1,928 research outputs found
Lattice QCD with domain wall quarks and applications to weak matrix elements
Using domain wall fermions, we estimate in
quenched QCD which is consistent with previous calculations. At \gbeta=6.0
and 5.85 we find the ratio in agreement with the experimental
value, within errors. These results support expectations that errors are
exponentially suppressed in low energy () observables, and
indicate that domain wall fermions have good scaling behavior at relatively
strong couplings. We also demonstrate that the axial current numerically
satisfies the lattice analog of the usual continuum axial Ward identity.Comment: Contribution to Lattice '97. 3 pages, 2 epsf figure
OT 060420: A Seemingly Optical Transient Recorded by All-Sky Cameras
We report on a ~5th magnitude flash detected for approximately 10 minutes by
two CONCAM all-sky cameras located in Cerro Pachon - Chile and La Palma -
Spain. A third all-sky camera, located in Cerro Paranal - Chile did not detect
the flash, and therefore the authors of this paper suggest that the flash was a
series of cosmic-ray hits, meteors, or satellite glints. Another proposed
hypothesis is that the flash was an astronomical transient with variable
luminosity. In this paper we discuss bright optical transient detection using
fish-eye all-sky monitors, analyze the apparently false-positive optical
transient, and propose possible causes to false optical transient detection in
all-sky cameras.Comment: 7 figures, 3 tables, accepted PAS
Domain wall fermions in vector gauge theories
I review domain wall fermions in vector gauge theories. Following a brief
introduction, the status of lattice calculations using domain wall fermions is
presented. I focus on results from QCD, including the light quark masses and
spectrum, weak matrix elements, the finite temperature phase
transition, and topology and zero modes and conclude with topics for future
study.Comment: LATTICE98. Plenary review talk. LaTeX(espcrc2.sty), 13 pages, 17 eps
figure
Massless Composite Fermions in Two Dimensions and the Overlap
There exist chiral gauge models in two dimensions that have massless
composite fermions. Two examples are presented and it is suggested that they be
accepted as benchmark test-cases for generic proposals of non-perturbatively
regulating chiral gauge theories in any dimension. We apply the overlap to the
simpler of the two benchmarks and present the results of a numerical simulation
of modest size.Comment: 12 pages, Plain TeX with epsf, 2 PS figure
SU(4) lattice gauge theory with decuplet fermions: Schr\"odinger functional analysis
We complete a program of study of SU(N) gauge theories coupled to two flavors
of fermions in the two-index symmetric representation by performing numerical
simulations in SU(4). The beta function, defined and calculated via the
Schr\"odinger functional, runs more slowly than the two-loop perturbative
result. The mass anomalous dimension levels off in strong coupling at a value
of about 0.45, rendering this theory unsuitable for walking technicolor. A
large-N comparison of this data with results from SU(2) and SU(3) reveals
striking regularities.Comment: 15 pages, 15 figure
One loop renormalization for the axial Ward-Takahashi identity in Domain-wall QCD
We calculate one-loop correction to the axial Ward-Takahashi identity given
by Furman and Shamir in domain-wall QCD. It is shown perturbatively that the
renormalized axial Ward-Takahashi identity is satisfied without fine tuning and
the ``conserved'' axial current receives no renormalization, giving .
This fact will simplify the calculation of the pion decay constant in numerical
simulations since the decay constant defined by this current needs no lattice
renormalization factor.Comment: 16 pages, 3 axodraw.sty figure
Learning with the Weighted Trace-norm under Arbitrary Sampling Distributions
We provide rigorous guarantees on learning with the weighted trace-norm under
arbitrary sampling distributions. We show that the standard weighted trace-norm
might fail when the sampling distribution is not a product distribution (i.e.
when row and column indexes are not selected independently), present a
corrected variant for which we establish strong learning guarantees, and
demonstrate that it works better in practice. We provide guarantees when
weighting by either the true or empirical sampling distribution, and suggest
that even if the true distribution is known (or is uniform), weighting by the
empirical distribution may be beneficial
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