94 research outputs found
The Cheshire Cap
A key role in black hole dynamics is played by the inner horizon; most of the
entropy of a slightly nonextremal charged or rotating black hole is carried
there, and the covariant entropy bound suggests that the rest lies in the
region between the inner and outer horizon. An attempt to match this onto
results of the microstate geometries program suggests that a `Higgs branch' of
underlying long string states of the configuration space realizes the degrees
of freedom on the inner horizon, while the `Coulomb branch' describes the
inter-horizon region and beyond. Support for this proposal comes from an
analysis of the way singularities develop in microstate geometries, and their
close analogy to corresponding structures in fivebrane dynamics. These
singularities signal the opening up of the long string degrees of freedom of
the theory, which are partly visible from the geometry side. A conjectural
picture of the black hole interior is proposed, wherein the long string degrees
of freedom resolve the geometrical singularity on the inner horizon, yet are
sufficiently nonlocal to communicate information to the outer horizon and
beyond.Comment: 64 pages, 8 figures. Version 2: References added, together with
substantial elaborations and clarification
Modeling Quantum Gravity Effects in Inflation
Cosmological models in 1+1 dimensions are an ideal setting for investigating
the quantum structure of inflationary dynamics -- gravity is renormalizable,
while there is room for spatial structure not present in the minisuperspace
approximation. We use this fortuitous convergence to investigate the mechanism
of slow-roll eternal inflation. A variant of 1+1 Liouville gravity coupled to
matter is shown to model precisely the scalar sector of cosmological
perturbations in 3+1 dimensions. A particular example of quintessence in 1+1d
is argued on the one hand to exhibit slow-roll eternal inflation according to
standard criteria; on the other hand, a field redefinition relates the model to
pure de Sitter gravity coupled to a free scalar matter field with no potential.
This and other examples show that the standard logic leading to slow-roll
eternal inflation is not invariant under field redefinitions, thus raising
concerns regarding its validity. Aspects of the quantization of Liouville
gravity as a model of quantum de Sitter space are also discussed.Comment: 43 pages, no figure
Hair-brane Ideas on the Horizon
We continue an examination of the microstate geometries program begun in
arXiv:1409.6017, focussing on the role of branes that wrap the cycles which
degenerate when a throat in the geometry deepens and a horizon forms. An
associated quiver quantum mechanical model of minimally wrapped branes exhibits
a non-negligible fraction of the gravitational entropy, which scales correctly
as a function of the charges. The results suggest a picture of AdS_3/CFT_2
duality wherein the long string that accounts for BTZ black hole entropy in the
CFT description, can also be seen to inhabit the horizon of BPS black holes on
the gravity side.Comment: 50 pages, 4 figures. v2: minor corrections, reference adde
- …