1,561 research outputs found
Breakdown of staggered fermions at nonzero chemical potential
The staggered fermion determinant is complex when the quark chemical
potential mu is nonzero. Its fourth root, used in simulations with dynamical
fermions, will have phase ambiguities that become acute when Re mu is
sufficiently large. We show how to resolve these ambiguities, but our
prescription only works very close to the continuum limit. We argue that this
regime is far from current capabilities. Other procedures require being even
closer to the continuum limit, or fail altogether, because of unphysical
discontinuities in the measure. At zero temperature the breakdown is expected
when Re mu is greater than approximately half the pion mass. Estimates of the
location of the breakdown at nonzero temperature are less certain.Comment: 6 pages RevTeX, 2 figures. Returning to v5 after erroneous
replacement. Apologie
Low energy effective action of domain-wall fermion and the Ginsparg-Wilson relation
We derive the effective action of the light fermion field of the domain-wall
fermion, which is referred as by Furman and Shamir. The inverse of the
effective Dirac operator turns out to be identical to the inverse of the
truncated overlap Dirac operator, except a local contact term which would give
the chiral symmetry breaking in the Ginsparg-Wilson relation. This result
allows us to relate the light fermion field and the fermion field described by
the truncated overlap Dirac operator and to understand the chiral property of
the light fermion through the exact chiral symmetry based on the
Ginsparg-Wilson relation.Comment: 35 pages, LaTeX2e, references added and updated, minor correction
Reducing Residual-Mass Effects for Domain-Wall Fermions
It has been suggested to project out a number of low-lying eigenvalues of the
four-dimensional Wilson--Dirac operator that generates the transfer matrix of
domain-wall fermions in order to improve simulations with domain-wall fermions.
We investigate how this projection method reduces the residual chiral
symmetry-breaking effects for a finite extent of the extra dimension. We use
the standard Wilson as well as the renormalization--group--improved gauge
action. In both cases we find a substantially reduced residual mass when the
projection method is employed. In addition, the large fluctuations in this
quantity disappear.Comment: 18 pages, 10 figures, references updated, comments adde
Chiral Fermions on the Lattice through Gauge Fixing -- Perturbation Theory
We study the gauge-fixing approach to the construction of lattice chiral
gauge theories in one-loop weak-coupling perturbation theory. We show how
infrared properties of the gauge degrees of freedom determine the nature of the
continuous phase transition at which we take the continuum limit. The fermion
self-energy and the vacuum polarization are calculated, and confirm that, in
the abelian case, this approach can be used to put chiral gauge theories on the
lattice in four dimensions. We comment on the generalization to the nonabelian
case.Comment: 31 pages, 5 figures, two refs. adde
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