802 research outputs found
Is the chiral U(1) theory trivial?
The chiral U(1) theory differs from the corresponding vector theory by an
imaginary contribution to the effective action which amounts to a phase factor
in the partition function. The vector theory, i.e. QED, is known to be trivial
in the continuum limit. It is argued that the presence of the phase factor will
not alter this result and the chiral theory is non-interacting as well.Comment: 4 pages, contribution to Lattice 2000 (Chiral Gauge Theories
Lattice Chiral Schwinger Model in the Continuum Formulation
We pursue further an approach to lattice chiral fermions in which the
fermions are treated in the continuum. To render the effective action gauge
invariant, counterterms have to be introduced. We determine the counterterms
for smooth gauge fields, both analytically and numerically. The final result is
that the imaginary part of the effective action can be computed analytically
from the lattice gauge field, while the real part is given by one half of the
action of the corresponding vector model.Comment: 3 pages, 2 figures, contribution to the LATTICE97 Proceeding
Parton distributions from the lattice
I review the current status of lattice calculations for two selected
observables related to nucleon structure: the second moment of the unpolarized
parton distribution, (u-d), and the first moment of the polarized parton
distribution, the non-singlet axial coupling gA. The major challenge is the
requirement to extract them sufficiently close to the chiral limit. In the
former case, there still remains a puzzling disagreement between lattice data
and experiment. For the latter quantity, however, we may be close to obtaining
its value from the lattice in the immediate future.Comment: Invited review at BARYONS 2004, Palaiseau, France, October 25 - 29,
200
Three-point functions in noncompact lattice QED
We calculate fermion-antifermion-"meson" three-point functions in noncompact
lattice QED with dynamical staggered fermions and use them to extract effective
Yukawa couplings. The results are consistent with the hypothesis that QED is
trivial.Comment: Latex article. 3 pages, ps file. Contribution to LAT93, Dallas,
U.S.A. HLRZ preprint 93-7
One-loop renormalisation for the second moment of GPDs with Wilson fermions
We calculate the non-forward quark matrix elements for operators with two
covariant derivatives in one-loop lattice perturbation theory using Wilson
fermions. These matrix elements are needed in the renormalisation of the second
moment of generalised parton distributions measured in lattice QCD. For some
commonly used representations of the hypercubic group we determine the sets of
all mixing operators and find the matrices of mixing and renormalisation
factors.Comment: Lattice 2004(improved), 3 pages, LaTeX style file, espcrc2.sty
include
Seeking the Equation of State of Non-Compact Lattice QED
We perform a high statistics calculation of the equation of state for
non-compact QED on large lattices. The calculation extends to fermionic
correlation lengths of , and it is combined with a finite size
scaling analysis of the lattice data.Comment: 32 pages, uuencoded Z-compressed postscript file. Also available from
http://www.desy.de/pub/preprints/desy/1996
Interpolation of Non-abelian Lattice Gauge Fields
We propose a method for interpolating non-abelian lattice gauge fields to the
continuum, or to a finer lattice, which satisfies the properties of (i)
transverse continuity, (ii) (lattice) rotation and translation covariance,
(iii) gauge covariance, (iv) locality. These are the properties required for
use in our earlier proposal for non-perturbative formulation and simulation of
chiral gauge theories.Comment: A few typos corrected, a reference and a clarifying comment added. To
appear in Nuclear Physics B. 16 pages, LateX, 1 figure. This interpolation
scheme is intended for use in our formulation of lattice chiral gauge theory,
Nucl. Phys. B455 (1990) 287, hep-ph/950633
Generalized parton distributions and structure functions from full lattice QCD
We present here the latest results from the QCDSF collaboration for (moments
of) structure functions and generalized form factors in full QCD with Nf=2
O(a)-improved Wilson fermions based on simulations closer to the chiral and
continuum limit.Comment: Talks presented by D.Pleiter and J.Zanotti at Lattice2004(weak),
Fermilab, June 21-26, 2004, 6 pages, 9 figure
Renormalisation of Composite Operators in Lattice Perturbation Theory with Clover Fermions: Non-forward Matrix Elements
We consider the renormalisation of lattice QCD operators with one and two
covariant derivatives related to the first and second moments of generalised
parton distributions and meson distribution amplitudes. Employing the clover
fermion action we calculate their non-forward quark matrix elements in one-loop
lattice perturbation theory. For some representations of the hypercubic group
commonly used in simulations we determine the sets of all possible mixing
operators and compute the matrices of renormalisation factors in one-loop
approximation. We describe how tadpole improvement is applied to the results.Comment: 16 pages; v2: eqs.(27), (28), (74)-(79) corrected, several signs
changed in section III.
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