Non-circular rotating beams and CMB experiments

This paper is concerned with small angular scale experiments for the observation of cosmic microwave background anisotropies. In the absence of beam, the effects of partial coverage and pixelisation are disentangled and analyzed (using simulations). Then, appropriate maps involving the CMB signal plus the synchrotron and dust emissions from the Milky Way are simulated, and an asymmetric beam --which turns following different strategies-- is used to smooth the simulated maps. An associated circular beam is defined to estimate the deviations in the angular power spectrum produced by beam asymmetry without rotation and, afterwards, the deviations due to beam rotation are calculated. For a certain large coverage, the deviations due to pure asymmetry and asymmetry plus rotation appear to be very systematic (very similar in each simulation). Possible applications of the main results of this paper to data analysis in large coverage experiments --as PLANCK-- are outlined.Comment: 13 pages, 9 figures, to appear in A&

Cosmological solutions in F(R) Horava-Lifshitz gravity

At the present work, it is studied the extension of F (R) gravities to the new recently proposed theory of gravity, the so-called Horava-Lifshitz gravity, which provides a way to make the theory power counting renormalizable by breaking Lorentz invariance. It is showed that dark energy can be well explained in the frame of this extension, just in terms of gravity. It is also explored the possibility to unify inflation and late-time acceleration under the same mechanism, providing a natural explanation the accelerated expansion.Comment: 4 pages. Contribution to the Proceedings of the Spanish Relativity Meeting (ERE) 2010, Granada, Spai

Symplectic matrices with predetermined left eigenvalues

We prove that given four arbitrary quaternion numbers of norm 1 there always exists a $2\times 2$ symplectic matrix for which those numbers are left eigenvalues. The proof is constructive. An application to the LS category of Lie groups is given.Comment: 7 page

Trade Shoks and Aggregate Fluctuations in an Oil-Exporting Economy

In this paper we analyze the role of trade shocks in shaping aggregate fluctuations in Venezuela from 1950 to 1995. To this end a stochastic general equilibrium model of a small open economy whose main productive activity rests in the exports of a single basic product is specified. Shocks to the terms of trade which are directly associated to oil price changes are modelled as a foreign transfer. We find that this approach gives predictions that are consistent with the time series properties of Venezuela when i) the income efect of consumption more than compensates the substitution effect that generates the oil transfer and, ii) there is imperfect capital mobility. In particular, our model specification captures the observed patterns of the main aggregates after the oil resource boom of 1974.Trade shocks, Aggregate fuctuations, Emerging economies.