We investigate the low-temperature critical properties of a classical Ising model in a transverse field. This is performed by applying the conventional Wilson renormalization group to the related Ginzburg-Landau functional emerging from a Hubbard-Stratonovich transformation. Results in 4–ε...

The effects of single-ion anisotropy on quantum criticality in a d-dimensional spin-S planar ferromagnet is explored by means of the two-time Green’s function method. We work at the Tyablikov decoupling level for exchange interactions and the Anderson-Callen decoupling level for single-ion...

A one-loop renormalization group treatment is used to investigate the quantum phase transition and the low-temperature critical properties of a planar Heisenberg ferromagnet in a transverse field. The phase diagram, the free energy density and the relevant critical exponents in the influence...

We investigate the role played by symmetry conserving quenched disorder on quantum criticality of a variety of d-dimensional systems with a continuous symmetry order parameter. We employ a non-standard procedure which combines a preliminary reduction to an effective classical random problem and...

We revisit quantum criticality of d-dimensional n-vector transverse Ising-like models by means of a conventional one-loop renormalization group (RG) approach with temperature scaling. Focusing on dimensionalities d≤3, a careful analysis of the quantum regime allows us to explore the...

The low-temperature properties and crossover phenomena of d-dimensional transverse Ising-like systems within the influence domain of the quantum critical point are investigated solving the appropriate one-loop renormalization group equations. The phase diagram is obtained near and at d=3 and...

A reduction procedure, suggested for classical systems some years ago, is extended to systems with quantum-phase transitions with the aim to generate exactly solvable models capturing fluctuation effects beyond the mean field approximation. For the reduced isotropic m-vector quantum models, an...

The low temperature grand canonical critical properties of a d-dimensional n-vector Bose system in the presence of a random field, which behaves like [h∗khk]av ∽ kθ (θ ⩾ 0), are investigated with the use of replica trick and the Hartree approximation. With a boson free particle spectrum,...

The one-loop renormalization group equations are derived and analysed for a wide class of quantum statistical models describing the critical behaviour of systems with short-range correlated random impurities. The classical and quantum critical properties are considered to first order in a double...