1,019 research outputs found
The nonlinear evolution of de Sitter space instabilities
We investigate the quantum evolution of large black holes that nucleate
spontaneously in de Sitter space. By numerical computation in the s-wave and
one-loop approximations, we verify claims that such black holes can initially
"anti-evaporate" instead of shrink. We show, however, that this is a transitory
effect. It is followed by an evaporating phase, which we are able to trace
until the black holes are small enough to be treated as Schwarzschild. Under
generic perturbations, the nucleated geometry is shown to decay into a ring of
de Sitter regions connected by evaporating black holes. This confirms that de
Sitter space is globally unstable and fragments into disconnected daughter
universes.Comment: 10 pages, 8 figures, to appear in PR
A covariant entropy bound conjecture on the dynamical horizon
As a compelling pattern for the holographic principle, our covariant entropy
bound conjecture is proposed for more general dynamical horizons. Then we apply
our conjecture to CDM cosmological models, where we find it imposes a
novel upper bound on the cosmological constant for our own universe
by taking into account the dominant entropy contribution from super-massive
black holes, which thus provides an alternative macroscopic perspective to
understand the longstanding cosmological constant problem. As an intriguing
implication of this conjecture, we also discuss the possible profound relation
between the present cosmological constant, the origin of mass, and the
anthropic principle.Comment: JHEP style, 9 pages, 1 figure, honorable mention award received from
Gravity Research Foundation for 2008 Essay Competitio
The Holographic Principle for General Backgrounds
We aim to establish the holographic principle as a universal law, rather than
a property only of static systems and special space-times. Our covariant
formalism yields an upper bound on entropy which applies to both open and
closed surfaces, independently of shape or location. It reduces to the
Bekenstein bound whenever the latter is expected to hold, but complements it
with novel bounds when gravity dominates. In particular, it remains valid in
closed FRW cosmologies and in the interior of black holes. We give an explicit
construction for obtaining holographic screens in arbitrary space-times (which
need not have a boundary). This may aid the search for non-perturbative
definitions of quantum gravity in space-times other than AdS.Comment: 15 pages, 4 figures. Based on a talk given at Strings '99. Includes a
reply to recent criticism. For more details, examples, and references, see
hep-th/9905177 and hep-th/990602
Quantum Global Structure of de Sitter Space
I study the global structure of de Sitter space in the semi-classical and
one-loop approximations to quantum gravity. The creation and evaporation of
neutral black holes causes the fragmentation of de Sitter space into
disconnected daughter universes. If the black holes are stabilized by a charge,
I find that the decay leads to a necklace of de Sitter universes (`beads')
joined by near-extremal black hole throats. For sufficient charge, more and
more beads keep forming on the necklace, so that an unbounded number of
universes will be produced. In any case, future infinity will not be connected.
This may have implications for a holographic description of quantum gravity in
de Sitter space.Comment: 37 pages, LaTeX2e, 10 figures. v2: references adde
Light Sheets and the Covariant Entropy Conjecture
We examine the holography bound suggested by Bousso in his covariant entropy
conjecture, and argue that it is violated because his notion of light sheet is
too generous. We suggest its replacement by a weaker bound.Comment: 5 pages, to appear in Classical and Quantum Gravit
Unified approach to study quantum properties of primordial black holes, wormholes and of quantum cosmology
We review the anomaly induced effective action for dilaton coupled spinors
and scalars in large N and s-wave approximation. It may be applied to study the
following fundamental problems: construction of quantum corrected black holes
(BHs), inducing of primordial wormholes in the early Universe (this effect is
confirmed) and the solution of initial singularity problem. The recently
discovered anti-evaporation of multiple horizon BHs is discussed. The existance
of such primordial BHs may be interpreted as SUSY manifestation. Quantum
corrections to BHs thermodynamics maybe also discussed within such scheme.Comment: LaTeX file and two eps files, to appear in MPLA, Brief Review
A covariant entropy conjecture on cosmological dynamical horizon
We here propose a covariant entropy conjecture on cosmological dynamical
horizon. After the formulation of our conjecture, we test its validity in
adiabatically expanding universes with open, flat and closed spatial geometry,
where our conjecture can also be viewed as a cosmological version of the
generalized second law of thermodynamics in some sense.Comment: JHEP style, 9 pages, 1 figure, typos corrected, accepted for
publication in JHE
Proliferation of de Sitter Space
I show that de Sitter space disintegrates into an infinite number of copies
of itself. This occurs iteratively through a quantum process involving two
types of topology change. First a handle is created semiclassically, on which
multiple black hole horizons form. Then the black holes evaporate and
disappear, splitting the spatial hypersurfaces into large parts. Applied to
cosmology, this process leads to the production of a large or infinite number
of universes in most models of inflation and yields a new picture of global
structure.Comment: 19 pages, LaTeX2e, 4 figure
Probing entropy bounds with scalar field spacetimes
We study covariant entropy bounds in dynamical spacetimes with naked
singularities. Specifically we study a spherically symmetric massless scalar
field solution. The solution is an inhomogeneous cosmology with an initial
spacelike singularity, and a naked timelike singularity at the origin. We
construct the entropy flux 4-vector for the scalar field, and show by explicit
computation that the generalized covariant bound is violated for light sheets in the neighbourhood of the (evolving)
apparent horizon. We find no violations of the Bousso bound (for which
), even though certain sufficient conditions for this bound do not
hold. This result therefore shows that these conditions are not necessary.Comment: 10 pages, 5 figures; published version with typos correcte
Thermodynamics of Schwarzschild-(Anti-)de Sitter Black Holes with account of quantum corrections
We discuss the quantum corrections to thermodynamics (and geometry) of S(A)dS
BHs using large one-loop anomaly induced effective action for dilaton
coupled matter (scalars and spinors). It is found the temperature, mass and
entropy with account of quantum effects for multiply horizon SdS BH and SAdS BH
what also gives the corresponding expressions for their limits: Schwarzschild
and de Sitter spaces. In the last case one can talk about quantum correction to
entropy of expanding Universe.
The anomaly induced action under discussion corresponds to 4d formulation
(s-wave approximation, 4d quantum matter is minimal one) as well as 2d
formulation (complete effective action, 2d quantum matter is dilaton coupled
one). Hence, most of results are given for the same gravitational background
with interpretation as 4d quantum corrected BH or 2d quantum corrected
dilatonic BH. Quantum aspects of thermodynamics of 4d 't Hooft BH model are
also considered.Comment: LaTeX file, 28 pages, some misprints are correcte
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