Modern Physics Letters A

Can we try to say what an electron (or a quark, gluon or photon) is, as opposed to just describing its properties. String theory can address that question.

This work deals with a detailed study of the dynamics of the apparent, event and particle horizons in the background of the inhomogeneous LTB spacetime. The comparative study among these horizons shows a distinct character for apparent horizon compared to the other horizons. The apparent horizon will be a trapping horizon if its acceleration is positive. The Kodama vector is also defined and its causal character is found to be similar to that in the FRW model.

Rastall's theory is a generalization of Einstein's equations in which the energy–momentum tensor is not a conserved quantity, its covariant derivative is proportional to the gradient of the Ricci scalar and this fact can be associated with quantum effects in curved spacetime. In this work we will go study the Rastall's gravity in the context of the Gödel-type universe.

We present some features of early universe cosmology in terms of Hankel functions index (ν). Actually, the recent data from observational cosmology indicate that our universe was nearly de Sitter spacetime in the early times which results in an approximate scale-invariant spectrum. This imposes some constrains on index ν [E. Yusofi and M. Mohsenzadeh, JHEP 09, 020 (2014)]. These constrains stimulate us to use general solution of inflaton field equation for . To obtain the general solution for the inflationary background, we use asymptotic expansion of Hankel functions up to nonlinear order of . We consider the nonlinear modes as the fundamental modes for early universe during the inflation. In this paper, we obtain the general form of the inflationary modes, scale factor expansion, equation of state and some nonlinear corrections of power spectrum in terms of index ν. These results are general and in quasi-de Sitter and de Sitter limit confirm the conventional results.

Ultra-relativistic inertial and non-inertial reference frames would be subjected to a forward-directed heat bath from the Lorentz transformed temperature of the Cosmic Microwave Background (CMB) radiation. Although the Lorentz transformations of heat and temperature continue to be unresolved issues in the literature,^1–6 this paper makes use of occupation number (number density of occupied states per phase space element) to support a Lorentz factor inflation of the rest frame temperature. Additionally, Doppler Boosting is examined.

Considering the mixing of scalar mesons, the ΩΩ and Ξ*Ω systems are dynamically investigated within the framework of the chiral SU(3) quark model by solving the resonating group method (RGM) equation. The model parameters are taken from our previous work, which gave a good description of the energies of the baryon ground states, the binding energy of deuteron, and the experimental data of the nucleon–nucleon (NN) and nucleon–hyperon (NY) scattering processes. Two different mixing cases, one is the ideal mixing and another is 19° mixing, are discussed. The results show that no matter what kind of mixing is adopted, the ΩΩ and Ξ*Ω systems are still bound states. It is also shown that they are deeply bound if 19° mixing is adopted.

We reconsider the classical Schwarzschild solution in the context of a Janus cosmological model. We show that the central singularity can be eliminated through a simple coordinate change and that the subsequent transit from one fold to the other is accompanied by mass inversion. In such scenario matter swallowed by black holes could be ejected as invisible negative mass and dispersed in space.