1,784 research outputs found
Non-perturbative BRST invariance and what it might be good for
We construct a local, gauge-fixed, lattice Yang-Mills theory with an exact
BRST invariance, and with the same perturbative expansion as the standard
Yang-Mills theory. The ghost sector, and some of its BRST transformation rules,
are modified to get around Neuberger's theorem. A special term is introduced in
the action to regularize the Gribov horizons, and the limit where the regulator
is removed is discussed. We conclude with a few comments on what might be the
physical significance of this theory. We speculate that there may exist new
strong-interaction phases apart from the anticipated confinement phase.Comment: 3 pages, Lattice2002(theoretical), For additional technical details
see ref.
Quenching effects in strong penguin contributions to
Quenching effects in strong penguin matrix elements are investigated. A
lattice determination of , the constant that appears in the
quenched ChPT relevant for the lattice analysis of matrix
elements, shows that this constant is large. The original RBC analysis of
matrix elements is revisited in light of this result. Also, the numerical
effects of choosing the singlet Golterman-Pallante method of quenching is
investigated.Comment: 3 pages, talk presented at Lattice2004(weak), Fermilab, June 21-26,
200
On tadpole improvement for staggered fermions
An explanation is proposed for the fact that Lepage--Mackenzie tadpole
improvement does not work well for staggered fermions. The idea appears to work
for all renormalization constants which appear in the staggered fermion
self-energy. Wilson fermions are also discussed.Comment: LATTICE98(improvement), 3 pages, 1 figure, latex, uses espcrc2.sty,
epsf.st
Why the overlap formula does not lead to chiral fermions
We describe a conceptually simple, but important test for the overlap
approach to the construction of lattice chiral gauge theories. We explain the
equivalence of the overlap formula with a certain waveguide model for a simple
set of gauge configurations (the trivial orbit). This equivalence is helpful in
carrying out the test, and casts serious doubts on the viability of the overlap
approach. A recent note by Narayanan and Neuberger which points out a mistake
in our previous work is irrelevant in this context.Comment: 4 pages, compressed postscript, contribution to Lattice'9
Manifestly Gauge Invariant Models of Chiral Lattice Fermions
A manifestly gauge invariant lattice action for nonanomalous chiral models is
proposed which leads in the continuum limit to the theory free of doublers.Comment: 9 pages, LaTeX. Revised version with an extended discussion of the
role of higher derivative regulators. Submitted to Phys.Lett.B. Preprint
SMI-9-9
SU(N) chiral gauge theories on the lattice: a quick overview
We describe how an SU(N) chiral gauge theory can be put on the lattice using
non-perturbative gauge fixing. In particular, we explain how the Gribov problem
is dealt with. Our construction is local, avoids doublers, and weak-coupling
perturbation theory applies at the critical point which defines the continuum
limit of our lattice chiral gauge theory.Comment: Parallel talk presented at Lattice2004(chiral), Fermilab, June 21-26,
200
Is there an Aoki phase in quenched QCD?
We argue that quenched QCD has non-trivial phase structure for negative quark
mass, including the possibility of a parity-flavor breaking Aoki phase. This
has implications for simulations with domain-wall or overlap fermions.Comment: Parallel talk presented at Lattice2004(spectrum), Fermilab, June
21-26, 200
Gauge Freedom in Chiral Gauge Theory with Vacuum Overlap
Dynamical nature of the gauge degrees of freedom and its effect to fermion
spectrum are studied at for two- and four-dimensional nonabelian
chiral gauge theories in the vacuum overlap formalism. It is argued that the
disordered gauge degrees of freedom does not contradict to the chiral spectrum
of lattice fermion.Comment: 3 pages. LaTeX with espcrc2. Talk given at Lattice '97, Edinburg
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