816 research outputs found
Effective Yukawa Couplings in Noncompact Lattice QED
We investigate effective Yukawa couplings of mesons to the elementary
fermions in noncompact lattice QED. The couplings are extracted from suitable
fermion-antifermion-meson three-point functions calculated by Monte Carlo
simulations with dynamical staggered fermions. The scaling behaviour is
compatible with expectations from perturbation theory, thus indicating
triviality of QED. The lines of constant Yukawa coupling are compared to flows
of other quantities. Consistency is seen, at most, for weak coupling.Comment: 12 pages, uuencoded compressed postscrip
Is the Chiral Phase Transition in Non-Compact Lattice QED Driven by Monopole Condensation?
We investigate the recent conjecture that the chiral phase transition in
non-compact lattice QED is driven by monopole condensation. The comparison of
analytic and numerical results shows that we have a quantitative understanding
of monopoles in both the quenched and dynamical cases. We can rule out monopole
condensation.Comment: 21 pages, 10 postscript figures include
Probing the Continuum Limit in Non-Compact QED: New Results on Large Lattices
We present new Monte Carlo results in non-compact lattice QED with staggered
fermions down to m_0 = 0.005. This extends our previous investigations on the
nature of the continuum limit of QED.Comment: 7 pages, uuencoded compressed PostScript, also available at
ftp://ftp.zib-berlin.de/pub/zib-publications/Reports/SC-94-31.ps.
The SU(3) Beta Function from Numerical Stochastic Perturbation Theory
The SU(3) beta function is computed from Wilson loops to 20th order numerical
stochastic perturbation theory. An attempt is made to include massless
fermions, whose contribution is known analytically to 4th order. The question
whether the theory admits an infrared stable fixed point is addressed.Comment: 10 pages, 7 figures, version to be published in Physics Letters
Perturbative renormalisation of quark bilinear operators for overlap fermions with and without stout links and improved gauge action
We calculate lattice renormalisation constants of local and one-link quark
operators for overlap fermions and improved gauge actions in one-loop
perturbation theory. For the local operators we stout smear the SU(3) links in
the fermionic action. Using the popular tadpole improved L\"uscher-Weisz
actions at and we present numerical values for the Z
factors in the scheme (partly as function of the stout smearing
strength). We compare various levels of mean field (tadpole) improvement which
have been applied to our results.Comment: 7 page
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