• Italiano
  • English

menu

ATENEO DI QUALITÀ ACCREDITATO ANVUR - FASCIA A

Mercoledì 10 Novembre 2021 Ore 16:30 Seminario INFN "Spontaneous Symmetry Breaking versus Berezinskii - Kosterlitz - Thouless scaling in d=2 long-range XY model"

Logo INFN

Luogo: Aula Maxwell 

Relatore: Guido Giachetti - SISSA and INFN, sezione di Trieste
 

Abstract:

In the past decades considerable efforts have been made in order to understand the critical features of long-range interacting models, i.e. those where the couplings decay algebraically as r^{-d-\sigma} with \sigma>0, d being the dimension of the system. According to the well-established Sak's criterion for O(N) models, the short-range critical behavior survives up to a given \sigma^{*} \leq 2. However, the applicability of this picture to describe the the two dimensional classical XY model is complicated by  the presence, in the short-range regime, of a line of RG fixed points, which gives rise to the celebrated Berezinskii - Kosterlitz - Thouless (BKT) phenomenology. Our first argument, based on Self-Consistent-Harmonic-Approximation, suggests that the BKT transition survives for \sigma < 2. This is confirmed by our more recent field-theoretical analysis. In particular we find there is not a specific, temperature-independent, value of \sigma^{*}: while for \sigma < 7/4 the BKT fixed line vanishes and we have an order-disorder transition, for 7/4 < \sigma < 2 we have the coexistence of a low-temperature broken phase and an intermediate quasi-ordered one. In this regime we were able to fully characterize the critical properties of this new transition.

 

 e-Mail di Riferimento dell'organizzatore (indispensabile e interno al Dipartimento): raffaella.burioni@unipr.it
Pubblicato Lunedì, 8 Novembre, 2021 - 10:50 | ultima modifica Lunedì, 8 Novembre, 2021 - 10:57