arXiv subjects

Pradosh Keshav MV

Publications and source records attributed to Pradosh Keshav MV.

7 recordsLinked to original sources

arXiv2026

Can Stochastic Clocks in FLRW Minisuperspace Prevent Dynamical Singularities?

We develop a stochastic extension of the Wheeler--DeWitt equation in FLRW minisuperspace and show that quantum backreaction can dynamically regulate the big bang singularity without imposing external boundary conditions. Using Laplace--Beltrami quantisation and an open-system treatment of coarse-grained graviton modes, we obtain a stochastic Hamiltonian evolution equation in which the diffusion coefficient takes the form $σ(a)\propto a^2$. This multiplicative noise vanishes at the origin and renders $a=0$ an entrance boundary in Feller's classification, leading to super-exponential suppression of the Laplace--Beltrami weighted stationary density and zero probability flux into the singular point. At large scale factor, the global behaviour depends on the cosmological sector: de Sitter and positive potential-dominated regimes exhibit power-law stationary tails, whereas confining potentials or negative effective cosmological constant lead to an entrance boundary at infinity and a globally normalizable steady state. Taken together, these results indicate that stochastic backreaction arising from semiclassical coarse-graining provides a consistent and dynamical mechanism for singularity avoidance in minisuperspace quantum cosmology.

gr-qc↗

arXiv2026

Universality Classes of Interacting Dark Energy from Spontaneous Symmetry Breaking

Phenomenological models of interacting dark energy (IDE) often treat the late-time activation history of the dark sector coupling as an independent function. We show that in conformally coupled scalar--tensor theories, this freedom is constrained by the local restoring structure of the symmetry-breaking potential. Within the adiabatic tracking regime, the coupling evolution satisfies $n=3/p$, where $p$ is the restoring order near the broken minimum thereby organizing distinct symmetry-breaking potentials such as quartic, Coleman--Weinberg, and axion-like forms into a common asymptotic dynamical class ($p=1$, $n=3$). We test this framework using Planck~2018 CMB lensing, RSD, and supernova data. Current observations provide only limited discrimination between the predicted activation classes and yield no statistically significant evidence for a nonzero interaction with $|β_0|\lesssim0.26$ at $95%$ credibility. The rigid asymptotic implementation ($n=3$) is strongly disfavored by the combined geometric and growth constraints indicating that the observable coupling history cannot be identified directly with its asymptotic attractor form. In the heavy-scalar adiabatic regime, the modifications to the growth rate $f(z)$ and growth factor $D(z)$ are of opposite sign throughout $0\le z\le2$, suppressing the net deviation in $fσ_8(z)$ to $Δfσ_8/fσ_8\lesssim0.3%$ across the posterior. Standard growth-rate measurements therefore have limited sensitivity to this class of models, shifting the observational focus toward probes that constrain $f(z)$ and $D(z)$ independently. Taken together, these results establish a dynamical classification of late-time IDE activation histories and clarify how finite-redshift observables are related to the asymptotic attractor structure and the local restoring properties of the underlying scalar potential.

astro-ph.CO↗

arXiv2025

Relational Time as a Stochastic Variable in ADM Gravity

The problem of time in canonical quantum gravity remains one of the most significant challenges, primarily due to the "frozen" formalism emerging from the Wheeler-DeWitt equation. Within the ADM formalism, we introduce a novel approach in which a scalar field is treated as a stochastic clock. By imposing a divergence-free condition on the scalar momentum, we integrate out quantum gravitational fluctuations and derive an effective noise term via the Hubbard-Stratonovich transformation. This noise drives dynamic adjustments in spacetime foliations, enabling a Schrodinger-like evolution that preserves diffeomorphism invariance and, upon noise averaging, maintains unitary evolution. Interestingly, by introducing stochastic variations in the foliations, the quantum indeterminacy of the clock recasts time as a diffusive process emerging from quantum fluctuations, where correlations between matter and geometry replace an absolute time parameter. This provides a potential pathway for understanding quantum time evolution while maintaining background independence in canonical quantum gravity.

