13,465 research outputs found
Time dependent transformations in deformation quantization
We study the action of time dependent canonical and coordinate
transformations in phase space quantum mechanics. We extend the covariant
formulation of the theory by providing a formalism that is fully invariant
under both standard and time dependent coordinate transformations. This result
considerably enlarges the set of possible phase space representations of
quantum mechanics and makes it possible to construct a causal representation
for the distributional sector of Wigner quantum mechanics.Comment: 16 pages, to appear in the J. Math. Phy
Noncommutative Black Holes and the Singularity Problem
A phase-space noncommutativity in the context of a Kantowski-Sachs
cosmological model is considered to study the interior of a Schwarzschild black
hole. Due to the divergence of the probability of finding the black hole at the
singularity from a canonical noncommutativity, one considers a non-canonical
noncommutativity. It is shown that this more involved type of noncommutativity
removes the problem of the singularity in a Schwarzschild black hole.Comment: Based on a talk by CB at ERE2010, Granada, Spain, 6th-10th September
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Limiting fragmentation in heavy-ion collisions and percolation of strings
The observed limiting fragmentation of charged particle distributions in
heavy ion collisions is difficult to explain as it does not apply to the proton
spectrum itself. On the other hand, string percolation provides a mechanism to
regenerate fast particles, eventually compensating the rapidity shift (energy
loss) of the nucleons. However a delicate energy-momentum compensation is
required, and in our framework we see no reason for limiting fragmentation to
be exact. A prediction, based on percolation arguments, is given for the
charged particle density in the full rapidity interval at LHC energy .Comment: 9 pages, 2 figures (2 eps files), late
Deformation quantization of noncommutative quantum mechanics and dissipation
We review the main features of the Weyl-Wigner formulation of noncommutative
quantum mechanics. In particular, we present a -product and a Moyal
bracket suitable for this theory as well as the concept of noncommutative
Wigner function. The properties of these quasi-distributions are discussed as
well as their relation to the sets of ordinary Wigner functions and positive
Liouville probability densities. Based on these notions we propose criteria for
assessing whether a commutative regime has emerged in the realm of
noncommutative quantum mechanics. To induce this noncommutative-commutative
transition, we couple a particle to an external bath of oscillators. The master
equation for the Brownian particle is deduced.Comment: 7 pages, Latex file, Based on a talk presented by Joao Prata at
D.I.C.E. 2006, Piombino, Ital
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