23,447 research outputs found
Evading the Infrared Problem of Thermal QCD
Due to asymptotic freedom, QCD is guaranteed to be accessible to perturbative
methods at asymptotically high temperatures. However, in 1979 Linde has pointed
out the existence of an "infrared wall", beyond which an infinite number of
Feynman diagrams contribute. Following a proposal by Braaten and Nieto, it is
shown explicitly how the limits to computability that this infrared problem
poses can be overcome in the framework of dimensionally reduced effective
theories.Comment: To appear in the proceedings of SEWM04, Helsinki, Finland, 16-19 Jun
200
Long-distance contributions to the QCD pressure
The QCD pressure is a most fundamental quantity, for which lattice data is
available up to a few times the critical temperature . Perturbation
theory, even at very high temperatures, has serious convergence problems.
Combining analytical and 3d numerical methods, we show that it is possible to
compute the QCD pressure from about to infinity. We also describe an
algorithm to generate and classify high order Feynman diagrams which is
tailored to minimize computational effort.Comment: 5 pages; talk at Statistical QCD, Bielefeld, August 26-30, 200
Tackling the infrared problem of thermal QCD
Perturbative calculations of corrections to the behavior of an ideal gas of
quarks and gluons, the limit that is formally realized at infinite temperature,
are obstructed by severe infrared divergences. The limits to computability that
the infrared problem poses can be overcome in the framework of dimensionally
reduced effective theories. Here, we give details on the evaluation of the
highest perturbative coefficient needed for this setup, in the continuum.Comment: 3 pages, Lattice2003(nonzero
Weak-coupling expansion of the hot QCD pressure
We review recent progress made in determining the pressure of hot QCD up to
the first non-perturbative term in its weak-coupling expansion.Comment: 11 pg, Talk given at 29th Johns Hopkins Workshop in Theoretical
Physics: Strong Matter in the Heavens, Budapest, Hungary, 1-3 Aug 200
Loops for Hot QCD
In this talk we review the status concerning vacuum integrals needed in
perturbative expansions of QCD at non-zero temperature. We will focus on the
differences as compared to familiar zero-temperature techniques, and provide a
list of known basic master integrals.Comment: 6 pages, to appear in the proceedings of the international conference
on Loops and Legs in Quantum Field Theory, Sondershausen, 20-25 April 200
Two-loop QCD gauge coupling at high temperatures
We determine the 2-loop effective gauge coupling of QCD at high temperatures,
defined as a matching coefficient appearing in the dimensionally reduced
effective field theory. The result allows to improve on one of the classic
non-perturbative probes for the convergence of the weak-coupling expansion at
high temperatures, the comparison of full and effective theory determinations
of an observable called the spatial string tension. We find surprisingly good
agreement almost down to the critical temperature of the deconfinement phase
transition. We also determine one new contribution of order O(g^6T^4) to the
pressure of hot QCD.Comment: 17 page
Feasibility of Using Cryostored Colorado Potato Beetle (Coleoptera: Chrysomelidae) Eggs for Rearing \u3ci\u3eEdovum Puttleri\u3c/i\u3e (Hymenoptera: Eulophidae)
Cryostored eggs of Colorado potato beetle, Leptinotarsa decemlineata (Say) eggs were suitable hosts for Edovum puttleri. Parasitism rates were low, however this study was first to show that rearing the parasite on eggs stored at ultra low temperatures (-70 0 C) is feasible. This method of storage will facilitate mass production of E. puttleri as well as prevent loss of the parasite in the event of a crash in the Colorado potato beetle colony
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