1,571 research outputs found
Casimir effect in a quantum space-time
We apply quantum field theory in quantum space-time techniques to study the
Casimir effect for large spherical shells. As background we use the recently
constructed exact quantum solution for spherically symmetric vacuum space-time
in loop quantum gravity. All calculations are finite and one recovers the usual
results without the need of regularization or renormalization. This is an
example of how loop quantum gravity provides a natural resolution to the
infinities of quantum field theories.Comment: 4 page
Quantum Transfiguration of Kruskal Black Holes
We present a new effective description of macroscopic Kruskal black holes
that incorporates corrections due to quantum geometry effects of loop quantum
gravity. It encompasses both the `interior' region that contains classical
singularities and the `exterior' asymptotic region. Singularities are naturally
resolved by the quantum geometry effects of loop quantum gravity, and the
resulting quantum extension of the full Kruskal space-time is free of all the
known limitations of previous investigations [1-11] of the Schwarzschild
interior. We compare and contrast our results with these investigations and
also with the expectations based on the AdS/CFT duality [12].Comment: 5 pages, 1 figure, minor changes, version to appear in PR
Quantum Extension of the Kruskal Space-time
A new description of macroscopic Kruskal black holes that incorporates the
quantum geometry corrections of loop quantum gravity is presented. It
encompasses both the `interior' region that contains classical singularities
and the `exterior' asymptotic region. Singularities are naturally resolved by
the quantum geometry effects of loop quantum gravity. The resulting quantum
extension of space-time has the following features: (i) It admits an infinite
number of trapped, anti-trapped and asymptotic regions; (ii) All curvature
scalars have uniform (i.e., mass independent) upper bounds; (iii) In the large
mass limit, all asymptotic regions of the extension have the same ADM mass;
(iv) In the low curvature region (e.g., near horizons) quantum effects are
negligible, as one would physically expect; and (v) Final results are
insensitive to the fiducial structures that have to be introduced to construct
the classical phase space description (as they must be). Previous effective
theories [1-10] shared some but not all of these features. We compare and
contrast our results with those of these effective theories and also with
expectations based on the AdS/CFT conjecture [11]. We conclude with a
discussion of limitations of our framework, especially for the analysis of
evaporating black holes.Comment: 47 pages, 5 figures, A short addendum is added after the last section
to address misleading remarks in a recent pre-print [50] that may confuse the
reade
Schr\"odinger-like quantum dynamics in loop quantized black holes
We show, following a previous quantization of a vacuum spherically symmetric
spacetime carried out in Ref. \cite{gop}, that this setting admits a
Schr\"odinger-like picture. More precisely, the technique adopted there for the
definition of parametrized Dirac observables (that codify local information of
the quantum theory) can be extended in order to accommodate different pictures.
In this new picture, the quantum states are parametrized in terms of suitable
gauge parameters and the observables constructed out of the kinematical ones on
this space of parametrized states.Comment: 19 pages, minor corrections have been incorporated in order to match
the published versio
Quantum black holes in Loop Quantum Gravity
We study the quantization of spherically symmetric vacuum spacetimes within
loop quantum gravity. In particular, we give additional details about our
previous work in which we showed that one could complete the quantization the
model and that the singularity inside black holes is resolved. Moreover, we
consider an alternative quantization based on a slightly different kinematical
Hilbert space. The ambiguity in kinematical spaces stems from how one treats
the periodicity of one of the classical variables in these models. The
corresponding physical Hilbert spaces solve the diffeomorphism and Hamiltonian
constraint but their intrinsic structure is radically different depending on
the kinematical Hilbert space one started from. In both cases there are quantum
observables that do not have a classical counterpart. However, one can show
that at the end of the day, by examining Dirac observables, both quantizations
lead to the same physical predictions.Comment: 20 pages. Some further change
Brief review on black hole loop quantization
Here, we present a review about the quantization of spherically-symmetric
spacetimes adopting loop quantum gravity techniques. Several models that have
been studied so far share similar properties: the resolution of the classical
singularity and some of them an intrinsic discretization of the geometry. We
also explain the extension to Reissner---Nordstr\"om black holes. Besides, we
review how quantum test fields on these quantum geometries allow us to study
phenomena, like the Casimir effect or Hawking radiation. Finally, we briefly
describe a recent proposal that incorporates spherically-symmetric matter,
discussing its relevance for the understanding of black hole evolution.Comment: 49 pages, several typos have been corrected, corrections included in
order to match the published versio
Classical axisymmetric gravity in real Ashtekar variables
We formulate axisymmetric general relativity in terms of real
Ashtekar--Barbero variables. We study the constraints and equations of motion
and show how the Kerr, Schwarzschild and Minkowski solutions arise. We also
discuss boundary conditions. This opens the possibility of a midisuperspace
quantization using loop quantum gravity techniques for spacetimes with axial
symmetry and time dependence.Comment: 14 pages, no figures, RevTex. Published versio
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