35,375 research outputs found
Baryons in Partially-Quenched Chiral Perturbation Theory
I discuss the inclusion of baryons into partially-quenched chiral
perturbation theory and describe one-loop calculations that have been
performed.Comment: Lattice2002(matrixel) : talk presented at Lattice 2002, 7 page
Discrete Torsion and Branes in M-theory from Mathematical Viewpoint
We study orbifold group actions on locally defined fields upon M-theory
branes in a three-form C-fields background. We derive some constraints from the
consistency of the orbifold group actions. We show the possibility of the
existence of M-theory discrete torsion for the fields on the worldvolume and
discuss its features.Comment: 14 pages, harvmac, typos corrected and refs. adde
Discrete Torsion in Perturbative Heterotic String Theory
In this paper we analyze discrete torsion in perturbative heterotic string
theory. In previous work we have given a purely mathematical explanation of
discrete torsion as the choice of orbifold group action on a B field, in the
case that d H = 0; in this paper, we perform the analogous calculations in
heterotic strings where d H is nonzero.Comment: 15 pages, LaTeX; v2: typos fixe
Problems with the Quenched Approximation in the Chiral Limit
In the quenched approximation, loops of the light singlet meson (the )
give rise to a type of chiral logarithm absent in full QCD. These logarithms
are singular in the chiral limit throwing doubt upon the utility of the
quenched approximation. In previous work, I summed a class of diagrams, leading
to non-analytic power dependencies such as \cond\propto
m_q^{-\delta/(1+\delta)}. I suggested, however, that these peculiar results
could be redefined away. Here I give an alternative derivation of the results,
based on the renormalization group, and argue that they cannot be redefined
away. I discuss the evidence (or lack thereof) for such effects in numerical
data.Comment: (talk given at Lattice '92), 4 pages latex, 3 postscript figures,
uses espcr2.sty and psfig.tex (all included) UW/PT-92-2
Miscellanies of mixing and
We have computed , using two different methods with staggered fermions
on a lattice at with two dynamical flavors
of a mass 0.01. % Using an improved wall source method, we have studied a
series of non-degenerate quark antiquark pairs and observed no effect on , although effects were seen on the individual terms making up .Comment: 4 pages (latex, including 8 postscript figures, uuencoded
gzip-compressed tar files), Nucl. Phys. B (Proc. Suppl.) Lattice 9
Partially Quenched QCD with Non-Degenerate Dynamical Quarks
We discuss the importance of using partially quenched theories with three
degenerate quarks for extrapolating to QCD, and present some relevant results
from chiral perturbation theory.Comment: LATTICE99 talk. 3 pages, 2 figures. Uses epsf and espcrc2.st
Using Staggered Fermions: An Update
Improved results for are discussed. Scaling corrections are argued to
be of , leading to a reduction in the systematic error. For a kaon
composed of degenerate quarks, the quenched result is .Comment: (poster presented at Lattice '93), 7 pages latex (it's in preprint
format!), 1 postscript figure, bundled with uufiles. Uses psfig.tex.
UW/PT-93-2
Discrete Torsion and Shift Orbifolds
In this paper we make two observations related to discrete torsion. First, we
observe that an old obscure degree of freedom (momentum/translation shifts) in
(symmetric) string orbifolds is related to discrete torsion. We point out how
our previous derivation of discrete torsion from orbifold group actions on B
fields includes these momentum lattice shift phases, and discuss how they are
realized in terms of orbifold group actions on D-branes. Second, we describe
the M theory dual of IIA discrete torsion, a duality relation to our knowledge
not previously understood. We show that IIA discrete torsion is encoded in
analogues of the shift orbifolds above for the M theory C field.Comment: 28 pages, LaTeX, 3 figures; v2: references adde
Notes on discrete torsion in orientifolds
In this short note we discuss discrete torsion in orientifolds. In
particular, we apply the physical understanding of discrete torsion worked out
several years ago, as group actions on B fields, to the case of orientifolds,
and recover some old results of Braun and Stefanski concerning group cohomology
and twisted equivariant K theory. We also derive new results including phase
factors for nonorientable worldsheets and analogues for C fields.Comment: 28 pages; v2: references adde
Finite Volume Effects and Quenched Chiral Logarithms
We have measured the valence pion mass and the valence chiral condensate on
lattice configurations generated with and without dynamical fermions. We find
that our data and that of others is well represented by a linear relationship
between and the valence quark mass, with a non-zero intercept. For
our data, we relate the intercept to finite volume effects visible in the
valence chiral condensate. We see no evidence for the singular behavior
expected from quenched chiral logarithms.Comment: 5 pages, Latex with included macro. 4 encapsulated postscript figures
included. Contribution to Lattice '9
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