220 research outputs found
An asymptotic framework for gravitational scattering
Asymptotically flat spacetimes have been studied in five separate regions:
future/past timelike infinity , future/past null infinity
, and spatial infinity . We formulate assumptions and
definitions such that the five infinities share a single Bondi-Metzner-Sachs
(BMS) group of asymptotic symmetries and associated charges. We show how
individual ingoing/outgoing massive bodies may be ascribed initial/final BMS
charges and derive global conservation laws stating that the change in total
charge is balanced by the corresponding radiative flux. This framework provides
a foundation for the study of asymptotically flat spacetimes containing ingoing
and outgoing massive bodies, i.e., for generalized gravitational scattering.
Among the new implications are rigorous definitions for quantities like
initial/final spin, scattering angle, and impact parameter in multi-body
spacetimes, without the use of any preferred background structure
Chiral Liouville Gravity
Classical two-dimensional Liouville gravity is often considered in conformal gauge which has a residual left and right Virasoro symmetry algebra. We consider an alternate, chiral, gauge which has a residual right Virasoro Kac-Moody algebra, and no left Virasoro algebra. The Kac-Moody zero mode is the left-moving energy. Dirac brackets of the constrained Hamiltonian theory are derived, and the residual symmetries are shown to be generated by integrals of the conserved chiral currents. The central charge and Kac-Moody level are computed. The possible existence of a corresponding quantum theory is discussed.Physic
New Boundary Conditions for
New chiral boundary conditions are found for quantum gravity with matter on . The associated asymptotic symmetry group is generated by a single right-moving U(1) Kac-Moody-Virasoro algebra with . The Kac-Moody zero mode generates global left-moving translations and equals, for a BTZ black hole, the sum of the total mass and spin. The level is positive about the global vacuum and negative in the black hole sector, corresponding to ergosphere formation. Realizations arising in Chern-Simons gravity and string theory are analyzed. The new boundary conditions are shown to naturally arise for warped in the limit that the warp parameter is taken to zero.Physic
Solitons in Five Dimensional Minimal Supergravity: Local Charge, Exotic Ergoregions, and Violations of the BPS Bound
We describe a number of striking features of a class of smooth solitons in
gauged and ungauged minimal supergravity in five dimensions. The solitons are
globally asymptotically flat or asymptotically AdS without any Kaluza-Klein
directions but contain a minimal sphere formed when a cycle pinches off in the
interior of the spacetime. The solutions carry a local magnetic charge and many
have rather unusual ergosurfaces. Perhaps most strikingly, many of the solitons
have more electric charge or, in the asymptotically AdS case, more electric
charge and angular momentum than is allowed by the usual BPS bound. We comment
on, but do not resolve, the new puzzle this raises for AdS/CFT.Comment: 60 pages, 12 figures, 3 table
Classical central extension for asymptotic symmetries at null infinity in three spacetime dimensions
The symmetry algebra of asymptotically flat spacetimes at null infinity in
three dimensions is the semi-direct sum of the infinitesimal diffeomorphisms on
the circle with an abelian ideal of supertranslations. The associated charge
algebra is shown to admit a non trivial classical central extension of Virasoro
type closely related to that of the anti-de Sitter case.Comment: 4 sign mistakes due to a change of conventions are corrected in
section 2, none of the conclusions are affected, takes precedence over
published version, including corrigendu
Relaxing the Parity Conditions of Asymptotically Flat Gravity
Four-dimensional asymptotically flat spacetimes at spatial infinity are
defined from first principles without imposing parity conditions or
restrictions on the Weyl tensor. The Einstein-Hilbert action is shown to be a
correct variational principle when it is supplemented by an anomalous
counter-term which breaks asymptotic translation, supertranslation and
logarithmic translation invariance. Poincar\'e transformations as well as
supertranslations and logarithmic translations are associated with finite and
conserved charges which represent the asymptotic symmetry group. Lorentz
charges as well as logarithmic translations transform anomalously under a
change of regulator. Lorentz charges are generally non-linear functionals of
the asymptotic fields but reduce to well-known linear expressions when parity
conditions hold. We also define a covariant phase space of asymptotically flat
spacetimes with parity conditions but without restrictions on the Weyl tensor.
In this phase space, the anomaly plays classically no dynamical role.
Supertranslations are pure gauge and the asymptotic symmetry group is the
expected Poincar\'e group.Comment: Four equations corrected. Two references adde
G2 Dualities in D=5 Supergravity and Black Strings
Five dimensional minimal supergravity dimensionally reduced on two commuting
Killing directions gives rise to a G2 coset model. The symmetry group of the
coset model can be used to generate new solutions by applying group
transformations on a seed solution. We show that on a general solution the
generators belonging to the Cartan and nilpotent subalgebras of G2 act as
scaling and gauge transformations, respectively. The remaining generators of G2
form a sl(2,R)+sl(2,R) subalgebra that can be used to generate non-trivial
charges. We use these generators to generalize the five dimensional Kerr string
in a number of ways. In particular, we construct the spinning electric and
spinning magnetic black strings of five dimensional minimal supergravity. We
analyze physical properties of these black strings and study their
thermodynamics. We also explore their relation to black rings.Comment: typos corrected (26 pages + appendices, 2 figures
Kerr/CFT, dipole theories and nonrelativistic CFTs
We study solutions of type IIB supergravity which are SL(2,R) x SU(2) x
U(1)^2 invariant deformations of AdS_3 x S^3 x K3 and take the form of products
of self-dual spacelike warped AdS_3 and a deformed three-sphere. One of these
backgrounds has been recently argued to be relevant for a derivation of
Kerr/CFT from string theory, whereas the remaining ones are holographic duals
of two-dimensional dipole theories and their S-duals. We show that each of
these backgrounds is holographically dual to a deformation of the DLCQ of the
D1-D5 CFT by a specific supersymmetric (1,2) operator, which we write down
explicitly in terms of twist operators at the free orbifold point. The
deforming operator is argued to be exactly marginal with respect to the
zero-dimensional nonrelativistic conformal (or Schroedinger) group - which is
simply SL(2,R)_L x U(1)_R. Moreover, in the supergravity limit of large N and
strong coupling, no other single-trace operators are turned on. We thus propose
that the field theory duals to the backgrounds of interest are nonrelativistic
CFTs defined by adding the single Schroedinger-invariant (1,2) operator
mentioned above to the original CFT action. Our analysis indicates that the
rotating extremal black holes we study are best thought of as finite
right-moving temperature (non-supersymmetric) states in the above-defined
supersymmetric nonrelativistic CFT and hints towards a more general connection
between Kerr/CFT and two-dimensional non-relativistic CFTs.Comment: 48+8 pages, 4 figures; minor corrections and references adde
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