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H. Amiri

Publications and source records attributed to H. Amiri.

4 recordsLinked to original sources
arXiv2024

Quantum cosmology in teleparallel gravity with a boundary term

We quantize a homogeneous and isotropic universe for two models of modified teleparallel gravity, wherein an arbitrary function of the boundary term, namely $B$, is present in the action and in the other model a scalar field that is non-minimally coupled to both the torsion and boundary term. In this regard, we study exact solutions of both the classical and quantum frameworks by utilizing the corresponding Wheeler-DeWitt (WDW) equations of the models. To correspond to the comprehensive classical and quantum levels, in the second model, we propose an appropriate initial condition for the wave packets and observe that they closely adhere to the classical trajectories and reach their peak. We quantify this correspondence using the de-Broglie Bohm interpretation of quantum mechanics. According to this proposal, the classical and Bohmian trajectories coincide when the quantum potential vanishes along the Bohmian paths. Furthermore, we apply the de-parameterization technique to our model in the realm of the problem of time in quantum cosmological models based on the WDW equation, utilizing the global internal time denoted as $χ$, which represents a scalar field.

gr-qc↗
arXiv2011

A 5D noncompact Kaluza -Klein cosmology in the presence of Null perfect fluid

For the description of the early inflation, and acceleration expansion of the Universe, compatible with observational data, the 5D noncompact Kaluza--Klein cosmology is investigated. It is proposed that the 5D space is filled with a null perfect fluid, resulting a perfect fluid in 4D universe, plus one along the fifth dimension. By analyzing the reduced field equations for flat FRW model, we show the early inflationary behavior and current acceleration of the universe.

gr-qc↗
arXiv2007

Relations between positive definite functions and irreducible representations on a locally compact groupoid

If $G$ is a locally compact groupoid with a Haar system $λ$, then a positive definite function $p$ on $G$ has a form $p(x)=< L(x)ξ(d(x)),ξ(r(x))>$, where $L$ is a representation of $G$ on a Hilbert bundle ${\h}=(G^0,\{H_u\},μ)$, $μ$ is a quasi invariant measure on $G^0$ and $ξ\in L^{\infty}(G^0,{\h})$. [10]. In this paper firt we prove that if $μ$ is a quasi invariant ergodic measure on $G^0$, then two corresponding representations of $G$ and $C_c(G)$ are irreducible in the same time. Then by using the theory of positive linear functionals on $C^*(G)$ we show that when $μ$ is an ergodic quasi invariant measure on $G^0$, for a positive definite function $p$ which is an extreme point of ${\mP}^μ_1(G)$ the corresponding representation $L$ is irreducible and conversely, every irreducible representation $L$ of $G$ on a Hilbert bundle ${\h}=(G^0,\{H_u\},μ)$ and every section $ξ\in {\h}(μ)$ with norm one, define an extreme point of ${\mP}^μ_1(G)$.

math.OA↗