399 research outputs found
Non-Singular Black Holes in Massive Gravity: Time-Dependent Solutions
When starting with a static, spherically-symmetric ansatz, there are two
types of black hole solutions in dRGT massive gravity: (i) exact Schwarzschild
solutions which exhibit no Yukawa suppression at large distances and (ii)
solutions in which the dynamical metric and the reference metric are
simultaneously diagonal and which inevitably exhibit coordinate-invariant
singularities at the horizon. In this work we investigate the possibility of
black hole solutions which can accommodate both a non-singular horizon and
Yukawa asymptotics. In particular, by adopting a time-dependent ansatz, we
derive perturbative analytic solutions which possess non-singular horizons.
These black hole solutions are indistinguishable from Schwarzschild black holes
in the limit of zero graviton mass. At finite graviton mass, they depend
explicitly on time. However, we demonstrate that the location of the apparent
horizon is not necessarily time-dependent, indicating that these black holes
are not necessarily accreting or evaporating (classically). In deriving these
results, we also review and extend known results about static black hole
solutions in massive gravity.Comment: 19 pages, 2 figure
Massive Spin-2 Scattering and Asymptotic Superluminality
We place model-independent constraints on theories of massive spin-2
particles by considering the positivity of the phase shift in eikonal
scattering. The phase shift is an asymptotic -matrix observable, related to
the time delay/advance experienced by a particle during scattering. Demanding
the absence of a time advance leads to constraints on the cubic vertices
present in the theory. We find that, in theories with massive spin-2 particles,
requiring no time advance means that either: (i) the cubic vertices must appear
as a particular linear combination of the Einstein-Hilbert cubic vertex and an
potential term or (ii) new degrees of freedom or strong coupling
must enter at parametrically the mass of the massive spin-2 field. These
conclusions have implications for a variety of situations. Applied to theories
of large- QCD, this indicates that any spectrum with an isolated massive
spin-2 at the bottom must have these particular cubic self-couplings. Applied
to de Rham-Gabadadze-Tolley massive gravity, the constraint is in accord with
and generalizes previous results obtained from a shockwave calculation: of the
two free dimensionless parameters in the theory there is a one parameter line
consistent with a subluminal phase shift.Comment: 46 pages, 1 figure. v2: Minor corrections. v3: Minor edits;
orthogonalized \oplus tensor polarizations. Results are unaffecte
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