ELFT HÍRADÓ

[StatFizSzeminar <statfiz AT glu.elte.hu>]

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             ELTE TTK Fizikai Intézet
         STATISZTIKUS FIZIKAI SZEMINÁRIUM


                  2019. február 20.

                       szerda 

                       11.00

                     Zsolt Szép

   MTA-ELTE Theoretical Physics Research Group

   "Thermodynamics of the O(4) model from the 
          Phi-derivable approximation"

We investigate the effects of higher order truncations
of the two-particle irreducible (2PI) action on the 
equilibrium FFT-based numerical solution of the model 
and the description of the phase transition. We find 
that the two-loop level truncation represents an 
improvement over the Hartree-Fock truncation, but at 
the next level of the truncation, the solution to the
coupled propagator and field equations is lost in some
temperature range. This feature is a result of the IR
sensitivity of the propagator equation and makes 
impossible the direct determination of the critical
temperature in the chiral limit. Vertex resummation 
provided by the 1/N expansion to next to leading order
in the 2PI effective action tames this problem to some
degree. At NLO in the 2PI-1/N expansion we determine 
the critical exponents and the universal scaling function
and compare them with their lattice counterparts.


1117, Budapest, Pázmány P. sétány 1/A, Északi tömb 2.54
        honlap: http://glu.elte.hu/~statfiz

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