The Mass Spectrum of X-Ray Binaries

This review summarizes the observational constraints on the mass spectrum of compact objects in X-ray binaries. We currently have 20 X-ray binaries with confirmed black holes, based on dynamical information (i.e. mass in excess of 3 Msun). In two cases, V404 Cyg and GRS 1915+105, the black hole mass exceeds the maximum predicted by current Type Ib supernovae models and challenges black hole formation scenarios. The great majority of black hole binaries are members of the class of X-ray Transients, where long periods of quiescence enable spectroscopic studies of the faint donor stars. On the other hand, neutron star binaries are mostly found in persistent binaries, where reprocessed light from the accretion disc overwhelms the companion star and precludes mass estimates. New results, based on the detection of optical fluorescent lines from the donor star and X-ray burst oscillations, provide the best prospects for mass constraints of neutron stars in persistent X-ray binaries.Comment: Invited review presented at the conference "The Many Scales of the Universe - JENAM 2004 Astrophysics Reviews", joint European and Spanish astronomical meeting, held in Granada (Spain) in September 2004. To be published by Kluwer Academic Publishers, eds. J. C. del Toro Iniesta et al. 10 pages, 6 figure

Proof of Church's Thesis

We prove that if our calculating capability is that of a universal Turing machine with a finite tape, then Church's thesis is true. This way we accomplish Post (1936) program.Comment: 6 page

Price setting and the steady-state effects of inflation

This paper examines how price setting plays a key role in explaining the steady-state effects of inflation in a monopolistic competition economy. Three pricing variants (optimal prices, indexed prices, and unchanged prices) are introduced through a generalization of the Calvo-type setting that allows the possibility of price indexation, i.e., prices may be adjusted by the rate of inflation. We found that in an economy with less indexed prices the steady-state negative impact of inflation on output is higher. In the extreme case without no price indexation at all (purely Calvo-type economy), unrealistically heavy falls in capital and output were reported when steady-state inflation increases. Regarding welfare analysis, our results support a long-run monetary policy aimed at price stability with a close-to-zero inflation target. This finding is robust to any price setting scenario. JEL Classification: E13, E31, E50price setting, superneutrality, welfare cost of inflation

A close look at model-dependent monetary policy design

This article first explores the implications of model specification on the design of targeting rules in a world of model certainty. As a general prescription, a targeting rule must counterbalance the private-sector dynamics: The more backward-looking behavior is observed in either the output gap or inflation, the more forward-looking monetary policy should be. Likewise, a more forward-looking economy would require stronger backward-looking reactions of the nominal interest rate to the output gap or inflation. The article also analyzes the effects of implementing monetary policy in an environment with uncertainty. Our results indicate that a simple model-invariant rule of the style proposed by Taylor (1993) performs better than a model-dependent targeting rule in the presence of moderate parameter uncertainty.Monetary policy

Hibernating black holes revealed by photometric mass functions

We present a novel strategy to uncover the Galactic population of quiescent black holes (BHs). This is based on a new concept, the photometric mass function (PMF), which opens up the possibility of an efficient identification of dynamical BHs in large fields-of-view. This exploits the width of the disc Halpha emission line, combined with orbital period information. We here show that Halpha widths can be recovered using a combination of customized Halpha filters. By setting a width cut-off at 2200 km/s we are able to cleanly remove other Galactic populations of Halpha emitters, including ~99.9% of cataclysmic variables (CVs). Only short period (Porb<2.1 h) eclipsing CVs and AGNs will contaminate the sample but these can be easily flagged through photometric variability and, in the latter case, also mid-IR colours. We also describe the strategy of a deep (r=22) Galactic plane survey based on the concept of PMFs: HAWKs, the HAlpha-Width Kilo-deg Survey. We estimate that ~800 sqr deg are required to unveil ~50 new dynamical BHs, a three-fold improvement over the known population. For comparison, a century would be needed to produce an enlarged sample of 50 dynamical BHs from X-ray transients at the current discovery rate.Comment: Accepted for publication in MNRAS, 17 pages, 13 figures, 5 Table

Exergy analysis of a solar photovoltaic module

PV energy is the direct conversion of solar radiation into electricity. In this paper, an analysis of the influence of parameters such as global irradiance or temperature in the performance of a PV installation has been carried out. A PV module was installed in a building at the University of Málaga, and these parameters were experimentally determined for different days and different conditions of irradiance and temperature. Moreover, IV curves were obtained under these conditions to know the open-circuit voltage and the short-circuit current of the module. With this information, and using the first law of thermodynamics, an energy analysis was performed to determine the energy efficiency of the installation. Similarly, using the second law of thermodynamics, an exergy analysis is used to obtain the exergy efficiency. The results show that the energy efficiency varies between 10% and 12% and the exergy efficiency between 14% and 17%. It was concluded that the exergy analysis is more suitable for studying the performance, and that only electric exergy must be considered as useful exergy. This exergy efficiency can be improved if heat is removed from the PV module surface, and an optimal temperature is reached.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

An Optimizing IS-LM Framework with Endogenous Investment

Dynamic optimizing models with an IS-LM-type structure and slow price adjustments have been used for much recent monetary policy analysis, but usually with capital and investment treated as exogenous a significant restriction. This paper demonstrates that investment decisions can be endogenized without undue complexity in such models and that these can be calibrated to provide reasonably realistic dynamic behavior. It is necessary, however, to include capital adjustment costs; models with no adjustment costs match cyclical data very poorly. Indeed, their match is considerably poorer than models with constant capital. The paper also finds that the preferred adjustment-cost specification is not close to quadratic.