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SUMMARY:The effects of higher order truncations in the 2PI description of
phase transitions
DTSTART;VALUE=DATE-TIME:20160712T113000Z
DTEND;VALUE=DATE-TIME:20160712T120000Z
DTSTAMP;VALUE=DATE-TIME:20200815T170414Z
UID:indico-contribution-2200163@indico.cern.ch
DESCRIPTION:Speakers: Gergely Marko (MTA-ELTE Statistical and Biological P
hysics Research Group)\nWe thoroughly investigated the applicability of th
e two-particle irreducible \n(2PI) formalism in the description of phase t
ransitions occurring at finite temperature in scalar field theories. We st
udied the importance of truncation effects on the order of the phase trans
ition and indeed found that the long known problem of the Hartree-Fock tru
ncation is cured by improving the approximation to the next level. during
the investigation of Bose-Einstein condensation at finite density we found
infrared problems one might face in the self-consistent treatment of the
propagators. We studied this problem in more detail developing various sem
i-analytical localized approximations. We have shown within a truncation a
t two-loop level that the so-called symmetry improved 2PI\, recently propo
sed in the literature to enforce the Goldstone theorem on the variational
propagator\, results in a loss of solution to the self-consistent propagat
or equations because the resummation cannot cope with the deep IR modes. W
e think that the most likely way out for this rather general problem is to
employ vertex resummations e.g. using 1/N expansion to next to leading or
der in the 2PI effective action.\n\nhttps://indico.cern.ch/event/507875/co
ntributions/2200163/
LOCATION:University of Stavanger Ø-130
URL:https://indico.cern.ch/event/507875/contributions/2200163/
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