16,903 research outputs found
Large q expansion of the 2D q-states Potts model
We present a recursive method to calculate a large q expansion of the 2d
q-states Potts model free energies based on the Fortuin-Kasteleyn
representation of the model. With this procedure, we compute directly the
ordered phase partition function up to order 10 in 1/sqrt{q}. The energy
cumulants at the transition can be obtained with suitable resummation and come
out large for q less or around 15. As a consequence, expansions of the free
energies around the transition temperature are useless for not large enough
values of q. In particular the pure phase specific heats are predicted to be
much larger, at q < 15, than the values extracted from current finite size
scaling analysis of extrema, whereas they agree very well with recent values
extracted at the transition point.Comment: 31 pages (tex) including 15 figures (Postscript
Non-perturbative improvement of bilinears in unquenched QCD
We describe how the improvement of quark bilinears generalizes from quenched
to unquenched QCD, and discuss which of the additional improvement constants
can be determined using Ward Identities.Comment: LATTICE99 (Improvement and Renormalization). 3 pages, no figures.
Corrected error (improvement coefficient is not needed
Critical Behavior of the Antiferromagnetic Heisenberg Model on a Stacked Triangular Lattice
We estimate, using a large-scale Monte Carlo simulation, the critical
exponents of the antiferromagnetic Heisenberg model on a stacked triangular
lattice. We obtain the following estimates: ,
. These results contradict a perturbative
Renormalization Group calculation that points to Wilson-Fisher O(4) behaviour.
While these results may be coherent with results from
Landau-Ginzburg analysis, they show the existence of an unexpectedly rich
structure of the Renormalization Group flow as a function of the dimensionality
and the number of components of the order parameter.Comment: Latex file, 10 pages, 1 PostScript figure. Was posted with a wrong
Title !
Non-perturbative Renormalization Constants using Ward Identities
We extend the application of vector and axial Ward identities to calculate
, and , coefficients that give the mass dependence of the
renormalization constants of the corresponding bilinear operators in the
quenched theory. The extension relies on using operators with non-degenerate
quark masses. It allows a complete determination of the improvement
coefficients for bilinears in the quenched approximation using Ward Identities
alone. Only the scale dependent normalization constants (or )
and are undetermined. We present results of a pilot numerical study using
hadronic correlators.Comment: 3 pages. Makefile and sources included. Talk presented at LATTICE98
(matrixelement
Phenomenology from 100 large lattices
We present a status report on simulations being done on 32^3 \times 64 lattices at \beta = 6.0 using quenched Wilson fermions. Phenomenologically relevant results for the spectrum, decay constants, the kaon B-parameter B_K, B_7, B_8, semi-leptonic and B\to K^* \gamma form factors are given based on a statistical sample of 100 configurations
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