854 research outputs found
Non-Pauli Effects from Noncommutative Spacetimes
Noncommutative spacetimes lead to nonlocal quantum field theories (qft's)
where spin-statistics theorems cannot be proved. For this reason, and also
backed by detailed arguments, it has been suggested that they get corrected on
such spacetimes leading to small violations of the Pauli principle. In a recent
paper \cite{Pauli}, Pauli-forbidden transitions from spacetime noncommutativity
were calculated and confronted with experiments. Here we give details of the
computation missing from this paper. The latter was based on a spacetime
different from the Moyal plane. We argue that it
quantizes time in units of . Energy is then conserved only mod
. Issues related to superselection rules raised by non-Pauli
effects are also discussed in a preliminary manner.Comment: 15 Pages, 1 Table, Full details and further developments of
arXiv:1003.2250. This version is close to the one accepted by JHE
Continuous Time-Dependent Measurements: Quantum Anti-Zeno Paradox with Applications
We derive differential equations for the modified Feynman propagator and for
the density operator describing time-dependent measurements or histories
continuous in time. We obtain an exact series solution and discuss its
applications. Suppose the system is initially in a state with density operator
and the projection operator is measured
continuously from to , where is a projector obeying and a unitary operator obeying and some smoothness
conditions in . Then the probability of always finding from to is unity. Generically and the watched system is sure to
change its state, which is the anti-Zeno paradox noted by us recently. Our
results valid for projectors of arbitrary rank generalize those obtained by
Anandan and Aharonov for projectors of unit rank.Comment: 16 pages, latex; new material and references adde
Phase Space Reduction and Vortex Statistics: An Anyon Quantization Ambiguity
We examine the quantization of the motion of two charged vortices in a
Ginzburg--Landau theory for the fractional quantum Hall effect recently
proposed by the first two authors. The system has two second-class constraints
which can be implemented either in the reduced phase space or
Dirac-Gupta-Bleuler formalism. Using the intrinsic formulation of statistics,
we show that these two ways of implementing the constraints are inequivalent
unless the vortices are quantized with conventional statistics; either
fermionic or bosonic.Comment: 14 pages, PHYZZ
Field theory on evolving fuzzy two-sphere
I construct field theory on an evolving fuzzy two-sphere, which is based on
the idea of evolving non-commutative worlds of the previous paper. The
equations of motion are similar to the one that can be obtained by dropping the
time-derivative term of the equation derived some time ago by Banks, Peskin and
Susskind for pure-into-mixed-state evolutions. The equations do not contain an
explicit time, and therefore follow the spirit of the Wheeler-de Witt equation.
The basic properties of field theory such as action, gauge invariance and
charge and momentum conservation are studied. The continuum limit of the scalar
field theory shows that the background geometry of the corresponding continuum
theory is given by ds^2 = -dt^2+ t d Omega^2, which saturates locally the
cosmic holographic principle.Comment: Typos corrected, minor changes, 23 pages, no figures, LaTe
Screening in Anyon Gas
Anyon gas with interparticle (retarded) Coulomb interaction has been studied.
The resulting system is shown to be a collection of dressed anyons, with a
screening factor introduced in their spin. Close structural similarity with the
Chern-Simons construction of anyons has helped considerably in computing the
screening effect. Finally the present model is compared with the conventional
Chern-Simons construction.Comment: 10 pages Late
Dual Response Models for the Fractional Quantum Hall Effect
It is shown that the Jain mapping between states of integer and fractional
quantum Hall systems can be described dynamically as a perturbative
renormalization of an effective Chern-Simons field theory. The effects of
mirror duality symmetries of toroidally compactified string theory on this
system are studied and it is shown that, when the gauge group is compact, the
mirror map has the same effect as the Jain map. The extrinsic ingredients of
the Jain construction appear naturally as topologically non-trivial field
configurations of the compact gauge theory giving a dynamical origin for the
Jain hierarchy of fractional quantum Hall states.Comment: 8 pages LaTe
Boundary degrees of freedom in fractional quantum Hall effect: Excitations on common boundary of two samples
Using the Carlip's method we have derived the boundary action for the fermion
Chern-Simons theory of quantum Hall effects on a planar region with a boundary.
We have computed both the bulk and edge responses of currents to the external
electric field. From this we obtain the well-known anomaly relation and the
boundary Hall current without introducing any ad hoc assumptions such as the
chirality condition. In addition, the edge current on the common boundary of
two samples is found to be proportional to the difference between Chern-Simons
coupling strengths.Comment: 20 pages, uses revte
Mixing at young ages: Beryllium abundances in cool main-sequence stars of the open clusters IC 2391 and IC 2602
The determination of lithium abundances in stars of young clusters have shown
that they deplete Li by different degrees during their pre-main sequence phase.
Beryllium abundances are complementary to the lithium ones, and can help
tracing the mixing processes in the stellar interiors. Our aim is to derive
beryllium abundances in a sample of G- and K-type stars of two young pre-main
sequence open clusters, IC 2391 and IC 2602. The Be abundances are used to
investigate the mixing of internal material in these stars. The reliability of
the Be lines as abundance indicators in low-temperatures is also investigated
in detail. We derived Be abundances from high-resolution, high signal-to-noise
UVES/VLT spectra using spectrum synthesis and model atmospheres. Atmospheric
parameters and other elemental abundances are adopted from a previous work. The
sample stars have masses in the range between 0.80 < M/Msun < 1.20. They have
been shown to differ in lithium abundance by about 0.60 dex, with lower A(Li)
in cooler and lower mass stars. Here, we find that all the stars have the same
Be abundance within the uncertainties. These observations show that the Be
abundance is not affected by the mixing events in the pre-main sequence, in
this mass range, in agreement with the expectation of evolutionary models. A
comparison with Be abundances in older clusters shows that, contrary to the
models, cool stars deplete Be during their main-sequence lifetime, confirming
what has been previously suggested in the literature.Comment: To appear in A&A, 12 pages, 12 figure
Fuzzy Torus via q-Parafermion
We note that the recently introduced fuzzy torus can be regarded as a
q-deformed parafermion. Based on this picture, classification of the Hermitian
representations of the fuzzy torus is carried out. The result involves
Fock-type representations and new finite dimensional representations for q
being a root of unity as well as already known finite dimensional ones.Comment: 12pages, no figur
- …