96 research outputs found
Newton's law on an Einstein "Gauss-Bonnet" brane
It is known that Newton's law of gravity holds asymptotically on a flat
"brane" embedded in an anti-de Sitter "bulk" ; this was shown not only when
gravity in the bulk is described by Einstein's theory but also in Einstein
"Lanczos Lovelock Gauss-Bonnet"'s theory. We give here the expressions for the
corrections to Newton's potential in both theories, in analytic form and valid
for all distances. We find that in Einstein's theory the transition from the
1/r behaviour at small r to the 1/r^2 one at large r is quite slow. In the
Einstein Gauss-Bonnet case on the other hand, we find that the correction to
Newton's potential can be small for all r. Hence, Einstein Gauss-Bonnet
equations in the bulk (rather than simply Einstein's) induce on the brane a
better approximation to Newton's law.Comment: typos corrected, reference added, version to be published in Progress
of Theoretical Physic
Conformal transformations and Nordstr\"om's scalar theory of gravity
As we shall briefly recall, Nordstr\"om's theory of gravity is
observationally ruled out. It is however an interesting example of non-minimal
coupling of matter to gravity and of the role of conformal transformations. We
show in particular that they could be useful to extend manifolds through
curvature singularities.Comment: 9 pages, no figure, prepared for the Proceedings of YKIS2010, to be
published in Progress of Theoretical Physics Supplemen
On the mechanical stability of asymptotically flat black holes with minimally coupled scalar hair
We show that the asymptotically flat hairy black holes, solutions of the
Einstein field equations minimally coupled to a scalar field, previously
discovered by one of us, present mode instability against linear radial
perturbations. It is also shown that the number of unstable modes is finite and
their frequencies can be made arbitrarily small.Comment: 11 pages, 6 figures, one reference fixe
- …