350 research outputs found
Non-perturbative formulation of the static color octet potential
By dressing Polyakov lines with appropriate functionals of the gauge fields,
we construct observables describing a fundamental representation static
quark-antiquark pair in the singlet, adjoint and average channels of SU(N) pure
gauge theory. Each of the potentials represents a gauge invariant eigenvalue of
the Hamiltonian. Numerical simulations are performed for SU(2) in 2+1
dimensions. The adjoint channel is found to be repulsive at small and confining
at large separations, suggesting the existence of a metastable (N^2-1)-plet
bound state. For small distances and temperatures above the deconfinement
transition, the leading order perturbative prediction for the ratio of singlet
and adjoint potentials is reproduced by the lattice data.Comment: 10 pages, 3 figure
Asymptotic Behavior of the Correlator for Polyakov Loops
The asymptotic behavior of the correlator for Polyakov loop operators
separated by a large distance is determined for high temperature QCD. It is
dominated by nonperturbative effects related to the exchange of magnetostatic
gluons. To analyze the asymptotic behavior, the problem is formulated in terms
of the effective field theory of QCD in 3 space dimensions. The Polyakov loop
operator is expanded in terms of local gauge-invariant operators constructed
out of the magnetostatic gauge field, with coefficients that can be calculated
using resummed perturbation theory. The asymptotic behavior of the correlator
is , where is the mass of the lowest-lying glueball in
-dimensional QCD. This result implies that existing lattice calculations
of the Polyakov loop correlator at the highest temperatures available do not
probe the true asymptotic region in .Comment: 10 pages, NUHEP-TH-94-2
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Pollution control and environmental monitoring efforts at DOE's Coal-Fired Flow Facility
Proof-of-Concept (POC) scale demonstration of such technology is currently being carried out at the US Department of Energy's (DOE's) Coal-Fired Flow Facility (CFFF), located at The University of Tennessee Space Institute (UTSI) in Tullahoma, Tennessee and at the Component Development and Integration Facility in Butte, Montana. The CFFF is dedicated to the evaluation of downstream (steam cycle) components and technology that may be considered for a full-scale MHD system. The objectives of the CFFF testing include the demonstration of various pollution control devices and techniques at a scale sufficient for future scale-up. The CFFF offers a unique test environment in which emissions control techniques can be developed and evaluated through emissions and environmental monitoring. Results thus far have demonstrated the ability of sulfur oxide (SO{sub x}), nitrogen oxide (NO{sub x}) and particulate emissions well below the New Source Performance Standards (NSPS). Regeneration of the potassium sulfate to produce sulfur-free compounds also has been demonstrated. The experimental program at the CFFF is now aimed at determining the optimum conditions for future commercial scale designs. Because of increased interests in Air Toxics, measurements of nitrous oxide (N{sub 2}O), a potential greenhouse gas, priority pollutants (inorganic as well as organics), and chlorine-containing species (Cl{sub 2} and HCl) are also included in our ongoing efforts. Environmental monitoring activities are being pursued to develop an environmental impact assessment data base. These include the use of three ambient air sites to determine the impacts of gaseous and particulate emissions, five lake water sites to determine impacts due to process water discharges and seven sites to collect terrestrial data on possible soil contamination and tree growth. In this paper, we will summarize the status of our ongoing environmental program. 16 refs., 15 figs., 3 tabs
Quarkonium Suppression
I discuss quarkonium suppression in equilibriated strongly interacting
matter. After a brief review of basic features of quarkonium production I
discuss the application of recent lattice data on the heavy quark potential to
the problem of quarkonium dissociation as well as the problem of direct lattice
determination of quarkonium properties in finite temperature lattice QCD.Comment: Invited plenary talk presented on 4th International Conference on
Physics and Astrophysics of Quark Gluon Plasma (ICPAQGP-2001), November
26-30, 2001, Jaipur; 12 pp, LaTeX, uses pramana.st
Multiple spin-orbit excitons and the electronic structure of 뱉RuCl3
The honeycomb compound α-RuCl_{3} is widely discussed as a proximate Kitaev spin-liquid material. This scenario builds on spin-orbit entangled j = 1/2 moments arising for a t_{2g}^{5} electron configuration with strong spin-orbit coupling λ and a large cubic crystal field. The actual low-energy electronic structure of α-RuCl_{3}, however, is still puzzling. In particular, infrared absorption features at 0.30, 0.53, and 0.75 eV seem to be at odds with a j = 1/2 scenario. Also the energy of the spin-orbit exciton, the excitation from j = 1/2 to 3/2, and thus the value of λ, are controversial. Combining infrared and Raman data, we show that the infrared features can be attributed to single, double, and triple spin-orbit excitons. We find λ = 0.16 eV and Π= 42(4) meV for the observed noncubic crystal-field splitting, supporting the validity of the j = 1/2 picture for α-RuCl_{3}. The unusual strength of the double excitation is related to the underlying hopping interactions, which form the basis for dominant Kitaev exchange
Phase structure of lattice QCD for general number of flavors
We investigate the phase structure of lattice QCD for the general number of
flavors in the parameter space of gauge coupling constant and quark mass,
employing the one-plaquette gauge action and the standard Wilson quark action.
