Paulo M. Sá

Nonlinear evolution of r-modes: The role of differential rotation

Recent work has shown that differential rotation, producing large scale drifts of fluid elements along stellar latitudes, is an unavoidable feature of r-modes in the nonlinear theory. We investigate the role of this differential rotation in the evolution of the l=2 r-mode instability of a newly born, hot, rapidly-rotating neutron star. It is shown that the amplitude of the r-mode saturates a few hundred seconds after the mode instability sets in. The saturation amplitude depends on the amount of differential rotation at the time the instability becomes active and can take values much smaller than unity. It is also shown that, independently of the saturation amplitude of the mode, the star spins down to rotation rates that are comparable to the inferred initial rotation rates of the fastest pulsars associated with supernova remnants. Finally, it is shown that, when the drift of fluid elements at the time the instability sets in is significant, most of the initial angular momentum of the star is transferred to the r-mode and, consequently, almost none is carried away by gravitational-radiation.

Black holes in three-dimensional dilaton gravity theories

Three dimensional black holes in a generalized dilaton gravity action theory are analysed. The theory is specified by two fields, the dilaton and the graviton, and two parameters, the cosmological constant and the Brans-Dicke parameter. It contains seven different cases, of which one distinguishes as special cases, string theory, general relativity and a theory equivalent to four dimensional general relativity with one Killing vector. We study the causal structure and geodesic motion of null and timelike particles in the black hole geometries and find the ADM masses of the different solutions.

Influence of differential rotation on the detectability of gravitational waves from the r-mode instability

Recently, it was shown that differential rotation is an unavoidable feature of nonlinear

Stationary black holes in a generalized three-dimensional theory of gravity

r

The two-dimensional analogue of general relativity

-modes. We investigate the influence of this differential rotation on the detectability of gravitational waves emitted by a newly born, hot, rapidly-rotating neutron star, as it spins down due to the

NON-SINGULAR CONSTANT CURVATURE TWO-DIMENSIONAL BLACK HOLE

r

Gravitational wave generation in hybrid quintessential inflationary models

-mode instability. We conclude that gravitational radiation may be detected by the advanced laser interferometer detector LIGO if the amount of differential rotation at the time the

Gravitational wave generation in power-law inflationary models

r

Parametric resonance and cosmological gravitational waves

-mode instability becomes active is not very high.

Gravitational wave generation in loop quantum cosmology

Abstract We consider a generalized three-dimensional theory of gravity which is achieved by the introduction of a dilaton field. Stationary black holes solutions of this theory are obtained and described.