arXiv subjects

Qi-Qi Fan

Publications and source records attributed to Qi-Qi Fan.

7 recordsLinked to original sources

arXiv2024

A Study of Decay Rate of Bound Negative Muons

A number of experiments show that the decay lifetimes of muons bound to atomic nuclei are longer than the decay lifetimes of free muons. In this paper, a scheme of extending quantum mechanics (EQM) is proposed to resolve this problem. The Schr$\ddot{\text{o}}$dinger's equation is obtained to prove the validation of this attempt. The decay ratio of bound muons is also calculated in EQM, and the result is in good agreement with the experimental data.

hep-ph↗

arXiv2020

Shadows of rotating Hayward-de Sitter black holes with astrometric observables

Motivated by recent work on rotating black hole shadow [Phys. Rev. D101, 084029 (2020)], we investigate the shadow behaviors of rotating Hayward-de Sitter black hole for static observers at a finite distance in terms of astronomical observables. This paper uses the newly introduced distortion parameter in [arXiv:2006.00685] to describe the shadow's shape quantitatively. We show that the spin parameter would distort shadows and the magnetic monopole charge would increase the degree of deformation. At the same time, the distortion could be relieved because of the cosmological constant and the distortion would increase with the distance from the black hole. Besides, the spin parameter, magnetic monopole charge and cosmological constant increase will cause the shadow to shrink.

gr-qc↗

arXiv2020

The cosmological constant from space-time discreteness

We regard the background of space-time as a physical system composed of discrete volume elements at the Planck scale and get the internal energy of space-time by Debye model. A temperature-dependent minimum energy limit of the particles is proposed from the thermal motion part of the internal energy. As decreases of the temperature caused by the expansion of the universe, more and more particles would be"released" because of the change of the energy limit, we regard these new particles as a source of dark energy. The minimum energy limit also leads to a corrected number of particles in universe and a modified conservation equation. According to the modified conservation equation, an effective cosmological constant consistent with its observed value is obtained.

gr-qc↗

arXiv2020

Optical properties of a Brane-World black hole as photons couple to the Weyl tensor

In this article, we have investigated the equations of motion of the photons coupled to Weyl tensor by the geometric optics approximation and the corresponding shadow in a Brane-World black hole spacetime. It is shown that there exists a double shadow for a black hole since the coupling photons with different polarization directions propagate along different paths in the spacetime. Furthermore, we discuss the effects of the metric parameter $α$ related to the cosmological constant, X-cold dark matter parameter $β$ and the coupling parameter $λ$ on the umbra (the overlap region of the double shadow) and the penumbra. We also obtain the finite-distance corrections to the deflection angle of light in the Brane-World black hole spacetime as the photons coupled to Weyl tensor by using a recent geometric method.

gr-qc↗

arXiv2019

The Varying Speed of Light in Eddington-inspired Born-Infield Gravity with Rainbow Metric

In this paper, we proposed that at each point of spacetime, in addition to the Riemannian metric tensor which describes the geometry of spacetime and the gravitational field, there is an rainbow metric tensor which shows the geometry of spacetime depends on the energy of the test particle. Because Eddington-inspired Born-Infield(EiBI) gravity can be seen as a special bi-metric gravity, we research a varying speed of light theory for a bi-metric gravity corresponding to EiBI gravity. For FRW universe, we find the energy of test particle will increase with rising energy density of universe. We also research the varying speed of light for three different kinds of rainbow functions and find the sign of parameter $κ$ would influence the trend of spend of light.

gr-qc↗

arXiv2019

Apparent horizon and gravitational thermodynamics of Universe in the Eddington-Born-Infeld theory

The thermodynamics of Universe in the Eddington-Born-Infeld (EBI) theory was restudied by utilizing the holographic-style gravitational equations that dominate the dynamics of the cosmical apparent horizon $Υ_{A}$ and the evolution of Universe. We started in rewriting the EBI action of the Palatini approach into the Bigravity-type action with an extra metric $q_{μν}$. With the help of the holographic-style dynamical equations, we discussed the property of the cosmical apparent horizon $Υ_{A}$ including timelike, spacelike and null characters, which depends on the value of the parameter of state $w_{m}$ in EBI Universe. The unified first law for the gravitational thermodynamics and the total energy differential for the open system enveloped by $Υ_{A}$ in EBI Universe were obtained. Finally, applying the positive-heat-out sign convention, we derived the generalized second law of gravitational thermodynamics in EBI universe.

gr-qc↗

arXiv2018

The evolution of universe in the two-scalar theory

We generalize f(R,T) gravity into the two-scalar theory that includes two independent scalar fields by the variational method, and we derive its field equations in Einstein frame using conformal transformation. Based on Friedmann equations and Raychaudhuri equation, with a consideration of the cosmic content as its perfect-fluid form, a further discussion leads us to an accelerated expanding condition of universe. In the two-scalar theory, universe has two states which are the accelerated expansion and decelerated contraction, and it has three stages during its evolution. The first and third stages are in the accelerated expanding state, and the second stage is in the decelerated contracting state. The third stage represents the present universe and it tends to become a dust universe.

gr-qc↗