14,602 research outputs found
Note on the Radion Effective Potential in the Presence of Branes
In String Theory compactification, branes are often invoked to get the
desired form of the radion effective potential. Current popular way of doing
this assumes that the introduction of branes will not modify the background
geometry in an important way. In this paper, we show by an explicit example
that at least in the codimension 2 case, the gravitational backreaction of the
brane cannot be neglected in deriving the radion effective potential. Actually,
in this case, the presence of branes will have no effect on the dynamics of
radion.Comment: 6 pages, no figures. Some discussion clarified, conclusion unchanged.
To appear in Phys. Rev.
Gravitational potential in Palatini formulation of modified gravity
General Relativity has so far passed almost all the ground-based and
solar-system experiments. Any reasonable extended gravity models should
consistently reduce to it at least in the weak field approximation. In this
work we derive the gravitational potential for the Palatini formulation of the
modified gravity of the L(R) type which admits a de Sitter vacuum solution. We
conclude that the Newtonian limit is always obtained in those class of models
and the deviations from General Relativity is very small for a slowly moving
source.Comment: 5 pages, no figure
The effects of massive graviton on the equilibrium between the black hole and radiation gas in an isolated box
It is well known that the black hole can has temperature and radiate the
particles with black body spectrum, i.e. Hawking radiation. Therefore, if the
black hole is surrounded by an isolated box, there is a thermal equilibrium
between the black hole and radiation gas. A simple case considering the thermal
equilibrium between the Schwarzschild black hole and radiation gas in an
isolated box has been well investigated previously in detail, i.e. taking the
conservation of energy and principle of maximal entropy for the isolated system
into account. In this paper, following the above spirit, the effects of massive
graviton on the thermal equilibrium will be investigated. For the gravity with
massive graviton, we will use the de Rham-Gabadadze-Tolley (dRGT) massive
gravity which has been proven to be ghost free. Because the graviton mass
depends on two parameters in the dRGT massive gravity, here we just investigate
two simple cases related to the two parameters, respectively. Our results show
that in the first case the massive graviton can suppress or increase the
condensation of black hole in the radiation gas although the diagram is
similar like the Schwarzschild black hole case. For the second case, a new
diagram has been obtained. Moreover, an interesting and important
prediction is that the condensation of black hole just increases from the zero
radius of horizon in this case, which is very different from the Schwarzschild
black hole case.Comment: 9 pages, 4 figure
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