arXiv subjects

Matthieu Tissier

Publications and source records attributed to Matthieu Tissier.

57 records · Page 4Linked to original sources

arXiv2005

Nonperturbative functional renormalization group for random field models: the way out of dimensional reduction

We have developed a non-perturbative functional renormalization group approach for the random field O(N) model (RFO(N)M) that allows us to investigate the ordering transition in any dimension and for any value of N including the Ising case. We show that the failure of dimensional reduction and standard perturbation theory is due to the non-analytic nature of the zero-temperature fixed point controlling the critical behavior, non-analycity which is associated with the existence of many metastable states. We find that this non-analycity leads to critical exponents differing from the dimensional reduction prediction only below a critical dimension d\_c(N)<6, with d\_c(N=1)>3.

cond-mat.dis-nn↗

arXiv2003

Competition between fluctuations and disorder in frustrated magnets

We investigate the effects of impurities on the nature of the phase transition in frustrated magnets, in d=4-epsilon dimensions. For sufficiently small values of the number of spin components, we find no physically relevant stable fixed point in the deep perturbative region (epsilon << 1), contrarily to what is to be expected on very general grounds. This signals the onset of important physical effects.

cond-mat.stat-mech↗

arXiv2002

Second order phase transitions induced by disorder in frustrated magnets

We study the critical properties of three dimensional frustrated magnets, diluted with non-magnetic impurities. We show that these systems exhibit a second order phase transition, corresponding to a new universality class. In the pure case, the phase transition is expected to be weakly of first order. We therefore argue that these frustrated systems can be used to study experimentally the rounding effect of disorder on discontinuous phase transitions. We give first estimates of the critical exponents associated with this universality class, by using the method of the effective average action.

cond-mat.stat-mech↗