106 research outputs found
Tunneling through the quantum horizon
The emergence of quantum-gravity induced corrective terms for the probability
of emission of a particle from a black hole in the Parikh-Wilczek tunneling
framework is studied. It is shown, in particular, how corrections might arise
from modifications of the surface gravity due to near horizon Planck-scale
effects. Our derivation provides an example of the possible linking between
Planck-scale departures from Lorentz invariance and the appearance of higher
order quantum gravity corrections in the black-hole entropy-area relation.Comment: 8 pages, no figures, REVTeX. Extensively revised version. New title
and modified paper structure. Main analysis unchanged. Some conclusions have
been removed and will be discussed in a forthcoming wor
Black-hole entropy and minimal diffusion
The density of states reproducing the Bekenstein-Hawking entropy-area scaling
can be modeled via a nonlocal field theory. We define a diffusion process based
on the kinematics of this theory and find a spectral dimension whose flow
exhibits surprising properties. While it asymptotes four from above in the
infrared, in the ultraviolet the spectral dimension diverges at a finite
(Planckian) value of the diffusion length, signaling a breakdown of the notion
of diffusion on a continuum spacetime below that scale. We comment on the
implications of this minimal diffusion scale for the entropy bound in a
holographic and field-theoretic context.Comment: 5 pages, 1 figure. v2: physical interpretation of the results
clarifie
UV dimensional reduction to two from group valued momenta
We describe a new model of deformed relativistic kinematics based on the
group manifold as a four-momentum space. We discuss the
action of the Lorentz group on such space and and illustrate the deformed
composition law for the group-valued momenta. Due to the geometric structure of
the group, the deformed kinematics is governed by {\it two} energy scales
and . A relevant feature of the model is that it exhibits a
running spectral dimension with the characteristic short distance
reduction to found in most quantum gravity scenarios.Comment: 15 pages, 1 figur
Localization and diffusion in polymer quantum field theory
Polymer quantization is a non-standard approach to quantizing a classical
system inspired by background independent approaches to quantum gravity such as
loop quantum gravity. When applied to field theory it introduces a
characteristic polymer scale at the level of the fields classical configuration
space. Compared with models with space-time discreteness or non-commutativity
this is an alternative way in which a characteristic scale can be introduced in
a field theoretic context. Motivated by this comparison we study here
localization and diffusion properties associated with polymer field observables
and dispersion relation in order to shed some light on the novel physical
features introduced by polymer quantization. While localization processes seems
to be only mildly affected by polymer effects, we find that polymer diffusion
differs significantly from the "dimensional reduction" picture emerging in
other Planck-scale models beyond local quantum field theory.Comment: 16 pages, 5 figure
Entanglement entropy, scale-dependent dimensions and the origin of gravity
We argue that the requirement of a finite entanglement entropy of quantum
degrees of freedom across a boundary surface is closely related to the
phenomenon of running spectral dimension, universal in approaches to quantum
gravity. If quantum geometry hinders diffusion, for instance when its structure
at some given scale is discrete or too rough, then the spectral dimension of
spacetime vanishes at that scale and the entropy density blows up. A finite
entanglement entropy is a key ingredient in deriving Einstein gravity in a
semi-classical regime of a quantum-gravitational theory and, thus, our
arguments strengthen the role of running dimensionality as an imprint of
quantum geometry with potentially observable consequences.Comment: 8 pages, 1 figure. Received an Honorable Mention in the 2017 Essay
Competition of the Gravity Research Foundatio
A fuzzy bipolar celestial sphere
We introduce a non-commutative deformation of the algebra of bipolar
spherical harmonics supporting the action of the full Lorentz algebra. Our
construction is close in spirit to the one of the non-commutative spherical
harmonics associated to the fuzzy sphere and, as such, it leads to a maximal
value of the angular momentum. We derive the action of Lorentz boost generators
on such non-commutative spherical harmonics and show that it is compatible with
the existence of a maximal angular momentum.Comment: 15 pages, 4 figures; v2: typos corrected, references added; v3 title
slightly changed, minor adjustments in the presentation, results unchanged.
References added, matches published versio
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