Thermostatistics with an invariant infrared cutoff

Quantum gravitational effects may affect the large scale dynamics of the universe. Phenomenologically, quantum gravitational effect at large distances can be encoded in an extended uncertainty principle that admits a minimal measurable momentum/energy or a maximal length. This maximal length can be considered as the size of the cosmological horizon today. In this paper we study thermostatistics of an expanding universe as a gaseous system and in the presence of an invariant infrared cutoff. We also compare the thermostatistics of different eras of the evolution of the universe in two classes, Fermions and Bosons.

NEW HOLOGRAPHIC CHAPLYGIN GAS MODEL OF DARK ENERGY

In this work, we investigate the holographic dark energy model with a new infrared cutoff (new HDE model), proposed by Granda and Oliveros. Using this new definition for the infrared cutoff, we establish the correspondence between the new HDE model and the standard Chaplygin gas (SCG), generalized Chaplygin gas (GCG) and modified Chaplygin gas (MCG) scalar field models in a nonflat universe. The potential and dynamics for these scalar field models, which describe the accelerated expansion of the universe, are reconstructed. According to the evolutionary behavior of the new HDE model, we derive the same form of dynamics and potential for the different SCG, GCG and MCG models. We also calculate the squared sound speed of the new HDE model as well as the SCG, GCG and MCG models, and investigate the new HDE Chaplygin gas models from the viewpoint of linear perturbation theory. In addition, all results in the nonflat universe are discussed in the limiting case of the flat universe, i.e. k = 0.

RECONSTRUCTING THE POTENTIALS FOR THE QUINTESSENCE AND TACHYON DARK ENERGY, FROM THE HOLOGRAPHIC PRINCIPLE

We propose holographic quintessence and tachyon models of dark energy. The correspondence between the quintessence and tachyon energy densities with the holographic density allows the reconstruction of the potentials and the dynamics for the quintessence and tachyon fields, in the flat FRW background. The proposed infrared cutoff for the holographic energy density works for two cases of the constant α: for α < 1 we reconstruct the holographic quintessence model in the region before the ω = -1 crossing for the EoS parameter. The cosmological dynamics for α > 1 is also reconstructed for the holographic quintessence and tachyon models.

NONLEPTONIC ANNIHILATION DECAYS OF B MESON WITH A NATURAL INFRARED CUTOFF

Within the QCD factorization approach we compute the amplitudes for pure annihilation channels of B mesons decays into final states containing two pseudoscalar particles. These decays may be plagued by effects like nonperturbative physics and breaking of the factorization hypothesis and imply, at some extent, the introduction of an infrared cutoff in the calculation of amplitudes. We compute the decays with the help of infrared finite gluon propagators and coupling constants that were obtained in different solutions of the QCD Schwinger–Dyson equations. These solutions yield a natural cutoff for the amplitudes, and we argue that a systematic study of these B decays may provide a test for the QCD infrared behavior.

ON THE GENERALIZED CHAPLYGIN GAS: WORSE THAN A BIG RIP OR QUIETER THAN A SUDDEN SINGULARITY?

Although it has been believed that models with generalized Chaplygin gas (GCG) do not contain singularities, in previous work we have studied how a big freeze could take place in some kinds of phantom-generalized Chaplygin gas. In the present work, we study some types of generalized Chaplygin gas in order to show how different sorts of singularities could appear in such models, either in the future or in the past. We point out that (i) singularities may not originate from the phantom nature of the fluid, and (ii) if initially the tension of the brane in a brane-world Chaplygin model is large enough, then an infrared cutoff appears in the past.