the energy-momentum tensor, respectively. We focus on a particular form of modified gravity defined by $f(R,L_m,T) = R - μL_m T - γ$, with $μ$ and $γ$ being positive constants. The matter sector is characterized by the Lagrangian density $L_m = -ρ$, where $ρ$ denotes the energy density of the cosmological fluid. We conduct an in-depth examination of the model using phase space analysis, thoroughly evaluating the evolution of cosmological solutions with dynamical system techniques. The results is illustrated through graphs in the phase space, the characteristics of critical points and the stable attractors within the proposed modified gravity $f(R,L_m,T)$ cosmological framework. We investigate the transition from the initial decelerating phase of the universe to its current accelerating phase. The behaviour of the EoS, deceleration parameter with the appropriate initial conditions have been investigated.

gr-qc↗

arXiv2025

Bouncing Cosmology in Interacting Scalar-Torsion Gravity

In this study we demonstrate the interacting teleparallel gravity models, to describe the matter bounce scenario. We discussed two interacting models and find both are suitable choice to describe the bouncing phenomena. The co-moving Hubble radius, is demonstrated to check the establishment of the matter bounce scenario. All the energy conditions and the behaviour of EoS parameter is analysed. The violation of NEC at bounce epoch is one of the crucial result to establish bouncing behaviour is found to be obeyed. The other energy conditions behaviour is in agreement with the EoS parameter which lies in the phantom region at the bounce epoch in both the models.

gr-qc↗

arXiv2025

Dynamical Evolution in Generalized Scalar-Torsion Gravity with Extended Couplings

In this study we explore the cosmological behavior of a non-minimally coupled scalar field that is linked to torsion gravity. We demonstrate the Sorkin-Schutz formalism with general power law teleparallel torsion coupling. The autonomous dynamical system has been formulated. The phase space diagrams have been analysed at each critical point. The critical points representing different eras of Universe evolution starting from radiation, dark matter (DM), and dark energy (DE) have been investigated. The scaling attractors with the viable range of model parameters have been obtained using exponential scalar field couplings. This modified version of the formalism describes some novel scaling solutions.

gr-qc↗

arXiv2025

Dynamical and Cosmological Aspects of Teleparallel and Extended Teleparallel Gravity

This thesis investigates modified teleparallel gravity models with a scalar field and teleparallel boundary terms, focusing on their cosmological implications for late-time cosmic acceleration. Teleparallel gravity, is an alternative to General Relativity, explains gravitation through torsion. The study presents the teleparallel analog of the Horndeski theory and its dynamical system approach, analyzing the newly developed $f(T,ϕ)$ gravity model with two potential functions. It examines the phase space, conditions for different cosmological epochs, and the transition from early to late-time cosmic evolution. The inclusion of boundary terms, such as the teleparallel boundary term $B$ and the Gauss-Bonnet term $T_G$, enhances gravitational interactions. The modified teleparallel gravity models, such as $f(T, B)$, $f(T, T_G)$, and $f(T, B, T_G, B_G)$, are explored in terms of their stability and cosmological scenarios, successfully describing the accelerated expansion and late-time attractors. The thesis assesses the impact of a non-canonical scalar field coupled to the boundary term $B$ on the Universe's evolution, comparing findings from Hubble data and Supernovae Ia data. Overall, the analysis suggests that modified teleparallel gravity models effectively explain early to late-time cosmic acceleration, revealing the strong dynamical foundation and offering a versatile framework for addressing challenges in cosmic evolution.

