9 research outputs found
The recovery of General Relativity in massive gravity via the Vainshtein mechanism
We study in detail static spherically symmetric solutions of non linear
Pauli-Fierz theory. We obtain a numerical solution with a constant density
source. This solution shows a recovery of the corresponding solution of General
Relativity via the Vainshtein mechanism. This result has already been presented
by us in a recent letter, and we give here more detailed information on it as
well as on the procedure used to obtain it. We give new analytic insights upon
this problem, in particular for what concerns the question of the number of
solutions at infinity. We also present a weak field limit which allows to
capture all the salient features of the numerical solution, including the
Vainshtein crossover and the Yukawa decay.Comment: 38 pages, 9 Figs, revtex
Recovering General Relativity from massive gravity
We obtain static, spherically symmetric, and asymptotically flat numerical
solutions of massive gravity with a source. Those solutions show, for the first
time explicitly, a recovery of the Schwarzschild solution of General Relativity
via the so-called Vainshtein mechanism.Comment: 4 pages, 3 figures; v2: minor changes, matches published versio
The Vainshtein mechanism in the Decoupling Limit of massive gravity
We investigate static spherically symmetric solutions of nonlinear massive
gravities. We first identify, in an ansatz appropriate to the study of those
solutions, the analog of the decoupling limit (DL) that has been used in the
Goldstone picture description. We show that the system of equations left over
in the DL has regular solutions featuring a Vainshtein-like recovery of
solutions of General Relativity (GR). Hence, the singularities found to arise
integrating the full nonlinear system of equations are not present in the DL,
despite the fact those singularities are usually thought to be due to a
negative energy mode also seen in this limit. Moreover, we show that the
scaling conjectured by Vainshtein at small radius is only a limiting case in an
infinite family of non singular solutions each showing a Vainshtein recovery of
GR solutions below the Vainshtein radius but a different common scaling at
small distances. This new scaling is shown to be associated with a zero mode of
the nonlinearities left over in the DL. We also show that, in the DL, this
scaling allows for a recovery of GR solutions even for potentials where the
original Vainshtein mechanism is not working. Our results imply either that the
DL misses some important features of nonlinear massive gravities or that
important features of the solutions of the full nonlinear theory have been
overlooked. They could also have interesting outcomes for the DGP model and
related proposals.Comment: 52 pages, 7 figures; v3: minor typos corrected, discussion of the
validity of the Decoupling Limit extended; accepted for publication in JHE
How Far Are We from the Quantum Theory of Gravity?
I give a pedagogical explanation of what it is about quantization that makes
general relativity go from being a nearly perfect classical theory to a very
problematic quantum one. I also explain why some quantization of gravity is
unavoidable, why quantum field theories have divergences, why the divergences
of quantum general relativity are worse than those of the other forces, what
physicists think this means and what they might do with a consistent theory of
quantum gravity if they had one. Finally, I discuss the quantum gravitational
data that have recently become available from cosmology.Comment: 106 page review article solicited by Reports on Progress in Physic
k-Mouflage gravity
We introduce a large class of scalar-tensor theories where gravity becomes
stronger at large distances via the exchange of a scalar that mixes with the
graviton. At small distances, i.e. large curvature, the scalar is screened via
an analog of the Vainshtein mechanism of massive gravity. The crossover
distance between the two regimes can be made cosmological by an appropriate
choice of the parameters.Comment: 9 pages, 1 figure. Essay written for the Gravity Research Foundation
2009 Awards for Essays on Gravitation, awarded a honorable mentio