1,633 research outputs found
Heavy quark free energies for three quark systems at finite temperature
We study the free energy of static three quark systems in singlet, octet,
decuplet and average color channels in the quenched approximation and in
2-flavor QCD at finite temperature. We show that in the high temperature phase
singlet and decuplet free energies of three quark systems are well described by
the sum of the free energies of three diquark systems plus self energy
contributions of the three quarks. In the confining low temperature phase we
find evidence for a Y-shaped flux tube in SU(3) pure gauge theory, which is
less evident in 2-flavor QCD due to the onset of string breaking. We also
compare the short distance behavior of octet and decuplet free energies to the
free energies of single static quarks in the corresponding color
representations.Comment: 11 pages, 17 figure
Application of Lurian Approach to Assessment of Perpetrators of Crimes
The central question in law is whether a defendant is responsible for his/her wrongdoing. Recent progress in neuroscience, especially in brain imaging, has shown potential for finding more objective tools for the evaluation of brain disorders. In the case of perpetrators, damage to the prefrontal area is believed to be of relevance in criminal responsibility, since it modulates and controls aggressive urges originating from the limbic system. To absolve guilt, a brain scan would have to show that a perpetrator was unable to control his/her behavior; however, it shows only what is and not what could be. It is therefore impossible to obtain behavioral data that would indicate a disorder of executive functioning at both the time of evaluation andthe instant offence. The diagnostic value of performing a neurolinguistics analysis of narratives elicited from brain-damaged patients was demonstrated in the first study. Another study supported the assumption of a frontal lobe defect in individuals with a history of violent behavior. The present study compared results obtained from three groups matched for age, sex, and education: perpetrators of crimes, healthy soldiers, and patients with lesions of the frontal lobes. A battery of tests measuring frontal lobe deficits was administered along with one of the tasks of the Narrative Abilities Test, based upon Luria’s approach to the examination of speech. Statistically significant differences were found between perpetrators and healthy controls but not between frontal lobe patients and perpetrators, which confirms frontal lobe deficits in that group.
Keywords: Lurian approach, perpetrators, neurolinguistics analysis, narrative
Renormalized Polyakov loops in many representations
We present a renormalization procedure for Polyakov loops which explicitly
implements the fact that the renormalization constant depends only on the
ultraviolet cutoff. Using this we study the renormalized Polyakov loops in all
representations upto the {\bf 27} of the gauge group SU(3). We find good
evidence for Casimir scaling of the Polyakov loops and for approximate large-N
factorization. By studying many loops together, we are able to show that there
is a matrix model with a single coupling which can describe the high
temperature phase of QCD, although it is hard to construct explicitly. We
present the first results for the non-vanishing renormalized octet loop in the
thermodynamic limit below the SU(3) phase transition, and estimate the
associated string breaking distance and the gluelump binding energy. By
studying the connection of the direct renormalization procedure with a
generalization of an earlier suggestion which goes by the name of the
renormalization procedure, we find that they are functionally equivalent.Comment: 17 pages, 24 figures, revtex
PNJL model with a Van der Monde term
We extend the Polyakov-Nambu-Jona-Lasinio (PNJL) model for two degenerate
flavours by including the effect of the SU(3) measure with a Van der Monde
(VdM) term. This ensures that the Polyakov loop always remains in the domain
[0,1]. The pressure, energy density, specific heat, speed of sound and
conformal measure show small or negligible effects from this term. However
various quark number and isospin susceptibilities are all found to approach
their respective ideal gas limits around 2 . We compare our methods with
other similar approaches in PNJL model and also present a quantitative
comparison with Lattice QCD data.Comment: 12 pages, 8 eps figures; extended discussion and reference added;
accepted in Phys. Rev.
