58,502 research outputs found
One-loop calculation of mass dependent improvement coefficients for the relativistic heavy quarks on the lattice
We carry out the one-loop calculation of mass dependent
improvement coefficients in the relativistic heavy quark action recently
proposed, employing the ordinary perturbation theory with the fictitious gluon
mass as an infrared regulator. We also determine renormalization factors and
improvement coefficients for the axial-vector current at the one-loop level. It
is shown that the improvement coefficients are infrared finite at the one-loop
level if and only if the improvement coefficients in the action are properly
tuned at the tree level.Comment: Lattice2003(improve), 3 page
Spontaneous Breaking of Flavor Symmetry and Parity in the Nambu-Jona-Lasinio Model with Wilson Fermions
We study the lattice \njl~model with two flavors of Wilson fermions in the
large limit, where is the number of `colors'. For large values of the
four-fermion coupling we find a phase in which both, flavor symmetry and
parity, are spontaneously broken. In accordance with general expectations there
are three massless pions on the phase boundary, but only two of them remain
massless inside the broken phase. This is analogous to earlier results obtained
in lattice QCD, indicating that this behavior is a very general feature of the
Wilson term.Comment: 7 pages, 4 figures, LATEX, tared and uuencode
Finite Temperature Phase Diagramm of QCD with improved Wilson fermions
We present first results of a study of two flavour QCD with Wilson fermions
at finite temperature. We have used tree level Symanzik improvement in both the
gauge and fermion part of the action. In a first step we explore the phase
diagramm on an lattice, with particular emphasis on checking
Aoki's conjecture with an improved action.Comment: Talk presented at LATTICE97(finite temperature), 3 pages, 3
Postscript figure
Perturbative Determination of Mass Dependent Improvement Coefficients for the Vector and Axial Vector Currents with a Relativistic Heavy Quark Action
We carry out a perturbative determination of mass dependent renormalization
factors and improvement coefficients for the vector and axial vector
currents with a relativistic heavy quark action, which we have designed to
control errors by extending the on-shell improvement program to
the case of with the heavy quark mass. We
discuss what kind of improvement operators are required for the heavy-heavy and
the heavy-light cases under the condition that the Euclidean rotational
symmetry is not retained anymore because of the corrections. Our
calculation is performed employing the ordinary perturbation theory with the
fictitious gluon mass as an infrared regulator. We show that all the
improvement coefficients are determined free from infrared divergences. Results
of the renormalization factors and the improvement coefficients are presented
as a function of for various improved gauge actions as well as the
plaquette action.Comment: 39 pages, 12 figures as eps-fil
Finite-Temperature Phase Structure of Lattice QCD with the Wilson Quark Action for Two and Four Flavors
We present further analyses of the finite-temperature phase structure of
lattice QCD with the Wilson quark action based on spontaneous breakdown of
parity-flavor symmetry. Results are reported on (i) an explicit demonstration
of spontaneous breakdown of parity-flavor symmetry beyond the critical line,
(ii) phase structure and order of chiral transition for the case of
flavors, and (iii) approach toward the continuum limit.Comment: Poster presented at LATTICE96(finite temperature); 4 pages, Latex,
uses espcrc2 and epsf, seven ps figures include
Structure of Critical Lines in Quenched Lattice QCD with the Wilson Quark Action
The structure of critical lines of vanishing pion mass for the Wilson quark
action is examined in quenched lattice QCD. The numerical evidence is presented
that critical lines spread into five branches beyond beta=5.6-5.7 at zero
temperature. It is also shown that critical lines disappear in the deconfined
phase for the case of finite temperatures.Comment: 11 pages, Latex, 7 Postscript figures, uses epsf.st
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
One-loop determination of mass dependent improvement coefficients for the heavy-light vector and axial-vector currents with relativistic heavy and domain-wall light quarks
We present the one-loop results of the mass dependent improvement
coefficients for the heavy-light vector and axial-vector currents consisting of
the relativistic heavy and the domain-wall light quarks. The calculations are
performed with the plaquette, Iwasaki and DBW2 gauge actions. The heavy quark
mass and domain-wall height dependence is investigated. We point out that the
exact chiral symmetry held by the lattice light quark action leads to an exact
relation between the improvement coefficients for the vector and axial-vector
currents without regard to the lattice heavy quark action.Comment: 3 pages, 1 figure, talk presented at Lattice2004(improved), Fermilab,
June 21-26, 200
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