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...

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 critical behaviour of thin films containing quenched random impurities and inhomogeneities is investigated by the renormalization-group method to the one-loop order within the framework of the n-component φ4-model. The finite-size crossover in impure films has been considered on the basis...