161,543 research outputs found
The QCD phase diagram at zero and small baryon density
No full textI review recent developments in determining the QCD phase diagram by means of lattice simulations.
Since the invention of methods to side-step the sign problem a few years ago, a number
of additional variants have been proposed, and progress has been made towards understanding
some of the systematics involved. All available techniques agree on the transition temperature
as a function of density in the regime mq/T <~1. There are by now four calculations with signals
for a critical point, two of them at similar parameter values and with consistent results. However,
it also emerges that the location of the critical point is exceedingly quark mass sensitive. At the
same time sizeable finite volume, cut-off and step size effects have been uncovered, demanding
additional investigations with exact algorithms on larger and finer lattices before quantitative conclusions
can be drawn. Depending on the sign of these corrections, there is ample room for the
eventual phase diagram to look as expected or also quite different, with no critical point at all
Wilson loop in classical lattice gauge theory and the thermal width of heavy quarkonium
No full textLaine M, Philipsen O, Tassler M. Wilson loop in classical lattice gauge theory and the thermal width of heavy quarkonium. In: PoS. 2007: 230
The Finite temperature real time H-bar**2 corrections in quantum mechanics
No full textBödeker D, Laine M, Philipsen O. The Finite temperature real time H-bar**2 corrections in quantum mechanics. Nucl.Phys. B. 1998;513(1-2):445-470
Infra-red fixed point structure characterizing SUSY SU(5) symmetry breaking
No full textWe analyze the one-loop renormalisation group equations for the parameters of the Higgs potential of a supersymmetric SU(5) model with first step of symmetry breaking involving an adjoint Higgs. In particular, we investigate the running of the parameters that decide the first step of symmetry breaking in an attempt to establish which symmetry-breaking scenarios would be most likely if the model is the effective low-energy description of some more fundamental theory. An infra-red fixed point is identified analytically. We show that it is located at the boundary between the region of Higgs parameter space corresponding to unbroken SU(5) and the region corresponding to the breaking of SU(5) to the Standard Model, and we elaborate on its implications. We also observe that certain forms of the Higgs potential discussed at tree level in the literature are not renormalisation group invariant
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Strong Coupling Series for QCD at Finite Temperature and Density
No full textLangelage J, Philipsen O. Strong Coupling Series for QCD at Finite Temperature and Density. Progress of Theoretical Physics Supplement. 2010;(186):567-571.We discuss the use of strong coupling expansions for Yang-Mills theory and QCD at finite temperature and density. In particular we consider the onset of temperature effects for the free energy and screening masses, derive the hadron resonance gas model from first principles and compute the weakening of the deconfinement transition with chemical potential
The non-perturbative QCD Debye mass from a Wilson line operator
No full textLaine M, Philipsen O. The non-perturbative QCD Debye mass from a Wilson line operator. Physics Letters B. 1999;459(1-3):259-264.According to a proposal by Arnold and Yaffe, the non-perturbative g(2)T-contribution to the Debye mass in the deconfined QCD plasma phase can be determined from a single Wilson line operator in the three-dimensional pure SU(3) gauge theory. We extend a previous SU(2) measurement of this quantity to the physical SU(3) case. We find a numerical coefficient which is more accurate and smaller than that obtained previously with another method, but still very large compared with the naive expectation: the correction is larger than the leading term up to T similar to 10(7)T(c), corresponding to g(2) similar to 0.4. At moderate temperatures T similar to 2T(c), a consistent picture emerges where the Debye mass is m(D) similar to 6T, the lightest gauge invariant screening mass in the system is similar to 3T, and the purely magnetic operators couple dominantly to a scale similar to 6T. Electric (similar to gT) and magnetic (similar to g(2)T) scales are therefore strongly overlapping close to the phase transition, and the colour-electric fields play an essential role in the dynamics. (C) 1999 Published by Elsevier Science B.V. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Gauge-invariant scalar and field strength correlators in three dimensions
No full textLaine M, Philipsen O. Gauge-invariant scalar and field strength correlators in three dimensions. Nuclear Physics B. 1998;523(1-2):267-289.Gauge-invariant non-local scalar and field strength operators have been argued to have significance, e.g., as a way to determine the behaviour of the screened static potential at large distances, as order parameters for confinement, as input parameters in models of confinement, and as gauge-invariant definitions of light constituent masses in bound-state systems. We measure such "correlators" in the 3d pure SU(2) and SU(2) + Higgs models on the lattice. We extract the corresponding mass parameters and discuss their scaling and physical interpretation. We find that the finite part of the scheme mass measured from the field strength correlator is large, more than half the glueball mass, We also determine the non-perturbative contribution to the Debye mass in the 4d finite T SU(2) gauge theory with a method due to Arnold and Yaffe, finding delta m(D) approximate to 1.06(4) g(2)T. (C) 1998 Elsevier Science B.V
- …
