QCD-like technicolor on the lattice

This talk gives an overview, aimed at non-experts, of the recent progress on the studies of technicolor models on the lattice. Phenomenologically successful technicolor models require walking coupling; thus, an emphasis is put on the determination of the beta-function of various models. As a case study we consider SU(2) gauge field theory with two adjoint representation fermions, so-called minimal walking technicolor theory.Comment: 6 pages; talk presented at "Quark Confinement and the Hadron Spectrum IX", Universidad Complutense de Madrid, 30 August--3 September 201

Quark number susceptibility of high temperature and finite density QCD

We utilize lattice simulations of the dimensionally reduced effective field theory (EQCD) to determine the quark number susceptibility of QCD at high temperature ($T>2T_c$). We also use analytic continuation to obtain results at finite density. The results extrapolate well from known perturbative expansion (accurate in extremely high temperatures) to 4d lower temperature lattice dataComment: 7 pages, 5 figures, Presented at the XXV International Symposium on Lattice Field Theory, July 30 - August 4 2007, Regensburg, German

Universal features of JIMWLK and BK evolution at small x

In this paper we present the results of numerical studies of the JIMWLK and BK equations with a particular emphasis on the universal scaling properties and phase space structure involved. The results are valid for near zero impact parameter in DIS. We demonstrate IR safety due to the occurrence of a rapidity dependent saturation scale Q_s(\tau). Within the set of initial conditions chosen both JIMWLK and BK equations show remarkable agreement. We point out the crucial importance of running coupling corrections to obtain consistency in the UV. Despite the scale breaking induced by the running coupling we find that evolution drives correlators towards an asymptotic form with near scaling properties. We discuss asymptotic features of the evolution, such as the \tau- and A-dependence of Q_s away from the initial condition.Comment: 30 page

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

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

Running coupling in SU(2) with adjoint fermions

We present a measurement of the Schr\"odinger Functional running coupling in SU(2) lattice gauge theory with adjoint fermions. We use HEX smearing and clover improvement to reduce the discretization effects. We obtain a robust continuum limit for the step scaling, which confirms the existence of a non-trivial fixed point.Comment: Contribution to SCGT12 "KMI-GCOE Workshop on Strong Coupling Gauge Theories in the LHC Perspective", 4-7 Dec. 2012, Nagoya University, 4 pages, 2 figure