17,649 research outputs found
Observing Hawking radiation in Bose-Einstein condensates via correlation measurements
Observing quantum particle creation by black holes (Hawking radiation) in the
astrophysical context is, in ordinary situations, hopeless. Nevertheless the
Hawking effect, which depends only on kinematical properties of wave
propagation in the presence of horizons, is present also in nongravitational
contexts, for instance in stationary fluids undergoing supersonic flow. We
present results on how to observe the analog Hawking radiation in Bose-Einstein
condensates by a direct measurement of the density correlations due to the
phonon pairs (Hawking quanta-partner) created by the acoustic horizon.Comment: 10 pages, 7 figures; talk given at SIF2012 (Naples, Italy), second
prize in the `Astroparticle physics, Astrophysics and Cosmology' sectio
Black Hole evaporation in a thermalized final-state projection model
We propose a modified version of the Horowitz-Maldacena final-state boundary
condition based upon a matter-radiation thermalization hypothesis on the Black
Hole interior, which translates into a particular entangled state with thermal
Schmidt coefficients. We investigate the consequences of this proposal for
matter entering the horizon, as described by a Canonical density matrix
characterized by the matter temperature . The emitted radiation is
explicitly calculated and is shown to follow a thermal spectrum with an
effective temperature . We analyse the evaporation process in the
quasi-static approximation, highlighting important differences in the late
stages with respect to the usual semiclassical evolution, and calculate the
fidelity of the emitted Hawking radiation relative to the infalling matter.Comment: 7 pages, 1 figur
Static quantum corrections to the Schwarzschild spacetime
We study static quantum corrections of the Schwarzschild metric in the
Boulware vacuum state. Due to the absence of a complete analytic expression for
the full semiclassical Einstein equations we approach the problem by
considering the s-wave approximation and solve numerically the associated
backreaction equations. The solution, including quantum effects due to pure
vacuum polarization, is similar to the classical Schwarzschild solution up to
the vicinity of the classical horizon. However, the radial function has a
minimum at a time-like surface close to the location of the classical event
horizon. There the g_{00} component of the metric reaches a very small but
non-zero value. The analysis unravels how a curvature singularity emerges
beyond this bouncing point. We briefly discuss the physical consequences of
these results by extrapolating them to a dynamical collapsing scenario.Comment: 10 pages; Talk given at QG05, Cala Gonone (Italy), September 200
Regularity of the stress-energy tensor for extremal Reissner-Nordstrom black holes
We calculate the expectation values of the stress-energy tensor for both a
massless minimally-coupled and dilaton-coupled 2D field propagating on an
extremal Reissner-Nordstrom black hole, showing its regularity on the horizon
in contrast with previous claims in the literature.Comment: 10 pages, 1 figure; Talk given at QG05, Cala Gonone (Italy),
September 200
Leptonic Electroweak Spin-Torsion Interactions
In this paper we consider the most general field equations for a system of
two fermions of which one single-handed, showing that the spin-torsion
interactions among these spinors have a structure identical to that of the
electroweak forces among leptons; possible extensions are discussed.Comment: 7 page
An Hilbert space approach for a class of arbitrage free implied volatilities models
We present an Hilbert space formulation for a set of implied volatility
models introduced in \cite{BraceGoldys01} in which the authors studied
conditions for a family of European call options, varying the maturing time and
the strike price an , to be arbitrage free. The arbitrage free
conditions give a system of stochastic PDEs for the evolution of the implied
volatility surface . We will focus on the family obtained
fixing a strike and varying . In order to give conditions to prove an
existence-and-uniqueness result for the solution of the system it is here
expressed in terms of the square root of the forward implied volatility and
rewritten in an Hilbert space setting. The existence and the uniqueness for the
(arbitrage free) evolution of the forward implied volatility, and then of the
the implied volatility, among a class of models, are proved. Specific examples
are also given.Comment: 21 page
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