1,300 research outputs found
Meson correlation functions in a QCD plasma
The temporal pseudoscalar meson correlation function in a QCD plasma is
investigated in a range of temperatures exceeding and yet of experimental
interest. Only the flavour-singlet channel is considered and the imaginary time
formalism is employed for the finite temperature calculations. The behaviour of
the meson spectral function and of the temporal correlator is first studied in
the HTL approximation, where one replaces the free thermal quark propagators
with the HTL resummed ones. This procedure satisfactory describes the soft
fermionic modes, but its application to the propagation of hard quarks is not
reliable. An improved version of the so-called NLA scheme, which allows a
better treatment of the hard fermionic modes, is then proposed. The impact of
the improved NLA on the pseudoscalar temporal correlator is investigated.Comment: 35 pages, 15 figure
DCC: Attractive Idea Seeks Serious Confirmation
The theoretical ideas relevant for the physics of the disoriented chiral
condensate (DCC) are reviewed.Comment: 18 pages LaTex, based on invited lecture given by A.Krzywicki at the
workshop "Quark, plasma and beyond", Zif, Bielefeld, May 1996 ; a reference
is correcte
Quark number susceptibilities from HTL-resummed thermodynamics
We compute analytically the diagonal quark number susceptibilities for a
quark-gluon plasma at finite temperature and zero chemical potential, and
compare with recent lattice results. The calculation uses the approximately
self-consistent resummation of hard thermal and dense loops that we have
developed previously. For temperatures between 1.5 to 5 , our results
follow the same trend as the lattice data, but exceed them in magnitude by
about 5-10%. We also compute the lowest order contribution, of order
, to the off-diagonal susceptibility. This
contribution, which is not a part of our self-consistent calculation, is
numerically small, but not small enough to be compatible with a recent lattice
simulation.Comment: 13 pages, 5 figures, uses elsart.cls; v2: minor corrections; v3: sign
in eq.(1) correcte
Renormalized Finite Temperature phi^4 theory from the 2PI Effective Action
We present an analytical and numerical study of scalar phi^4 theory at finite
temperature with a renormalized 2-loop truncation of the 2PI effective action.Comment: 4 pages. Presented at International Conference on Strong and
Electroweak Matter (SEWM 2006), Upton, New York, 10-13 May 200
Comparing different hard-thermal-loop approaches to quark number susceptibilities
We compare our previously proposed hard-thermal-loop (HTL) resummed
calculation of quark number susceptibilities using a self-consistent two-loop
approximation to the quark density with a recent calculation of the same
quantity at the one-loop level in a variant of HTL-screened perturbation
theory. Besides pointing out conceptual problems with the latter approach, we
show that it severely over-includes the leading-order interaction effects while
including none of the plasmon term which after all is the reason to construct
improved resummation schemes.Comment: 6 pages, 6 figures. Revised version to appear in Eur. J. Phys.
Universal shocks in the Wishart random-matrix ensemble - a sequel
We study the diffusion of complex Wishart matrices and derive a partial
differential equation governing the behavior of the associated averaged
characteristic polynomial. In the limit of large size matrices, the inverse
Cole-Hopf transform of this polynomial obeys a nonlinear partial differential
equation whose solutions exhibit shocks at the evolving edges of the eigenvalue
spectrum. In a particular scenario one of those shocks hits the origin that
plays the role of an impassable wall. To investigate the universal behavior in
the vicinity of this wall, a critical point, we derive an integral
representation for the averaged characteristic polynomial and study its
asymptotic behavior. The result is a Bessoid function.Comment: 7 pages, 2 figure
The thermodynamics of the quark-gluon plasma: Self-consistent resummations vs. lattice data
We discuss a recent approach for overcoming the poor convergence of the
perturbative expansion for the thermodynamic potential of QCD. This approach is
based on self-consistent approximations which allow for a gauge-invariant and
manifestly ultraviolet-finite resummation of the essential physics of the hard
thermal/dense loops. The results thus obtained are in good agreement with
available lattice data down to temperatures of about twice the critical
temperature. Calculations for a plasma with finite quark density (i.e., with a
non-zero chemical potential ) are no more difficult than at .Comment: 4 pages LaTeX2e, contribution to the proceedings of the 15th
International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (QM
2001), Long Island, New York, January 15 - 20, 200
Thermodynamics of the high-temperature quark-gluon plasma
We review the various methods which have been employed recently to describe
the thermodynamics of the high temperature quark-gluon plasma using weak
coupling techniques, and we compare their results with those of most recent
lattice gauge calculations. Many of the difficulties encountered with
perturbation theory at finite temperature are in fact not specific to QCD but
are present in any field theory at finite temperature and will be discussed
first in the simple example of the scalar field theory. We discuss the merits
and limitations of various techniques which have been used to go beyond
perturbation theory in the soft sector, such as dimensional reduction, screened
perturbation theory or hard-thermal-loop perturbation theory, and Phi-derivable
approximations. In the last part of the review, we focus on the later, which
lead to a remarkably simple expression for the entropy of the quark-gluon
plasma. When complemented with further, physically motivated, approximations,
this approach reproduces accurately the entropy obtained from lattice gauge
calculations at temperatures above 2.5 T_c, where T_c is the deconfinement
temperature. This calculation thus provides also support to the physical
picture of the quark-gluon plasma as a gas of weakly interacting
quasiparticles.Comment: Review for "Quark-Gluon Plasma 3", eds. R.C. Hwa and X.-N. Wang,
World Scientific, Singapore. 63 pages, 21 figures. v2: minor corrections and
2 references adde
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