1,750 research outputs found
Two-particle wave function in four dimensional Ising model
An exploratory study of two-particle wave function is carried out with a four
dimensional simple model. The wave functions not only for two-particle ground
and first excited states but also for an unstable state are calculated from
three- and four-point functions using the diagonalization method suggested by
L\"uscher and Wolff. The scattering phase shift is evaluated from these wave
functions.Comment: Poster presented at Lattice2004(spectrum), Fermilab, June 21-26, 200
Nonperturbatively Improved Hadron Spectroscopy Near the Continuum Limit
We report the results of our quenched lattice simulations of the Wilson
action with a nonperturbatively determined clover term at beta=6.2 and compare
them with those of the standard Wilson action at the same beta value.Comment: 3 pages, including 3 figures; talk given at LATTICE9
Volume dependence of light hadron masses in full lattice QCD
The aim of the GRAL project is to simulate full QCD with standard Wilson
fermions at light quark masses on small to medium-sized lattices and to obtain
infinite-volume results by extrapolation. In order to establish the functional
form of the volume dependence we study systematically the finite-size effects
in the light hadron spectrum. We give an update on the status of the GRAL
project and show that our simulation data for the light hadron masses depend
exponentially on the lattice size.Comment: 3 pages, 1 figure, Lattice2003(spectrum
A perturbative determination of O(a) boundary improvement coefficients for the Schr\"odinger Functional coupling at 1-loop with improved gauge actions
We determine O() boundary improvement coefficients up to 1-loop level for
the Schr\"odinger Functional coupling with improved gauge actions including
plaquette and rectangle loops. These coefficients are required to implement
1-loop O() improvement in full QCD simulations for the coupling with the
improved gauge actions. To this order, lattice artifacts of step scaling
function for each improved gauge action are also investigated. In addition,
passing through the SF scheme, we estimate the ratio of -parameters
between the improved gauge actions and the plaquette action more accurately.Comment: 17 pages, 2 figures, 6 table
Renormalization of lattice gauge theories with massless Ginsparg Wilson fermions
Using functional techniques, we prove, to all orders of perturbation theory,
that lattice vector gauge theories with Ginsparg Wilson fermions are
renormalizable. For two or more massless fermions, they satisfy a flavour
mixing axial vector Ward identity. It involves a lattice specific part that is
quadratic in the vertex functional and classically irrelevant. We show that it
stays irrelevant under renormalization. This means that in the continuum limit
the (standard) chiral symmetry becomes restored. In particular, the flavour
mixing current does not require renormalization.Comment: 13 pages, Latex2
Linked Cluster Expansions on non-trivial topologies
Linked cluster expansions provide a useful tool both for analytical and
numerical investigations of lattice field theories. The expansion parameter is
the interaction strength fields at neighboured lattice sites are coupled. They
result into convergent series for free energies, correlation functions and
susceptibilities. The expansions have been generalized to field theories at
finite temperature and to a finite volume. Detailed information on critical
behaviour can be extracted from the high order behaviour of the susceptibility
series. We outline some of the steps by which the 20th order is achieved.Comment: 3 pages, Talk presented at LATTICE96(Theoretical Developments
Lattice QED and Universality of the Axial Anomaly
We give a perturbative proof that U(1) lattice gauge theories generate the
axial anomaly in the continuum limit under very general conditions on the
lattice Dirac operator. These conditions are locality, gauge covariance and the
absense of species doubling. They hold for Wilson fermions as well as for
realizations of the Dirac operator that satisfy the Ginsparg-Wilson relation.
The proof is based on the lattice power counting theorem. The results
generalize to non-abelian gauge theories.Comment: LATTICE99(theoretical developments) 3 page
A simple construction of fermion measure term in U(1) chiral lattice gauge theories with exact gauge invariance
In the gauge invariant formulation of U(1) chiral lattice gauge theories
based on the Ginsparg-Wilson relation, the gauge field dependence of the
fermion measure is determined through the so-called measure term. We derive a
closed formula of the measure term on the finite volume lattice. The Wilson
line degrees of freedom (torons) of the link field are treated separately to
take care of the global integrability. The local counter term is explicitly
constructed with the local current associated with the cohomologically trivial
part of the gauge anomaly in a finite volume. The resulted formula is very
close to the known expression of the measure term in the infinite volume with a
single parameter integration, and would be useful in practical implementations.Comment: 25 pages, uses JHEP3.cls, the version to appear in JHE
Spectrum of the Hermitian Wilson-Dirac Operator for a Uniform Magnetic Field in Two Dimensions
It is shown that the eigenvalue problem for the hermitian Wilson-Dirac
operator of for a uniform magnetic field in two dimensions can be reduced to
one-dimensional problem described by a relativistic analog of the Harper
equation. An explicit formula for the secular equations is given in term of a
set of polynomials. The spectrum exhibits a fractal structure in the infinite
volume limit. An exact result concerning the index theorem for the overlap
Dirac operator is obtained.Comment: 8 pages, latex, 3 eps figures, minor correction
Computation of the one-loop Symanzik coefficients for the square action
We compute the one-loop coefficients for an alternative Symanzik improved
pure gauge SU{N} lattice action (N=2 and N=3). For the standard Symanzik
improved action we confirm previous results by L\"{u}scher and Weisz.Comment: 45 pages, LaTeX, includes library.ps for generating Feynman diagram
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