6,133 research outputs found
Loop Corrections to the Universal Hypermultiplet
The universal hypermultiplet arises as a subsector of every Calabi-Yau
compactification of M-theory or Type II string theory. Classically its moduli
space is the quaternionic space . We show that this moduli space
receives a one-loop correction proportional to the Euler character of the
Calabi-Yau, which can locally be absorbed by a certain constant shift of the
fields. The correction vanishes in the limit that the Planck mass is taken to
infinity, and hence is essentially gravitational in nature.Comment: 14 pages, harvmac. Added discussion of field redefinitions and the
exact metri
Black Hole Entropy from Near-Horizon Microstates
Black holes whose near-horizon geometries are locally, but not necessarily
globally, AdS (three-dimensional anti-de Sitter space) are considered.
Using the fact that quantum gravity on AdS is a conformal field theory, we
microscopically compute the black hole entropy from the asymptotic growth of
states. Precise numerical agreement with the Bekenstein-Hawking area formula
for the entropy is found. The result pertains to any consistent quantum theory
of gravity, and does not use string theory or supersymmetry.Comment: 11 pages, harvmac. Minor corrections, reference
On BMS Invariance of Gravitational Scattering
BMS+ transformations act nontrivially on outgoing gravitational scattering
data while preserving intrinsic structure at future null infinity (I+). BMS-
transformations similarly act on ingoing data at past null infinity (I-). In
this paper we apply - within a suitable finite neighborhood of the Minkowski
vacuum - results of Christodoulou and Klainerman to link I+ to I- and thereby
identify "diagonal" elements BMS0 of (BMS+)X(BMS-). We argue that BMS0 is a
nontrivial infinite-dimensional symmetry of both classical gravitational
scattering and the quantum gravity S-matrix. It implies the conservation of net
accumulated energy flux at every angle on the conformal S2 at I+. The
associated Ward identity is shown to relate S-matrix elements with and without
soft gravitons. Finally, BMS0 is recast as a U(1) Kac-Moody symmetry and an
expression for the Kac-Moody current is given in terms of a certain soft
graviton operator on the boundary of null infinity.Comment: 24 pages, 1 figure, minor edits in v
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