23 research outputs found
Cosmological term as a source of mass
In the spherically symmetric case the dominant energy condition together with
the requirements of regularity at the center, asymptotic flatness and
fineteness of the ADM mass, defines the family of asymptotically flat globally
regular solutions to the Einstein minimally coupled equations which includes
the class of metrics asymptotically de Sitter at approaching the regular
center. The source term corresponds to an r-dependent cosmological term given
by the second rank symmetric tensor invariant under boosts in the radial
direction and evolving from de Sitter vacuum in the origin to Minkowski vacuum
at infinity. Space-time symmetry changes smoothly from the de Sitter group at
the center to the Lorentz group at infinity through the radial boosts in
between. The standard formula for the ADM mass relates it to the de Sitter
vacuum replacing a central singularity at the scale of symmetry restoration.
For masses exceeding a certain critical value m_{crit} de Sitter-Schwarzschild
geometry describes a vacuum nonsingular black hole, while beyond m_{crit} it
describes a G-lump which is a vacuum selfgravitating particlelike structure
without horizons. Quantum energy spectrum of G-lump is shifted down by the
binding energy, and zero-point vacuum mode is fixed at the value corresponding
to the Hawking temperature from the de Sitter horizon.Comment: 8 pages, revtex, 8 figures incorporated, to appear in Classical and
Quantum Gravit
The Beginning and Evolution of the Universe
We review the current standard model for the evolution of the Universe from
an early inflationary epoch to the complex hierarchy of structure seen today.
We summarize and provide key references for the following topics: observations
of the expanding Universe; the hot early Universe and nucleosynthesis; theory
and observations of the cosmic microwave background; Big Bang cosmology;
inflation; dark matter and dark energy; theory of structure formation; the cold
dark matter model; galaxy formation; cosmological simulations; observations of
galaxies, clusters, and quasars; statistical measures of large-scale structure;
and measurement of cosmological parameters. We conclude with discussion of some
open questions in cosmology. This review is designed to provide a graduate
student or other new worker in the field an introduction to the cosmological
literature.Comment: 69 pages. Invited review article for Publications of the Astronomical
Society of the Pacific. Supplementary references, tables, and more concise
PDF file at http://www.physics.drexel.edu/univers
Orbital effects of a monochromatic plane gravitational wave with ultra-low frequency incident on a gravitationally bound two-body system
We analytically compute the long-term orbital variations of a test particle
orbiting a central body acted upon by an incident monochromatic plane
gravitational wave. We assume that the characteristic size of the perturbed
two-body system is much smaller than the wavelength of the wave. Moreover, we
also suppose that the wave's frequency is much smaller than the particle's
orbital one. We make neither a priori assumptions about the direction of the
wavevector nor on the orbital geometry of the planet. We find that, while the
semi-major axis is left unaffected, the eccentricity, the inclination, the
longitude of the ascending node, the longitude of pericenter and the mean
anomaly undergo non-vanishing long-term changes. They are not secular trends
because of the slow modulation introduced by the tidal matrix coefficients and
by the orbital elements themselves. They could be useful to indepenedently
constrain the ultra-low frequency waves which may have been indirectly detected
in the BICEP2 experiment. Our calculation holds, in general, for any
gravitationally bound two-body system whose characteristic frequency is much
larger than the frequency of the external wave. It is also valid for a generic
perturbation of tidal type with constant coefficients over timescales of the
order of the orbital period of the perturbed particle.Comment: LaTex2e, 24 pages, no figures, no tables. Changes suggested by the
referees include