Catálogo de publicaciones - libros

We use two models in order to deal with a rotating universe. The first one is a thin rotating spherical shell. When we introduce in this shell an Hydrogen atom we found that the gravitomagnetic field of this universe can split the energy levels of the atom in a way analogous to the Zeeman effect.

The second model is the Gödel universe. There we use the solution of the Dirac equation on an arbitrary spacetime to find the shifts on energy levels of Hydrogen atoms caused by the rotation of the universe.

In both cases the interaction energy is very small, so we have to study the effect of cosmic rotation on Hydrogen atoms in a rotating expanding universe.

One approach to studying the epoch of galaxy formation is to infer formation redshifts from the ages of galaxies at known redshifts. When observed with optical instruments, galaxies lying at redshifts of z ~ 1 reveal their restframe UV spectra, which contain some features that show promise for breaking age-metallicity degeneracies inherent in techniques used for estimating galaxy ages. Early-type galaxies around the z ~ 1 epoch are of additional interest because they lie only a few Gyrs after the probable peak when galaxy mergers occurred. The spectra of young galaxies, such as these merger products, with ages of 1–5 Gyr are much more distinguishable than those of older galaxies, which results in more accurate age estimates.

We report a 3-dimensional numerical study of the accretion of stellar winds onto Sgr A*, the super-massive black hole at the centre of our Galaxy. Compared with previous investigations, we allow the stars to be on realistic orbits, include the recently discovered slow wind sources, and allow for optically thin radiative cooling. We find that the slow winds shock and rapidly cool, forming cold gas clumps and filaments that coexist with the hot X-ray emitting gas. The accretion rate in this case consists of two components: the hot quasi steady-state one, and the cold one that is highly variable on time-scales of tens to hundreds of years. Such variability can in principle lead to a strongly non-linear response through accretion flow physics not resolved here, making Sgr A* an important energy source for the Galactic centre.

We propose a cosmological model in which Bose-Einstein condensation works as Dark Energy. We obtain a novel mechanism of inflation, very early formation of highly non-linear objects, and log-z periodicity in the BEC collapsing time.

We study the inspiral of double black holes orbiting inside a massive rotationally supported gaseous disk with masses in the Laser Interferometer Space Antenna () window of detectability. Using high–resolution SPH simulations, we follow the black hole dynamics in the early phase when gas–dynamical friction acts on the black holes individually, and continue our simulation until they form a close binary. We find that in the early sinking the black holes lose memory of their initial orbital eccentricity, if they co–rotate with the gaseous disk. As a consequence the massive black holes . During the inspiral, gravitational capture of gas by the black holes occurs mainly when they move on circular orbits and may ignite AGN activity: eccentric orbits imply instead high relative velocities and weak gravitational focusing.

Recent progress in modeling type Ia supernovae by means of 3-dimensional hydrodynamic simulations as well as several of the still open questions are addressed in this article. It will be shown that the new models have considerable predictive power which allows us to study observable properties such as light curves and spectra without adjustable non-physical parameters. This is a necessary requisite to improve our understanding of the explosion mechanism and to settle the question of the applicability of SNe Ia as distance indicators for cosmology. We explore the capabilities of the models by comparison with observations and show in a preliminary approach, how such a model can be applied to study the origin of the diversity of SNe Ia which could be a source of considerable systematic errors in their distances.

We have placed an upper limit on the magnitude of the rotation measure of 7 × 10^5 rad m for the putative Faraday screen (magnetized plasma) in front of Sgr A*, the radio source associated with the black hole in the Galactic Center. There is evidence that the actual rotation measure is about -5 ×10 rad m. With a simple model of equipartition of energy and reasonable inner radius for the screen, the accretion rate is estimated to be less than 10Myr. In addition, we have detected, for the first time, intra-day variability in the polarization of Sgr A*, which may be due to either intrinsic variations in Sgr A* or variations in the composition of the Faraday screen.

In this contribution I review the mechanism proposed earlier for producing a gamma-ray burst from the rapidly spinning neutron star in an X-ray binary (Spruit 1999), with a discussion of some more recent developments and outstanding issues.

We use two models in order to deal with a rotating universe. The first one is a thin rotating spherical shell. When we introduce in this shell an Hydrogen atom we found that the gravitomagnetic field of this universe can split the energy levels of the atom in a way analogous to the Zeeman effect.

The second model is the Gödel universe. There we use the solution of the Dirac equation on an arbitrary spacetime to find the shifts on energy levels of Hydrogen atoms caused by the rotation of the universe.

In both cases the interaction energy is very small, so we have to study the effect of cosmic rotation on Hydrogen atoms in a rotating expanding universe.

Magnetic field behaviour in a spherically-symmetric accretion flow for parameters typical of single black holes in the Galaxy is discussed. It is shown that in the majority of the Galaxy volume, accretion onto single stellar-mass black holes will be spherical and have a low accretion rate (10 - 10 of the Eddington rate). An analysis of plasma internal energy growth during the infall is performed. Adiabatic heating of collisionless accretion flow due to magnetic adiabatic invariant conservation is 25% more efficient than in the standard non-magnetized gas case. It is shown that magnetic field line reconnections in discrete current sheets lead to significant nonthermal electron component formation. In a framework of quasi-diffusion acceleration, the “energy-radius” electron distribution is computed and the function describing the shape of synchrotron radiation spectrum is constructed. It is shown that nonthermal electron emission leads to formation of a hard (UV, X-ray, up to gamma), highly variable spectral component in addition to the standard synchrotron optical component first derived by Shvartsman generated by thermal electrons in the magnetic field of accretion flow. For typical interstellar medium parameters, a black hole at 100 pc distance will be a 16-25^m optical source coinciding with the highly variable bright X-ray counterpart, while the variable component of optical emission will be about 18-27^m. The typical time scale of the variability is 10 sec, with relative flare amplitudes of 0.2-6% in various spectral bands. Possible applications of these results to the problem of search for single black holes are discussed.