509 research outputs found
Yang-Mills correlators across the deconfinement phase transition
We compute the finite temperature ghost and gluon propagators of Yang-Mills
theory in the Landau-DeWitt gauge. The background field that enters the
definition of the latter is intimately related with the (gauge-invariant)
Polyakov loop and serves as an equivalent order parameter for the deconfinement
transition. We use an effective gauge-fixed description where the
nonperturbative infrared dynamics of the theory is parametrized by a gluon mass
which, as argued elsewhere, may originate from the Gribov ambiguity. In this
scheme, one can perform consistent perturbative calculations down to infrared
momenta, which have been shown to correctly describe the phase diagram of
Yang-Mills theories in four dimensions as well as the zero-temperature
correlators computed in lattice simulations. In this article, we provide the
one-loop expressions of the finite temperature Landau-DeWitt ghost and gluon
propagators for a large class of gauge groups and present explicit results for
the SU(2) case. These are substantially different from those previously
obtained in the Landau gauge, which corresponds to a vanishing background
field. The nonanalyticity of the order parameter across the transition is
directly imprinted onto the propagators in the various color modes. In the
SU(2) case, this leads, for instance, to a cusp in the electric and magnetic
gluon susceptibilities as well as similar signatures in the ghost sector. We
mention the possibility that such distinctive features of the transition could
be measured in lattice simulations in the background field gauge studied here.Comment: 28 pages, 17 figures; published versio
Critical properties of a continuous family of XY noncollinear magnets
Monte Carlo methods are used to study a family of three dimensional XY
frustrated models interpolating continuously between the stacked triangular
antiferromagnets and a variant of this model for which a local rigidity
constraint is imposed. Our study leads us to conclude that generically weak
first order behavior occurs in this family of models in agreement with a recent
nonperturbative renormalization group description of frustrated magnets.Comment: 5 pages, 3 figures, minor changes, published versio
An Infrared Safe perturbative approach to Yang-Mills correlators
We investigate the 2-point correlation functions of Yang-Mills theory in the
Landau gauge by means of a massive extension of the Faddeev-Popov action. This
model is based on some phenomenological arguments and constraints on the
ultraviolet behavior of the theory. We show that the running coupling constant
remains finite at all energy scales (no Landau pole) for and argue that
the relevant parameter of perturbation theory is significantly smaller than 1
at all energies. Perturbative results at low orders are therefore expected to
be satisfactory and we indeed find a very good agreement between 1-loop
correlation functions and the lattice simulations, in 3 and 4 dimensions.
Dimension 2 is shown to play the role of an upper critical dimension, which
explains why the lattice predictions are qualitatively different from those in
higher dimensions.Comment: 16 pages, 7 figures, accepted for publication in PR
Competition between fluctuations and disorder in frustrated magnets
We investigate the effects of impurities on the nature of the phase
transition in frustrated magnets, in d=4-epsilon dimensions. For sufficiently
small values of the number of spin components, we find no physically relevant
stable fixed point in the deep perturbative region (epsilon << 1), contrarily
to what is to be expected on very general grounds. This signals the onset of
important physical effects.Comment: 4 pages, 3 figures, published versio
Critical thermodynamics of three-dimensional chiral model for N > 3
The critical behavior of the three-dimensional -vector chiral model is
studied for arbitrary . The known six-loop renormalization-group (RG)
expansions are resummed using the Borel transformation combined with the
conformal mapping and Pad\'e approximant techniques. Analyzing the fixed point
location and the structure of RG flows, it is found that two marginal values of
exist which separate domains of continuous chiral phase transitions and where such
transitions are first-order. Our calculations yield and
. For the structure of RG flows is identical to
that given by the and 1/N expansions with the chiral fixed point
being a stable node. For the chiral fixed point turns out to be a
focus having no generic relation to the stable fixed point seen at small
and large . In this domain, containing the physical values and , phase trajectories approach the fixed point in a spiral-like
manner giving rise to unusual crossover regimes which may imitate varying
(scattered) critical exponents seen in numerous physical and computer
experiments.Comment: 12 pages, 3 figure
Chiral phase transitions: focus driven critical behavior in systems with planar and vector ordering
The fixed point that governs the critical behavior of magnets described by
the -vector chiral model under the physical values of () is
shown to be a stable focus both in two and three dimensions. Robust evidence in
favor of this conclusion is obtained within the five-loop and six-loop
renormalization-group analysis in fixed dimension. The spiral-like approach of
the chiral fixed point results in unusual crossover and near-critical regimes
that may imitate varying critical exponents seen in physical and computer
experiments.Comment: 4 pages, 5 figures. Discussion enlarge
Monte Carlo renormalization group study of the Heisenberg and XY antiferromagnet on the stacked triangular lattice and the chiral model
With the help of the improved Monte Carlo renormalization-group scheme, we
numerically investigate the renormalization group flow of the antiferromagnetic
Heisenberg and XY spin model on the stacked triangular lattice (STA-model) and
its effective Hamiltonian, 2N-component chiral model which is used in
the field-theoretical studies. We find that the XY-STA model with the lattice
size exhibits clear first-order behavior. We also
find that the renormalization-group flow of STA model is well reproduced by the
chiral model, and that there are no chiral fixed point of
renormalization-group flow for N=2 and 3 cases. This result indicates that the
Heisenberg-STA model also undergoes first-order transition.Comment: v1:15 pages, 15 figures v2:updated references v3:added comments on
the higher order irrelevant scaling variables v4:added results of larger
sizes v5:final version to appear in J.Phys.Soc.Jpn Vol.72, No.
Spin Stiffness of Stacked Triangular Antiferromagnets
We study the spin stiffness of stacked triangular antiferromagnets using both
heat bath and broad histogram Monte Carlo methods. Our results are consistent
with a continuous transition belonging to the chiral universality class first
proposed by Kawamura.Comment: 5 pages, 7 figure
Critical behavior of frustrated systems: Monte Carlo simulations versus Renormalization Group
We study the critical behavior of frustrated systems by means of Pade-Borel
resummed three-loop renormalization-group expansions and numerical Monte Carlo
simulations. Amazingly, for six-component spins where the transition is second
order, both approaches disagree. This unusual situation is analyzed both from
the point of view of the convergence of the resummed series and from the
possible relevance of non perturbative effects.Comment: RevTex, 10 pages, 3 Postscript figure
Regulation of proliferating cell nuclear antigen ubiquitination in mammalian cells
After exposure to DNA-damaging agents that block the progress of the replication fork, monoubiquitination of proliferating cell nuclear antigen (PCNA) mediates the switch from replicative to translesion synthesis DNA polymerases. We show that in human cells, PCNA is monoubiquitinated in response to methyl methanesulfonate and mitomycin C, as well as UV light, albeit with different kinetics, but not in response to bleomycin or camptothecin. Cyclobutane pyrimidine dimers are responsible for most of the PCNA ubiquitination events after UV-irradiation. Failure to ubiquitinate PCNA results in substantial sensitivity to UV and methyl methanesulfonate, but not to camptothecin or bleomycin. PCNA ubiquitination depends on Replication Protein A (RPA), but is independent of ATR-mediated checkpoint activation. After UV-irradiation, there is a temporal correlation between the disappearance of the deubiquitinating enzyme USP1 and the presence of PCNA ubiquitination, but this correlation was not found after chemical mutagen treatment. By using cells expressing photolyases, we are able to remove the UV lesions, and we show that PCNA ubiquitination persists for many hours after the damage has been removed. We present a model of translesion synthesis behind the replication fork to explain the persistence of ubiquitinated PCNA
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