4,463 research outputs found
The infrared fixed point of Landau gauge Yang-Mills theory: A renormalization group analysis
The infrared behavior of gluon and ghost propagators in Landau gauge
Yang-Mills theory has been at the center of an intense debate over the last
decade. Different solutions of the Dyson-Schwinger equations show a different
behavior of the propagators in the infrared: in the so-called scaling solutions
both propagators follow a power law, while in the decoupling solutions the
gluon propagator shows a massive behavior. The latest lattice results favor the
decoupling solutions. In this contribution, after giving a brief overview of
the present status of analytical and semi-analytical approaches to the infrared
regime of Landau gauge Yang-Mills theory, we will show how Callan-Symanzik
renormalization group equations in an epsilon expansion reproduce both types of
solutions and single out the decoupling solutions as the infrared-stable ones
for space-time dimensions greater than two, in agreement with the lattice
calculations.Comment: 17 pages. Talk delivered at the XIII Mexican Workshop on Particles
and Fields in Leon, Guanajuato, Mexico, October 2011. Slightly extended
version of the contribution to the conference proceeding
Effective action for the order parameter of the deconfinement transition of Yang-Mills theories
The effective action for the Polyakov loop serving as an order parameter for
deconfinement is obtained in one-loop approximation to second order in a
derivative expansion. The calculation is performed in dimensions,
mostly referring to the gauge group SU(2). The resulting effective action is
only capable of describing a deconfinement phase transition for
. Since, particularly in , the system is
strongly governed by infrared effects, it is demonstrated that an additional
infrared scale such as an effective gluon mass can change the physical
properties of the system drastically, leading to a model with a deconfinement
phase transition.Comment: 23 pages, 4 figures, minor improvements, version to appear in PR
A non-perturbative study of matter field propagators in Euclidean Yang-Mills theory in linear covariant, Curci-Ferrari and maximal Abelian gauges
In this work, we study the propagators of matter fields within the framework
of the Refined Gribov-Zwanziger theory, which takes into account the effects of
the Gribov copies in the gauge-fixing quantization procedure of Yang-Mills
theory. In full analogy with the pure gluon sector of the Refined
Gribov-Zwanziger action, a non-local long-range term in the inverse of the
Faddeev-Popov operator is added in the matter sector. Making use of the recent
BRST invariant formulation of the Gribov-Zwanziger framework achieved in [Capri
et al 2016], the propagators of scalar and quark fields in the adjoint and
fundamental representations of the gauge group are worked out explicitly in the
linear covariant, Curci-Ferrari and maximal Abelian gauges. Whenever lattice
data are available, our results exhibit good qualitative agreement.Comment: 27 pages, no figures; V2, minor modifications, to appear in EPJ
Exact Results in Gauge Theories: Putting Supersymmetry to Work. The 1999 Sakurai Prize Lecture
Powerful methods based on supersymmetry allow one to find exact solutions to
certain problems in strong coupling gauge theories. The inception of some of
these methods (holomorphy in the gauge coupling and other chiral parameters, in
conjunction with instanton calculations) dates back to the 1980's. I describe
the early exact results -- the calculation of the beta function and the gluino
condensate -- and their impact on the subsequent developments. A brief
discussion of the recent breakthrough discoveries where these results play a
role is given.Comment: Based on the talk at the Centennial Meeting of The American Physical
Society, March 20-26, Atlanta, GA. LaTex (uses sprocl.sty), 36 pages, 5 eps
figures include
How higher-spin gravity surpasses the spin two barrier: no-go theorems versus yes-go examples
Aiming at non-experts, we explain the key mechanisms of higher-spin
extensions of ordinary gravity. We first overview various no-go theorems for
low-energy scattering of massless particles in flat spacetime. In doing so we
dress a dictionary between the S-matrix and the Lagrangian approaches,
exhibiting their relative advantages and weaknesses, after which we high-light
potential loop-holes for non-trivial massless dynamics. We then review positive
yes-go results for non-abelian cubic higher-derivative vertices in constantly
curved backgrounds. Finally we outline how higher-spin symmetry can be
reconciled with the equivalence principle in the presence of a cosmological
constant leading to the Fradkin--Vasiliev vertices and Vasiliev's higher-spin
gravity with its double perturbative expansion (in terms of numbers of fields
and derivatives).Comment: LaTeX, 50 pages, minor changes, many refs added; version accepted for
publication in Reviews of Modern Physic
A Center-Symmetric 1/N Expansion
The free energy of U(N) gauge theory is expanded about a center-symmetric
topological background configuration with vanishing action and vanishing
Polyakov loops. We construct this background for SU(N) lattice gauge theory and
show that it uniquely describes center-symmetric minimal action orbits in the
limit of infinite lattice volume. The leading contribution to the free energy
in the 1/N expansion about this background is of O(N^0) rather than O(N^2) as
one finds when the center symmetry is spontaneously broken. The contribution of
planar 't Hooft diagrams to the free energy is O(1/N^2) and sub-leading in this
case. The change in behavior of the diagrammatic expansion is traced to Linde's
observation that the usual perturbation series of non-Abelian gauge theories
suffers from severe infrared divergences. This infrared problem does not arise
in a center-symmetric expansion. The 't Hooft coupling \lambda=g^2 N is found
to decrease proportional to 1/\ln(N) for large N. There is evidence of a
vector-ghost in the planar truncation of the model.Comment: 27 pages, 2 figures; extended and corrected version with additional
material and reference
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