arXiv subjects

R. Saadati

Publications and source records attributed to R. Saadati.

5 recordsLinked to original sources

arXiv2024

Dynamics of charged spin-$\frac{1}{2}$ particles in superposed states minimally coupled to electromagnetism in curved spacetime within the WKB approximation

We investigate the curved-spacetime dynamics of charged spin-$\frac{1}{2}$ particles minimally coupled to the electromagnetic field and propagating in superposed states of different masses. For that purpose, we make use of a Wentzel-Kramers-Brillouin approximation of the Dirac equation with a minimal coupling to the Maxwell field in curved spacetime. We obtain the spin dynamics as well as the deviation from geodesic motion of such particles. The problem of having the mass eigenstates experience different proper times, as opposed to the case of neutral particles, is here dealt with by first extracting the second-order differential equation obeyed by each superposition. This strategy proves to be not only powerful, but also very economical.

hep-ph↗

arXiv2024

Curved-spacetime dynamics of spin-$\tfrac{1}{2}$ particles in superposed states from a WKB approximation of the Dirac equation

We investigate the dynamics of spin-$\tfrac{1}{2}$ particles that are freely propagating in superposed states in curved spacetime. We first make use of a Wentzel-Kramers-Brillouin approximation of the Dirac equation in curved spacetime to extract the corresponding Mathisson-Papapetrou-Dixon equations that describe the deviation from geodesic motion as well as the spin precession of such particles. We then discuss, in light of our results, the case of flavour neutrinos which are, by nature, a superposition of mass eigenstates.

hep-ph↗

arXiv2021

Regular Kiselev black hole with a de Sitter core

We present some new aspects of Kiselev black hole and then study the null and timelike thin shell collapse in this spacetime. For the latter, we show that Kiselev black hole can be matched to de Sitter core with a thin timelike dust shell to produce a non-singular black hole space-time. It is argued that for timelike hypersurface, the equation of state parameter must be non-negative. Using Barrabes-Israel junction conditions, the equation of motion of the shell is obtained. The stability of stationary solutions of the shell is discussed and some appropriate ranges for the parameters of shell and Kiselev geometry are found for which a stable stationary black hole is constructed.

gr-qc↗

arXiv2019

Bending of light in the Universe filled with quintessential dark energy

As a local effect of dynamical dark energy, bending of light in the presence of a spherically symmetric and static black hole surrounded by quintessence has been studied. Having in mind recent observational data, we have treated the problem as a deviation from Kottler space-time. This deviation is measured by a perturbation parameter $\varepsilon$ included in the equation of state parameter of quintessence as $ω_q=-1+\frac{1}{3}\varepsilon$. Here, the deflection angle is calculated and then the result is compared with \cite{Arakida:2011th} in the limit $\varepsilon\rightarrow 0$ where the quintessence behaves like the cosmological constant. It is shown that unlike the cosmological constant, the effect of quintessence on the photon energy equation can not be absorbed into the definition of impact parameter. Moreover in this paper, we generalize the Kiselev black hole to the case that there is a modified Chaplygin gas as the dark energy component of the universe and show that the resulted metric can be reduced to the Kiselev metric by adjusting some arbitrary parameters.

gr-qc↗

arXiv2005

Some results in Generalized Šerstnev spaces

In this paper, we show that D-compactness in Generalized Šerstnev spaces implies D-boundedness and as in the classical case, a D-bounded and closed subset of a characteristic Generalized Šerstnev is not D-compact in general. Finally, in the finite dimensional Generalized Šerstnev spaces a subset is D-compact if and only if is D-bounded and closed.

math.GN↗