35 research outputs found
Regularization ambiguity and van der Waals black hole in 2 + 1 dimensions
Charged black holes in a (2+1
)-dimensional anti-de Sitter space-time suffer from some limitations such as the ambiguity in the definition of the mass and the bad short distance behavior. In this paper we present a way to resolve such issues. By extending the parameter space of the BTZ geometry, we properly identify the integration constants in order to remove the conical singularity sitting at the origin. In such a way we obtain a well defined Minkowski limit and horizons also in the case of de Sitter background space. On the thermodynamic side, we obtain a proper internal energy, by invoking the consistency with the Area Law, even if the mass parameter does not appear in the metric coefficients. As a further improvement, we show that it is sufficient to assume a finite size of the electric charge to obtain a short scale regular geometry. The resulting solution, generalizing the charged BTZ metric, is dual to a van der Waals gas
Production and evaporation of Planck scale black holes at the LHC
We review the phenomenology of mini black holes at colliders in light of the latest data from the LHC. By improving the conventional production cross-section, we show that the current non-observation of black hole signals can be explained in terms of quantum gravity effects. In the most optimistic case, black hole production could take place at a scale slightly above the LHC design energy. We also analyse possible new signatures of quantum-corrected Planck-scale black holes: in contrast to the semiclassical scenario the emission would take place in terms of soft particles mostly on the brane
A model of radiating black hole in noncommutative geometry
The phenomenology of a radiating Schwarzschild black hole is analyzed in a
noncommutative spacetime. It is shown that noncommutativity does not depend on
the intensity of the curvature. Thus we legitimately introduce noncommutativity
in the weak field limit by a coordinate coherent state approach. The new
interesting results are the following: i) the existence of a minimal non-zero
mass to which black hole can shrink; ii) a finite maximum temperature that the
black hole can reach before cooling down to absolute zero; iii) the absence of
any curvature singularity. The proposed scenario offers a possible solution to
conventional difficulties when describing terminal phase of black hole
evaporation.Comment: 10 pages, 4 figure
TeV Mini Black Hole Decay at Future Colliders
It is generally believed that mini black holes decay by emitting elementary
particles with a black body energy spectrum. The original calculation lead to
the conclusion that about the 90% of the black hole mass is radiated away in
the form of photons, neutrinos and light leptons, mainly electrons and muons.
With the advent of String Theory, such a scenario must be updated by including
new effects coming from the stringy nature of particles and interactions.By
taking for granted that black holes can be produced in hadronic collisions,
then their decay must take into account that: (i) we live in a D3-Brane
embedded into an higher dimensional bulk spacetime; (ii) fundamental
interactions, including gravity, are unified at TeV energy scale. Thus, the
formal description of the Hawking radiation mechanism has to be extended to the
case of more than four spacetime dimensions and include the presence of
D-branes. Furthermore, unification of fundamental interactions at an energy
scale many order of magnitude lower than the Planck energy implies that any
kind of fundamental particle, not only leptons, is expected to be emitted. A
detailed understanding of the new scenario is instrumental for optimal tuning
of detectors at future colliders, where, hopefully, this exciting new physics
will be tested. In this article we review higher dimensional black hole decay,
considering not only the emission of particles according to Hawking mechanism,
but also their near horizon QED/QCD interactions. The ultimate motivation is to
build up a phenomenologically reliable scenario, allowing a clear experimental
signature of the event.Comment: 22 pages, 9 figures, 4 tables; ``quick review'' for Class. and
Quantum Gra
Self-completeness and spontaneous dimensional reduction
A viable quantum theory of gravity is one of the biggest challenges facing
physicists. We discuss the confluence of two highly expected features which
might be instrumental in the quest of a finite and renormalizable quantum
gravity -- spontaneous dimensional reduction and self-completeness. The former
suggests the spacetime background at the Planck scale may be effectively
two-dimensional, while the latter implies a condition of maximal compression of
matter by the formation of an event horizon for Planckian scattering. We
generalize such a result to an arbitrary number of dimensions, and show that
gravity in higher than four dimensions remains self-complete, but in lower
dimensions it is not. In such a way we established an "exclusive disjunction"
or "exclusive or" (XOR) between the occurrence of self-completeness and
