18,104 research outputs found
Can black holes and naked singularities be detected in accelerators?
We study the conditions for the existence of black holes that can be produced
in colliders at TeV-scale if the space-time is higher dimensional. On employing
the microcanonical picture, we find that their life-times strongly depend on
the details of the model. If the extra dimensions are compact (ADD model),
microcanonical deviations from thermality are in general significant near the
fundamental TeV mass and tiny black holes decay more slowly than predicted by
the canonical expression, but still fast enough to disappear almost
instantaneously. However, with one warped extra dimension (RS model),
microcanonical corrections are much larger and tiny black holes appear to be
(meta)stable. Further, if the total charge is not zero, we argue that naked
singularities do not occur provided the electromagnetic field is strictly
confined on an infinitely thin brane. However, they might be produced in
colliders if the effective thickness of the brane is of the order of the
fundamental length scale (~1/TeV).Comment: 6 pages, RevTeX 3, 1 figure and 1 table, important changes and
addition
No Time Asymmetry from Quantum Mechanics
With CPT-invariant initial conditions that commute with CPT-invariant final
conditions, the respective probabilities (when defined) of a set of histories
and its CPT reverse are equal, giving a CPT-symmetric universe. This leads me
to question whether the asymmetry of the Gell-Mann--Hartle decoherence
functional for ordinary quantum mechanics should be interpreted as an asymmetry
of {\it time} .Comment: 14 pages, Alberta-Thy-11-9
Unifying Parsimonious Tree Reconciliation
Evolution is a process that is influenced by various environmental factors,
e.g. the interactions between different species, genes, and biogeographical
properties. Hence, it is interesting to study the combined evolutionary history
of multiple species, their genes, and the environment they live in. A common
approach to address this research problem is to describe each individual
evolution as a phylogenetic tree and construct a tree reconciliation which is
parsimonious with respect to a given event model. Unfortunately, most of the
previous approaches are designed only either for host-parasite systems, for
gene tree/species tree reconciliation, or biogeography. Hence, a method is
desirable, which addresses the general problem of mapping phylogenetic trees
and covering all varieties of coevolving systems, including e.g., predator-prey
and symbiotic relationships. To overcome this gap, we introduce a generalized
cophylogenetic event model considering the combinatorial complete set of local
coevolutionary events. We give a dynamic programming based heuristic for
solving the maximum parsimony reconciliation problem in time O(n^2), for two
phylogenies each with at most n leaves. Furthermore, we present an exact
branch-and-bound algorithm which uses the results from the dynamic programming
heuristic for discarding partial reconciliations. The approach has been
implemented as a Java application which is freely available from
http://pacosy.informatik.uni-leipzig.de/coresym.Comment: Peer-reviewed and presented as part of the 13th Workshop on
Algorithms in Bioinformatics (WABI2013
Dedication of the Palomar Observatory and the Hale Telescope
The dedication of the Palomar Observatory, if it were being held in England, would be accompanied by brilliant pageantry both of the state, with its knights, heralds, pursuivants, kings at arms, admirals and captains, and of the church with its bishops, priests and deacons, crucifiers and choirs; and I am sure that we feel the quality of religion in this ceremony. We would hear the choirs chanting in antiphony that great canticle which so delights the choir boys: Benedicite, omnia opera Domini
Design and analysis issues of integrated control systems for high-speed civil transports
A study was conducted to identify, rank, and define development plans for the critical guidance and control design and analysis issues as related to economically viable and environmentally acceptable high-speed civil transport. The issues were identified in a multistep process. First, pertinent literature on supersonic cruise aircraft was reviewed, and experts were consulted to establish the fundamental characteristics and problems inherent to supersonic cruise aircraft. Next, the advanced technologies and strategies being pursued for the high-speed civil transport were considered to determine any additional unique control problems the transport may have. Finally, existing technologies and methods were examined to determine their capabilities for the design and analysis of high-speed civil transport control systems and to identify the shortcomings and issues. Three priority levels - mandatory, highly beneficial, and desirable - were established. Within each of these levels, the issues were further ranked. Technology development plans for each issue were defined. Each plan contains a task breakdown and schedule
Rotating Black Holes in Higher Dimensions with a Cosmological Constant
We present the metric for a rotating black hole with a cosmological constant
and with arbitrary angular momenta in all higher dimensions. The metric is
given in both Kerr-Schild and Boyer-Lindquist form. In the Euclidean-signature
case, we also obtain smooth compact Einstein spaces on associated S^{D-2}
bundles over S^2, infinitely many for each odd D\ge 5. Applications to string
theory and M-theory are indicated.Comment: 8 pages, Latex. Short version, with more compact notation, of
hep-th/0404008. To appear in Phys. Rev. Let
Entanglement, recoherence and information flow in an accelerated detector - quantum field system: Implications for black hole information issue
We study an exactly solvable model where an uniformly accelerated detector is
linearly coupled to a massless scalar field initially in the Minkowski vacuum.
Using the exact correlation functions we show that as soon as the coupling is
switched on one can see information flowing from the detector to the field and
propagating with the radiation into null infinity. By expressing the reduced
density matrix of the detector in terms of the two-point functions, we
calculate the purity function in the detector and study the evolution of
quantum entanglement between the detector and the field. Only in the ultraweak
coupling regime could some degree of recoherence in the detector appear at late
times, but never in full restoration. We explicitly show that under the most
general conditions the detector never recovers its quantum coherence and the
entanglement between the detector and the field remains large at late times. To
the extent this model can be used as an analog to the system of a black hole
interacting with a quantum field, our result seems to suggest in the prevalent
non-Markovian regime, assuming unitarity for the combined system, that black
hole information is not lost but transferred to the quantum field degrees of
freedom. Our combined system will evolve into a highly entangled state between
a remnant of large area (in Bekenstein's black hole atom analog) without any
information of its initial state, and the quantum field, now imbued with
complex information content not-so-easily retrievable by a local observer.Comment: 16 pages, 12 figures; minor change
Constants of Geodesic Motion in Higher-Dimensional Black-Hole Spacetimes
In [arXiv:hep-th/0611083] we announced the complete integrability of geodesic
motion in the general higher-dimensional rotating black-hole spacetimes. In the
present paper we prove all the necessary steps leading to this conclusion. In
particular, we demonstrate the independence of the constants of motion and the
fact that they Poisson commute. The relation to a different set of constants of
motion constructed in [arXiv:hep-th/0612029] is also briefly discussed.Comment: 8 pages, no figure
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