Atom chips with two-dimensional electron gases: theory of near surface trapping and ultracold-atom microscopy of quantum electronic systems
We show that current in a two-dimensional electron gas (2DEG) can trap
ultracold atoms m away with orders of magnitude less spatial noise than
a metal trapping wire. This enables the creation of hybrid systems, which
integrate ultracold atoms with quantum electronic devices to give extreme
sensitivity and control: for example, activating a single quantized conductance
channel in the 2DEG can split a Bose-Einstein condensate (BEC) for atom
interferometry. In turn, the BEC offers unique structural and functional
imaging of quantum devices and transport in heterostructures and graphene.Comment: 5 pages, 4 figures, minor change
Static quark anti-quark free energy and the running coupling at finite temperature
We analyze the free energy of a static quark anti-quark pair in quenched QCD
at short and large distances. From this we deduce running couplings, g^2(r,T),
and determine the length scale that separates at high temperature the short
distance perturbative regime from the large distance non-perturbative regime in
the QCD plasma phase. Ambiguities in the definition of a coupling beyond the
perturbative regime are discussed in their relation to phenomenological
considerations on heavy quark bound states in the quark gluon plasma. Our
analysis suggests that it is more appropriate to characterize the
non-perturbative properties of the QCD plasma phase close to T_c in terms
remnants of the confinement part of the QCD force rather than a strong
Coulombic force.Comment: 8 pages, 9 EPS-files, revtex
Electrical conductivity and thermal dilepton rate from quenched lattice QCD
We report on a continuum extrapolation of the vector current correlation
function for light valence quarks in the deconfined phase of quenched QCD. This
is achieved by performing a systematic analysis of the influence of cut-off
effects on light quark meson correlators at using clover
improved Wilson fermions. We discuss resulting constraints on the electrical
conductivity and the thermal dilepton rate in a quark gluon plasma. In addition
new results at 1.2 and 3.0 will be presented.Comment: 4 pages, 6 eps figures, to appear in the proceedings of Quark Matter
2011, 23-28 May 2011, Annecy, Franc
Effective potential for Polyakov loops from a center symmetric effective theory in three dimensions
We present lattice simulations of a center symmetric dimensionally reduced
effective field theory for SU(2) Yang Mills which employ thermal Wilson lines
and three-dimensional magnetic fields as fundamental degrees of freedom. The
action is composed of a gauge invariant kinetic term, spatial gauge fields and
a potential for the Wilson line which includes a "fuzzy" bag term to generate
non-perturbative fluctuations. The effective potential for the Polyakov loop is
extracted from the simulations including all modes of the loop as well as for
cooled configuration where the hard modes have been averaged out. The former is
found to exhibit a non-analytic contribution while the latter can be described
by a mean-field like ansatz with quadratic and quartic terms, plus a
Vandermonde potential which depends upon the location within the phase diagram.Comment: 10 pages, 22 figures, v2: published version (minor clarifications,
update of reference list
Matter formed at the BNL relativistic heavy ion collider
We suggest that the "new form of matter" found just above by RHIC is
made up of tightly bound quark-antiquark pairs, essentially 32 chirally
restored (more precisely, nearly massless) mesons of the quantum numbers of
, , and . Taking the results of lattice gauge
simulations (LGS) for the color Coulomb potential from the work of the
Bielefeld group and feeding this into a relativistic two-body code, after
modifying the heavy-quark lattice results so as to include the
velocity-velocity interaction, all ground-state eigenvalues of the 32 mesons go
to zero at just as they do from below as predicted by the vector
manifestation (VM in short) of hidden local symmetry. This could explain the
rapid rise in entropy up to found in LGS calculations. We argue that how
the dynamics work can be understood from the behavior of the hard and soft
glue.Comment: Final versio
Control of serpentinisation rate by reaction-induced cracking
Serpentinisation of mantle rocks requires the generation and maintenance of transport pathways for water. The solid volume increase during serpentinisation can lead to stress build-up and trigger cracking, which ease fluid penetration into the rock. The quantitative effect of this reaction-induced cracking mechanism on reactive surface generation is poorly constrained, thus hampering our ability to predict serpentinisation rate in geological environments. Here we use a combined approach with numerical modelling and observations in natural samples to provide estimates of serpentinisation rate at mid-ocean ridges. We develop a micromechanical model to quantify the propagation of serpentinisation-induced cracks in olivine. The maximum crystallisation pressure deduced from thermodynamic calculations reaches several hundreds of megapascals but does not necessary lead to crack propagation if the olivine grain is subjected to high compressive stresses. The micromechanical model is then coupled to a simple geometrical model to predict reactive surface area formation during grain splitting, and thus bulk reaction rate. Our model reproduces quantitatively experimental kinetic data and the typical mesh texture formed during serpentinisation. We also compare the model results with olivine grain size distribution data obtained on natural serpentinised peridotites from the Marum ophiolite and the Papuan ultramafic belt (Papua New Guinea). The natural serpentinised peridotites show an increase of the number of olivine grains for a decrease of the mean grain size by one order of magnitude as reaction progresses from 5 to 40%. These results are in agreement with our model predictions, suggesting that reaction-induced cracking controls the serpentinisation rate. We use our model to estimate that, at mid-ocean ridges, serpentinisation occurs up to 12km depth and reaction-induced cracking reduces the characteristic time of serpentinisation by one order of magnitude, down to values comprised between 10 and 1000yr. The increase of effective pressure with depth also prevents cracking, which positions the peak in serpentinisation rate at shallower depths, 4km above previous predictions
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