Two-stage melting in quasi-two-dimensional dissipative Yukawa systems

The results of numerical study of physical characteristics (the pair and triplet correlation functions, the isothermal compressibility, the heat capacities, and the diffusion constants) are presented for quasi-2D dissipative Yukawa systems. The specific features of these characteristics (reflecting the two-stage melting scenario) are investigated.     

Quantum Probing Topological Phase Transitions by Non‐Markovianity

Understanding the physical significance and probing the global invariants characterizing quantum topological phases in extended systems is a main challenge in modern physics with major impact in different areas of science. Here, a quantum‐information‐inspired probing method is proposed where topological phase transitions are revealed by a non‐Markovianity quantifier. The idea is illustrated by considering the decoherence dynamics of an external read‐out qubit that probes a Su–Schrieffer–Heeger (SSH) chain with either pure dephasing or dissipative coupling. Qubit decoherence features and non‐Markovianity measure clearly signal the topological phase transition of the SSH chain.     

Durabiity of Neutron Star Crust

How long do neutron star mountains last? The durability of elastically deformed crust is important for neutron star physics including pulsar glitches, emission of gravitational waves from static mountains, and flares from star quakes. The durability is defined by the strength properties of the Yukawa crystals of ions, which make up the crust. In this paper we extend our previous results [Mon. Not. R. Astron. Soc. 407 , L54 (2010)] and accurately describe the dependence of the durability on crust composition (which can be reduced to the dependence on the screening length λ of the Yukawa potential). We perform several molecular dynamics simulations of crust breaking and describe their results with a phenomenological model based on the kinetic theory of strength. We provide an analytical expression for the durability of neutron star crust matter for different densities, temperatures, stresses, and compositions. This expression can also be applied to estimate durability of Yukawa crystals in other systems, such as dusty plasmas in the laboratory (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Processes of energy exchange in systems of nonidentical particles with inhomogeneous sources of heat

Processes of energy exchange in dissipative systems of nonidentical interacting particles (having different sizes, charges, etc.) with an inhomogeneous distribution of sources of heat and/or any other sources of stochastic kinetic energy are considered. A theoretical model is proposed for analyzing the energy balance in such systems. Analytical relations describing the redistribution of the “kinetic temperature” between interacting particles of the system are obtained within this model. These relations are tested by the numerical simulation of the problem for Yukawa systems.     

Heat transfer coefficients in two-dimensional Yukawa systems (numerical simulations)

New data on heat transfer in two-dimensional Yukawa systems have been obtained. The results of a numerical study of the thermal conductivity for equilibrium systems with parameters close to the conditions of laboratory experiments in dusty plasma are presented. The Green-Kubo relations are used to calculate the heat transfer coefficients. The influence of dissipation (internal friction) on the heat transfer processes in nonideal systems is studied. New approximations are proposed for the thermal conductivity and diffusivity for nonideal dissipative systems. The results obtained are compared with the existing experimental and numerical data.     

Dynamic Shear Viscosity in a 2D Yukawa System

We present non‐equilibrium molecular dynamics simulation studies on the dynamic (complex) shear viscosity of a 2D many‐particle system interacting via a Yukawa (Debye‐Hückel) type inter‐particle potential. Our investigations reveal the complex interplay of dissipative and elastic processes, as well as the effect of single particle resonances and enhanced collective excitations, and the influence of the external forces on the structural correlations in the system (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Functional Interdependence in Coupled Dissipative Structures: Physical Foundations of Biological Coordination

Coordination within and between organisms is one of the most complex abilities of living systems, requiring the concerted regulation of many physiological constituents, and this complexity can be particularly difficult to explain by appealing to physics. A valuable framework for understanding biological coordination is the coordinative structure, a self-organized assembly of physiological elements that collectively performs a specific function. Coordinative structures are characterized by three properties: (1) multiple coupled components, (2) soft-assembly, and (3) functional organization. Coordinative structures have been hypothesized to be specific instantiations of dissipative structures, non-equilibrium, self-organized, physical systems exhibiting complex pattern formation in structure and behaviors. We pursued this hypothesis by testing for these three properties of coordinative structures in an electrically-driven dissipative structure. Our system demonstrates dynamic reorganization in response to functional perturbation, a behavior of coordinative structures called reciprocal compensation. Reciprocal compensation is corroborated by a dynamical systems model of the underlying physics. This coordinated activity of the system appears to derive from the system’s intrinsic end-directed behavior to maximize the rate of entropy production. The paper includes three primary components: (1) empirical data on emergent coordinated phenomena in a physical system, (2) computational simulations of this physical system, and (3) theoretical evaluation of the empirical and simulated results in the context of physics and the life sciences. This study reveals similarities between an electrically-driven dissipative structure that exhibits end-directed behavior and the goal-oriented behaviors of more complex living systems.     

