arXiv subjects

S. Abarghouei Nejad

Publications and source records attributed to S. Abarghouei Nejad.

3 recordsLinked to original sources

arXiv2025

De Sitter-Invariant Black Holes

In the de Sitter-invariant approach to gravitation, all solutions to the gravitational field equations are spacetimes that reduce locally to de Sitter. Consequently, besides including an event horizon, the de Sitter-invariant black hole also has a cosmic horizon. Accordingly, it can lodge ordinary and dark energies. Owing to this additional structure concerning Poincaré-invariant general relativity, such a black hole can establish a link between the black hole dynamics and the universe's evolution. Possible implications for cosmology are discussed, and a comparison with recent observations indicating the existence of a cosmological coupling of black holes is presented.

gr-qc↗

arXiv2021

On the Hydrogen Atom in the Holographic Universe

We investigate the holographic bound utilizing a homogeneous, isotropic, and non-relativistic neutral hydrogen gas present in the de Sitter space. Concretely, we propose to employ de Sitter holography intertwined with quantum deformation of the hydrogen atom using the framework of quantum groups. Particularly, the $\mathcal U_q(so(4))$ quantum algebra is used to construct a finite-dimensional Hilbert space of the hydrogen atom. As a consequence of the quantum deformation of the hydrogen atom, we demonstrate that the Rydberg constant is dependent on the de Sitter radius, $L_Λ$. This feature is then extended to obtain a finite-dimensional Hilbert space for the full set of all hydrogen atoms in the de Sitter universe. We then show that the dimension of the latter Hilbert space satisfies the holographic bound. We further show that the mass of a hydrogen atom $m_\text{atom}$, the total number of hydrogen atoms at the universe, $N$, and the retrieved dimension of the Hilbert space of neutral hydrogen gas, $\text{Dim}{\mathcal H}_\text{bulk}$, are related to the de Sitter entropy, $S_\text{dS}$, the Planck mass, $m_\text{Planck}$, the electron mass, $m_\text{e}$, and the proton mass $m_\text{p}$, by $m_\text{atom}\simeq m_\text{Planck}S_\text{dS}^{-\frac{1}{6}}$, $N\simeq S_\text{dS}^\frac{2}{3}$ and $\text{Dim}{\mathcal H}_\text{bulk}=2^{\frac{m_\text{e}}{m_\text{p}}α^2S_\text{dS}}$, respectively.

gr-qc↗

arXiv2020

Classical Universe Arising from Quantum Cosmology

In this paper, we study the classical limit and unitary evolution of quantum cosmology by applying the Weyl--Wigner--Groenewold--Moyal formalism of deformation quantization to quantum cosmology of a homogeneous and isotropic universe with positive spatial curvature and conformally coupled scalar field. The corresponding quantum cosmology (similar to the Schrödinger interpretation in canonical quantization scheme of quantum cosmology) is described by the Moyal--Wheeler--DeWitt equation which has an exact solution in Moyal phase space, resulting in Wigner quasiprobability distribution function, peaking over the classical solutions. We show that for a large value of the quantum number $n$, the emerged classical universe is filled with radiation with quantum mechanical origin. Also, we introduce a canonical transformation on the scalar field sector of the model such that the conjugate momenta of the new canonical variable appear linearly in the transformed total Hamiltonian. Using this canonical transformation, we show that, it may lead to disentangle the time from the true dynamical variables. We obtain the time-dependent Wigner function for a coherent as well as for squeezed states. We show that the peak of these Wigner functions follows the classical trajectory in the phase space.

gr-qc↗