95 research outputs found
Renormalization Group and Universality
It is argued that universality is severely limited for models with multiple
fixed points. As a demonstration the renormalization group equations are
presented for the potential and the wave function renormalization constants in
the scalar field theory. Our equations are superior compared with the
usual approach which retains only the contributions that are non-vanishing in
the ultraviolet regime. We find an indication for the existence of relevant
operators at the infrared fixed point, contrary to common expectations. This
result makes the sufficiency of using only renormalizable coupling constants in
parametrizing the long distance phenomena questionable.Comment: 32pp in plain tex; revised version to appear in PR
Non-perturbative thermal flows and resummations
We construct a functional renormalisation group for thermal fluctuations.
Thermal resummations are naturally built in, and the infrared problem of
thermal fluctuations is well under control. The viability of the approach is
exemplified for thermal scalar field theories. In gauge theories the present
setting allows for the construction of a gauge-invariant thermal
renormalisation group.Comment: 16 pages, eq (38) added to match published versio
Fermion-Higgs model with Reduced Staggered Fermions
We introduce a lattice fermion-Higgs model with one component `reduced
staggered' fermions. In order to use the fermion field as efficiently as
possible we couple the two {\em staggered} flavors to the O(4) Higgs field
leading to a model with only one SU(2) doublet in the scaling region. The
number of fermions is doubled in a numerical investigation of the model with
the hybrid Monte Carlo algorithm. We present results for the phase diagram,
particle masses and renormalized couplings on lattices ranging in size from
to .Comment: 11 pages of text plus 4 postscript figures. Amsterdam ITFA 92-13,
Juelich HLRZ 92-2
From quantum to classical dynamics: The relativistic model in the framework of the real-time functional renormalization group
We investigate the transition from unitary to dissipative dynamics in the
relativistic vector model with the
interaction using the nonperturbative functional renormalization group in the
real-time formalism. In thermal equilibrium, the theory is characterized by two
scales, the interaction range for coherent scattering of particles and the mean
free path determined by the rate of incoherent collisions with excitations in
the thermal medium. Their competition determines the renormalization group flow
and the effective dynamics of the model. Here we quantify the dynamic
properties of the model in terms of the scale-dependent dynamic critical
exponent in the limit of large temperatures and in
spatial dimensions. We contrast our results to the behavior expected at
vanishing temperature and address the question of the appropriate dynamic
universality class for the given microscopic theory.Comment: 32 pages, 12 captioned figures; revised and extended version accepted
for publication in PR
Center clusters in the Yang-Mills vacuum
Properties of local Polyakov loops for SU(2) and SU(3) lattice gauge theory
at finite temperature are analyzed. We show that spatial clusters can be
identified where the local Polyakov loops have values close to the same center
element. For a suitable definition of these clusters the deconfinement
transition can be characterized by the onset of percolation in one of the
center sectors. The analysis is repeated for different resolution scales of the
lattice and we argue that the center clusters have a continuum limit.Comment: Table added. Final version to appear in JHE
Universality and the Renormalisation Group
Several functional renormalisation group (RG) equations including Polchinski
flows and Exact RG flows are compared from a conceptual point of view and in
given truncations. Similarities and differences are highlighted with special
emphasis on stability properties. The main observations are worked out at the
example of O(N) symmetric scalar field theories where the flows, universal
critical exponents and scaling potentials are compared within a derivative
expansion. To leading order, it is established that Polchinski flows and ERG
flows - despite their inequivalent derivative expansions - have identical
universal content, if the ERG flow is amended by an adequate optimisation. The
results are also evaluated in the light of stability and minimum sensitivity
considerations. Extensions to higher order and further implications are
emphasized.Comment: 15 pages, 2 figures; paragraph after (19), figure 2, and references
adde
Free energy for parameterized Polyakov loops in SU(2) and SU(3) lattice gauge theory
We present a study of the free energy of parameterized Polyakov loops P in
SU(2) and SU(3) lattice gauge theory as a function of the parameters that
characterize P. We explore temperatures below and above the deconfinement
transition, and for our highest temperatures T > 5 T_c we compare the free
energy to perturbative results.Comment: Minor changes. Final version to appear in JHE
Invariant measure in hot gauge theories
We investigate properties of the invariant measure for the gauge field
in finite temperature gauge theories both on the lattice and in the continuum
theory. We have found the cancellation of the naive measure in both cases. The
result is quite general and holds at any finite temperature. We demonstrate,
however, that there is no cancellation at any temperature for the invariant
measure contribution understood as Z(N) symmetrical distribution of gauge field
configurations. The spontaneous breakdown of Z(N) global symmetry is entirely
due to the potential energy term of the gluonic interaction in the effective
potential. The effects of this measure on the effective action, mechanism of
confinement and condensation are discussed.Comment: Latex file, 65.5kB, no figure
Meta-stable SUSY Breaking Model in Supergravity
We analyze a supersymmetry (SUSY) breaking model proposed by Intriligator,
Seiberg and Shih in a supergravity (SUGRA) framework. This is a simple and
natural setup which demands neither extra superpotential interactions nor an
additional gauge symmetry. In the SUGRA setup, the U(1)R symmetry is explicitly
broken by the constant term in the superpotential, and pseudo-moduli field
naturally takes non-zero vacuum expectation value through a vanishing
cosmological constant condition. Sfermions tend to be heavier than gauginos,
and the strong-coupling scale is determined once a ratio of sfermion to gaugino
masses is fixed.Comment: 13 page
The antiferromagnetic phi4 Model, II. The one-loop renormalization
It is shown that the four dimensional antiferromagnetic lattice phi4 model
has the usual non-asymptotically free scaling law in the UV regime around the
chiral symmetrical critical point. The theory describes a scalar and a
pseudoscalar particle. A continuum effective theory is derived for low
energies. A possibility of constructing a model with a single chiral boson is
mentioned.Comment: To appear in Phys. Rev.
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