arXiv subjects

E. P. Yukalova

Publications and source records attributed to E. P. Yukalova.

At least 37 records · Page 2Linked to original sources

arXiv2023

Regulating spin dynamics in magnetic nanomaterials

Magnetic nanomaterials can be used in the construction of devices for information processing and memory storage. For this purpose, they have to enjoy two contradictory properties, from one side being able of keeping for long time magnetization frozen, hence information stored, and from the other side allowing for quick change of magnetization required for fast erasing of memory and rewriting new information. Methods of resolving this dilemma are suggested based on triggering resonance, dynamic resonance tuning, and on quadratic Zeeman effect. These methods make it possible to realize effective regulation of spin dynamics in such materials as magnetic nanomolecules and magnetic nanoclusters.

cond-mat.mes-hall↗

arXiv2023

Discrete Versus Continuous Algorithms in Dynamics of Affective Decision Making

The dynamics of affective decision making is considered for an intelligent network composed of agents with different types of memory: long-term and short-term memory. The consideration is based on probabilistic affective decision theory, which takes into account the rational utility of alternatives as well as the emotional alternative attractiveness. The objective of this paper is the comparison of two multistep operational algorithms of the intelligent network: one based on discrete dynamics and the other on continuous dynamics. By means of numerical analysis, it is shown that, depending on the network parameters, the characteristic probabilities for continuous and discrete operations can exhibit either close or drastically different behavior. Thus, depending on which algorithm is employed, either discrete or continuous, theoretical predictions can be rather different, which does not allow for a uniquely defined description of practical problems. This finding is important for understanding which of the algorithms is more appropriate for the correct analysis of decision-making tasks. A discussion is given, revealing that the discrete operation seems to be more realistic for describing intelligent networks as well as affective artificial intelligence.

cs.AI↗

arXiv2023

Models of Mixed Matter

The review considers statistical systems composed of several phases that are intermixed in space at mesoscopic scale and systems representing a mixture of several components of microscopic objects. These types of mixtures should be distinguished from the Gibbs phase mixture, where the system is filled by macroscopic pieces of phases. The description of the macroscopic Gibbs mixture is rather simple, consisting in the consideration of pure phases separated by a surface, whose contribution becomes negligible in thermodynamic limit. The properties of mixtures, where phases are intermixed at mesoscopic scale, are principally different. The emphasis in the review is on the matter with phases mixed at mesoscopic scale. Heterogeneous materials composed of mesoscopic mixtures are ubiquitous in nature. A general theory of such mesoscopic mixtures is presented and illustrated by several condensed matter models. A mixture of several components of microscopic objects is illustrated by clustering quark-hadron matter.

cond-mat.stat-mech↗

arXiv2023

Statistical model of a superfluid solid

A microscopic statistical model of a quantum solid is developed, where inside a crystalline lattice there can exist regions of disorder, such as dislocation networks or grain boundaries. The cores of these regions of disorder are allowed for exhibiting fluid-like properties. If the solid is composed of Bose atoms, then the fluid-like aggregations inside the regions of disorder can exhibit Bose-Einstein condensation and hence superfluidity. The regions of disorder are randomly distributed throughout the sample, so that for describing the overall properties of the solid requires to accomplish averaging over the disordered aggregation configurations. The averaging procedure results in a renormalized Hamiltonian of a solid that can combine the properties of a crystal and superfluidity. The possibility of such a combination depends on the system parameters. In general, there exists a range of the model parameters allowing for the occurrence of superfluidity inside the disordered aggregations. This microscopic statistical model gives the opportunity to answer which real quantum crystals can exhibit the property of superfluidity and which cannot.

cond-mat.stat-mech↗

arXiv2022

Method of dynamic resonance tuning in spintronics of nanosystems

A method is advanced allowing for fast regulation of magnetization direction in magnetic nanosystems. The examples of such systems are polarized nanostructures, magnetic nanomolecules, magnetic nanoclusters, magnetic graphene, dipolar and spinor trapped atoms, and quantum dots. The emphasis in the paper is on magnetic nanomolecules and nanoclusters. The method is based on two principal contrivances: First, the magnetic sample is placed inside a coil of a resonant electric circuit creating a feedback field, and second, there is an external magnetic field that can be varied so that to dynamically support the resonance between the Zeeman frequency of the sample and the natural frequency of the circuit during the motion of the sample magnetization. This method can find applications in the production of memory devices and other spintronic appliances.