gr-qc↗

arXiv2025

Spontaneous Symmetry Breaking as a Late-Time Trigger for Interacting Dark Energy

Persistent tensions in the Hubble constant (H0) and the matter clustering parameter (S8) motivate late-time new physics that suppresses structure growth without significantly altering the background expansion history of the LambdaCDM model. We study a class of dark-sector dynamics in which a scalar dark energy field, governed by a Z2-symmetric quartic potential, interacts with dark matter through Yukawa and portal couplings. When the matter density drops below a critical threshold, a cosmological spontaneous symmetry breaking mechanism generates a time-dependent vacuum expectation value v(a) and activates an effective coupling eta(a). This creates a symmetric phase (a <= ac) identical to LambdaCDM at early times, and a broken phase (a > ac) in which eta(a) > 0 transfers energy from dark matter to dark energy, suppressing linear structure growth. Using RSD, BAO, cosmic chronometers, Pantheon+SH0ES supernovae, and compressed Planck distance priors, we compare a fixed LambdaCDM background with a self-consistent coupled-scalar evolution. The RSD-only analysis shows a strong shift: the dynamical background gives Omega_m ~ 0.31 +/- 0.10 and sigma8,0 ~ 0.59 +/- 0.01, while the fixed-background case gives Omega_m ~ 0.20 +/- 0.09 and sigma8,0 ~ 0.75 +/- 0.05. In the full joint fit, we obtain Omega_m = 0.29 +/- 0.01, H0 = 69.7 +/- 0.6 km s^-1 Mpc^-1, and sigma8,0 = 0.78 +/- 0.01. A late-time interaction triggered by spontaneous symmetry breaking can therefore damp structure growth and ease the S8 tension while leaving the expansion history and the inferred H0 essentially unchanged, suggesting distinct physical origins for the two tensions.

astro-ph.CO↗

arXiv2025

Conformal Invariance and Phase Transitions: Implications for Stable Black Hole Horizons?

The behavior of black hole horizons under extreme conditions-such as near collapse or phase transitions-remains less understood, particularly in the context of soft hair and Aretakis instabilities. We show that the breakdown of conformal symmetry during the balding phase induces a topological reorganization of the horizon, leading to divergent entropy corrections and emergent pressure terms. These corrections exhibit universal scaling laws, analogous to quantum phase transitions in condensed matter systems, with extremal limits functioning as quantum critical points. Interestingly, by employing quasi-equilibrium boundary conditions, one could stabilize horizon dynamics without explicitly introducing ad hoc higher-order corrections, further limiting the universal applicability of conformal invariance in black hole physics.

gr-qc↗

arXiv2024

Interacting Dark Energy and Its Implications for Unified Dark Sector

Alternative dark energy models were proposed to address the limitation of the standard concordance model. Though different phenomenological considerations of such models are widely studied, scenarios where they interact with each other remain unexplored. In this context, we study interacting dark energy scenarios (IDEs), incorporating alternative dark energy models. The three models that are considered in this study are time-varying Λ, Generalized Chaplygin Gas (GCG), and K-essence. Each model includes an interaction rate Γto quantify energy density transfer between dark energy and matter. Among them, GCG coupled with an interaction term shows promising agreement with the observed TT power spectrum, particularly for l < 70, when Γfalls within a specific range. The K-essence model (Γ<= 0.1) is more sensitive to Γdue to its non-canonical kinetic term, while GCG (Γ>= 1.02) and the time-varying Λ(Γ<= 0.01) models are less sensitive, as they involve different parameterizations. We then derive a general condition when the non-canonical scalar field ϕ (with a kinetic term Xn) interacts with GCG. This has not been investigated in general form before. We find that current observational constraints on IDEs suggest a unified scalar field with a balanced regime, where it mimics quintessence behavior at n < 1 and phantom behavior at n > 1. We outline a strong need to consider alternative explanations and fewer parameter dependencies while addressing potential interactions in the dark sector.

gr-qc↗

arXiv2021

On the dynamics between gravity and entanglement

Recent developments on Bell's experiments demonstrate that entanglement could indeed eliminate the gap between classical and quantum physics. At the same time, it is difficult for a classical theory to include a particular feature like entanglement without compromising the theory's smooth working on a four-dimensional scale geometry. A unified theory should reconsider this difficulty. On the other hand, pregeometry hold the assumption of a non-commutative space where the Requardt-Roy model seems to be a promising one. From the ordinary five-dimensional approach first initiated by Kaluza-Klein, a toy model is proposed to show the insignificant description of gravity at Planck's scale physics. It is found that the classical nature of quantum correlations are fine tuned within the geometry of space-time at four dimensions. Such a nature can be better understood by studying the pregeometric effects of gravity at five-dimensions. A combined description of gravity and entanglement is found sufficient to explain the fundamental difficulties of discrete space-time manifolds in both the theories.

physics.gen-ph↗