Shear Viscosity of Liquid‐Phase Yukawa Plasmas from Molecular Dynamics Simulations on Graphics Processing Units

We have carried out million‐particle equilibrium molecular dynamics simulations of 3‐dimensional Yukawa liquids in order to determine the shear viscosity coefficient. The computations have been executed on Graphics Processing Unit (GPU) architectures with our largely parallelized code. The results cover the strongly coupled liquid phase, with Γ up to the vicinity of the freezing transition, for the 1 ≤ κ ≤ 3 domain of the screening parameter of the Yukawa potential. The good agreement of the present results with those obtained from earlier simulations of significantly smaller systems (consisting of several hundred to several thousand particles) verifies that the viscosity data derived in these smaller scale simulations are also acceptable (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thermodynamics and phase transitions in two-dimensional Yukawa systems

The results of numerical simulations of strongly-coupled two-dimensional dissipative Yukawa systems are presented. The thermodynamic characteristics of these systems were studied, namely the internal energy, the specific heat and the entropy. For the first time, it is discovered that the considered characteristics have two singular points on the melting line; one of these points corresponds to the first-order phase transition from crystal to the hexatic phase, and another point corresponds to the second-order phase transition from the hexatic phase to the isotropic liquid. The obtained results are compared to the existing numerical and analytical data.     

Instabilities in Yukawa Liquids

A strongly coupled Yukawa liquid is a system of charged particles which interact via a screened Coulomb interaction and in which the electrostatic energy between neighboring particles is larger than their thermal energy but not large enough for crystallization. Various plasma systems including ultracold neutral plasmas and complex (dusty) plasmas can exist in this strongly coupled liquid phase.Here we investigate instabilities driven by the relative streaming of plasma components in three‐dimensional Yukawa liquids with a focus on complex plasmas. This includes a dust acoustic instability driven by weakly coupled ions streaming through the dust liquid, and a dust‐dust instability driven by the counter‐streaming of strongly coupled dust grains. Compared to the Vlasov behavior we find there can be a substantial modification of the unstable wavenumber spectrum due to strong coupling effects (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Quantum Emulation of Extreme Non‐Equilibrium Phenomena with Trapped Atoms

Ultracold atomic physics experiments offer a nearly ideal context for the investigation of quantum systems far from equilibrium. We describe three related emerging directions of research into extreme non‐equilibrium phenomena in atom traps: quantum emulation of ultrafast atom‐light interactions, coherent phasonic spectroscopy in tunable quasicrystals, and realization of Floquet matter in strongly‐driven lattice systems. We show that all three should enable quantum emulation in parameter regimes inaccessible in solid‐state experiments, facilitating a complementary approach to open problems in non‐equilibrium condensed matter.     

Properties of Structure and Dynamics of a Two-Dimensional Dissipative Yukawa Dusty Plasma

In this paper, the structural and single-particle motive properties of a two-dimensional dusty plasmas are investigated numerically by molecular dynamics simulation within the framework of a dissipative Yukawa model. The pair correlation function, the mean square displacement, the static structure factor, and the bond angle correlation function characterizing the structural properties, and the velocity autocorrelation function with Fourier spectrum function characterizing the single-particle motion have been calculated for different values of coupling constant r and viscous damping constant vf. The results show that the system will coagulate quickly with increasing viscous damping constant and coupling constant, and the critical value of friction parameter decreases with increasing the coupling constant in the system.     

Collective Grain Interaction I. New Paradigm for Plasma Crystal Formation

The concept of collective grain interaction in complex plasmas is developed for large non‐linearity in grain screening. It is shown that for the case where the characteristic collective radius exceeds the non‐linear screening radius the collective interactions can fully determine the non‐linear collective attraction well. Based on the physics of collective non‐linear grain attraction a new paradigm for plasma crystal formation is formulated according to which the plasma crystal formation is related with localization of grains in non‐linear collective attraction wells. Nonlinearity in screening is an important feature of new paradigm and takes into account that the grain charges are large in accordance with most experiments where the plasma crystals where observed. The physical consequence of large non‐linearity is the presence of relative large potential well at distances only several times larger then the non‐linear screening radius. The calculated location of the potential well is of the order of the observed inter‐grain distances in plasma crystals and the deepness of the potential well is close to observed temperature of phase transition. The new paradigm considers formation of plasma crystal as result of grain trapping in the collective non‐linear potential well. The grain interactions close to the position of the potential well are in this paradigm relatively weak contrary to previous paradigm relating the plasma crystal formation with strong grain interactions. This new approach opens the possibility for direct calculation of the deepness of the attraction collective well, the critical value of the coupling constant. Results of these calculations show a reasonable agreement with both the observations of crystals in low pressure high‐frequency discharges and in large pressure discharges. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of the non‐linear screening on a modification of the Debye–Hückel plus hole approximation in complex plasma

