On the Space Time of a Galaxy

We present an exact solution of the averaged Einstein's field equations in the presence of two real scalar fields and a component of dust with spherical symmetry. We suggest that the space-time found provides the characteristics required by a galactic model that could explain the supermassive central object and the dark matter halo at once, since one of the fields constitutes a central oscillaton surrounded by the dust and the other scalar field distributes far from the coordinate center and can be interpreted as a halo. We show the behavior of the rotation curves all along the background. Thus, the solution could be a first approximation of a ``long exposition photograph'' of a galaxy.Comment: 8 pages REVTeX, 11 eps figure

Entangled coherent states and squeezing in N trapped ions

We consider a resonant bichromatic excitation of N trapped ions that generates displacement and squeezing in their collective motion conditioned to their ionic internal state, producing eventually Scrhodinger cat states and entangled squeezing. Furthermore, we study the case of tetrachromatic illumination or producing the so called entangled coherent states in two motional normal modes.Comment: 4 Revtex pages, no figures. To appear in Proceedings of "Mysteries, Puzzles and Paradoxes in Quantum Mechanics", Garda Lake, Italy (2001

Generalized Gross--Perry--Sorkin--Like Solitons

In this paper, we present a new solution for the effective theory of Maxwell--Einstein--Dilaton, Low energy string and Kaluza--Klein theories, which contains among other solutions the well known Kaluza--Klein monopole solution of Gross--Perry--Sorkin as special case. We show also the magnetic and electric dipole solutions contained in the general one.Comment: 10 latex pages, no figures. To appear in Class. Quant. Gravity

The forward- and the equity-premium puzzles: two symptoms of the same illness?

Using information on US domestic financial data only, we build a stochastic discountfactor—SDF— and check whether it accounts for foreign markets stylized factsthat escape consumption based models. By interpreting our SDF as the projection ofa pricing kernel from a fully specified model in the space of returns, our results indicatethat a model that accounts for the behavior of domestic assets goes a long waytoward accounting for the behavior of foreign assets prices. We address predictabilityissues associated with the forward premium puzzle by: i) using instruments that areknown to forecast excess returns in the moments restrictions associated with Eulerequations, and; ii) by pricing Lustig and Verdelhan (2007)’s foreign currency portfolios.Our results indicate that the relevant state variables that explain foreign-currencymarket asset prices are also the driving forces behind U.S. domestic assets behavior.