EPJ B Colloquium - Particles, conformal invariance and criticality in pure and disordered systems

Amplitude in the replicated q-state Potts model that becomes q-independent in the limit of n=0 replicas corresponding to quenched disorder. This provides the analytical mechanism able to explain the numerically observed superuniversality (i.e. symmetry-independence) of the correlation length critical exponent.

The two-dimensional case occupies a special position in the theory of critical phenomena due to the exact results provided by lattice solutions and, directly in the continuum, by the infinite-dimensional character of the conformal algebra. However, some sectors of the theory, and most notably criticality in systems with quenched disorder and short range interactions, have appeared out of reach of exact methods and lacked the insight coming from analytical solutions.

In a new Colloquium published in EPJB, G. Delfino (Scuola Internazionale Superiore di Studi Avanzati, Italy) reviews recent progress achieved implementing conformal invariance within the particle description of field theory. The formalism yields exact unitarity equations whose solutions classify critical points with a given symmetry. It provides new insight in the case of pure systems, as well as the first exact access to criticality in presence of short range quenched disorder. Analytical mechanisms emerge that in the random case allow the superuniversality of some critical exponents and make explicit the softening of first order transitions by disorder.

Gesualdo Delfino (2021),
Particles, conformal invariance and criticality in pure and disordered systems
,
European Physical Journal B 94:65, DOI: 10.1140/epjb/s10051-021-00076-0

ISSN: 2195-7045 (Electronic Edition)

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