The authors analyse two‐component electroneutral systems of classical macroions of finite size and point‐like oppositely charged microions. This article deals with the modification of the Debye–Hückel plus hole approximation when a non‐linear screening effect is taken into account in a complex plasma. Parameters of non‐linear screening of the macroions by surrounding microions are calculated within the framework of the Poisson–Boltzmann approximation. Two effects are found as a result of such calculations: (a) subdivision of all microions into two subclasses, free microions and bound microions and (b) a significant reduction of an effective charge Z^* of the macroion in comparison with its true value Z due to the non‐linear screening by a thin high‐density envelope of the bound microions. We show that the value of a non‐ideal portion of an internal energy differs considerably in the case when the non‐linear screening effect is taken into account in the vicinity of the macroion.     

Numerical Relativity and the Discovery of Gravitational Waves

Solving Einstein's equations precisely for strong‐field gravitational systems is essential to determining the full physics content of gravitational wave detections. Without these solutions it is not possible to infer precise values for initial and final‐state system parameters. Obtaining these solutions requires extensive numerical simulations, as Einstein's equations governing these systems are much too difficult to solve analytically. These difficulties arise principally from the curved, non‐linear nature of spacetime in general relativity. Developing the numerical capabilities needed to produce reliable, efficient calculations has required a Herculean 50‐year effort involving hundreds of researchers using sophisticated physical insight, algorithm development, computational technique, and computers that are a billion times more capable than they were in 1964 when computations were first attempted. The purpose of this review is to give an accessible overview for non‐experts of the major developments that have made such dramatic progress possible.     

The diffusion of macroparticles and criteria of phase transitions for dust structures in weakly ionized plasma

The dynamics of charged particles is investigated under conditions close to those of experiments in a weakly ionized laboratory gas-discharge dust plasma. The existing phenomenological criteria of phase transitions for dust structures in such a plasma are treated, and new criteria are suggested. The parameters responsible for the order and scaling of dynamic processes in Yukawa dissipative systems are determined. The relation for the diffusion coefficient D of macroparticles in strongly correlated liquid structures is derived.     

Nonlinearly saturated dynamical state of a three-wave mode-coupled dissipative system with linear instability

Linearly unstable dissipative systems with quadratic nonlinearity occurring in plasma physics, optics, fluid mechanics, etc. are often modeled by a general set of three-wave mode-coupled ordinary differential equations for complex variables. Bounded attractors of the set approximate nonlinearly saturated turbulent states of real physical systems. Exact criteria for boundedness of the attractors are found. Fundamentally different kinds of asymptotic behavior of the wave triad are classified in the parameter space and quantitatively assessed.     

Structural Characteristics and Equation of State of the Complex Plasmas

In this paper weakly and strongly non‐ideal plasmas are considered. In both cases the equations of state for hydrogen and dusty plasmas were studied on the basis of effective potentials. In the first case the thermodynamic properties for hydrogen plasmas were studied by the method of effective potentials taking into account quantummechanical diffraction, symmetry and screening effects. For strongly non‐ideal plasma or dusty plasma the equations of state were considered using radial distribution functions and effective interaction potential, which describes interactions of charged dust grains with dipole moments. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Obtaining gauge invariant actions via symplectic embedding formalism

The concept of gauge invariance is one of the most subtle and useful concepts in modern theoretical physics. It is one of the Standard Model cornerstones. The main benefit due to the gauge invariance is that it can permit the comprehension of difficult systems in physics with an arbitrary choice of a reference frame at every instant of time. It is the objective of this work to show a path of obtaining gauge invariant theories from non‐invariant ones. Both are named also as first‐ and second‐class theories respectively, obeying Dirac's formalism. Namely, it is very important to understand why it is always desirable to have a bridge between gauge invariant and non‐invariant theories. Once established, this kind of mapping between first‐class (gauge invariant) and second‐class systems, in Dirac's formalism can be considered as a sort of equivalence. This work describe this kind of equivalence obtaining a gauge invariant theory starting with a non‐invariant one using the symplectic embedding formalism developed by some of us some years back. To illustrate the procedure it was analyzed both Abelian and non‐Abelian theories. It was demonstrated that this method is more convenient than others. For example, it was shown exactly that this embedding method used here does not require any special modification to handle with non‐Abelian systems.