191 research outputs found
Empirical central limit theorems for ergodic automorphisms of the torus
Let T be an ergodic automorphism of the d-dimensional torus T^d, and f be a
continuous function from T^d to R^l. On the probability space T^d equipped with
the Lebesgue-Haar measure, we prove the weak convergence of the sequential
empirical process of the sequence (f o T^i)_{i \geq 1} under some mild
conditions on the modulus of continuity of f. The proofs are based on new limit
theorems and new inequalities for non-adapted sequences, and on new estimates
of the conditional expectations of f with respect to a natural filtration.Comment: 32 page
Ghost-gluon coupling, power corrections and from twisted-mass lattice QCD at
A non-perturbative calculation of the ghost-gluon running QCD coupling
constant is performed using twisted-mass dynamical fermions. The
extraction of in the chiral limit reveals the presence of
a non-perturbative OPE contribution that is assumed to be dominated by a
dimension-two \VEV{A^2} condensate. In this contest a novel method for
calibrating the lattice spacing in lattice simulations is presented.Comment: 7 pages, 4 figures, XXVIII International Symposium on Lattice Field
Theory 201
Modified instanton profile effects from lattice Green functions
We trace here instantons through the analysis of pure Yang-Mills gluon Green
functions in the Landau gauge for a window of IR momenta (0.4 GeV
GeV). We present lattice results that can be fitted only after substituting the
BPST profile in the Instanton liquid model (ILM) by one based on the Diakonov
and Petrov variational methods. This also leads us to gain information on the
parameters of ILM.Comment: 32 pagex, 6 figure
A Ghost Story II: Ghosts, Gluons and the Gluon condensate beyond the IR of QCD
Beyond the deep IR, the analysis of ghost and gluon propagators still keeps
very interesting non-perturbative information. The Taylor-scheme coupling can
be computed and applied to obtain the parameter from Landau
gauge lattice simulations. Furthermore, a dimension-two gluon condensate, that
can be understood in the instanton liquid model, plays an important role in the
game.Comment: 12 pp., 3 fig
Yukawa model on a lattice: two body states
We present first results of the solutions of the Yukawa model as a Quantum
Field Theory (QFT) solved non perturbatively with the help of lattice
calculations. In particular we will focus on the possibility of binding two
nucleons in the QFT, compared to the non relativistic result.Comment: 3 pages, talk at "IVth International Conference on Quarks and Nuclear
Physics" (Madrid, June 2006
Two body scattering length of Yukawa model on a lattice
The extraction of scattering parameters from Euclidean simulations of a
Yukawa model in a finite volume with periodic boundary conditions is analyzed
both in non relativistic quantum mechanics and in quantum field theory.Comment: 4 pages, talk at "18th International IUPAP conference on Few Body
Problems in Physics" (Sao Paulo, August 2006
Renormalisation of quark propagators from twisted-mass lattice QCD at =2
We present results concerning the non-perturbative evaluation of the
renormalisation constant for the quark field, , from lattice simulations
with twisted mass quarks and three values of the lattice spacing. We use the
RI'-MOM scheme. has very large lattice spacing artefacts; it is
considered here as a test bed to elaborate accurate methods which will be used
for other renormalisation constants. We recall and develop the non-perturbative
correction methods and propose tools to test the quality of the correction.
These tests are also applied to the perturbative correction method. We check
that the lattice spacing artefacts scale indeed as . We then study the
running of with particular attention to the non-perturbative effects,
presumably dominated by the dimension-two gluon condensate \VEV{A^2} in
Landau gauge. We show indeed that this effect is present, and not small. We
check its scaling in physical units confirming that it is a continuum effect.
It gives a contribution at 2 GeV. Different variants are used in
order to test the reliability of our result and estimate the systematic
uncertainties. Finally combining all our results and using the known Wilson
coefficient of \VEV{A^2} we find g^2(\mu^2) \VEV{A^2}_{\mu^2\; CM} =
2.01(11)(^{+0.61}_{- 0.73}) \;\mathrm {GeV}^2 at , in
fair agreement within uncertainties with the value indepently extracted from
the strong coupling constant.Comment: 38 pages, 8 tables, 8 figure
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