The Leslie–Ericksen coefficients of a thermotropic nematic are determined by using an approximate solution of the Fokker–Planck equation for the one-particle distribution function over orientations of the nematic molecules. The results show that the well-known Doi–Edwards theory of the...

We perform Monte Carlo simulations of a symmetric 1D diffusive epidemic propagation process. The system presents a continuous phase transition between a stationary vacuum state and a steady reactive state. Renormalization group calculations have predicted that the dynamical critical exponent z=2...

We provide a direct quantitative evidence that the critical behavior of the Ising model on self-similar lattices depends upon the geometrical features of the underlying structure. Intensive Monte Carlo simulations enable to show that the values of the ratio of exponents γ/ν depend upon the...

A model of polar fluid is studied theoretically. The interaction potential, in addition to dipole–dipole term, possesses a dispersion contribution of the van der Waals–London form. It is found that when the dispersion force is comparable to dipole–dipole interaction, the fluid separates...

Phase diagrams of the micromaser system are mapped out in terms of the physical parameters at hand like the atom cavity transit time τ, the atom–photon frequency detuning Δω, the number of thermal photons nb and the probability a for a pump atom to be in its excited state. Critical...

A novel order parameter Φ for spin glasses is defined based on topological criteria and with a clear physical interpretation. Φ is first investigated for well known magnetic systems and then applied to the Edwards–Anderson ±J model on a square lattice, comparing its properties with the...

The Ising model in the presence of a random field is investigated within the mean field approximation based on Landau expansion. The random field is drawn from the trimodal probability distribution P(hi)=pδ(hi−h0)+qδ(hi+h0)+rδ(hi), where the probabilities p,q,r take on values within the...

In their comment to the paper “Theory of the evaporation/condensation transition of equilibrium droplets in finite volumes” [Physica A 319 (2003) 99], Biskup et al. claim that in finite systems at fixed density “the physical significance of the conjugate thermodynamic variable is of...

We study the well-known sociological phenomenon of gang aggregation and territory formation through an interacting agent system defined on a lattice. We introduce a two-gang Hamiltonian model where agents have red or blue affiliation but are otherwise indistinguishable. In this model, all...

In this work we present the first exact solution of a system of interacting particles with phase transitions of order higher than two. The presented analytical derivation shows that the Ising model on the Cayley tree exhibits a line of third order phase transition points, between temperatures...