We study stochastic sandpile models with a height restriction in one and two dimensions. A site can topple if it has a height of two, as in Manna's model, but, in contrast to previously studied sandpiles, here the height (or number of particles per site), cannot exceed two. This yields a considerable simplification over the unrestricted case, in which the number of states per site is unbounded....

We investigated cluster formation in model colloids where the interparticle potential beyond the collision diameter includes a short-ranged attraction and a longer-ranged repulsion. The structure and thermodynamic properties of the model system can be accurately described by the first-order mean-spherical approximation (FMSA) and a perturbation theory for bulk phases and by a nonlocal density-f...

A basic micromechanical model for deformation of solids with only one tuning parameter (weakening epsilon) is introduced. The model can reproduce observed stress-strain curves, acoustic emissions and related power spectra, event statistics, and geometrical properties of slip, with a continuous phase transition from brittle to ductile behavior. Exact universal predictions are extracted using mea...

The Landau theory' of continuous phase transitions provides a powerful tool for understanding transitions between solid phases whose symmetries have a group-subgroup relationship. In the Landau theory, the thermodynamic free energy F of the crystal is written as a function of an order parameter Q. In the high-symmetry phase, the minimum of F is at Q = 0. In the low-symmetry phase, the minimum o...

We report the observation of a Skyrmion lattice in the chiral multiferroic insulator Cu2OSeO3 using Cu L3-edge resonant soft x-ray diffraction. We observe the unexpected existence of two distinct Skyrmion sublattices that arise from inequivalent Cu sites with chemically identical coordination numbers but different magnetically active orbitals. The Skyrmion sublattices are rotated with respect t...

If a fluctuating medium is confined, the ensuing perturbation of its fluctuation spectrum generates Casimir-like effective forces acting on its confining surfaces. Near a continuous phase transition of such a medium the corresponding order parameter fluctuations occur on all length scales and therefore close to the critical point this effect acquires a universal character, i.e., to a large exte...

We present a study, employing high level ab initio methods, of electron localization-delocalization transitions along the dissociation path of the C4- anion to C2 and C2-. We find that at the equilibrium geometry, the symmetrical and nonsymmetrical configurations of the linear C4- anion are almost isoenergetic. However, along a collinear dissociation path, the dipole moment drops abruptly to ze...

%e have classified continuous phase transitions in physical systems where the order parameter transforms as a four-dimensional representation of a three-dimensional space group. For most active four-dimensional space-group representations the "phase diagrams" are obtained. %'e also give prescriptions to lift the degeneracy, occurring at the fourth-degree polynomical expansion of the free energy...

We show that if the excitations which become gapless at a quantum critical point also carry the electrical current, then a resistivity linear in temperature, as is observed in the copper-oxide high-temperature superconductors, obtains only if the dynamical exponent z satisfies the unphysical constraint, z < 0. At fault here is the universal scaling hypothesis that, at a continuous phase transit...