206 research outputs found
The fixed point action of the Schwinger model
We compute the fixed point action for the Schwinger model through an
expansion in the gauge field. The calculation allows a check of the locality of
the action. We test its perfection by computing the 1-loop mass gap at finite
spatial volume.Comment: 3 pages, LaTeX, 2 figures, uses styles [twoside,fleqn,espcrc2,
epsfig], talk presented at Lattice 9
Partially quenched chiral perturbation theory and numerical simulations
The dependence of the pseudoscalar meson mass and decay constant is compared
to one-loop Partially Quenched Chiral Perturbation Theory (PQChPT) in a
numerical simulation with two light dynamical quarks. The characteristic
behaviour with chiral logarithms is observed. The values of the fitted
PQChPT-parameters are in a range close to the expectation in continuum in spite
of the fact that the lattice spacing is still large, namely a=0.28 fm.Comment: 11 pages, 3 figures; discussion of the results in section 3 extende
Wilson, fixed point and Neuberger's lattice Dirac operator for the Schwinger model
We perform a comparison between different lattice regularizations of the
Dirac operator for massless fermions in the framework of the single and two
flavor Schwinger model. We consider a) the Wilson-Dirac operator at the
critical value of the hopping parameter; b) Neuberger's overlap operator; c)
the fixed point operator. We test chiral properties of the spectrum, dispersion
relations and rotational invariance of the mesonic bound state propagators.Comment: Revised version; 13 pages (LaTeX), 3 figures (EPS
The Volume Source Technique for flavor singlets: a second look
We reconsider the Volume Source Technique (VST) for the determination of
flavor singlet quantities on the lattice. We point out a difficulty arising in
the case of fermions in real representations of the gauge group and propose an
improved version of the method (IVST) based on random gauge transformations of
the background configuration. We compare the performance of IVST with the
method based on stochastic estimators (SET). We consider the case of the N=1
Supersymmetric Yang-Mills Theory (SYM), where just one fermionic flavor is
present, the gluino in the adjoint representation, and only flavor singlet
states are possible. The work is part of an inclusive analysis of the spectrum
of the lightest particles of the theory, based on the simulation of the model
on a lattice with dynamical gluinos in the Wilson scheme.Comment: 11 pages, 6 figures, some formulations change
Masses and Decay Constants of Pseudoscalar Mesons to Two Loops in Two-Flavor Partially Quenched Chiral Perturbation Theory
This paper presents a first study of the masses and decay constants of the
charged, or flavor-off-diagonal, pseudoscalar mesons to two loops for two
flavors of sea-quarks, in Partially Quenched Chiral Perturbation Theory
(PQPT). Explicit analytical expressions up to in the
momentum expansion are given. The calculations have been performed within the
supersymmetric formulation of PQPT. A numerical analysis is done to
indicate the size of the corrections.Comment: 20 pages, subsection about determining the LECs from lattice results
added, v3 one misprint correcte
Lattice Spacing Dependence of the First Order Phase Transition for Dynamical Twisted Mass Fermions
Lattice QCD with Wilson fermions generically shows the phenomenon of a first
order phase transition. We study the phase structure of lattice QCD using
Wilson twisted mass fermions and the Wilson plaquette gauge action are used in
a range of beta values where such a first order phase transition is observed.
In particular, we investigate the dependence of the first order phase
transition on the value of the lattice spacing. Using only data in one phase
and neglecting possible problems arising from the phase transition we are able
to perform a first scaling test for physical quantities using this action.Comment: 15 pages, 7 figures, typo corrected, web-list of authors correcte
Lattice QCD with light dynamical quarks
We report on the simulation of QCD with light dynamical quarks using the
two-step multi-boson (TSMB) algorithm.
In an exploratory study with two flavours of quarks at lattice spacing about
0.27 fm and with quark mass down to one sixth of the strange quark mass
eigenvalue spectra and autocorrelations have been studied.
Here we present results on the volume dependence as well as tests of possible
algorithmic improvements.Comment: 6 pages, Lattice2002(spectrum
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