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

Scalar field induced dynamical evolution in teleparallel gravity

In this paper, we investigate the role of scalar field potentials in the dynamical evolution of the Universe. A gravity theory with a non-minimally coupled scalar field with torsion in the geometrical action simulating effective dark energy is considered to study an extended matter bounce scenario. The dynamical behaviour of the equation of state parameter has been studied near the bouncing epoch. Keeping in mind the inflationary behaviour near the bounce, five different scalar field potential functions are explored, and their effect on the equation of state parameter is investigated.

gr-qc↗

arXiv2024

Dynamical System Analysis for Scalar Field Potential in Teleparallel Gravity

In this paper, we have presented a power law cosmological model and its dynamical system analysis in $f(T,ϕ)$ gravity, where $T$ is the torsion scalar and $ϕ$ is the canonical scalar field. The two well-motivated forms of the non-minimal coupling function $F(ϕ)$, the exponential form and the power law form, with exponential potential function, are investigated. The dynamical system analysis is performed by establishing the dimensionless dynamical variables, and the critical points were obtained. The evolution of standard density parameters is analysed for each case. The behaviour of the equation of state (EoS) and deceleration parameter show agreement with the result of cosmological observations. The model parameters are constrained using the existence and the stability conditions of the critical points describing different epochs of the evolution of the Universe.

gr-qc↗

arXiv2024

Constraining $f(T,B,T_G,B_G)$ gravity by dynamical system analysis

The evolutionary behavior of the Universe has been analysed through the dynamical system analysis in $f(T,B,T_G,B_G)$ gravity, where $T$, $B$, $T_G$, and $B_G$ respectively represent torsion, boundary term, teleparallel Gauss-Bonnet term and Gauss-Bonnet boundary term. We use the transformation, $f(T,B,T_G,B_G)=-T+\mathcal{F}(T, B, T_G, B_G)$ in order to obtain the deviation from the Teleparallel Equivalent of General Relativity (TEGR). Two cosmological models pertaining to the functional form of $\mathcal{F}(T, B, T_G, B_G)$ have been studied. The well motivated forms are: (i) $\mathcal{F}(T, B, T_G, B_G) = f_{0} T^{m} B^{n}T_{G}^{k}$ and (ii) $\mathcal{F}(T, B, T_G, B_G)=b_{0} B + g_{0} T_{G}^{k} $. The evolutionary phases of the Universe have been identified through the detailed analysis of the critical points. Further, with the eigenvalues and phase space diagrams, the stability and attractor nature of the accelerating solution have been explored. The evolution plots have been analyzed for the corresponding cosmology and compatibility with the present observed value of standard density parameters have been shown.

gr-qc↗

arXiv2023

Dynamical Complexity in Teleparallel Gauss-Bonnet Gravity

The stable critical points and their corresponding cosmology are derived in the teleparallel gravity with an added Gauss-Bonnet topological invariant term. We have analyzed the dynamics of the Universe by presenting two cosmological viable models, showing the potential to describe different phases of the evolution of the Universe. The value of the deceleration parameter ($q$), total equation of state parameter ($ω_{tot}$) and dark energy equation of state parameter ($ω_{DE}$) have been presented against each critical point. The existence and stability conditions are also presented. We study the behavior of the phase space trajectories at each critical point. Finally, the evolutionary behavior of the deceleration parameter and the equation of state parameters have been assessed with the initial condition of the dynamical variables, and compatibility has been observed in connection with the present cosmological scenario.

gr-qc↗

arXiv2023

Dynamical system analysis in teleparallel gravity with boundary term

In this paper, we perform the dynamical system analysis of the cosmological models framed in the extended teleparallel gravity, the $f (T, B)$ gravity. We use the mapping, $f(T, B)$ $\rightarrow$-$T$+$\tilde{f}(T, B)$, and define the dynamical variables to form the autonomous dynamical system. The critical points are obtained in two well-motivated forms of $f (T, B)$, one that involves the logarithmic form of the boundary term B, and the other one is the non-linear form of the boundary term. The position of critical points is shown in the different evolutionary phases of the Universe such as radiation, matter, and de-Sitter phase. The stability condition of each of the critical points of both the models is derived and the behavior of each point has been obtained mathematically and through the phase portrait. The evolution of standard density parameters such as radiation ($Ω_{r}$), matter ($Ω_{m}$), and dark energy ($Ω_{DE}$) are also analyzed. Further to connect with the present cosmological scenario, the behavior of deceleration and equation of state parameter both in the dark energy phase ($ω_{DE}$) and total ($ω_{tot}$) are shown from the initial condition of the dynamical variables. The accelerating behaviour has been obtained for both models.

gr-qc↗