dimensional reduction, with the goal of actually reducing the unknowns for the
scenario of the physics at the Planck scale. Potential phenomenological
implications of this result are considered by studying the case of a
two-dimensional dilaton gravity model resulting from dimensional reduction of
Einstein gravity.Comment: 12 pages, 3 figures; v3: final version in press on Eur. Phys. J. Plu
Spinning Loop Black Holes
In this paper we construct four Kerr-like spacetimes starting from the loop
black hole Schwarzschild solutions (LBH) and applying the Newman-Janis
transformation. In previous papers the Schwarzschild LBH was obtained replacing
the Ashtekar connection with holonomies on a particular graph in a
minisuperspace approximation which describes the black hole interior. Starting
from this solution, we use a Newman-Janis transformation and we specialize to
two different and natural complexifications inspired from the complexifications
of the Schwarzschild and Reissner-Nordstrom metrics. We show explicitly that
the space-times obtained in this way are singularity free and thus there are no
naked singularities. We show that the transformation move, if any, the
causality violating regions of the Kerr metric far from r=0. We study the
space-time structure with particular attention to the horizons shape. We
conclude the paper with a discussion on a regular Reissner-Nordstrom black hole
derived from the Schwarzschild LBH and then applying again the Newmann-Janis
transformation.Comment: 18 pages, 18 figure
Minimal Scales from an Extended Hilbert Space
We consider an extension of the conventional quantum Heisenberg algebra,
assuming that coordinates as well as momenta fulfil nontrivial commutation
relations. As a consequence, a minimal length and a minimal mass scale are
implemented. Our commutators do not depend on positions and momenta and we
provide an extension of the coordinate coherent state approach to
Noncommutative Geometry. We explore, as toy model, the corresponding quantum
field theory in a (2+1)-dimensional spacetime. Then we investigate the more
realistic case of a (3+1)-dimensional spacetime, foliated into noncommutative
planes. As a result, we obtain propagators, which are finite in the ultraviolet
as well as the infrared regime.Comment: 16 pages, version which matches that published on CQ
The Hawking-Page crossover in noncommutative anti-deSitter space
We study the problem of a Schwarzschild-anti-deSitter black hole in a
noncommutative geometry framework, thought to be an effective description of
quantum-gravitational spacetime. As a first step we derive the noncommutative
geometry inspired Schwarzschild-anti-deSitter solution. After studying the
horizon structure, we find that the curvature singularity is smeared out by the
noncommutative fluctuations. On the thermodynamics side, we show that the black
hole temperature, instead of a divergent behavior at small scales, admits a
maximum value. This fact implies an extension of the Hawking-Page transition
into a van der Waals-like phase diagram, with a critical point at a critical
cosmological constant size in Plank units and a smooth crossover thereafter. We
speculate that, in the gauge-string dictionary, this corresponds to the
confinement "critical point" in number of colors at finite number of flavors, a
highly non-trivial parameter that can be determined through lattice
simulations.Comment: 24 pages, 6 figure, 1 table, version matching that published on JHE
Gravitational Collapse of the Shells with the Smeared Gravitational Source in Noncommutative Geometry
We study the formation of the (noncommutative) Schwarzschild black hole from
collapsing shell {of the} generalized matters containing polytropic and
Chaplygin gas. We show that this collapsing shell depending on various
parameters forms either a black hole or a naked singular shell with the help of
the pressure.Furthermore, by considering the smeared gravitational sources, we
investigate the noncommutative black holes formation. Though this mild
noncommutative correction of matters cannot ultimately resolve the emergence of
the naked singularity, we show that in some parameter region the collapsing
shell evolves to a noncommutative black hole before becoming a naked singular
shell.Comment: 16 pages, LateX, 9 figures, Title changed in this published versio
Tunneling of massive and charged particles from noncommutative Reissner-Nordstr\"{o}m black hole
Massive charged and uncharged particles tunneling from commutative
Reissner-Nordstrom black hole horizon has been studied with details in
literature. Here, by adopting the coherent state picture of spacetime
noncommutativity, we study tunneling of massive and charged particles from a
noncommutative inspired Reissner-Nordstrom black hole horizon. We show that
Hawking radiation in this case is not purely thermal and there are correlations
between emitted modes. These correlations may provide a solution to the
information loss problem. We also study thermodynamics of noncommutative
horizon in this setup.Comment: 10 pages, 2 figure