107 research outputs found
Renormalization of strongly coupled U(1) lattice gauge theories
Recent numerical studies of the 4D pure compact U(1) lattice gauge theory, I
have participated in, are reviewed. We look for a possibility to construct an
interesting nonperturbatively renormalizable continuum theory at the phase
transition between the confinement and Coulomb phases. First I describe the
numerical evidence, obtained from calculation of bulk observables on spherical
lattices, that the theory has a non-Gaussian fixed point. Further the
gauge-ball spectrum in the confinement phase is presented and its universality
confirmed. The unexpected result is that, in addition to massive states, the
theory contains a very light, possibly massless scalar gauge ball. I also
summarize results of studies of the compact U(1) lattice theory with fermion
and scalar matter fields and point out that at strong coupling it represents a
model of dynamical fermion mass generation.Comment: Talk presented at the 31st International Symposium Ahrenshoop on the
Theory of Elementary Particles, Buckow, September 2-6, 1997. 8 page
Interplay of universality classes in a three-dimensional Yukawa model
We investigate numerically on the lattice the interplay of universality
classes of the three-dimensional Yukawa model with U(1) chiral symmetry, using
the Binder method of finite size scaling. At zero Yukawa coupling the scaling
related to the magnetic Wilson--Fisher fixed point is confirmed. At
sufficiently strong Yukawa coupling the dominance of the chiral fixed point
associated with the 3D Gross--Neveu model is observed for various values of the
coupling parameters, including infinite scalar selfcoupling. In both cases the
Binder method works consistently in a broad range of lattice sizes. However,
when the Yukawa coupling is decreased the finite size behavior gets complicated
and the Binder method gives inconsistent results for different lattice sizes.
This signals a cross-over between the universality classes of the two fixed
points.Comment: 24 pp. LaTeX 2e src, needs psfig.st
New universality class of chiral symmetry breaking in the strongly coupled U(1) model
We describe a 4D U(1) lattice gauge theory with charged scalar and
fermion matter fields ( model). At sufficiently strong
gauge coupling, the chiral symmetry is broken and the mass of the unconfined
composite fermion is generated dynamically by gauge
interaction. The scalar supresses this symmetry breaking and induces a line of
second order transitions with scaling properties similar to the
Nambu--Jona-Lasinio model. However, in the vicinity of a particular,
tricritical point the scaling properties are different. Here we study the
effective Yukawa coupling between the massive fermion and the Goldstone boson.
The perturbative triviality bound of Yukawa models is nearly saturated. The
theory is similar to strongly coupled Yukawa models except the occurrence of an
additional state -- a gauge ball of mass . This, and
non-classical values of tricritical exponents suggest that at the tricritical
point the model constitutes a new universality class.
Nevertheless, it might be a microscopic model for the Higgs-Yukawa mechanism of
symmetry breaking.Comment: LATTICE98(yukawa
Strongly coupled lattice gauge theory with dynamical fermion mass generation in three dimensions
We investigate the critical behaviour of a three-dimensional lattice
\chiU\phi_3 model in the chiral limit. The model consists of a staggered
fermion field, a U(1) gauge field (with coupling parameter ) and a
complex scalar field (with hopping parameter ). Two different methods
are used: 1) fits of the chiral condensate and the mass of the neutral
unconfined composite fermion to an equation of state and 2) finite size scaling
investigations of the Lee-Yang zeros of the partition function in the complex
fermion mass plane. For strong gauge coupling () the critical
exponents for the chiral phase transition are determined. We find strong
indications that the chiral phase transition is in one universality class in
this interval: that of the three-dimensional Gross-Neveu model with two
fermions. Thus the continuum limit of the \chiU\phi_3 model defines here a
nonperturbatively renormalizable gauge theory with dynamical mass generation.
At weak gauge coupling and small , we explore a region in which the
mass in the neutral fermion channel is large but the chiral condensate on
finite lattices very small. If it does not vanish in the infinite volume limit,
then a continuum limit with massive unconfined fermion might be possible in
this region, too.Comment: 27 pages, 16 figure
Study of the Asymptotic Freedom of 2D Yukawa Models on the Lattice
We investigate on the lattice the Yukawa models in 2 dimensions with Z(2) and
U(1) symmetries. These models reduce to the usual and chiral Gross-Neveu
models, respectively, when the kinetic and the selfcoupling terms of the scalar
field are turned off. The numerical data and mean field arguments suggest that,
at least for some range of the scalar field hopping parameter, fermion mass is
dynamically generated for arbitrarily weak Yukawa coupling. The models are
asymptotically free in this coupling, like the Gross-Neveu models, even when
the scalar quartic selfcoupling is strong.Comment: LaTeX, 11 pages (including 4 postscript figures); OUTP-93-01P (HLRZ
93-15
Observation of String Breaking in QCD
We numerically investigate the transition of the static quark-antiquark
string into a static-light meson-antimeson system. Improving noise reduction
techniques, we are able to resolve the signature of string breaking dynamics
for n_f=2 lattice QCD at zero temperature. This result can be related to
properties of quarkonium systems. We also study short-distance interactions
between two static-light mesons.Comment: 27 pages, 22 figures, changed decimal place of errors in 3 entries of
Table, corrected reference
Finite Size Analysis of the U(1) Phase Transition using the World-sheet Formulation
We present a high statistics analysis of the pure gauge compact U(1) lattice
theory using the the world-sheet or Lagrangian loop representation. We have
applied a simulation method that deals directly with (gauge invariant) integer
variables on plaquettes. As a result we get a significant amelioration of the
simulation that allows to work with large lattices avoiding the metaestability
problems that appear using the standard Wilson formulation.Comment: 14 pages, 4 figures. REVTEX and eps
Dirac Relation and Renormalization Group Equations for Electric and Magnetic Fine Structure Constants
The quantum field theory describing electric and magnetic charges and
revealing a dual symmetry was developed in the Zwanziger formalism. The
renormalization group (RG) equations for both fine structure constants -
electric and magnetic - were obtained. It was shown
that the Dirac relation is valid for the renormalized and at the arbitrary scale, but these RG equations can be considered
perturbatively only in the small region: with given by the Dirac
relation: = 1/4.Comment: 15 pages, 4 figures, made corrections of physics after comments from
Kim Milto
THE CRITICAL EXPONENTS OF THE DECONFINEMENT TRANSITION IN SU(2) LATTICE GAUGE-THEORY
Engels J, JERSAK J, KANAYA K, et al. THE CRITICAL EXPONENTS OF THE DECONFINEMENT TRANSITION IN SU(2) LATTICE GAUGE-THEORY. NUCLEAR PHYSICS B. 1987;280(4):577-598
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