physics.app-ph↗

arXiv2022

Self-excited waves in complex social systems

A social system is considered whose agents choose between several alternatives of possible actions. The system is described by the fractions of agents preferring the corresponding alternatives. The agents interact with each other by exchanging information on their choices. Each alternative is characterized by three attributes: utility, attractiveness, and replication. The agents are heterogeneous having different initial conditions and different types of memory, which can be long-term or short-term. The agent interactions, generally, can depend on the distance between the agents, varying from short-range to long-range interactions. The emphasis in the paper is on long-range interactions. In a mixed society consisting of agents with both long-term and short-term memory, there appears the effect of spontaneous excitation of preference waves, when the fractions of agents preferring this or that alternative suddenly start strongly oscillating, either periodically or chaotically. Since the considered society forms a closed system, without any external influence, the arising waves are internally self-excited by the society.

physics.soc-ph↗

arXiv2022

Calculating critical temperature and critical exponents by self-similar approximants

Self-similar approximation theory allows for defining effective sums of asymptotic series. The method of self-similar factor approximants is applied for calculating the critical temperature and critical exponents of the $O(N)$-symmetric $φ^4$ field theory in three dimensions by summing asymptotic $\varepsilon$ expansions. This method is shown to be essentially simpler than other summation techniques involving complicated numerical calculations, while enjoying comparable accuracy.

cond-mat.stat-mech↗

arXiv2022

Role of collective information in networks of quantum operating agents

A network of agents is considered whose decision processes are described by the quantum decision theory previously advanced by the authors. Decision making is done by evaluating the utility of alternatives, their attractiveness, and the available information, whose combinations form the probabilities to choose a given alternative. As a result of the interplay between these three contributions, the process of choice between several alternatives is multimodal. The agents interact by exchanging information, which can take two forms: (i) information that an agent can directly receive from another agent and (ii) information collectively created by the members of the society. The information field common to all agents tends to smooth out sharp variations in the temporal behaviour of the probabilities and can even remove them. For agents with short-term memory, the probabilities often tend to their limiting values through strong oscillations and, for a range of parameters, these oscillations last for ever, representing an ever lasting hesitation of the decision makers. Switching on the information field makes the amplitude of the oscillations smaller and even can halt the everlasting oscillations forcing the probabilities to converge to fixed limits. The dynamic disjunction effect is described.

physics.soc-ph↗

arXiv2022

Triggering spin reversal in nanomolecules and nanoclusters on demand

Spin reversal in magnetic nanomolecules and nanoclusters is considered. A method is suggested allowing, from one side, to keep for long time magnetic polarization in a metastable state and, from the other side, for starting the reversal process at any required time. This method can find applications for the operation of storage memory devices and for the regulation of processes in spintronics.

cond-mat.mes-hall↗

arXiv2022

Self-similar sequence transformation for critical exponents

Self-similar sequence transformation is an original type of nonlinear sequence transformations allowing for defining effective limits of asymptotic sequences. The method of self-similar factor transformations is shown to be regular. This method is applied for calculating the critical exponents of the $O(N)$-symmetric $φ^4$ theory in three dimensions by summing asymptotic $\varepsilon$ expansions. It is shown that this method is straightforward and essentially simpler than other summation techniques involving complicated numerical calculations, while enjoying comparable accuracy.

cond-mat.stat-mech↗

arXiv2022

Statistical theory of structures with extended defects

Many materials contain extended defects of nanosize scale, such as dislocations, cracks, pores, polymorphic inclusions, and other embryos of competing phases. When one is interested not in the precise internal structure of a sample with such defects, but in its overall properties as a whole, one needs a statistical picture giving a spatially averaged description. In this chapter, an approach is presented for a statistical description of materials with extended nanosize defects. A method is developed allowing for the reduction of the problem to the consideration of a set of system replicas representing homogeneous materials characterized by effective renormalized Hamiltonians. This is achieved by defining a procedure of averaging over heterophase configurations. The method is illustrated by a lattice model with randomly distributed regions of disorder.

cond-mat.stat-mech↗

arXiv2021

Zeroth-Order Nucleation Transition under Nanoscale Phase Separation

Materials with nanoscale phase separation are considered. A system representing a heterophase mixture of ferromagnetic and paramagnetic phases is studied. After averaging over phase configurations, a renormalized Hamiltonian is derived describing the coexisting phases. The system is characterized by direct and exchange interactions and an external magnetic field. The properties of the system are studied numerically. The stability conditions define the stable state of the system. At a temperature of zero, the system is in a pure ferromagnetic state. However, at finite temperature, for some interaction parameters, the system can exhibit a zeroth-order nucleation transition between the pure ferromagnetic phase and the mixed state with coexisting ferromagnetic and paramagnetic phases. At the nucleation transition, the finite concentration of the paramagnetic phase appears via a jump.

