79,306 research outputs found
Conservation of Statistics and Generalized Grassmann Numbers
Conservation of statistics requires that fermions be coupled to Grassmann
external sources. Correspondingly, conservation of statistics requires that
parabosons, parafermions and quons be coupled to external sources that are the
appropriate generalizations of Grassmann numbers.Comment: 10 pages, late
N-quantum approach to quantum field theory at finite T and : the NJL model
We extend the N-quantum approach to quantum field theory to finite
temperature () and chemical potential () and apply it to the NJL model.
In this approach the Heisenberg fields are expressed using the Haag expansion
while temperature and chemical potential are introduced simultaneously through
a generalized Bogoliubov transformation. Known mean field results are recovered
using only the first term in the Haag expansion. In addition, we find that at
finite T and in the broken symmetry phase of the model the mean field
approximation can not diagonalize the Hamiltonian. Inclusion of scalar and
axial vector diquark channels in the SU(2) SU(3)
version of the model can lead to a lowering of the vacuum energy density. We
discuss how to go beyond the mean field approximation by including higher order
terms in the Haag expansion.Comment: 14 pages including 2 eps figures. Modified sentences on the lowering
of the vacuum energy densit
The Voltage-Current Characteristic of high T_c DC SQUID: theory, simulation, experiment
The analytical theory for the voltage-current characteristics of the large
inductance (L>100 pH) high-T_c DC SQUIDs that has been developed previously is
consistently compared with the computer simulations and the experiment. The
theoretical voltage modulation for symmetric junctions is shown to be in a good
agreement with the results of known computer simulations. It is shown that the
asymmetry of the junctions results in the increase of the voltage modulation if
the critical current is in excess of some threshold value (about 8 microAmps).
Below this value the asymmetry leads to the reduction of the voltage modulation
as compared to the symmetric case. The comparison with the experiment shows
that the asymmetry can explain a large portion of experimental values of the
voltage modulation which lie above the theoretical curve for symmetric DC
SQUID. It also explains experimental points which lie below the curve at small
critical currents. However, a significant portion of these values which lie
below the curve cannot be explained by the junction asymmetry.Comment: 22 pages, 14 figure
Neutrino statistics and non-standard commutation relations
Recently it was suggested that the neutrino may violate the Pauli exclusion
Principle (PEP). This renews interest in the systematic search for bilinear
commutation relations that could describe deviations from PEP. In the context
of this search we prove a no-go theorem which forbids a finite occupancy limit
for an arbitrary system with a bilinear commutation relation. In other words,
either the upper limit on the occupancy number is 1 (the ordinary fermionic
case) or there is no upper limit at all. Some examples of the latter class
include the usual Bose statistics, as well as non-standard quon statistics and
infinite statistics.Comment: 11 pages, RevTeX
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