223 research outputs found
Chiral Extension of Lattice Gauge Theory
Two approaches are presented to coupling explicit Goldstone modes to
flavors of massless quarks preserving exact chiral
symmetry on the lattice. The first approach is a generalization a chiral
extension to QCD (aka XQCD) proposed by Brower, Shen and Tan consistent with
the Ginsparg-Wilson relation. The second approach based on the Callan,Coleman,
Wess and Zumino coset construction has a real determinant atzero quark axial
coupling, .Comment: Lattice2003 3 pages, 1 figur
The M\"obius Domain Wall Fermion Algorithm
We present a review of the properties of generalized domain wall Fermions,
based on a (real) M\"obius transformation on the Wilson overlap kernel,
discussing their algorithmic efficiency, the degree of explicit chiral
violations measured by the residual mass () and the Ward-Takahashi
identities. The M\"obius class interpolates between Shamir's domain wall
operator and Bori\c{c}i's domain wall implementation of Neuberger's overlap
operator without increasing the number of Dirac applications per conjugate
gradient iteration. A new scaling parameter () reduces chiral
violations at finite fifth dimension () but yields exactly the same
overlap action in the limit . Through the use of 4d
Red/Black preconditioning and optimal tuning for the scaling , we
show that chiral symmetry violations are typically reduced by an order of
magnitude at fixed . At large we argue that the observed scaling for
for Shamir is replaced by for the
properly tuned M\"obius algorithm with Comment: 59 pages, 11 figure
Saturation and Confinement: Analyticity, Unitarity and AdS/CFT Correspondence
In expansion, analyticity and crossing lead to crossing even and odd
() vacuum exchanges at high-energy, the {\em Pomeron} and the {\em
Odderon}. We discuss how, using {\em String/Gauge duality}, these can be
identified with a reggeized {\em Graviton} and the anti-symmetric {\em
Kalb-Ramond fields} in background. With confinement, these Regge
singularities interpolate with glueball states. We also discuss unitarization
based on eikonal sum in .Comment: more references added. presented at ISMD 2008, 15-20 Sept. 200
Magnetic monopole loop for the Yang-Mills instanton
We investigate 't Hooft-Mandelstam monopoles in QCD in the presence of a
single classical instanton configuration. The solution to the Maximal Abelian
projection is found to be a circular monopole trajectory with radius
centered on the instanton. At zero loop radius, there is a marginally stable
(or flat) direction for loop formation to . We argue that loops
will form, in the semi-classical limit, due to small perturbations such as the
dipole interaction between instanton anti-instanton pairs. As the instanton gas
becomes a liquid, the percolation of the monopole loops may therefore provide a
semi-classical precursor to the confinement mechanism.Comment: 19 pages, ReVTeX, 5 Encaptulated Postscript figure
On the Eikonal Approximation in AdS Space
We explore the eikonal approximation to graviton exchange in AdS_5 space, as
relevant to scattering in gauge theories. We restrict ourselves to the regime
where conformal invariance of the dual gauge theory holds, and to large 't
Hooft coupling where the computation involves pure gravity. We give a heuristic
argument, a direct loop computation, and a shock wave derivation. The scalar
propagator in AdS_3 plays a key role, indicating that even at strong coupling,
two-dimensional conformal invariance controls high-energy four-dimensional
gauge-theory scattering.Comment: 22 pages, 2 figures; published version: updated references and
several clarifying remarks adde
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