Simplicial minisuperspace models in the presence of a massive scalar field with arbitrary scalar coupling

We extend previous simplicial minisuperspace models to account for arbitrary scalar coupling \eta R\phi^2.Comment: 24 pages and 9 figures. Accepted for publication by Classical and Quantum Gravit

Anisotropic simplicial minisuperspace model

The computation of the simplicial minisuperspace wavefunction in the case of anisotropic universes with a scalar matter field predicts the existence of a large classical Lorentzian universe like our own at late timesComment: 19 pages, Latex, 6 figure

Intra-group diffuse light in compact groups of galaxies. HCG 79, HCG 88 and HCG 95

Deep $B$ and $R$ images of three Hickson Compact Groups, HCG 79, HCG 88 and HCG 95, were analyzed using a new wavelet technic to measure possible intra-group diffuse light present in these systems. The method used, OV\_WAV, is a wavelet technic particularly suitable to detect low-surface brightness extended structures, down to a $S/N = 0.1$ per pixel, which corresponds to a 5-$\sigma$-detection level in wavelet space. The three groups studied are in different evolutionary stages, as can be judged by their very different fractions of the total light contained in their intra-group halos: $46\pm11$% for HCG 79 and $11\pm26$% for HCG 95, in the $B$ band, and HCG 88 had no component detected down to a limiting surface brightness of $29.1 B mag arcsec^{-2}$. For HCG 95 the intra-group light is red, similar to the mean colors of the group galaxies themselves, suggesting that it is formed by an old population with no significant on-going star formation. For HCG 79, however, the intra-group material has significantly bluer color than the mean color of the group galaxies, suggesting that the diffuse light may, at least in part, come from stripping of dwarf galaxies which dissolved into the group potential well.Comment: Two suggested references added to the introductio

Irreversible processes and the accelerated-decelerated phases of the Universe

A model for the Universe is proposed where it is considered as a mixture of scalar and matter fields. The particle production is due to an irreversible transfer of energy from the gravitational field to the matter field and represented by a non-equilibrium pressure. This model can simulate three distinct periods of the Universe: (a) an accelerated epoch where the energy density of the scalar field prevails over the matter field, (b) a past decelerated period where the energy density of the matter field becomes more predominant than the scalar energy density, and (c) a present acceleration phase where the scalar energy density overcomes the energy density of the matter field.Comment: 6 pages, 2 figures, to be published in Brazilian Journal of Physic

Questing for Algebraic Mass Dimension One Spinor Fields

This work deals with new classes of spinors of mass dimension one in Minkowski spacetime. In order to accomplish it, the Lounesto classification scheme and the inversion theorem are going to be used. The algebraic framework shall be revisited by explicating the central point performed by the Fierz aggregate. Then the spinor classification is generalized in order to encompass the new mass dimension one spinors. The spinor operator is shown to play a prominent role to engender the new mass dimension one spinors, accordingly.Comment: 7 pages, final version to appear in Eur. Phys. J.

Collision-Dependent Atom Tunnelling Rate in Bose-Einstein Condensates

We show that the interaction (cross-collision) between atoms trapped in distinct sites of a double-well potential can significantly increase the atom tunneling rate for special trap configurations leading to an effective linear Rabi regime of population oscillation between the trap wells. The inclusion of cross-collisional effects significantly extends the validity of the two-mode model approach allowing it to be alternatively employed to explain the recently observed increase of tunneling rates due to nonlinear interactions.Comment: 4 pages, 2 figures. Replaced with improved versio