Random field and random anisotropy effects in defect-free three-dimensionalXYmodels

Two-loop Functional Renormalization Group of the Random Field and Random Anisotropy O(N) Models

Random-anisotropy-axis magnet with infinite anisotropy.

We have studied the random-axis magnet with infinite anisotropy by three methods: Cayley-tree approximation, Migdal-Kadanoff renormalization group (MKRG), and Imry-Ma scaling. In the Cayley-tree approximation, by an examination of susceptibilities, it is shown that there exists a competition between the coordination number z and the number of components n of the spins which leads to either ferr...

(RF) — Random Forest Random Field

We combine random forest (RF) and conditional random field (CRF) into a new computational framework, called random forest random field (RF). Inference of (RF) uses the Swendsen-Wang cut algorithm, characterized by MetropolisHastings jumps. A jump from one state to another depends on the ratio of the proposal distributions, and on the ratio of the posterior distributions of the two states. Prior...

Random Field effects in field-driven quantum critical points

We investigate the role of disorder for field-driven quantum phase transitions of metallic antiferromagnets. For systems with sufficiently low symmetry, the combination of a uniform external field and non-magnetic impurities leads effectively to a random magnetic field which strongly modifies the behavior close to the critical point. Using perturbative renormalization group, we investigate in w...

The random-anisotropy model in the strong-anisotropy limit

We investigate the nature of the critical behaviour of the randomanisotropy Heisenberg model (RAM), which describes a magnetic system with random uniaxial single-site anisotropy, such as some amorphous alloys of rare earths and transition metals. In particular, we consider the strong-anisotropy limit (SRAM), in which the Hamiltonian can be rewritten as the one of an Ising spin-glass model with ...