Casimir Effect in the Horava-Lifshitz Gravity with a Cosmological Constant

We calculate the Casimir energy of a massless scalar field confined between two nearby parallel plates formed by ideal uncharged conductors, placed tangentially to the surface of a sphere with mass M and radius R. To this end, we take into account a static and spherically symmetric solution of Ho\v{r}ava-Lifshitz (HL) gravity, with a cosmological constant term, in lower orders of approximation, considering both weak-field and infrared limits. We show that the Casimir energy, just in the second order weak-field approximation, is modified due to the parameter of the HL gravity as well as to the cosmological constant.Comment: 18 pages. Improved conclusions. One figure and several references added. To appear in Annals of Physic

Implications of the Modigliani-Miller Theorem for the Study of Exchange Rate Regimes

We extend the Modigliani-Miller Theorem to the composition of the public debt and show that in a deterministic model the structure of a government's assets and liabilities is undetermined. Hence, a floating exchange rate regime can implement any attainable competitive equilibrium. Concerning stochastic economies, if the government issues nominal bonds of several maturities, then the same result may hold. Thus, a conceivable link between the choice of an exchange rate regime and economic outcomes may be due to factors often not considered in standard macroeconomic models.Modigliani-Miller Theorem, exchange rate regime, indeterminacy

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