311 research outputs found
The numerical approach to quantum field theory in a non-commutative space
Numerical simulation is an important non-perturbative tool to study quantum
field theories defined in non-commutative spaces. In this contribution, a
selection of results from Monte Carlo calculations for non-commutative models
is presented, and their implications are reviewed. In addition, we also discuss
how related numerical techniques have been recently applied in computer
simulations of dimensionally reduced supersymmetric theories.Comment: 15 pages, 6 figures, invited talk presented at the Humboldt Kolleg
"Open Problems in Theoretical Physics: the Issue of Quantum Space-Time", to
appear in the proceedings of the Corfu Summer Institute 2015 "School and
Workshops on Elementary Particle Physics and Gravity" (Corfu, Greece, 1-27
September 2015
Thermodynamics of the strongly interacting gluon plasma in the large-N limit
We report on our recent study of equilibrium thermodynamic observables in
SU(N) gauge theories with N=3, 4, 5, 6 and 8 colors at temperatures T in the
range from 0.8 T_c to 3.4 T_c (where T_c denotes the critical deconfinement
temperature). The results, which show a very weak dependence on the number of
colors, are compared with gauge/gravity models of the QCD plasma, including the
improved holographic QCD model proposed by Kiritsis and collaborators, and with
the supergravity prediction for the entropy density deficit. Furthermore, we
investigate the possibility that the trace anomaly may receive contributions
proportional to T^2 at temperatures close to T_c. Finally, we present the
extrapolated results for the pressure, trace anomaly, energy and entropy
densities in the limit for N going to infinity.Comment: 7 pages, 8 eps figures, presented at the XXVII International
Symposium on Lattice Field Theory, July 26-31 2009, Peking University,
Beijing, China; v2: added reference
Quantum Field Theory in a Non-Commutative Space: Theoretical Predictions and Numerical Results on the Fuzzy Sphere
We review some recent progress in quantum field theory in non-commutative
space, focusing onto the fuzzy sphere as a non-perturbative regularisation
scheme. We first introduce the basic formalism, and discuss the limits
corresponding to different commutative or non-commutative spaces. We present
some of the theories which have been investigated in this framework, with a
particular attention to the scalar model. Then we comment on the results
recently obtained from Monte Carlo simulations, and show a preview of new
numerical data, which are consistent with the expected transition between two
phases characterised by the topology of the support of a matrix eigenvalue
distribution.Comment: This is a contribution to the Proc. of the O'Raifeartaigh Symposium
on Non-Perturbative and Symmetry Methods in Field Theory (June 2006,
Budapest, Hungary), published in SIGMA (Symmetry, Integrability and Geometry:
Methods and Applications) at http://www.emis.de/journals/SIGMA
Casimir scaling and renormalization of Polyakov loops in large-N gauge theories
We study Casimir scaling and renormalization properties of Polyakov loops in
different irreducible representations in SU(N) gauge theories; in particular,
we investigate the approach to the large-N limit, by performing lattice
simulations of Yang-Mills theories with an increasing number of colors, from 2
to 6. We consider the twelve lowest irreducible representations for each gauge
group, and find strong numerical evidence for nearly perfect Casimir scaling of
the bare Polyakov loops in the deconfined phase. Then we discuss the
temperature dependence of renormalized loops, which is found to be
qualitatively and quantitatively very similar for the various gauge groups. In
particular, close to the deconfinement transition, the renormalized Polyakov
loop increases with the temperature, and its logarithm reveals a characteristic
dependence on the inverse of the square of the temperature. At higher
temperatures, the renormalized Polyakov loop overshoots one, reaches a maximum,
and then starts decreasing, in agreement with weak-coupling predictions. The
implications of these findings are discussed.Comment: 1+33 pages, 14 figures; v2: expanded discussion in sections 2 and 3,
added references: version published in JHE
Momentum broadening of partons on the light cone from the lattice
The jet quenching parameter describes the momentum broadening of a
high-energy parton moving through the quark-gluon plasma. Following an approach
originally proposed by Caron-Huot, we discuss how one can extract information
on the collision kernel associated with the parton momentum broadening, from
the analysis of certain gauge-invariant operators in dimensionally reduced
effective theories, and present numerical results from a lattice study.Comment: 7 pages, 3 pdf figures, talk presented at the 31st International
Symposium on Lattice Field Theory "Lattice 2013" (29 July - 3 August 2013,
Mainz, Germany
A numerical study of a confined Q anti-Q system in compact U(1) lattice gauge theory in 4D
We present a numerical study about the confining regime of compact U(1) lattice gauge theory in 4D. To address the problem, we exploit the duality properties of the theory. The main features of this method are presented, and its possible advantages and limits with respect to alternative techniques are briefly discussed. In Monte Carlo simulations, we focus our attention onto the case when a pair of static external charges is present. Some results are shown, concerning different observables which are of interest in order to understand the confinement mechanism, like the profile of the electric field induced by the static charges, and the ratios between Polyakov loop correlation functions at different distances
Jet quenching in a strongly interacting plasma - A lattice approach
The phenomenon of jet quenching, related to the momentum broadening of a
high-energy parton, provides important experimental evidence for the production
of a strongly coupled, deconfined medium in heavy-ion collisions. Its
theoretical description has been addressed in a number of works, both
perturbatively and non-perturbatively (using the gauge-gravity duality). In
this contribution, following a proposal by Caron-Huot, we discuss a novel
approach to this problem, enabling one to extract non-perturbative information
on this real-time phenomenon from simulations on a Euclidean lattice.Comment: 6 pages, 3 pdf figures, talk presented at the 2013 European Physical
Society Conference on High Energy Physics "EPS HEP 2013" (18-24 July 2013,
Stockholm, Sweden
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