ABSTRACT
Based on Glauber-type stochastic dynamics intertwined with mean field theory, we have investigated a graphene nanoisland's out-of-equilibrium magnetic and thermomagnetic behaviors with a mixed ferrimagnetic spin (1/2, 1) configuration in the presence of an oscillating magnetic field. The influence of the oscillating external magnetic field, single-ion anisotropy and temperature on the dynamic magnetic properties (dynamic phase transitions, hysteresis loop areas, correlations, and phase diagrams) of the system is studied in detail. The results illustrate that single ion anisotropy and the magnetic field play important roles in the system's dynamic order parameters, phase transitions and phase diagrams. Dynamic phase diagrams display some dynamic special points such as dynamic tricritical points, quadruple points and some sort of reentrant phenomena, which strongly depend on interaction parameters. Our predicted results may provide a reference for future experimental and theoretical studies of the nanostructures.
ABSTRACT
The current study investigates the impact of Russia-Ukraine war on topological properties of the international bond market by adopting econophysics methodologies, namely hierarchical structure methods (minimal spanning tree, (MST) and hierarchical tree, (HT)). We examine the network structure in bond markets by using daily data for 10-years government bond yields for 25 developed and developing economies including European countries as well as countries with largest bond market such as the United States, China, and Japan. We have also concentrated the co-movements among European Union (EU) member countries since most of them adopt the euro as common currency while few still use their local currency as an official currency. Our sample covers the period from beginning of January, 2015 to the end of August, 2022, which also include the Russia-Ukraine war. Hence, we have divided the period into two sub-periods to investigate the influence of Russia-Ukraine war on the structuring and clustering linkages in government bond markets. Our results indicate that the networks of relationships between EU government bond markets, using the Euro as an official currency, are closely connected to each other according to their economic tie. The countries with largest bond markets are not located at the center of the trees. It is also obtaining that the Russia-Ukraine war have affected network structure of the government bond markets.
ABSTRACT
Nonequilibrium magnetic properties in a two-dimensional kinetic mixed spin-2 and spin-5/2 Ising system in the presence of a time-varying (sinusoidal) magnetic field are studied within the effective-field theory (EFT) with correlations. The time evolution of the system is described by using Glauber-type stochastic dynamics. The dynamic EFT equations are derived by employing the Glauber transition rates for two interpenetrating square lattices. We investigate the time dependence of the magnetizations for different interaction parameter values in order to find the phases in the system. We also study the thermal behavior of the dynamic magnetizations, the hysteresis loop area, and dynamic correlation. The dynamic phase diagrams are presented in the reduced magnetic field amplitude and reduced temperature plane and we observe that the system exhibits dynamic tricritical and reentrant behaviors. Moreover, the system also displays a double critical end point (B), a zero-temperature critical point (Z), a critical end point (E), and a triple point (TP). We also performed a comparison with the mean-field prediction in order to point out the effects of correlations and found that some of the dynamic first-order phase lines, which are artifacts of the mean-field approach, disappeared.
Subject(s)
Magnetic Fields , Models, Statistical , Nonlinear Dynamics , Stochastic Processes , Computer Simulation , KineticsABSTRACT
We present a study, within a mean-field approach, of the stationary states of the kinetic spin-3/2 Blume-Capel model in the presence of a time-dependent oscillating external magnetic field. We use the Glauber-type stochastic dynamics to describe the time evolution of the system. We have found that the behavior of the system strongly depends on the crystal-field interaction. We can identify two types of solutions: a symmetric one where the magnetization (m) of the system oscillates in time around zero, which corresponds to a paramagnetic phase (P), and an antisymmetric one where m oscillates in time around a finite value different from zero, namely +/-3/2 and +/-1/2 that corresponds to the ferromagnetic-3/2 (F3/2) and the ferromagnetic-1/2 (F1/2) phases, respectively. There are coexistence regions of the phase space where the F3/2, F1/2, (F3/2 + F1/2), F3/2, P(F3/2 + P), F1/2, and P(F1/2 + P), F3/2, F1/2, P(F3/2 + F1/2 + P) phases coexist, hence the system exhibits seven different phases. We obtain the dynamic phase transition points and find six fundamental phase diagrams which exhibit one or three dynamic tricritical points. We have also calculated the Liapunov exponent to verify the stability of the solutions and the dynamic phase transition points.
