35,211 research outputs found

    Baryons in Partially-Quenched Chiral Perturbation Theory

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    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

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    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

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    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

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    In the quenched approximation, loops of the light singlet meson (the ő∑‚Ä≤\eta') 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 K0‚ąíKňČ0 K^0 - \bar{K}^0 mixing and BK B_K

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    We have computed BK B_K , using two different methods with staggered fermions on a 163√ó40 16^3 \times 40 lattice at ő≤=5.7 \beta = 5.7 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 BK B_K , although effects were seen on the individual terms making up BK B_K .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

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    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

    BKB_K Using Staggered Fermions: An Update

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    Improved results for BKB_K are discussed. Scaling corrections are argued to be of O(a2)O(a^2), leading to a reduction in the systematic error. For a kaon composed of degenerate quarks, the quenched result is B^K=0.825¬Ī0.027¬Ī0.023{\widehat{B}_K} = 0.825 \pm 0.027 \pm 0.023.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

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    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

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    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

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    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 mŌÄ2m_{\pi}^2 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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