719 research outputs found
CPT anomaly: a rigorous result in four dimensions
The existence of a CPT anomaly is established for a particular
four-dimensional Abelian lattice gauge theory with Ginsparg-Wilson fermions.Comment: LaTeX with elsart.cls, 24 pages, v3: published versio
A sphaleron for the non-Abelian anomaly
A self-consistent Ansatz for a new sphaleron of SU(3) Yang-Mills-Higgs theory
is presented. With a single triplet of Weyl fermions added, there exists, most
likely, one pair of fermion zero modes, which is known to give rise to the
non-Abelian (Bardeen) anomaly as a Berry phase. The corresponding SU(3) gauge
field configuration could take part in the nonperturbative dynamics of Quantum
Chromodynamics.Comment: LaTeX with elsart.cls, 26 pages, v4: published versio
Combining a ractopamine feeding regime and porcine somatotropin has additive effects on finisher pig performance
Treatment of finisher pigs with dietary ractopamine (RAC; Paylean®, Elanco Animal Health, NSW) improves daily gain and feed efficiency commensurate with increased protein deposition in finishing pigs (Dunshea et al., 1993). However, effects of RAC on P2 fat deposition are equivocal. Dunshea et al. (1993) found no change in gilts and barrows, whilst a trend towards reduced P2 depth was observed in boars fed dietary RAC. Exogenous porcine somatotropin (pST; Reporcin®, OzBioPharm Pty Ltd, Victoria) improves daily gain and feed efficiency and increases the ratio oflean to fat in carcases of boars, gilts and barrows (Campbell et al., 1989). As both technologies are applied at the end of the finishing phase, it is of interest to determine whether a combination of RAC and pST has additive effects on pig performance
Z-string global gauge anomaly and Lorentz non-invariance
Certain (3+1)-dimensional chiral non-Abelian gauge theories have been shown
to exhibit a new type of global gauge anomaly, which in the Hamiltonian
formulation is due to the fermion zero-modes of a Z-string-like configuration
of the gauge potential and the corresponding spectral flow. Here, we clarify
the relation between this Z-string global gauge anomaly and other anomalies in
both 3+1 and 2+1 dimensions. We then point out a possible trade-off between the
(3+1)-dimensional Z-string global gauge anomaly and the violation of CPT and
Lorentz invariance.Comment: 11 pages, LaTe
Increasing ractopamine levels in finisher pig diets improves growth performance in light, medium and heavy boars
The objective of this study was to determine the dose response to RAC in light, medium and heavy-weight boars
Spectral flow of chiral fermions in nondissipative Yang-Mills gauge field backgrounds
Real-time anomalous fermion number violation is investigated for massless
chiral fermions in spherically symmetric SU(2) Yang-Mills gauge field
backgrounds which can be weakly dissipative or even nondissipative. Restricting
consideration to spherically symmetric fermion fields, the zero-eigenvalue
equation of the time-dependent effective Dirac Hamiltonian is studied in
detail. For generic spherically symmetric SU(2) gauge fields in Minkowski
spacetime, a relation is presented between the spectral flow and two
characteristics of the background gauge field. These characteristics are the
well-known ``winding factor,'' which is defined to be the change of the
Chern-Simons number of the associated vacuum sector of the background gauge
field, and a new ``twist factor,'' which can be obtained from the
zero-eigenvalue equation of the effective Dirac Hamiltonian but is entirely
determined by the background gauge field. For a particular class of (weakly
dissipative) Luscher-Schechter gauge field solutions, the level crossings are
calculated directly and nontrivial contributions to the spectral flow from both
the winding factor and the twist factor are observed. The general result for
the spectral flow may be relevant to electroweak baryon number violation in the
early universe.Comment: REVTeX, 43 pages, v4: final versio
Charged-Particle Multiplicities in Charged-Current Neutrino-- and Anti-Neutrino--Nucleus Interactions
The CHORUS experiment, designed to search for
oscillations, consists of a nuclear emulsion target and electronic detectors.
In this paper, results on the production of charged particles in a small sample
of charged-current neutrino-- and anti-neutrino--nucleus interactions at high
energy are presented. For each event, the emission angle and the ionization
features of the charged particles produced in the interaction are recorded,
while the standard kinematic variables are reconstructed using the electronic
detectors. The average multiplicities for charged tracks, the pseudo-rapidity
distributions, the dispersion in the multiplicity of charged particles and the
KNO scaling are studied in different kinematical regions. A study of
quasi-elastic topologies performed for the first time in nuclear emulsions is
also reported. The results are presented in a form suitable for use in the
validation of Monte Carlo generators of neutrino--nucleus interactions.Comment: 17 pages, 5 figure
Fitting the integrated Spectral Energy Distributions of Galaxies
Fitting the spectral energy distributions (SEDs) of galaxies is an almost
universally used technique that has matured significantly in the last decade.
Model predictions and fitting procedures have improved significantly over this
time, attempting to keep up with the vastly increased volume and quality of
available data. We review here the field of SED fitting, describing the
modelling of ultraviolet to infrared galaxy SEDs, the creation of
multiwavelength data sets, and the methods used to fit model SEDs to observed
galaxy data sets. We touch upon the achievements and challenges in the major
ingredients of SED fitting, with a special emphasis on describing the interplay
between the quality of the available data, the quality of the available models,
and the best fitting technique to use in order to obtain a realistic
measurement as well as realistic uncertainties. We conclude that SED fitting
can be used effectively to derive a range of physical properties of galaxies,
such as redshift, stellar masses, star formation rates, dust masses, and
metallicities, with care taken not to over-interpret the available data. Yet
there still exist many issues such as estimating the age of the oldest stars in
a galaxy, finer details ofdust properties and dust-star geometry, and the
influences of poorly understood, luminous stellar types and phases. The
challenge for the coming years will be to improve both the models and the
observational data sets to resolve these uncertainties. The present review will
be made available on an interactive, moderated web page (sedfitting.org), where
the community can access and change the text. The intention is to expand the
text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics &
Space Scienc
A measurement of the tau mass and the first CPT test with tau leptons
We measure the mass of the tau lepton to be 1775.1+-1.6(stat)+-1.0(syst.) MeV
using tau pairs from Z0 decays. To test CPT invariance we compare the masses of
the positively and negatively charged tau leptons. The relative mass difference
is found to be smaller than 3.0 10^-3 at the 90% confidence level.Comment: 10 pages, 4 figures, Submitted to Phys. Letts.
Measurement of the B0 Lifetime and Oscillation Frequency using B0->D*+l-v decays
The lifetime and oscillation frequency of the B0 meson has been measured
using B0->D*+l-v decays recorded on the Z0 peak with the OPAL detector at LEP.
The D*+ -> D0pi+ decays were reconstructed using an inclusive technique and the
production flavour of the B0 mesons was determined using a combination of tags
from the rest of the event. The results t_B0 = 1.541 +- 0.028 +- 0.023 ps, Dm_d
= 0.497 +- 0.024 +- 0.025 ps-1 were obtained, where in each case the first
error is statistical and the second systematic.Comment: 17 pages, 4 figures, submitted to Phys. Lett.
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