The phase diagrams of the three-state Ghatak-Sherrington spin-glass (or random Blume-Capel) model are obtained in mean-field theory with replica symmetry in order to study the effects of a ferromagnetic bias and finite random connectivity in which each spin is connected to a finite number of other spins. It is shown that inverse melting from a ferromagnetic to a low-temperature paramagnetic pha...

We study the quantum transition at T = 0 in the spin-12 Ising spin–glass in a transverse field in two dimensions. The world line path integral representation of this model corresponds to an effective classical system in (2+1) dimensions, which we study by Monte Carlo simulations. Values of the critical exponents are estimated by a finite-size scaling analysis. We find that the dynamical exponen...

The out of equilibrium dynamics of finite dimensional spin glasses is considered from a point of view going beyond the standard ‘mean-field theory’ versus ‘droplet picture’ debate of the last decades. The main predictions of both theories concerning the spin glass dynamics are discussed. It is shown, in particular, that predictions originating from mean-field ideas concerning the violations of ...

A spin-1 model, appropriated to study the competition between bilinear (JijSiSj) and biquadratic (KijS 2 i S 2 j ) random interactions, both of them with zero mean, is investigated. The interactions are infinite-ranged and the replica method is employed. Within the replica-symmetric assumption, the system presents two phases, namely, paramagnetic and spin-glass, separated by a continuous transi...

W epresenta generaltechniqueto com putehow theenergy ofa con guration variesasa function ofits overlap with the ground state in the case ofoptim ization problem s. O ur approach is based on a generalization ofthe cavity m ethod to a system interacting with its ground state. W ith this technique we study the random m atching problem aswellasthe m ean eld diluted spin glass. As a byproductofthisa...

A single crystal of U2NiSi3 was investigated by means of magnetization, electrical resistivity and heat capacity measurements. Whereas the DC magnetic data clearly manifest strongly anisotropic ferromagnetism, the AC magnetic susceptibility data are consistent with spin-glass behaviour, reported previously for polycrystalline samples. Moreover, no distinct anomalies around TC occur in the speci...

We compute numerically small window overlaps in the three dimensional Edwards Anderson spin glass. We show that they behave in the way implied by the Replica Symmetry Breaking Ansatz, that they do not qualitatively differ from the full volume overlap and do not tend to a trivial function when increasing the lattice volume. On the contrary we show they are affected by small finite volume effects...

Identities and inequalities are proved for the order parameters, correlation functions and their derivatives of the Ising spin glass. The results serve as additional evidence that the ferromagnetic phase is composed of two regions, one with strong ferromagnetic ordering and the other with the effects of disorder dominant. The Nishimori line marks a crossover between these two regions. PACS numb...

We implement Monte Carlo algorithms for the simulation of spin-glass systems and optimize our codes for recent multi-core CPU and GPU architectures. We consider both the Ising (binary) and Heisenberg (floating-point) spin-glass models. We provide performance figures for the Intel Nehalem and the IBM Cell/BE CPUs and the Nvidia Tesla C1060 GPU; we also draw a comparison with the performance of d...

The dielectric permittivity of the orientational glass methanol(x50.73)-b-hydroquinone-clathrate has been studied as function of temperature and waiting time using different temperature-time protocols. We study aging, rejuvenation, and memory effects in the glassy phase and discuss similarities and differences to aging in spin glasses. We argue that the diluted methanol-clathrate, although conc...