arXiv subjects

A. Chamorro

Publications and source records attributed to A. Chamorro.

7 recordsLinked to original sources

arXiv2012

Demonstration of Communication using Neutrinos

Beams of neutrinos have been proposed as a vehicle for communications under unusual circumstances, such as direct point-to-point global communication, communication with submarines, secure communications and interstellar communication. We report on the performance of a low-rate communications link established using the NuMI beam line and the MINERvA detector at Fermilab. The link achieved a decoded data rate of 0.1 bits/sec with a bit error rate of 1% over a distance of 1.035 km, including 240 m of earth.

hep-ex↗

arXiv2000

A Tolman-Bondi-Lemaitre Cell-Model for the Universe and Gravitational Collapse

A piecewise Tolman-Bondi-Lemaitre (TBL) cell-model for the universe incorporating local collapsing and expanding inhomogeneities is presented here. The cell-model is made up of TBL underdense and overdense spherical regions surrounded by an intermediate region of TBL shells embedded in an expanding universe. The cell-model generalizes the Friedmann as well as Einstein-Straus swiss-cheese models and presents a number of advantages over other models, and in particular the time evolution of the cosmological inhomogeneities is now incorporated within the scheme. Important problem of gravitational collapse of a massive dust cloud, such as a cluster of galaxies or even a massive star, in such a cosmological background is examined. It is shown that the collapsing local inhomogeneities in an expanding universe could result in either a black hole, or a naked singularity, depending on the nature of the set of initial data which consists of the matter distribution and the velocities of the collapsing shells in the cloud at the initial epoch from which the collapse commences.

gr-qc↗

arXiv2000

Gravitational Collapse and Cosmological Constant

We consider here the effects of a non-vanishing cosmological term on the final fate of a spherical inhomogeneous collapsing dust cloud. It is shown that depending on the nature of the initial data from which the collapse evolves, and for a positive value of the cosmological constant, we can have a globally regular evolution where a bounce develops within the cloud. We characterize precisely the initial data causing such a bounce in terms of the initial density and velocity profiles for the collapsing cloud. In the cases otherwise, the result of collapse is either formation of a black hole or a naked singularity resulting as the end state of collapse. We also show here that a positive cosmological term can cover a part of the singularity spectrum which is visible in the corresponding dust collapse models for the same initial data.

gr-qc↗

arXiv2000

Assisted inflation in Friedmann-Robertson-Walker and Bianchi spacetimes

We use exact general solutions for the spatially flat FRW and the anisotropic Bianchi I cosmologies to show that generically uncoupled scalar fields cooperate to make inflation more probable, while the presence of several interacting fields hinders the occurrence of the phenomenon, in accordance with previous results based on particular power-law solutions. Similar conclusions are reached in the case of Bianchi VI$_0$ spacetimes, for power-law solutions which are proved to be attractors.

gr-qc↗

arXiv1996

Energy associated with charged dilaton black holes

It is known that certain properties of charged dilaton black holes depend on a free parameter $β$ which controls the strength of the coupling of the dilaton to the Maxwell field. We obtain the energy associated with static spherically symmetric charged dilaton black holes for arbitrary value of the coupling parameter and find that the energy distribution depends on the value of $β$. With increasing radial distance, the energy in a sphere increases for $β= 0$ as well as for $β< 1$, decreases for $β> 1$, and remains constant for $β= 1$. However, the total energy turns out to be the same for all values of $β$.

hep-th↗

arXiv1996

A radiating dyon solution

We give a non-static exact solution of the Einstein-Maxwell equations (with null fluid), which is a non-static magnetic charge generalization to the Bonnor-Vaidya solution and describes the gravitational and electromagnetic fields of a nonrotating massive radiating dyon. In addition, using the energy-momentum pseudotensors of Einstein and Landau and Lifshitz we obtain the energy, momentum, and power output of the radiating dyon and find that both prescriptions give the same result.

hep-th↗

arXiv1996

Energy of a spherically symmetric charged dilaton black hole

The energy associated with a static and spherically symmetric charged dilaton black hole is obtained for arbitrary value of the coupling parameter (which regulates the strength of the coupling of the dilaton to the Maxwell field) $β$. The energy distribution depends on $β$, whereas the total energy is independent of this and is given by the mass parameter of the black hole.

gr-qc↗