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SUMMARY:Free energy according to Poincare' and Landau - Gaeta\, G (Univers
 ita' di Milano)
DTSTART:20130111T102000Z
DTEND:20130111T110000Z
UID:TALK42391@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:In the Landau theory of phase transitions one considers an eff
 ective potential U whose symmetry group G and degree d depend on the syste
 m under consideration\; generally speaking\, U is the most general G-invar
 iant polynomial of degree d. When such a U turns out to be too complicate 
 for a direct analysis\, it is essential to be able to drop unessential ter
 ms\, i.e.\, to apply a simplifying criterion. Criteria based on singularit
 y theory exist and have a rigorous foundation\, but are often very difficu
 lt to apply in practice. Here we consider a simplifying criterion and rigo
 rously justify it on the basis of classical Lie-Poincar
e theory\; this bu
 ilds on (and justifies) a proposal by Gufan.\n
LOCATION:Seminar Room 1\, Newton Institute
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