arXiv subjects

Moncy Vilavinal John

Publications and source records attributed to Moncy Vilavinal John.

3 recordsLinked to original sources

arXiv2026

On the reality of quantum states: A pedagogic survey from classical to quantum mechanics

Some recent experiments claim to show that any model in which a quantum state represents mere information about an underlying physical reality of the system must make predictions which contradict those of quantum theory. The present work undertakes to investigate the issue of reality, treading a more fundamental route from the Hamilton-Jacobi equation of classical mechanics to the Schrodinger equation of quantum mechanics. Motivation for this is a similar approach from the eikonal equation in geometrical optics to the wave equation in electromagnetic theory. We rewrite the classical Hamilton-Jacobi equation as a wave equation and seek to generalise de Broglie's wave particle duality by demanding that both particle and light waves have the freedom of being described by any square-integrable function. This generalisation, which allows superposition also for matter wave functions, helps us to obtain the Schrodinger equation, whose solution can be seen to be as much objective as the classical mechanics wave function. Several other equations which one writes in quantum mechanics, including the eigenvalue equations for observables, series expansion of energy states in terms of eigenstates of observables other than energy, etc., can be written in the classical case too. Absence of any collapse of the wave function, entanglement, etc. in the classical realm have their origin in the nonlinearity of the classical wave equation. These considerations indicate that many of the puzzles in quantum mechanics are present also in classical mechanics in a dormant form, which fact shall help to demystify quantum mechanics to a great extent.

quant-ph↗

arXiv2024

Evolution of Hubble parameter from Pantheon+ data and comparison of cosmological models using cosmic chronometers

The evolution of the Hubble parameter $H(z)$ with redshift $z$ is estimated from the Pantheon+ data of Type Ia supernovae, for the $Λ$CDM model and the three special cases of the eternal coasting (EC) cosmological model with three different spatial geometries. The scatter associated with $H(z)$ is seen to grow markedly with redshift. This behaviour, which is deduced directly from the SNe Hubble diagram, raises the question of whether the universe is undergoing a stochastic expansion, which scenario can offer an explanation for the Hubble tension in cosmology. From the estimated $H(z)$ values, the present value of the Hubble parameter $H_0$ is evaluated for each of these models through regression, and the scatter using the Monte Carlo method. Bayesian comparison between these models is carried out using the data of 35 cosmic chronometers (CC). The comparative study favours the $Λ$CDM model, with some strong evidence. However, exclusion of four outlier CC data points with small errorbars leads to large reduction in the Bayes factor value. The unusually large value of Bayes factor obtained while using the full set of CC data raises some concerns about its tension with other data, such as that of the SNe Ia. While using the remaining 31 CC data points, it is observed that the resulting Bayes factor still favours the $Λ$CDM model, but with a much smaller value of the Bayes factor. When EC models are compared among themselves, the $Ω= 2$ model has strong evidence than the $Ω= 1$ (also known as $R_h = ct$) and the $Ω= 0$ (Milne-type) models.

astro-ph.CO↗

arXiv2021

Bouncing and coasting universe with exact quantum-classical correspondence

When the scale factor of expansion of the universe is written as $ a(t)\equiv Ae^{α(t)}$, with $A$ as some real constant and $α(t)$ a real function, the gravitational action $I_G$ appears in the same form as the matter action $I_M$ for a homogeneous and isotropic scalar field with a specific scale factor-dependent potential. We observe that by making analytic continuation of the Lagrangian function in this $I_G$ to the complex plane of $α$, one can obtain terms corresponding to both parts of a total action that describes a viable cosmological model. The solution gives a bouncing and coasting universe, which first contracts and then expands linearly, with a smooth bounce in between them. Such a bounce, called a Tolman wormhole, is due to a Casimir-like negative energy that appears naturally in the solution. In a novel approach to quantum cosmology, we perform canonical quantization of the above model using the operator method and show that it can circumvent the operator ordering ambiguity in the conventional formalism. It leads to a quantum wave equation for the universe, solving which we get the interesting result that the universe is in a ground state with nonzero energy. This solution is different from the Wheeler-DeWitt wave function and possesses exact quantum-classical correspondence during all epochs.

gr-qc↗