arXiv subjects

Mohd Shahalam

Publications and source records attributed to Mohd Shahalam.

3 recordsLinked to original sources

arXiv2026

Classical and Loop Quantum Cosmology of Interacting Dark Energy: A Dynamical System Analysis with Superfluid Dark Matter and Dust Matter

We study the cosmological dynamics of interacting dark energy and dark matter in Classical Einstein Gravity and Loop Quantum Cosmology. Two dark matter scenarios are considered: superfluid dark matter described by a generalized cubic equation of state and the standard pressureless fluid. The dark energy component is modeled using both a generalized nonlinear equation of state and a constant equation of state. We examine two phenomenological interaction terms, $Q=α\dotρ_m$ and $Q=β\dotρ_d$, which govern the energy transfer between the dark sectors. In classical gravity, the pressureless matter model exhibits stable late-time attractors, whereas the superfluid dark matter model admits only saddle and non-hyperbolic critical points. Extending the analysis to Loop Quantum Cosmology, quantum geometric corrections replace the Big Bang singularity with a nonsingular quantum bounce, and significantly modify the phase-space dynamics. As a result, the stable attractors of the classical pressureless matter model disappear, and all interacting models possess only saddle and non-hyperbolic critical points. These findings highlight the significant influence of both dark matter properties and quantum gravitational effects on the asymptotic evolution of interacting dark-sectors.

gr-qc↗

arXiv2026

Nonminimally Coupled Quintessence with Double Exponential Potential: Observational Evidence Against Big Crunch Singularity

We investigate a class of scalar field dark energy models non-minimally coupled to gravity, characterized by a double exponential potential and parameterized coupling $ξ$. We study the cosmological dynamics for a recently proposed descending dark energy model, namely, Q-SC-CDM. Initially, we choose distinct values of coupling parameter. For some values of $ξ$, the evolution of the universe is split up into three different phases: {\it decelerated expansion (early time), accelerated expansion (late-time) and slow-contraction (future era)}, and provide Big Crunch Singularity at distant future. In other scenario, the phase of slow-contraction vanishes, cosmic acceleration is obtained at current epoch, and the universe gets de-Sitter expansion at distant future. We confront the model with various datasets, including Cosmic Chronometers, Type Ia Supernovae (Pantheon+, DES, and Union 3), and Baryon Acoustic Oscillation measurements from DESI. Our analysis reveals that observational constraints naturally favor regions of parameter space in which the model avoids future singularities and slow-contraction phases, even for relatively small values of $ξ\simeq 0.12$. The preferred solutions yield values of $Ω_{m}$, $H_0$, and $r_d$ that are consistent with those of $Λ$CDM at the $68\%$ confidence level. In contrast, the models with fixed couplings $ξ=0.3$ and $ξ=0.5$, which predict $H_0>70$ km/s/Mpc, are strongly disfavored relative to $Λ$CDM by the current datasets. Finally, the phase-space analysis confirms that the observationally constrained model with $ξ\simeq 0.12$ evolves toward a stable de Sitter attractor.

gr-qc↗

arXiv2026

Galileon versus Quintessence: A comparative phase space analysis and late-time cosmic relevance

We perform a comparative phase space analysis of the light mass Galileon model and standard Quintessence in the context of late--time cosmic acceleration. Focusing on a spatially flat FLRW background, we consider a cubic Galileon interaction supplemented by a scalar potential and examine three representative choices of the potential: a generalized cosh potential, a simple cosh potential, and a linear potential. By introducing suitable dimensionless variables, the cosmological field equations are reformulated as an autonomous dynamical system, allowing a systematic investigation of the stationary points and their stability properties. For the light mass Galileon scenario, we find that although the phase space admits scalar field dominated solutions, all critical points are of saddle type for the potentials considered. In particular, no stable late-time accelerating attractor emerges, even in the presence of de-Sitter like configurations. In contrast, the Quintessence limit admits stable de-Sitter attractors for cosh potentials, providing a viable description of the observed late--time acceleration. Our results highlight a key qualitative distinction between Galileon and Quintessence cosmologies and indicate that, within the light mass Galileon framework, the higher-order Galileon interactions may be required to realize a stable accelerating Universe.

gr-qc↗