422 research outputs found
Spacetime torsion and parity violation: a gauge invariant formulation
The possibility of parity violation through spacetime torsion has been
explored in a scenario containing fields with different spins. Taking the
Kalb-Ramond field as the source of torsion, an explicitly parity violating
gauge invariant theory has been constructed by extending the KR
field with a Chern-Simons term.Comment: 4 pages, RevTe
Lagrangian versus Quantization
We discuss examples of systems which can be quantized consistently, although
they do not admit a Lagrangian description.Comment: 8 pages, no figures; small corrections, references adde
Quantization of Nonstandard Hamiltonian Systems
The quantization of classical theories that admit more than one Hamiltonian
description is considered. This is done from a geometrical viewpoint, both at
the quantization level (geometric quantization) and at the level of the
dynamics of the quantum theory. A spin-1/2 system is taken as an example in
which all the steps can be completed. It is shown that the geometry of the
quantum theory imposes restrictions on the physically allowed nonstandard
quantum theories.Comment: Revtex file, 23 pages, no figure
Worldline deviations of charged spinning particles
The geodesic deviation equation is generalized to worldline deviation
equations describing the relative accelerations of charged spinning particles
in the framework of Dixon-Souriau equations of motion
Torsion-induced spin precession
We investigate the motion of a spinning test particle in a spatially-flat
FRW-type space-time in the framework of the Einstein-Cartan theory. The
space-time has a torsion arising from a spinning fluid filling the space-time.
We show that for spinning particles with nonzero transverse spin components,
the torsion induces a precession of particle spin around the direction of the
fluid spin. We also show that a charged spinning particle moving in a
torsion-less spatially-flat FRW space-time in the presence of a uniform
magnetic field undergoes a precession of a different character.Comment: latex, 4 eps figure
Consistency of Semiclassical Gravity
We discuss some subtleties which arise in the semiclassical approximation to
quantum gravity. We show that integrability conditions prevent the existence of
Tomonaga-Schwinger time functions on the space of three-metrics but admit them
on superspace. The concept of semiclassical time is carefully examined. We
point out that central charges in the matter sector spoil the consistency of
the semiclassical approximation unless the full quantum theory of gravity and
matter is anomaly-free. We finally discuss consequences of these considerations
for quantum field theory in flat spacetime, but with arbitrary foliations.Comment: 12 pages, LATEX, Report Freiburg THEP-94/2
Bohm potential is real and its effects are measurable
We analyze Bohm's potential effects both in the realms of Quantum Mechanics
and Optics, as well as in the study of other physical phenomena described in
terms of classical and quantum wave equations. We approach this subject by
using theoretical arguments as well as experimental evidence. We find that the
effects produced by Bohm's potential are both theoretically responsible for the
early success of Quantum Mechanics correctly describing atomic and nuclear
phenomena and, more recently, by confirming surprising accelerating behavior of
free waves and particles experimentally, for instance.Comment: 4 pages, no figures, Accepted in Opti
Propagation of light in linear and quadratic GRIN media: The Bohm potential
It is shown that field propagation in linear and quadratic gradient-index
(GRIN) media obeys the same rules of free propagation in the sense that a field
propagating in free space has a (mathematical) form that may be {\it exported}
to those particular GRIN media. The Bohm potential is introduced in order to
explain the reason of such behavior: it changes the dynamics by modifying the
original potential. The concrete cases of two different initials conditions for
each potential are analyzed
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