Performing a series of simulations for the number of flavors --360 with
degenerate-mass quarks, we find that when there is a line of a bulk
first order phase transition between the confined phase and a deconfined phase
at a finite current quark mass in the strong coupling region and the
intermediate coupling region. The massless quark line exists only in the
deconfined phase. Based on these numerical results in the strong coupling limit
and in the intermediate coupling region, we propose the following phase
structure, depending on the number of flavors whose masses are less than
which is the physical scale characterizing the phase transition in
the weak coupling region: When , there is only a trivial IR fixed
point and therefore the theory in the continuum limit is free. On the other
hand, when , there is a non-trivial IR fixed point and
therefore the theory is non-trivial with anomalous dimensions, however, without
quark confinement. Theories which satisfy both quark confinement and
spontaneous chiral symmetry breaking in the continuum limit exist only for .Comment: RevTeX, 20 pages, 43 PS figure
Heavy Quark Free Energies and Screening in SU(2) Gauge Theory
We investigate the singlet, triplet and colour average heavy quark free
energies in SU(2) pure gauge theory at various temperatures T. We focus on the
long distance behaviour of the free energies, studying in particular the
temperature dependence of the string tension and the screening masses. The
results are qualitatively similar to the SU(3) scenario, except near the
critical temperature Tc of the deconfining transition. Finally we test a
recently proposed method to renormalize the Polyakov loop.Comment: 5 pages, 4 figures, contribution to the Proceedings of SEWM 2002
(Heidelberg
Heavy Quark Potentials in Quenched QCD at High Temperature
Heavy quark potentials are investigated at high temperatures. The temperature
range covered by the analysis extends from values just below the
deconfinement temperature up to about in the deconfined phase. We
simulated the pure gauge sector of QCD on lattices with temporal extents of 4,
6 and 8 with spatial volumes of . On the smallest lattice a tree level
improved action was employed while in the other two cases the standard Wilson
action was used. Below we find a temperature dependent logarithmic term
contributing to the confinement potential and observe a string tension which
decreases with rising temperature but retains a finite value at the
deconfinement transition. Above the potential is Debye-screened, however
simple perturbative predictions do not apply.Comment: 20 pages, 9 figure
Relation between the Polyakov loop and the chiral order parameter at strong coupling
We discuss the relation between the Polyakov loop and the chiral order
parameter at finite temperature by using the Gocksch-Ogilvie model with
fundamental or adjoint quarks. The model is based on the double expansion of
strong coupling and large dimensionality on the lattice. In an analytic way
with the mean field approximation employed, we show that the confined phase
must be accompanied by the spontaneous breaking of the chiral symmetry for both
fundamental and adjoint quarks. Then we proceed to numerical analysis to look
into the coupled dynamics of the Polyakov loop and the chiral order parameter.
In the case of fundamental quarks, the pseudo-critical temperature inferred
from the Polyakov loop behavior turns out to coincide with the pseudo-critical
temperature of the chiral phase transition. We discuss the physical implication
of the coincidence of the pseudo-critical temperatures in two extreme cases;
one is the deconfinement dominance and the other is the chiral dominance. As
for adjoint quarks, the deconfinement transition of first order persists and
the chiral phase transition occurs distinctly at higher temperature than the
deconfinement transition does. The present model study gives us a plausible
picture to understand the results from the lattice QCD and aQCD simulations.Comment: 19 pages, 9 figures, to appear in Phys.Rev.D. Appendix A is modified;
references are adde
Thermodynamics of lattice QCD with two light quark flavours on a 16^3 x 8 lattice II
We have extended our earlier simulations of the high temperature behaviour of
lattice QCD with two light flavours of staggered quarks on a
lattice to lower quark mass (m_q=0.00625). The transition from hadronic matter
to a quark-gluon plasma is observed at corresponding to a
temperature of MeV. We present measurements of observables
which probe the nature of the quark-gluon plasma and serve to distinguish it
from hadronic matter. Although the transition is quite abrupt, we have seen no
indications that it is first order.Comment: 23 pages, RevteX, 6 encapsulated postscript figure
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