5,676 research outputs found
Comment on "Statistical Mechanics of Non-Abelian Chern-Simons Particles"
The second virial coefficient for non-Abelian Chern-Simons particles is
recalculated. It is shown that the result is periodic in the flux parameter
just as in the Abelian theory.Comment: 3 pages, latex fil
Gravitational waves in general relativity: XIV. Bondi expansions and the ``polyhomogeneity'' of \Scri
The structure of polyhomogeneous space-times (i.e., space-times with metrics
which admit an expansion in terms of ) constructed by a
Bondi--Sachs type method is analysed. The occurrence of some log terms in an
asymptotic expansion of the metric is related to the non--vanishing of the Weyl
tensor at Scri. Various quantities of interest, including the Bondi mass loss
formula, the peeling--off of the Riemann tensor and the Newman--Penrose
constants of motion are re-examined in this context.Comment: LaTeX, 28pp, CMA-MR14-9
New Gauge Invariant Formulation of the Chern-Simons Gauge Theory
A new gauge invariant formulation of the relativistic scalar field
interacting with Chern-Simons gauge fields is considered. This formulation is
consistent with the gauge fixed formulation. Furthermore we find that canonical
(Noether) Poincar\'e generators are not gauge invariant even on the constraints
surface and do not satisfy the (classical) Poincar\'e algebra. It is the
improved generators, constructed from the symmetric energy-momentum tensor,
which are (manifestly) gauge invariant and obey the classical Poincar\'e
algebra.Comment: Shortened, to appear as Papid Communication-PRD/Nov/9
Discrepancy between experimental and theoretical -decay rates resolved from first principles
-decay, a process that changes a neutron into a proton (and vice
versa), is the dominant decay mode of atomic nuclei. This decay offers a unique
window to physics beyond the standard model, and is at the heart of
microphysical processes in stellar explosions and the synthesis of the elements
in the Universe. For 50 years, a central puzzle has been that observed
-decay rates are systematically smaller than theoretical predictions.
This was attributed to an apparent quenching of the fundamental coupling
constant 1.27 in the nucleus by a factor of about 0.75 compared
to the -decay of a free neutron. The origin of this quenching is
controversial and has so far eluded a first-principles theoretical
understanding. Here we address this puzzle and show that this quenching arises
to a large extent from the coupling of the weak force to two nucleons as well
as from strong correlations in the nucleus. We present state-of-the-art
computations of -decays from light to heavy nuclei. Our results are
consistent with experimental data, including the pioneering measurement for
Sn. These theoretical advances are enabled by systematic effective
field theories of the strong and weak interactions combined with powerful
quantum many-body techniques. This work paves the way for systematic
theoretical predictions for fundamental physics problems. These include the
synthesis of heavy elements in neutron star mergers and the search for
neutrino-less double--decay, where an analogous quenching puzzle is a
major source of uncertainty in extracting the neutrino mass scale.Comment: 20 pages, 18 figure
HS 1857+5144 : a hot and young pre-cataclysmic variable
Aims. We report the discovery of a new white dwarf/M dwarf binary, HS 1857+5144, identified in the Hamburg Quasar Survey (HQS).
Methods. Time-resolved optical spectroscopy and photometry were carried out to determine the properties of this new cataclysmic variable progenitor (pre-CV).
Results. The light curves of HS 1857+5144 display a sinusoidal variation with a period of Porb = 383.52 min and peak-to-peak amplitudes of 0.7 mag and 1.1mag in the B-band and R-band, respectively. The large amplitude of the brightness variation results from a reflection effect on the heated inner hemisphere of the companion star, suggesting a very high temperature of the white
dwarf. Our radial velocity study confirms the photometric period as the orbital period of the system. A model atmosphere fit to the spectrum of the white dwarf obtained at minimum light provides limits to its mass and temperature of Mwd 0.6−1.0 M and Twd 70 000−100 000 K, respectively. The detection of He II λ4686 absorption classifies the primary star of HS 1857+5144 as a
DAO white dwarf. Combining the results from our spectroscopy and photometry, we estimate the mass of the companion star and the binary inclination to be Msec 0.15−0.30 M and i 45◦−55◦, respectively.
Conclusions. We classify HS 1857+5144 as one of the youngest pre-CV known to date. The cooling age of the white dwarf suggests that the present system has just emerged from a common envelope phase ∼105 yr ago. HS 1857+5144 will start mass transfer within or below the 2–3 h period gap
Operator Ordering Problem of the Nonrelativistic Chern-Simons Theory
The operator ordering problem due to the quantization or regularization
ambiguity in the Chern-Simons theory exists. However, we show that this can be
avoided if we require Galilei covariance of the nonrelativistic Abelian
Chern-Simons theory even at the quantum level for the extended sources. The
covariance can be recovered only by choosing some particular operator orderings
for the generators of the Galilei group depending on the quantization
ambiguities of the commutation relation. We show that the
desired ordering for the unusual prescription is not the same as the well-known
normal ordering but still satisfies all the necessary conditions. Furthermore,
we show that the equations of motion can be expressed in a similar form
regardless of the regularization ambiguity. This suggests that the different
regularization prescriptions do not change the physics. On the other hand, for
the case of point sources the regularization prescription is uniquely
determined, and only the orderings, which are equivalent to the usual one, are
allowed.Comment: 18 page
Electron-positron pair production in the Aharonov-Bohm potential
In the framework of QED we evaluate the cross section for electron-positron
pair production by a single photon in the presence of the external
Aharonov-Bohm potential in first order of perturbation theory. We analyse
energy, angular and polarization distributions at different energy regimes:
near the threshold and at high photon energies.Comment: LaTeX file, 13 page
Vortex Pull by an External Current
In the context of a dynamical Ginzburg-Landau model it is shown numerically
that under the influence of a homogeneous external current J the vortex drifts
against the current with velocity in agreement to earlier analytical
predictions. In the presence of dissipation the vortex undergoes skew
deflection at an angle with respect to the
external current. It is shown analytically and verified numerically that the
angle and the speed of the vortex are linked through a simple
mathematical relation.Comment: 19 pages, LATEX, 6 Postscript figures included in separate compressed
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