[SEMINARI]: Dr. Kalashnikov: Bose and Fermi Excitations in Hot and Dense QCD

[Arcadi Santamaria]

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                              S E M I N A R I

            [Image]    Departament de Física Teòrica     [Image]
                          Universitat de València
                      46100 Burjassot (València) Spain

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                 Bose and Fermi Excitations in Hot and Dense QCD

                              Oleg Kalashnikov

                           (Lebedev Inst., Moscow)

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                     Aula de Seminaris de Física Teòrica
                Thursday 18 of February of 1999 at 12:00 AM
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                                    Resum

   The spectra of Bose and Fermi excitations are reviewed in hot and dense
Abelian and non-Abelian theories for different gauges. Due to the medium all
these spectra are multi-split and their branches have, as a rule, the finite
energy gap at zero momentum (the effective thermal mass). The Bose (gluon or
     photon) spectra always have three branches (two transversal and one
   longitudinal) with the equal thermal masses proportional gT. The Fermi
  spectra have four or more branches which are very sensitive to the chosen
     gauge and the values of the m,\mu-parameters. Usually there are two
 one-particle (perturbative) branches and four collective ones: two branches
 represent the massive quasi-particle excitations with the usual properties
   and the other two - quasi-hole ones which occur only in the medium. The
  problem of gauge invariance which stays especially sharply for all Fermi
spectra remains unsolved and we only demonstrate this difficulty comparing a
   number of the calculational results in the Feynman and Coulomb gauges.

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