20,716 research outputs found
Spontaneous Flavor and Parity Breaking with Wilson Fermions
We discuss the phase diagram of Wilson fermions in the -- plane for
two-flavor QCD. We argue that, as originally suggested by Aoki, there is a
phase in which flavor and parity are spontaneously broken. Recent numerical
results on the spectrum of the overlap Hamiltonian have been interpreted as
evidence against Aoki's conjecture. We show that they are in fact consistent
with the presence of a flavor-parity broken ``Aoki phase''. We also show how,
as the continuum limit is approached, one can study the lattice theory using
the continuum chiral Lagrangian supplemented by additional terms proportional
to powers of the lattice spacing. We find that there are two possible phase
structures at non-zero lattice spacing: (1) there is an Aoki phase of width
with two massless Goldstone pions; (2) there is no
symmetry breaking, and all three pions have an equal non-vanishing mass of
order . Present numerical evidence suggests that the former option is
realized for Wilson fermions. Our analysis then predicts the form of the pion
masses and the flavor-parity breaking condensate within the Aoki phase. Our
analysis also applies for non-perturbatively improved Wilson fermions.Comment: 22 pages, LaTeX, 5 figures (added several references and a comment
Tau polarization effects in the CNGS tau-neutrino appearance experiments
We studied tau polarization effects on the decay distributions of tau
produced in the CNGS tau-neutrino appearance experiments. We show that energy
and angular distributions for the decay products in the laboratory frame are
significantly affected by the tau polarization. Rather strong azimuthal
asymmetry about the tau momentum axis is predicted, which may have observable
consequences in experiments even with small statistics.Comment: 5 pages, 6 eps figures, espcrc2.sty; Proceedings of the 4th
International Workshop on Neutrino-Nucleus Interactions in the Few GeV Region
(NuInt05), September 26-29, 2005, Okayama, Japa
Nucleon-nucleon interactions via Lattice QCD: Methodology --HAL QCD approach to extract hadronic interactions in lattice QCD--
We review the potential method in lattice QCD, which has recently been
proposed to extract nucleon-nucleon interactions via numerical simulations. We
focus on the methodology of this approach by emphasizing the strategy of the
potential method, the theoretical foundation behind it, and special numerical
techniques. We compare the potential method with the standard finite volume
method in lattice QCD, in order to make pros and cons of the approach clear. We
also present several numerical results for the nucleon-nucleon potentials.Comment: 12 pages, 10 figure
Detection of Iron Emission in the z = 5.74 QSO SDSSp J104433.04-012502.2
We obtained near-infrared spectroscopy of the z=5.74 QSO, SDSSp
J104433.04-012 502.2 with the Infrared Camera and Spectrograph of the Subaru
telescope. The redshift of 5.74 corresponds to a cosmological age of 1.0 Gyr
for the current Lambda-dominated cosmology. We found a similar strength of the
Fe II (3000-3500 A) emission lines in SDSSp J104433.04-012502.2 as in low
redshift QSOs. This is the highest redshift detection of iron. We subtracted a
power-law continuum from the spectrum and fitted model Fe II emission and
Balmer continuum. The rest equivalent width of Fe II (3000-3500 A) is ~30 A
which is similar to those of low redshift QSOs measured by the same manner. The
chemical enrichment models that assume the life time of the progenitor of SNe
Ia is longer than 1 Gyr predict that weaker Fe II emission than low red shift.
However, none of the observed high redshift (z > 3) QSOs show a systematic dec
rease of Fe II emission compared with low redshift QSOs. This may due to a
shorter lifetime of SNe Ia in QSO nuclei than in the solar neighborhood.
Another reason of strong Fe II emission at z=5.74 may be longer cosmological
age due to smaller Omega_M.Comment: 5 pages, 3 figure
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