# Universality of the glassy transitions in the two-dimensional +- J Ising model

Toldin, Francesco Parisen and Pelissetto, Andrea and Vicari, Ettore (2010) Universality of the glassy transitions in the two-dimensional +- J Ising model. Physical review. E, Statistical, nonlinear, and soft matter physics, 82 . 021106. ISSN 1550-2376

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## Abstract

We investigate the zero-temperature glassy transitions in the square-lattice +- J Ising model, with bond distribution $P(J_{xy}) = p \delta(J_{xy} - J) + (1-p) \delta(J_{xy} + J)$; p=1 and p=1/2 correspond to the pure Ising model and to the Ising spin glass with symmetric bimodal distribution, respectively. We present finite-temperature Monte Carlo simulations at p=4/5, which is close to the low-temperature paramagnetic-ferromagnetic transition line located at p=0.89, and at p=1/2. Their comparison provides a strong evidence that the glassy critical behavior that occurs for $1-p_0<p<p_0$, $p_0=0.897$, is universal, i.e., independent of p. Moreover, we show that glassy and magnetic modes are not coupled at the multicritical zero-temperature point where the paramagnetic-ferromagnetic transition line and the T=0 glassy transition line meet. On the theoretical side we discuss the validity of finite-size scaling in glassy systems with a zero-temperature transition and a discrete Hamiltonian spectrum. Because of a freezing phenomenon which occurs in a finite volume at sufficiently low temperatures, the standard finite-size scaling limit in terms of $TL^{1/\nu}$ does not exist: the renormalization-group invariant quantity $\xi/L$ should be used instead as basic variable.

Item Type: Article Imported from arXiv Area02 - Scienze fisiche > FIS/02 - Fisica teorica, modelli e metodi matematici Dipartimenti (until 2012) > DIPARTIMENTO DI FISICA " E. FERMI" dott.ssa Sandra Faita 09 Apr 2015 16:20 09 Apr 2015 16:20 http://eprints.adm.unipi.it/id/eprint/1859

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