69,286 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
Nucleon Decay with Domain-Wall Fermions
We report on our on-going project to calculate the nucleon decay matrix
elements with domain-wall fermions. Operator mixing is discussed employing a
non-perturbative renormalization. Bare matrix elements of all the possible
decay modes induced by the dimension-six operators are calculated with the
direct method, which are compared with the indirect calculation using chiral
perturbation theory.Comment: Lattice2003(matrix), 3 pages, 2 figure
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
Perturbative determination of mass dependent renormalization and improvement coefficients for the heavy-light vector and axial-vector currents with relativistic heavy and domain-wall light quarks
We determine the mass dependent renormalization as well as improvement
coefficients for the heavy-light vector and axial-vector currents consisting of
the relativistic heavy and the domain-wall light quarks through the standard
matching procedure. The calculation is carried out perturbatively at the one
loop level to remove the systematic error of O(\alpha_s (am_Q)^n a\p) as well
as (0), where \p is a typical momentum scale in
the heavy-light system. We point out that renormalization and improvement
coefficients of the heavy-light vector current agree with those of the
axial-vector current, thanks to the exact chiral symmetry for the light quark.
The results obtained with three different gauge actions, plaquette, Iwasaki and
DBW2, are presented as a function of heavy quark mass and domain-wall height.Comment: 33 pages, 6 figure
Chiral perturbation theory with Wilson-type fermions including effects: degenerate case
We have derived the quark mass dependence of , and
, using the chiral perturbation theory which includes the effect
associated with the explicit chiral symmetry breaking of the Wilson-type
fermions, in the case of the degenerate quarks. Distinct features of
the results are (1) the additive renormalization for the mass parameter
in the Lagrangian, (2) corrections to the chiral log ()
term, (3) the existence of more singular term, , generated by
contributions, and (4) the existence of both and terms
in the quark mass from the axial Ward-Takahashi identity, . By
fitting the mass dependence of and , obtained by the
CP-PACS collaboration for full QCD simulations, we have found that the
data are consistently described by the derived formulae. Resumming the most
singular terms , we have also derived the modified formulae, which
show a better control over the next-to-leading order correction.Comment: 21 pages, 4 figures (10 eps files), Revtex4, some discussions and
references added, the final version to appear in PR
Two-dimensional Lattice Gross-Neveu Model with Wilson Fermion Action at Finite Temperature and Chemical Potential
We investigate the phase structure of the two-dimensional lattice Gross-Neveu
model formulated with the Wilson fermion action to leading order of 1/N
expansion. Structural change of the parity-broken phase under the influence of
finite temperature and chemical potential is studied. The connection between
the lattice phase structure and the chiral phase transition of the continuum
theory is clarified.Comment: 42 pages, 20 EPS figures, using REVTe
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