794 research outputs found
Renormalization and resummation in the O(N) model
In the O(N) model for the large N expansion one needs resummation which makes
the renormalization of the model difficult. In the paper it is discussed, how
can one perform a consistent perturbation theory at zero as well as at finite
temperature with the help of momentum dependent renormalization schemes.Comment: 4 pages, presented at International Conference on Strong and
Electroweak matter (SEWM 2008), Amsterdam, The Netherlands, 26-29 Aug 200
Transport coefficients in non-quasiparticle systems
Transport coefficeints, in particular the shear viscosity to entropy density
ratio is studied in systems where the small-width quasiparticle assumption is
not valid. It is found that has no unversal lower bound, the minimal
value depends on the system and the temperature, and can be even zero. We
construct models where the conjectured bound is violated.Comment: 5 pages, uses svjour; talk presented in HCBM 2010, International
Workshop on Hot & Cold Baryonic Matter 15-20 August 2010, Budapest - Hungar
Hadron melting and QCD thermodynamics
We study in this paper mechanisms of hadron melting based on the spectral
representation of hadronic quantum channels, and examine the hadron width
dependence of the pressure. The findings are applied to a statistical hadron
model of QCD thermodynamics, where hadron masses are distributed by the
Hagedorn model and a uniform mechanism for producing hadron widths is assumed.
According to this model the hadron - quark gluon plasma transition occurs at
-250 MeV, the numerically observable MeV crossover
temperature is relevant for the onset of the hadron melting process.Comment: 10 pages, 12 figures, revtex
Resummation and damping in the O(N) model
In this talk I summarize the one loop and higher loop calculations of the
effective equations of motion of the O(N) symmetric scalar model in the linear
response approximation. At one loop one finds essential difference in long time
behavior for the fields below and above a dynamically generated length scale. A
partial resummation assuming quasi-particle propagation seems to cancel the
relevance of this scale.Comment: Talk given at SEWM2000. 5 page
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