Greybody factor for black string in dRGT massive gravity

The greybody factor from the black string in the de Rham-Gabadadze-Tolley (dRGT) massive gravity theory is investigated in this study. The dRGT massive gravity theory is one of the modified gravity theories used in explaining the current acceleration in the expansion of the universe. By using cylindrical symmetry, black strings in dRGT massive gravity are shown to exist. When quantum effects are taken into account, black strings can emit thermal radiation called Hawking radiation. The Hawking radiation at spatial infinity differs from that at the source by the so-called greybody factor. In this paper, we examined the rigorous bounds on the greybody factors from the dRGT black strings. The results show that the greybody factor crucially depends on the shape of the potential characterized by model parameters. The results agree with ones in quantum mechanics, the higher the potential, the harder it is for the waves to penetrate and also lower the bound for the rigorous bounds.Comment: 18 pages, 12 figures; V2 accepted to EPJC, minor change, two column 11 pages, 12 figure

{\AE}ther Field, Casimir Energy and Stabilization of The Extra Dimension

In our five-dimensional cosmological model, we investigate the role of a Lorentz violating vector "{\ae}ther" field on the moduli stabilization mechanism. We consider the case of a space-like {\ae}ther field on a compact circle with Maxwell-type kinetic term. The Casimir energy of certain combinations of massless and massive bulk fields generates a stabilizing potential for the radius of the compact direction while driving the accelerated expansion in the non-compact directions. It is shown that the {\ae}ther field can reduce the influence of the Casimir force and slow down the oscillation of the radion field. This property proves crucial to the stability of the extra dimension in the universe where non-relativistic matter is present. We speculate that this scenario might reveal a hidden connection between the dimensionality of spacetime and the spontaneous breaking of Lorentz symmetry.Comment: 19 pages, 5 figures, added references and comments from refere

Casimir dark energy, stabilization of the extra dimensions and Gauss–Bonnet term

A Casimir dark energy model in a five-dimensional and a six-dimensional spacetime including non-relativistic matter and a Gauss–Bonnet term is investigated. The Casimir energy can play the role of dark energy to drive the late-time acceleration of the universe while the radius of the extra dimensions can be stabilized. The qualitative analysis in four-dimensional spacetime shows that the contribution from the Gauss–Bonnet term will effectively slow down the radion field at the matter-dominated or radiation-dominated epochs so that it does not pass the point at which the minimum of the potential will arise before the minimum has formed. The field then is trapped at the minimum of the potential after the formation leading to the stabilization of the extra dimensions