7 research outputs found
Improvements of L\"uscher's local bosonic fermion algorithm
We discuss the application of hybrid over-relaxation, even-odd
preconditioning and a modified local updating procedure to the local bosonic
fermion algorithm. Studies on autocorrelation times and the tuning of the
parameters of the algorithm are done on various lattice sizes simulating
SU(2)-LGT with 2 flavours of Wilson quarks. A substantial decrease of the
computational cost could be achieved.Comment: 20 pages, uuencoded compressed postscrip
Performance Tests of the Kramers Equation and Boson Algorithms for Simulations of QCD
We present a performance comparison of the Kramers equation and the boson
algorithms for simulations of QCD with two flavors of dynamical Wilson fermions
and gauge group . Results are obtained on , and
lattices. In both algorithms a number of optimizations are installed.Comment: uuencoded postscript file, no figures, 10 page
Critical Behavior at the Chiral Phase Transition
Quantum chromodynamics with two zero mass flavors is expected to exhibit a
phase transition with O(4) critical behavior. Fixing the universality class is
important for phenomenology and for facilitating the extrapolation of
simulation data to physical quark mass values. At Lattice '96 the Tsukuba and
Bielefeld groups reported results from new simulations with dynamical staggered
quarks at , which suggested a departure from the expected critical
behavior. We report observations of similar deviations and discuss efforts in
progress to understand this phenomenon.Comment: 3 pp, LaTeX with 6 encapsulated Postscript figures. Lattice '97
proceeding
Neutrino Oscillations and the Supernova 1987A Signal
We study the impact of neutrino oscillations on the interpretation of the
supernova (SN) 1987A neutrino signal by means of a maximum-likelihood analysis.
We focus on oscillations between with or
with those mixing parameters that would solve the solar
neutrino problem. For the small-angle MSW solution (, ), there are no
significant oscillation effects on the Kelvin-Helmholtz cooling signal; we
confirm previous best-fit values for the neutron-star binding energy and
average spectral temperature. There is only marginal overlap
between the upper end of the 95.4\% CL inferred range of and the lower end of the range of theoretical
predictions. Any admixture of the stiffer spectrum by
oscillations aggravates the conflict between experimentally inferred and
theoretically predicted spectral properties. For mixing parameters in the
neighborhood of the large-angle MSW solution (, ) the oscillations in the SN are adiabatic,
but one needs to include the regeneration effect in the Earth which causes the
Kamiokande and IMB detectors to observe different spectra. For
the solar vacuum solution (,
) the oscillations in the SN are nonadiabatic; vacuum
oscillations take place between the SN and the detector. If either of the
large-angle solutions were borne out by the upcoming round of solar neutrino
experiments, one would have to conclude that the SN~1987A
and/or spectra had been much softer than predicted by currentComment: Final version with very minor wording changes, to be published in
Phys. Rev.
Performance tests of the Kramers equation and boson algorithms for simulations of QCD
We present a performance comparison of the Kramers equation and the boson algorithms for simulations of QCD with two flavors of dynamical Wilson fermions and gauge group SU(2). Results are obtained on 6312, 8312 and 164 lattices. In both algorithms a number of optimizations are installed