79 research outputs found
Scaling behavior at the tricritical point in the fermion-gauge-scalar model
We investigate a strongly coupled U(1) gauge theory with fermions and scalars
on the lattice and analyze whether the continuum limit might be a
renormalizable theory with dynamical mass generation. Most attention is paid to
the phase with broken chiral symmetry in the vicinity of the tricritical point
found in the model. There we investigate the scaling of the masses of the
composite fermion and of some bosonic bound states. As a by-product we confirm
the mean-field exponents at the endpoint in the U(1)-Higgs model, by analyzing
the scaling of the Fisher zeros.Comment: Talk presented at LATTICE96(other models), 4 page
Strongly coupled U(1) lattice gauge theory as a microscopic model of Yukawa theory
Dynamical chiral symmetry breaking in a strongly coupled U(1) lattice gauge
model with charged fermions and scalar is investigated by numerical simulation.
Several composite neutral states are observed, in particular a massive fermion.
In the vicinity of the tricritical point of this model we study the effective
Yukawa coupling between this fermion and the Goldstone boson. The perturbative
triviality bound of Yukawa models is nearly saturated. The theory is quite
similar to strongly coupled Yukawa models for sufficiently large coupling
except the occurrence of an additional state -- a gauge ball of mass about half
the mass of the fermion.Comment: 4 page
Analysis of the Lee-Yang zeros in a dynamical mass generation model in three dimensions
We investigate a strongly U(1) gauge theory with fermions and scalars on a
three dimensional lattice and analyze whether the cintinuum limit might be a
renormalizable theory with dynamical mass generation. Most attention is paid to
the weak coupling region where a possible new dynamical mass generation
mechanism might exist. There we investigate the mass of the composite fermion,
the chiral condensate and the scaling of the Lee-Yang zeros.Comment: 3 pages,4 figures,talk presented at Lattice97(Edinburgh
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
Chiral transition in a strongly coupled fermion-gauge-scalar model
We report the recent results from the computer simulations of a
fermion-gauge-scalar model with dynamical chiral-symmetry breaking and chiral
transition induced by the scalar field. This model might be considered to be a
possible alternative to the Higgs mechanism of mass generation. A new scheme is
developed for detecting the chiral transition. Our results show with higher
precision than the earlier works that the chiral transition line joins the
Higgs phase transition line, separating the Higgs and Nambu (chiral-symmetry
breaking) phases. The end point of the Higgs transition with divergent
correlation lengths is therefore suitable for an investigation of the continuum
limit.Comment: 3 pages, 3 eps figs, encoded with uufiles (Contribution to Lattice
94
Two-dimensional model of dynamical fermion mass generation in strongly coupled gauge theories
We generalize the Schwinger model on the lattice by adding a charged
scalar field. In this so-called model the scalar field shields
the fermion charge, and a neutral fermion, acquiring mass dynamically, is
present in the spectrum. We study numerically the mass of this fermion at
various large fixed values of the gauge coupling by varying the effective
four-fermion coupling, and find an indication that its scaling behavior is the
same as that of the fermion mass in the chiral Gross-Neveu model. This suggests
that the model is in the same universality class as the
Gross-Neveu model, and thus renormalizable and asymptotic free at arbitrary
strong gauge coupling.Comment: 18 pages, LaTeX2e, requires packages rotating.sty and curves.sty from
CTA
Spectrum and scaling in a strongly coupled fermion-gauge-scalar model
The strongly coupled lattice gauge models show an interesting mechanism of
dynamical mass generation. If a suitable continuum limit can be found, one may
think of it as an alternative to the Higgs mechanism. We present data on the
spectrum, obtained in the model with U(1) gauge symmetry with dynamical
fermions. They indicate that the fermion mass scales in the vicinity of the
whole chiral phase transition line. In contrast to this, the composite scalar
boson mass seems to get small only in the region near the endpoint E of the
Higgs phase transition. Thus this point is the most interesting candidate for
approaching the continuum limit. The masses of fermion--antifermion bound
states are also discussed.Comment: 3 pages, 2 eps figs, encoded with uufiles (Contribution to Lattice
94
Tricritical point in strongly coupled U(1) gauge theory with fermions and scalars
We investigate the tricritical point in the lattice fermion--gauge--scalar
model with U(1) gauge symmetry. In the vicinity of this point, in the phase
with the broken chiral symmetry, we observe the scaling behavior of the chiral
condensate and of the masses of composite fermion and composite scalar,
indicating the existence of an interesting continuum limit of the model at this
point.Comment: Contribution to Lattice 95, LaTeX file (4 pages), 5 ps-figures
appended (uuencoded
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