3,047 research outputs found
De Sitter quantum scalar field and horizon holography
We show explicitly that free quantum field theory in de Sitter background
restricted on the cosmological horizon produces another quantum field theory
unitarily equivalent with the original one. Symmetry properties descending from
the dual theory are also remarked. In the restricted theory the thermal
properties, known for de Sitter quantum field theory, can be proved
straightforwardly.Comment: 14 pages, 1 figure, minor corrections, added reference
QFT holography near the horizon of Schwarzschild-like spacetimes
It is argued that free QFT can be defined on the event horizon of a
Schwarzschild-like spacetime and that this theory is unitarily and
algebraically equivalent to QFT in the bulk (near the horizon). Under that
unitary equivalence the bulk hidden SL(2,R) symmetry found in a previous work
becomes manifest on the event horizon, it being induced by a group of horizon
diffeomorphisms. The class of generators of that group can be enlarged to
include a full Virasoro algebra of fields which are defined on the event
horizon. These generators have a quantum representation in QFT on the event
horizon and thus in the bulk.Comment: 8 pages, 1 figure, latex 2e, Relevant references adde
Local incompatibility of the microlocal spectrum condition with the KMS property along spacelike directions in quantum field theory on curved spacetime
States of a generic quantum field theory on a curved spacetime are considered which satisfy the KMS condition with respect to an evolution associated with a complete (Killing) vector field. It is shown that at any point where the vector field is spacelike, such states cannot satisfy a certain microlocal condition which is weaker than the microlocal spectrum condition in the case of asymptotically free fields
Black hole entropy from classical Liouville theory
In this article we compute the black hole entropy by finding a classical
central charge of the Virasoro algebra of a Liouville theory using the Cardy
formula. This is done by performing a dimensional reduction of the Einstein
Hilbert action with the ansatz of spherical symmetry and writing the metric in
conformally flat form. We obtain two coupled field equations. Using the near
horizon approximation the field equation for the conformal factor decouples.
The one concerning the conformal factor is a Liouville equation, it posses the
symmetry induced by a Virasoro algebra. We argue that it describes the
microstates of the black hole, namely the generators of this symmetry do not
change the thermodynamical properties of the black hole.Comment: LaTeX, 11 pages, to appear on JHE
Rigorous steps towards holography in asymptotically flat spacetimes
Scalar QFT on the boundary at null infinity of a general
asymptotically flat 4D spacetime is constructed using the algebraic approach
based on Weyl algebra associated to a BMS-invariant symplectic form. The
constructed theory is invariant under a suitable unitary representation of the
BMS group with manifest meaning when the fields are interpreted as suitable
extensions to of massless minimally coupled fields propagating in the
bulk. The analysis of the found unitary BMS representation proves that such a
field on coincides with the natural wave function constructed out of
the unitary BMS irreducible representation induced from the little group
, the semidirect product between SO(2) and the two dimensional
translational group. The result proposes a natural criterion to solve the long
standing problem of the topology of BMS group. Indeed the found natural
correspondence of quantum field theories holds only if the BMS group is
equipped with the nuclear topology rejecting instead the Hilbert one.
Eventually some theorems towards a holographic description on of QFT in
the bulk are established at level of algebras of fields for strongly
asymptotically predictable spacetimes. It is proved that preservation of a
certain symplectic form implies the existence of an injective -homomorphism
from the Weyl algebra of fields of the bulk into that associated with the
boundary . Those results are, in particular, applied to 4D Minkowski
spacetime where a nice interplay between Poincar\'e invariance in the bulk and
BMS invariance on the boundary at is established at level of QFT. It
arises that the -homomorphism admits unitary implementation and Minkowski
vacuum is mapped into the BMS invariant vacuum on .Comment: 62 pages, amslatex, xy package; revised section 2 and the
conclusions; corrected some typos; added some references; accepted for
pubblication on Rev. Math. Phy
Artificial intelligence evaluation of confocal microscope prostate images: our preliminary experience
Poisson Algebra of Diffeomorphism Generators in a Spacetime Containing a Bifurcation
In this article we will analyze the possibility of a nontrivial central
extension of the Poisson algebra of the diffeomorphism generators, which
respect certain boundary conditions on the black hole bifurcation. The origin
of a possible central extension in the algebra is due to the existence of
boundary terms in the in the canonical generators. The existence of such
boundary terms depend on the exact boundary conditions one takes. We will check
two possible boundary conditions i.e. fixed bolt metric and fixed surface
gravity. In the case of fixed metric the the action acquires a boundary term
associated to the bifurcation but this is canceled in the Legendre
transformation and so absent in the canonical generator and so in this case the
possibility of a nontrivial central extension is ruled out. In the case of
fixed surface gravity the boundary term in the action is absent but present in
the Hamiltonian. Also in this case we will see that there is no nontrivial
central extension, also if there exist a boundary term in the generator.Comment: LaTex 20 pages, some misprints corrected, 2 references added.
Accepted for publication on Phys. Rev.
Central charges and boundary fields for two dimensional dilatonic black holes
In this paper we first show that within the Hamiltonian description of
general relativity, the central charge of a near horizon asymptotic symmetry
group is zero, and therefore that the entropy of the system cannot be estimated
using Cardy's formula. This is done by mapping a static black hole to a two
dimensional space. We explain how such a charge can only appear to a static
observer who chooses to stay permanently outside the black hole. Then an
alternative argument is given for the presence of a universal central charge.
Finally we suggest an effective quantum theory on the horizon that is
compatible with the thermodynamics behaviour of the black hole.Comment: 16 pages, no figures, LaTex 2e, references adde
Horizons, Constraints, and Black Hole Entropy
Black hole entropy appears to be ``universal''--many independent
calculations, involving models with very different microscopic degrees of
freedom, all yield the same density of states. I discuss the proposal that this
universality comes from the behavior of the underlying symmetries of the
classical theory. To impose the condition that a black hole be present, we must
partially break the classical symmetries of general relativity, and the
resulting Goldstone boson-like degrees of freedom may account for the
Bekenstein-Hawking entropy. In particular, I demonstrate that the imposition of
a ``stretched horizon'' constraint modifies the algebra of symmetries at the
horizon, allowing the use of standard conformal field theory techniques to
determine the asymptotic density of states. The results reproduce the
Bekenstein-Hawking entropy without any need for detailed assumptions about the
microscopic theory.Comment: 16 pages, talk given at the "Peyresq Physics 10 Meeting on Micro and
Macro structures of spacetime
Tunnelling Methods and Hawking's radiation: achievements and prospects
The aim of this work is to review the tunnelling method as an alternative
description of the quantum radiation from black holes and cosmological
horizons. The method is first formulated and discussed for the case of
stationary black holes, then a foundation is provided in terms of analytic
continuation throughout complex space-time. The two principal implementations
of the tunnelling approach, which are the null geodesic method and the
Hamilton-Jacobi method, are shown to be equivalent in the stationary case. The
Hamilton-Jacobi method is then extended to cover spherically symmetric
dynamical black holes, cosmological horizons and naked singularities. Prospects
and achievements are discussed in the conclusions.Comment: Topical Review commissioned and accepted for publication by
"Classical and Quantum Gravity". 101 pages; 6 figure
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