Modern Physics Letters A

We review some of the most striking properties of the phase diagrams of higher dimensional black holes in pure gravity. We focus on static black hole solutions with Kaluza–Klein asymptotics and stationary black hole solutions in flat Minkowski space. Both cases exhibit a rich pattern of interconnected phases and merger points with topology changing transitions. In the first case, the phase diagram includes uniform and non-uniform black strings, localized black holes and sequences of Kaluza–Klein bubbles. In the latter case, it includes Myers–Perry black holes, black rings, black saturns and pinched black holes.

The unparticle field operator can be expanded in terms of creation and destruction operators corresponding to particles with a continuous mass spectrum. Hence, when the four-momentum of an unparticle is measured, then the unparticle manifests as an ordinary particle with a definite (but arbitrary) mass.

We obtained the spectrum of probability of the bremsstrahlung emission accompanying the α-decay of ²²⁶Ra(E_α = 4.8 MeV) by measuring the α-γ coincidences and using the model presented in our previous study on the α-decay of ²¹⁴Po(E_α = 7.7 MeV). We compare the experimental data with the quantum mechanical calculation and find a good agreement between theory and experiment. We discuss the differences between the photon spectra connected with the α-decay of the ²²⁶Ra and ²¹⁴Po nuclei. For the two mentioned nuclei, we analyze the bremsstrahlung emission contributions from the tunneling and external regions of the nucleus barrier into the total spectrum, and we find the destructive interference between these contributions. We also find that the emission of photons during tunneling of the α-particle gives an important contribution to the bremsstrahlung spectrum in the whole E_γ energy range of the studied ²²⁶Ra nucleus.

Previously, we have shown that the Kasner solution

In the past few years, a possibility is investigated, where curvature itself behaves as a source of dark energy. So, it is natural to think whether curvature can produce dark matter too. It is found that, at classical level, higher-derivative gravity yields curvature inspired particles namely riccions.³¹ Here, it is probed whether riccion can be a possible source of dark matter. Further, it is found that the late universe accelerates. Here, it is interesting to see that acceleration is obtained from curvature without using any dark energy source of exotic matter.

In this paper we propose a specific modification for Friedmann equation which leads during the matter-dominated era to a Cardassian type model, with the usual two undetermined parameters but with an important difference however, the usual parameter B which is constant in the Cardassian model becomes a function of time in this model. We found that although the model leads to acceleration at recent epoch. The acceleration values are more moderate than in the usual Cardassian model because B(t) is a reducing function of time. The model further leads to an increase in the abundance of light element during nucleosynthesis. We use the difference between the predicted and measured values of big bang nucleosynthesis of helium to obtain a value for n and B(t).

The shear viscosity of quark–gluon plasma (QGP) at leading logarithm order at finite temperature and chemical potential in weakly coupled limit is studied by solving transport equations. The result shows that the chemical potential effect adds a positive μ²/T² correction to the pure temperature case and thus increases the shear viscosity.