540 research outputs found
Quantum Mechanical Breaking of Local GL(4) Invariance
We consider the gravitational coupling of a scalar field, in a reformulation
of General Relativity exhibiting local GL(4) invariance at the classical level.
We compute the one-loop contribution of the scalar to the quantum effective
potential of the vierbein and find that it does not have GL(4) invariance. The
minima of the effective potential occur for a vierbein which is proportional to
the unit matrix.Comment: 9 pages, plain-TeX, no figure
On the use of Mellin transform to a class of q-difference-differential equations
We explore the possibility of using the method of classical integral
transforms to solve a class of -difference-differential equations. The
Laplace and the Mellin transform of -derivatives are derived. The results
show that the Mellin transform of the -derivative resembles most closely the
corresponding expression in classical analysis, and it could therefore be
useful in solving certain -difference equations.Comment: 13 pages, LaTex, no figure
A model for the continuous q-ultraspherical polynomials
We provide an algebraic interpretation for two classes of continuous
-polynomials. Rogers' continuous -Hermite polynomials and continuous
-ultraspherical polynomials are shown to realize, respectively, bases for
representation spaces of the -Heisenberg algebra and a -deformation of
the Euclidean algebra in these dimensions. A generating function for the
continuous -Hermite polynomials and a -analog of the Fourier-Gegenbauer
expansion are naturally obtained from these models
Tests of Complete Positivity in Fiber Optics
We consider the propagation of polarized photons in optical fibers under the
action of randomly generated noise. In such situation, the change in time of
the photon polarization can be described by a quantum dynamical semigroup. We
show that the hierarchy among the decay constants of the polarization density
matrix elements as prescribed by complete positivity can be experimentally
probed using standard laboratory set-ups.Comment: 10 pages, LaTe
Open system approach to neutrino oscillations
Neutrino oscillations are studied in the general framework of open quantum
systems by means of extended dynamics that take into account possible
dissipative effects. These new phenomena induce modifications in the neutrino
oscillation pattern that in general can be parametrized by means of six
phenomenological constants. Although very small, stringent bounds on these
parameters are likely to be given by future planned neutrino experiments.Comment: 15 pages, plain-TeX, to appear in JHE
Complete positivity and neutron interferometry
We analyze the dynamics of neutron beams in interferometry experiments using
quantum dynamical semigroups. We show that these experiments could provide
stringent limits on the non-standard, dissipative terms appearing in the
extended evolution equations.Comment: 12 pages, plain Te
Direct CP-violation as a test of quantum mechanics
Direct CP-violating effects in the neutral kaon system result in violations
of certain Bell-like inequalities. The new experimental results on the
determination of the phenomenological parameter epsilon' allow to dismiss a
large class of ``hidden variable'' alternatives to quantum mechanics.Comment: 15 pages, Te
Massless neutrino oscillations
Quantum dynamical semigroups provide a general framework for studying the
evolution of open systems. Neutrino propagation both in vacuum and in matter
can be analyzed using these techniques: they allow a consistent treatment of
non-standard, dissipative effects that can alter the pattern of neutrino
oscillations. In particular, initially massless neutrinos can give rise to a
nonvanishing flavour transition probability, involving in addition the Majorana
CP-violating mixing phase.Comment: 27 pages, plain-TeX, no figure
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