ELFT HÍRADÓ

[tcsaba AT eik.bme.hu]

                            MEGHÍVÓ

       a BME Fizikai Intézete Elméleti Fizika Tanszékének

                         szemináriumára:


                          Péter Mati
              BME Department of Theoretical Physics


      "The scalar O(N) model in the framework of the Functional
    Renormalization Group: the large N limit and truncation effects"


We study fixed points of three-dimensional scalar field theories in the
large-$N$ limit using functional renormalisation. Exact global solutions
are found including the Wilson-Fisher fixed point and a line of tricritical
fixed points. At its endpoint, non-analyticities arise leading to the
spontaneous breaking of scale invariance. Although the explicit form of
these non-analyticities is non-universal, we establish that the occurrence
of the phenomenon is a universal property of the theory.
We will also discuss how the truncations effect on the occurrence of
spontaneous symmetry breaking (SSB) for $O(N)$ models in general. We show
that even the local potential approximation (LPA), when treated exactly, is
sufficient to give qualitatively correct results for systems with
continuous symmetry, in agreement with the Mermin-Wagner theorem. However
solutions of the LPA equations for various truncations using a finite
number of terms, showing that SSB always occurs even where it should not.


Helye: BME Fizikai Intézet, Elméleti Fizika Tanszék
Budafoki út 8. F-épület, III lépcsöház
Szemináriumi szoba

Ideje: 2014. november 7. péntek, 10:15.


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