1,720,964 research outputs found
Exploring the bulk of tidal charged micro-black holes
No full textWe study the bulk corresponding to tidal charged brane-world black holes. We employ a propagating algorithm which makes use of the three-dimensional multipole expansion and analytically yields the metric elements as functions of the five-dimensional coordinates and of the Adler-Deser-Misner mass, tidal charge, and brane tension. Since the projected brane equations cannot determine how the charge depends on the mass, our main purpose is to select the combinations of these parameters for which black holes of microscopic size possess a regular bulk. Our results could, in particular, be relevant for a better understanding of TeV-scale black holes
A Quantum Cosmic Conjecture
No full textFor a quantum mechanically Gaussian shaped, electrically charged,
massive particle, we compute the Horizon Wave-function(s) in order to study (a) the
existence of the inner Cauchy horizon of the corresponding Reissner–Nordström
space-time when the charge-to-mass ratio 0 < α < 1 and (b) the survival of a naked
singularity when the charge-to-mass ratio α > 1. Our results suggest that any semi-
classical instability one expects near the inner horizon may not occur in quantum
black holes, with a mass around the Planck scale, and that no states with charge-to-
mass ratio greater than a critical value (of the order of 2) should exist
Minimum black hole mass from colliding Gaussian packets
No full textWe study the formation of a black hole in the col- lision of two Gaussian packets. Rather than following their dynamical evolution in detail, we assume a horizon forms when the mass function for the two packets becomes larger than half the flat areal radius, as it would occur in a spher- ically symmetric geometry. This simple approximation al- lows us to determine the existence of a minimum black hole mass solely related to the width of the packets. We then com- ment on the possible physical implications, both in classical and quantum physics, and models with extra spatial dimen- sions
Theoretical survey of tidal-charged black holes at the LHC
No full textWe analyse a family of brane-world black holes which solve the effective four-dimensional Einstein equations for a wide range of parameters related to the unknown bulk/brane physics. We first constrain the parameters using known experimental bounds and, for the allowed cases, perform a numerical analysis of their time evolution, which includes accretion through the Earth. The study is aimed at predicting the typical behavior one can expect if such black holes were produced at the LHC. Most notably, we find that, under no circumstances, would the black holes reach the (hazardous) regime of Bondi accretion. Nonetheless, the possibility remains that black holes live long enough to escape from the accelerator (and even from the Earth’s gravitational field) and result in missing energy from the detectors
Moving mirrors and black hole evaporation in noncommutative space-times
No full textWe study the evaporation of black holes in noncommutative space-times. We do this by calculating the correction to the detector's response function for a moving mirror in terms of the noncommutativity parameter Theta and then extracting the number density as modified by this parameter. We find that allowing space and time to be noncommutative increases the decay rate of a black hole
Boundaries and the Casimir effect in noncommutative space-time
No full textWe calculate modifications to the scalar Casimir force between two parallel plates due to space-time noncommutativity. We devise a heuristic approach to overcome the difficulties of describing boundaries in noncommutative theories and predict that boundary corrections are of the same order as noncommutative volume corrections. Further, both corrections have the form of more conventional finite surface effects
Effect of brane thickness on microscopic tidal-charged black holes
No full textWe study the phenomenological implications stemming from the dependence of the tidal charge on the brane thickness L for the evaporation and decay of microscopic black holes. In general, the larger L, the longer are the black hole lifetimes and the greater their maximum mass for those cases in which the black hole can grow. In particular, we again find that tidal-charged black holes might live long enough to escape the detectors and even the gravitational field of the Earth, thus resulting in large amounts of missing energy. However, under no circumstances could TeV-scale black holes grow enough to enter the regime of Bondi accretion
Brane-world black holes and the scale of gravity
No full textA particle in four dimensions should behave like a classical black hole if the horizon radius is larger than the Compton wavelength or, equivalently, if its degeneracy (measured by entropy in units of the Planck scale) is large. For spherically symmetric black holes in 4 + d dimensions, both arguments again lead to a mass threshold M C and degeneracy scale M deg of the order of the fundamental scale of gravity M G. In the brane-world, deviations from the Schwarzschild metric induced by bulk effects alter the horizon radius and effective four-dimensional Euclidean action in such a way that M C ≃ M deg might be either larger or smaller than M G. This opens up the possibility that black holes exist with a mass smaller than M G and might be produced at the LHC even if M G ≳ 10 TeV, whereas effects due to bulk graviton exchanges remain undetectable because suppressed by inverse powers of M G. Conversely, even if black holes are not found at the LHC, it is still possible that M C ≫ M G and M G ≃ 1 TeV
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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