317 research outputs found

### Lorentz invariance without trans-Planckian physics?

We explore the possibility that, in a quantum field theory with Planck scale
cutoff Lambda=Mp, observable quantities for low-energy processes respect the
Lorentz symmetry. In particular, we compute the one-loop radiative correction
Pi to the self-energy of a scalar field with lambda phi^4 interaction, using a
modified (non-invariant) propagator which vanishes in the trans-Planckian
regime, as expected in the "classicalization" scenario. We then show that, by
imposing the result does not depend on Lambda (in the limit Lambda to Mp), an
explicit (albeit not unique) expression for Pi can be derived, which is similar
to the one simply obtained with the standard Feynman propagator and a cutoff
Lambda=Mp.Comment: 9 pages, 1 figure, section about fluctuating cutoff added, final
version to appear in PL

### Gravitational tests of the Generalized Uncertainty Principle

We compute the corrections to the Schwarzschild metric necessary to reproduce
the Hawking temperature derived from a Generalized Uncertainty Principle (GUP),
so that the GUP deformation parameter is directly linked to the deformation of
the metric. Using this modified Schwarzschild metric, we compute corrections to
the standard General Relativistic predictions for the light deflection and
perihelion precession, both for planets in the solar system and for binary
pulsars. This analysis allows us to set bounds for the GUP deformation
parameter from well-known astronomical measurements.Comment: 20 pages, 2 figure

### Brane-world stars from minimal geometric deformation, and black holes

We build analytical models of spherically symmetric stars in the brane-world,
in which the external space-time contains both an ADM mass and a tidal charge.
In order to determine the interior geometry, we apply the principle of minimal
geometric deformation, which allows one to map General Relativistic solutions
to solutions of the effective four-dimensional brane-world equations. We
further restrict our analysis to stars with a radius linearly related to the
total General Relativistic mass, and obtain a general relation between the
latter, the brane-world ADM mass and the tidal charge. In these models, the
value of the star's radius can then be taken to zero smoothly, thus obtaining
brane-world black hole metrics with a tidal charge solely determined by the
mass of the source and the brane tension. General conclusions regarding the
minimum mass for semiclassical black holes will also be drawn.Comment: 23 pages, 2 figures, references added and update

### Polytropic stars in bootstrapped Newtonian gravity

We study self-gravitating stars in the bootstrapped Newtonian picture for
polytropic equations of state. We consider stars that span a wide range of
compactness values. Both matter density and pressure are sources of the
gravitational potential. Numerical solutions show that the density profiles can
be well approximated by Gaussian functions. Later we assume Gaussian density
profiles to investigate the interplay between the compactness of the source,
the width of the Gaussian density profile and the polytropic index. We also
dedicate a section to comparing the pressure and density profiles of the
bootstrapped Newtonian stars to the corresponding General Relativistic
solutions. We also point out that no Buchdahl limit is found, which means that
the pressure can in principle support a star of arbitrarily large compactness.
In fact, we find solutions representing polytropic stars with compactness above
the Buchdhal limit.Comment: 21 pages, 10 figure

### The role of collapsed matter in the decay of black holes

We try to shed some light on the role of matter in the final stages of black
hole evaporation from the fundamental frameworks of classicalization and the
black-to-white hole bouncing scenario. Despite being based on very different
grounds, these two approaches attempt at going beyond the background field
method and treat black holes as fully quantum systems rather than considering
quantum field theory on the corresponding classical manifolds. They also lead
to the common prediction that the semiclassical description of black hole
evaporation should break down and the system be disrupted by internal quantum
pressure, but they both arrive at this conclusion neglecting the matter that
formed the black hole. We instead estimate this pressure from the bootstrapped
description of black holes, which allows us to express the total
Arnowitt-Deser-Misner mass in terms of the baryonic mass still present inside
the black hole. We conclude that, although these two scenarios provide
qualitatively similar predictions for the final stages, the corpuscular model
does not seem to suggest any sizeable deviation from the semiclassical time
scale at which the disruption should occur, unlike the black-to-white hole
bouncing scenario. This, in turn, makes the phenomenology of corpuscular black
holes more subtle from an astrophysical perspective.Comment: 5 pages, no figur

### The Method of Comparison Equations for Schwarzschild Black Holes

We employ the method of comparison equations to study the propagation of a
massless minimally coupled scalar field on the Schwarzschild background. In
particular, we show that this method allows us to obtain explicit approximate
expressions for the radial modes with energy below the peak of the effective
potential which are fairly accurate over the whole region outside the horizon.
This case can be of particular interest, for example, for the problem of black
hole evaporation.Comment: 7 pages, added figures. Version to appear in PR

### The horizon of the lightest black hole

We study the properties of the poles of the resummed graviton propagator obtained by resumming bubble matter diagrams which correct the classical graviton propagator. These poles have been previously interpreted as black holes precursors. Here, we show using the Horizon Wave-Function formalism that these poles indeed have properties which make them compatible with being black hole precursors. In particular, when modeled with a Breit-Wigner distribution, they have a well defined gravitational radius. The probability that the resonance is inside its own gravitational radius, and thus that it is black hole, is about one half. Our results confirm the interpretation of these poles as black hole precursors

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