MG11 
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Neutron star equation of state from gravitational waves detections

We briefly review the properties of quasi-normal modes of neutron stars and black holes. Specially addressing our study to the Brazilian spherical antenna, on which a possible detection would occur at 3.0-3.4 kHz, we analyze the consequences of a possible detection of such quasi-normal modes. Since the source can be identified, by its characteristic damping time, we are able to extract information about the neutron star or black hole. These information lead to a strong constrain in the nuclear matter equation of state, namely, the compression modulus should be K = 220 MeV.

Primordial black-hole gravitational wave background noise in the LISA, DECIGO and BBO frequency bands

According to the standard model primordial black holes (PBHs) could have been generated during the first few moments after the big bang as consequence of density fluctuations of matter. Although most regions of high density would be quickly dispersed by the expansion of the universe, primordial black holes would be stable, persisting to the present. If this really happened the Laser Interferometer Space Antenna (LISA), the DECihertz Interferometer Gravitational wave Observatory (DECIGO), and the Big Bang Observer (BBO) will probably detect the gravitational wave background produced by those PBHs. Here we calculated this background as a function of the PBH population in the neighborhood of Earth. Depending of what population is assumed the gravitational wave background produced may give trouble for these space interferometers in their task to detect other signals. Very large ground base interferometers such as LIGO and VIRGO can soon give information that would put stringent constraints on this population.

Galactic disks in theories with Yukawian gravitational potential

We present a new solution for the rotation curves of galactic disks in theories with gravitational potential of the Yukawa type. We follow the technique employed by Toomre in the study of galactic disks in the Newtonian theory. We then apply our formulation to the study of rotation curves for a zero-thickness exponential disk and compare with the Newtonian case studied by Freeman. As an additional result of the mathematical tool developed here, we show that in any theory of gravity with a massive graviton (this means a gravitational potential of the Yukawa type), a strong limit can be imposed on the mass (m_{g}) of this particle. For example, in order to obtain a galactic disk with a scale length of b=10 kpc, we should have a massive graviton of m_{g}<< 10^{-59} g. This result is much more restrictive than those inferred from solar system observations.