arXiv subjects
Publications and source records attributed to A. G. Agnese.
A one-parameter family of static and spherically symmetric solutions to Einstein equations with a traceless energy-momentum tensor is found. When the nonzero parameter $β$ lies in the open interval $(0,1)$ one obtains traversable Lorentzian wormholes. One also obtains naked singularities when either $β< 0$ or $β> 1$ and the Schwarzschild black hole for $β= 1$.
We introduce the concept of "quasi-universe" and describe the Einstein-Rosen bridge as an extreme wormhole connecting two quasi-universes.
We introduce, by means of the Brans-Dicke scalar field, space-time fluctuations at scale comparable to Planck length near the event horizon of a black hole and examine their dramatic effects.
We introduce, by means of the Brans-Dicke scalar field, space-time fluctuations at scale comparable to Planck length near the event horizon of a black hole and examine their dramatic effects.
The exterior and interior Schwarzschild solutions are rewritten replacing the usual radial variable with an angular one. This allows to obtain some results otherwise less apparent or even hidden in other coordinate systems.
We employ a theorem due to Campbell to build some simple 4-dimensional cosmological models which originate from solutions describing waves propagating along the extra-dimension of a 5-dimensional Ricci-flat space. The dimensional reduction is performed in the Jordan frame according to the induced-matter theory of Wesson.
Starting from a previously stated hypothesis concerning the discretization of the orbits for periodic celestial motions, the mass of ups-Andromedae and the periods of its b- and d- companions are estimated using the accurately known period of the massive c-companion. Moreover, the periods and the orbital major semiaxes of other hypotetically existing and not yet discovered smaller planets of ups-Andromedae are guessed.
We reconsider the Kerr metric with cosmological term $Λ$ imposing the condition that the angular velocity $ω$ of the dragging of the inertial frames vanishes at spatial boundaries. Some properties of the extreme black holes in the revisited solutions are discussed.
Starting from the knowledge of the four fundamental quantities length L, mass M, time T, absolute temperature $θ$ and accepting the validity of Gauss's law in all dimensions, we generalize, by the theory of physical dimensions, the expression of the Stephan-Boltzmann law and of the Planck's formula for the black-body radiation to a spacetime with one time and n spatial coordinates. In the particular case n=3 we shall recover the known results.
We consider a (4+d)-dimensional spacetime broken up into a (4-n)-dimensional Minkowski spacetime (where n goes from 1 to 3) and a compact (n+d)-dimensional manifold. At the present time the n compactification radii are of the order of the Universe size, while the other d compactification radii are of the order of the Planck length.
We extend previous analyses of soliton solutions in (4+1) gravity to new ranges of their defining parameters. The geometry, as studied using invariants, has the topology of wormholes found in (3+1) gravity. In the induced-matter picture, the fluid does not satisfy the strong energy conditions, but its gravitational mass is positive. We infer the possible existance of (4+1) wormholes which, compared to their (3+1) counterparts, are less exotic.
The Old Quantum Mechanics actions discretization rules for periodic motions on the atomic scale (Bohr-Sommerfeld) have been suitably modified in order to account the gravitational field instead of the electrostatic one. The new rules are used to calculate a few mechanical quantities pertinent to the periodic motions of celestial bodies. Several values have been obtained which result in reasonable agreement with the corresponding experimental data. A gravitational dimensionless structure constant has been determined, using the data relative to the solar sistem, which allows to quantitatively account for phenomena on a much wider scale. In particular, some information is acquired about the recently discovered extrasolar planetary systems and about the general empirical law which connects the spin of a celestial body with the square of its mass.
We obtain the vacuum spherical symmetric solutions for the gravitational sector of a (4+d)-dimensional Kaluza-Klein theory. In the various regions of parameter space, the solutions can describe either naked singularities or black-holes or wormholes. We also derive, by performing a conformal rescaling, the corresponding picture in the four-dimensional space-time.