Matej Bel University

About: Matej Bel University is a education organization based out in Banská Bystrica, Slovakia. It is known for research contribution in the topics: Tourism & Fuzzy set. The organization has 721 authors who have published 1497 publications receiving 11573 citations. The organization is also known as: Matej Bel & Univerzita Mateja Bela.

Field-induced phase transitions in the helimagnet Ba 2 CuGe 2 O 7

Abstract: We present a theoretical study of the two-dimensional spiral antiferromagnet ${\mathrm{Ba}}_{2}{\mathrm{CuGe}}_{2}{\mathrm{O}}_{7}$ in the presence of an external magnetic field. We employ a suitable nonlinear $\ensuremath{\sigma}$ model to calculate the $T=0$ phase diagram and the associated low-energy spin dynamics for arbitrary canted magnetic fields, in general agreement with experiment. In particular, when the field is applied parallel to the $c$ axis, a previously anticipated Dzyaloshinskii-type incommensurate-to-commensurate phase transition is actually mediated by an intermediate phase, in agreement with our earlier theoretical prediction confirmed by the recent observation of the so-called double-$k$ structure. The sudden $\ensuremath{\pi}/2$ rotations of the magnetic structures observed in experiment are accounted for by a weakly broken $U(1)$ symmetry of our model. Finally, our analysis suggests a nonzero weak-ferromagnetic component in the underlying Dzyaloshinskii-Moriya anisotropy, which is important for quantitative agreement with experiment.

On dynamics in a two-sector Keynesian model of business cycles

Abstract: The paper investigates a two-sector Keynesian model of business cycles, describing the fluctuations of consumption and investment goods. It makes an analysis of issues concerning the existence of limit cycles around its equilibrium. There is derived the bifurcation equation of the model, giving conditions for the existence of limit cycles and their stability. The achieved results are illustrated on an example with numerical simulations.

The effect of inclusion of Δ resonances in relativistic mean-field model with scaled hadron masses and coupling constants

Abstract: Knowledge of the equation of state of the baryon matter plays a decisive role in the description of neutron stars. With an increase of the baryon density the filling of Fermi seas of hyperons and Δ isobars becomes possible. Their inclusion into standard relativistic mean-field models results in a strong softening of the equation of state and a lowering of the maximum neutron star mass below the measured values. We extend a relativistic mean-field model with scaled hadron masses and coupling constants developed in our previous works and take into account now not only hyperons but also the Δ isobars. We analyze available empirical information to put constraints on coupling constants of Δs to mesonic mean fields. We show that the resulting equation of state satisfies majority of presently known experimental constraints.