Condensate formation with three-component ultracold fermions

We investigate the formation of Bose-Einstein condensation and population imbalance in a three-component Fermi superfluid by increasing the U(3) invariant attractive interaction. We consider the system at zero temperature in three dimensions and also in two dimensions. Within the mean-field theory, we derive explicit formulas for number densities, gap order parameter, condensate density and condensate fraction of the uniform system, and analyze them in the crossover from the Bardeen-Cooper-Schrieffer (BCS) state of Cooper pairs to the Bose-Einstein Condensate (BEC) of strongly-bound molecular dimers. In addition, we study this Fermi mixture trapped by a harmonic potential: we calculate the density profiles of the three components and the condensate density profile of Cooper pairs in the BCS-BEC crossover.Comment: 6 pages, 3 figures, accepted for publication in Physical Review A (regular article

Continuity of the torsionless limit as a selection rule for gravity theories with torsion

While one can in principle augment gravity theory with torsion, it is generally thought that any such torsion affects would be too small to be of consequence. Here we show that this cannot in general be the case. We show that the limit of vanishing torsion is not necessarily a continuous one, with the theory obtained in the limit not necessarily coinciding with the theory in which torsion had never been present at all. However, for a standard torsion tensor that is antisymmetric in two of its indices we have found two cases in which the vanishing torsion limit is in fact continuous, namely Einstein gravity and conformal gravity. For other gravity theories of common interest to possess a continuous limit the torsion tensor would need to be antisymmetric in all three of its indices.Comment: 6 pages, revtex4. Final version, to appear in Phys. Rev.

Cointegration Rank Test and Long Run Specification: A Note on the Robustness of Structural Demand Systems

Private demand systems provide a practical application for analyzing identification issues in cointegration analysis. The paper conducts Montecarlo simulation experiments of cointegrated demand systems by assuming non-separability of government consumption. This framework enables further to test the robustness of models under alternative empirical specifications in which the homogeneity restriction is assumed to hold. The results highlight that separability of utility function with respect to government spending and the over-inclusion of lagged dependent variables introduce important bias in identifying the long run demand system, while the model specification with homogeneity restriction perform better when the theoretical hypothesis is contained in the data.Length: 34 pagesNon-separable structural models, Demand systems, Homogeneity.