972 research outputs found
Strong cosmic censorship: The nonlinear story
A satisfactory formulation of the laws of physics entails that the future
evolution of a physical system should be determined from appropriate initial
conditions. The existence of Cauchy horizons in solutions of the Einstein field
equations is therefore problematic, and expected to be an unstable artifact of
General Relativity. This is asserted by the Strong Cosmic Censorship
Conjecture, which was recently put into question by an analysis of the
linearized equations in the exterior of charged black holes in an expanding
universe. Here, we numerically evolve the nonlinear Einstein-Maxwell-scalar
field equations with a positive cosmological constant, under spherical
symmetry, and provide strong evidence that mass inflation indeed does not occur
in the near extremal regime. This shows that nonlinear effects might not
suffice to save the Strong Cosmic Censorship Conjecture.Comment: 9 pages, 8 figures. v2: Matches published versio
Message in a bottle: energy extraction from bouncing geometries
Quantum gravity phenomenology suggests the interesting possibility that black
holes are not eternal. Collapse could be halted by some unknown mechanism, or
Hawking radiation might leave behind a regular spacetime. Here we investigate a
simple bouncing geometry, with (outer and inner) apparent horizons but no event
horizon. We show that the inner horizon blueshifts radiation, which can lead to
a gigantic amplification of energy observable from far away regions. Thus, if
such phenomena exists in our universe, they can power high-energy bursts at
late stages in their lives, when the horizons disappear and spacetime bounces
back to a flat geometry.Comment: 5 pages,3 figure
Simultaneous occurrence of sliding and crossing limit cycles in piecewise linear planar vector fields
In the present study, we consider planar piecewise linear vector fields with two zones separated by the straight line x = 0. Our goal is to study the existence of simultaneous crossing and sliding limit cycles for such a class of vector fields. First, we provide a canonical form for these systems assuming that each linear system has centre, a real one for y0, and such that the real centre is a global centre. Then, working with a first-order piecewise linear perturbation we obtain piecewise linear differential systems with three crossing limit cycles. Second, we see that a sliding cycle can be detected after a second-order piecewise linear perturbation. Finally, imposing the existence of a sliding limit cycle we prove that only one adittional crossing limit cycle can appear. Furthermore, we also characterize the stability of the higher amplitude limit cycle and of the infinity. The main techniques used in our proofs are the Melnikov method, the Extended Chebyshev systems with positive accuracy, and the Bendixson transformation
Sustainability of the Water Resources of a River Basin
Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv
Black hole collision with a scalar particle in four, five and seven dimensional anti-de Sitter spacetimes: ringing and radiation
In this work we compute the spectra, waveforms and total scalar energy
radiated during the radial infall of a small test particle coupled to a scalar
field into a -dimensional Schwarzschild-anti-de Sitter black hole. We focus
on and 7, extending the analysis we have done for . For small
black holes, the spectra peaks strongly at a frequency , which
is the lowest pure anti-de Sitter (AdS) mode. The waveform vanishes
exponentially as , and this exponential decay is governed
entirely by the lowest quasinormal frequency. This collision process is
interesting from the point of view of the dynamics itself in relation to the
possibility of manufacturing black holes at LHC within the brane world
scenario, and from the point of view of the AdS/CFT conjecture, since the
scalar field can represent the string theory dilaton, and 4, 5, 7 are
dimensions of interest for the AdS/CFT correspondence.Comment: 16 pages, 13 figures. Published versio
The underrepresentation and misrepresentation of invertebrates in the IUCN Red List
Copyright © 2012 Elsevier Ltd. All rights reserved
Scalar Synchrotron Radiation in the Schwarzschild-anti-de Sitter Geometry
We present a complete relativistic analysis for the scalar radiation emitted
by a particle in circular orbit around a Schwarzschild-anti-de Sitter black
hole. If the black hole is large, then the radiation is concentrated in narrow
angles- high multipolar distribution- i.e., the radiation is synchrotronic.
However, small black holes exhibit a totally different behavior: in the small
black hole regime, the radiation is concentrated in low multipoles. There is a
transition mass at , where is the AdS radius. This behavior is
new, it is not present in asymptotically flat spacetimes.Comment: 13 pages, 6 figures, published version. References adde
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