cond-mat.mes-hall↗

arXiv2021

From Asymptotic Series to Self-Similar Approximants

The review presents the development of an approach of constructing approximate solutions to complicated physics problems, starting from asymptotic series, through optimized perturbation theory, to self-similar approximation theory. The close interrelation of underlying ideas of these theories is emphasized. Applications of the developed approach are illustrated by typical examples demonstrating that it combines simplicity with good accuracy.

cond-mat.stat-mech↗

arXiv2021

Self-similar extrapolation of nonlinear problems from small-variable to large-variable limit

Complicated physical problems usually are solved by resorting to perturbation theory leading to solutions in the form of asymptotic series in powers of small parameters. However, finite, and even large values of the parameters often are of the main physical interest. A method is described for predicting the large-variable behavior of solutions to nonlinear problems from the knowledge of only their small-variable expansions. The method is based on self-similar approximation theory resulting in self-similar factor approximants. The latter can well approximate a large class of functions, rational, irrational, and transcendental. The method is illustrated by several examples from statistical and condensed matter physics, where the self-similar predictions can be compared with the available large-variable behavior. It is shown that the method allows for finding the behavior of solutions at large variables when knowing just a few terms of small-variable expansions. Numerical convergence of approximants is demonstrated.

math-ph↗

arXiv2021

Hartree-Fock-Bogolubov method in the theory of Bose-condensed systems

The Hohenberg-Martin dilemma of conserving versus gapless theories for systems with Bose-Einstein condensate is considered. This dilemma states that, generally, a theory characterizing a system with broken global gauge symmetry, which is necessary for Bose-Einstein condensation, is either conserving, but has a gap in its spectrum, or is gapless, but does not obey conservation laws. In other words, such a system either displays a gapless spectrum, which is necessary for condensate existence, but is not conserving, which implies that it corresponds to an unstable system, or it respects conservation laws, describing a stable system, but the spectrum acquires a gap, which means that the condensate cannot appear. An approach is described, resolving this dilemma, and it is shown to give good quantitative agreement with experimental data. Calculations are accomplished in the Hartree-Fock-Bogolubov approximation.

cond-mat.quant-gas↗

arXiv2021

Self-similar extrapolation in quantum field theory

Calculations in field theory are usually accomplished by employing some variants of perturbation theory, for instance using loop expansions. These calculations result in asymptotic series in powers of small coupling parameters, which as a rule are divergent for finite values of the parameters. In this paper, a method is described allowing for the extrapolation of such asymptotic series to finite values of the coupling parameters, and even to their infinite limits. The method is based on self-similar approximation theory. This theory approximates well a large class of functions, rational, irrational, and transcendental. A method is presented, resulting in self-similar factor approximants allowing for the extrapolation of functions to arbitrary values of coupling parameters from only the knowledge of expansions in powers of small coupling parameters. The efficiency of the method is illustrated by several problems of quantum field theory.

hep-ph↗

arXiv2020

Characteristic quantities for nonequilibrium Bose systems

The paper discusses what characteristic quantities could quantify nonequilibrium states of Bose systems. Among such quantities, the following are considered: effective temperature, Fresnel number, and Mach number. The suggested classification of nonequilibrium states is illustrated by studying a Bose-Einstein condensate in a shaken trap, where it is possible to distinguish eight different nonequilibrium states: weak nonequilibrium, vortex germs, vortex rings, vortex lines, deformed vortices, vortex turbulence, grain turbulence, and wave turbulence. Nonequilibrium states are created experimentally and modeled by solving the nonlinear Schrödinger equation.

cond-mat.quant-gas↗

arXiv2020

On ultrafast polarization switching in ferroelectrics

Recently, a method of ultrafast polarization switching in ferroelectrics has been suggested. The basic idea of the method is to employ the effect of self-acceleration of polarization dynamics due to a resonator feedback field. This is the idea of principle whose efficiency is demonstrated by an Ising-type model in a transverse field. Of course, the practical realization of the method requires the choice of appropriate materials, which is a separate problem. For example, the standard order-disorder ferroelectrics with spatially symmetric double-well potentials cannot be used for this purpose, since, because of the symmetry, they lack the transverse polarization. However, ferroelectrics with asymmetric potentials, possessing this polarization, can be used. Moreover, if the potential asymmetry, hence the transverse polarization, could be regulated, e.g., by shear stress or shear strain, this could provide a tool for governing the process of polarization switching.

cond-mat.mes-hall↗