Beyond the Mean Field Approximation for Spin Glasses

We study the d-dimensional random Ising model using a Bethe-Peierls approximation in the framework of the replica method. We take into account the correct interaction only inside replicated clusters of spins. Our ansatz is that the interaction of the borders of the clusters with the external world can be described via an effective interaction among replicas. The Bethe-Peierls model is mapped into a single Ising model with a random gaussian field, whose strength (related to the effective coupling between two replicas) is determined via a self-consistency equation. This allows us to obtain analytic estimates of the internal energy and of the critical temperature in d dimensions.Comment: plane TeX file,19 pages. 3 figures may be requested to Paladin at axscaq.aquila.infn.i

On the concept of complexity in random dynamical systems

We introduce a measure of complexity in terms of the average number of bits per time unit necessary to specify the sequence generated by the system. In random dynamical system, this indicator coincides with the rate K of divergence of nearby trajectories evolving under two different noise realizations. The meaning of K is discussed in the context of the information theory, and it is shown that it can be determined from real experimental data. In presence of strong dynamical intermittency, the value of K is very different from the standard Lyapunov exponent computed considering two nearby trajectories evolving under the same randomness. However, the former is much more relevant than the latter from a physical point of view as illustrated by some numerical computations for noisy maps and sandpile models.Comment: 35 pages, LaTe

Constrained annealing for spin glasses

The quenched free energy of spin glasses is estimated by means of annealed averages where the frustration is constrained to its average value. We discuss the case of d-dimensional Ising models with random nearest neighbour coupling, and we introduce a new method to obtain constrained annealed averages without recurring to Lagrange multipliers. It requires to perform quenched averages either on small volumes in an analytic way, or on finite size strips via products of random transfer matrices. We thus give a sequence of converging lower bounds for the quenched free energy of 2d spin glasses.Comment: plane TeX file,24 pages. 6 figures may be requested to Paladin at vxscaq.aquila.infn.i

Dejavniki neverbalne komunikacije v povezavi s prepričljivostjo posameznika

Poleg verbalnih sporočil so v komunikaciji zelo pomembna neverbalna sporočila,saj jim praviloma zaupamo bolj kot verbalni komponenti komunikacije. Ena od funkcij neverbalne komunikacije je prepričevanje. Dosedanje raziskave so pokazale, da očesni stik, slog oblačenja, določene vokalične značilnosti ter nekatere vrste dotika vplivajo na prepričljivost posameznika. Raziskava, ki smo jo izvedli, je pokazala, da anketiranci menijo,da je za nekoga, ki želi biti prepričljiv, pomembno, kako določeno informacijo posreduje. Na oblikovanje mnenj o vplivu znakov neverbalne komunikacije na prepričljivost vplivajo različni dejavniki. Rezultati naše raziskave so pokazali nekatere zanimive razlike v primerjavi z dosedanjimi raziskavami

L'opera di Vezio Crisafulli tra diritto e politica

Pur con tutti i limiti delle operazioni di revisione costituzionale, delle quali Crisafulli si mostrava consapevole, il suo sguardo era dunque rivolto in avanti e non verso il passato. Se gli fossero stati concessi altri anni di vita, egli avrebbe certamente preso parte alle tante controversie, politiche, giurisprudenziali e dottrinali, che hanno accompagnato e seguito il crollo del tradizionale quadro politico italiano. Rimane per me il solo dubbio sulle sue reazioni al confuso dibattito che sta accompagnando l'attuale tentativo di una grande riforma. Sarebbero prevalsi il suo spirito polemico oppure il senso civico di cui parlava Nocilla? Che cosa avrebbe pensato Crisafulli del cosiddetto federalismo all'italiana, del semipresidenzialismo oscillante tra la Francia e l'Austria, della Corte costituzionale alterata e gravata da innumerevoli compiti? Questo -purtroppo- lo possiamo soltanto immaginare

Laž in laganje

Laž in laganje sta tako del vsakdanjega življenja kot tudi del managementa. Najbolj strnjeno bi lahko rekli, da je namen laži z namernim zavajanjem škodovati nekomu. Kanalov za zaznavanje laži in laganja je veliko: višina, glasnost, hitrost, jasnost in vsebina govora, očesni gibi, geste z rokami ter telesni in obrazni gibi. Sklepanje o neiskrenosti govorca na podlagi enega samega znaka je lahko zavajajoče. Nujno je upoštevati več znakov hkrati ter iskati nekonsistentnost med njimi. Pogledi na vlogo laži in laganja v managementu so različni. Medtem ko sta za nekatere laž in laganje del igre, sta za druge nedopustna in nezaželena

Stochastic Resonance in Deterministic Chaotic Systems

We propose a mechanism which produces periodic variations of the degree of predictability in dynamical systems. It is shown that even in the absence of noise when the control parameter changes periodically in time, below and above the threshold for the onset of chaos, stochastic resonance effects appears. As a result one has an alternation of chaotic and regular, i.e. predictable, evolutions in an almost periodic way, so that the Lyapunov exponent is positive but some time correlations do not decay.Comment: 9 Pages + 3 Figures, RevTeX 3.0, sub. J. Phys.

Lack of self-average in weakly disordered one dimensional systems

We introduce a one dimensional disordered Ising model which at zero temperature is characterized by a non-trivial, non-self-averaging, overlap probability distribution when the impurity concentration vanishes in the thermodynamic limit. The form of the distribution can be calculated analytically for any realization of disorder. For non-zero impurity concentration the distribution becomes a self-averaging delta function centered on a value which can be estimated by the product of appropriate transfer matrices.Comment: 17 pages + 5 figures, TeX dialect: Plain TeX + IOP macros (included