Critical phenomena in a disc-percolation model and their application to relativistic heavy ion collisions

By studying the critical phenomena in continuum-percolation of discs, we find a new approach to locate the critical point, i.e. using the inflection point of P∞ as an evaluation of the percolation threshold. The susceptibility, defined as the derivative of P∞, possesses a finite-size scaling property, where the scaling exponent is the reciprocal of v, the critical exponent of the correlation length. A possible application of this approach to the study of the critical phenomena in relativistic heavy ion collisions is discussed. The critical point for deconfinement can be extracted by the inflection point of PQGP -- the probability for the event with QGP formation. The finite-size scaling of its derivative can give the critical exponent v, which is a rare case that can provide an experimental measure of a critical exponent in heavy ion collisions.

Critical Behavior of the Gaussian Model with Periodic Interactions on Diamond—Type Hierarchical Lattices in External Magnetic Fields

The Gaussian spin model with periodic interactions on the diamond-type hierarchical lattices is constructed by generalizing that with uniform interactions on translationally invariant lattices according to a class of substitution sequences. The Gaussian distribution constants and imposed external magnetic fields are also periodic depending on the periodic characteristic of the interaction bonds. The critical behaviors of this generalized Gaussian model in external magnetic fields are studied by the exact renormalization-group approach and spin rescaling method. The critical points and all the critical exponents are obtained. The critical behaviors are found to be determined by the Gaussian distribution constants and the fractal dimensions of the lattices. When all the Gaussian distribution constants are the same, the dependence of the critical exponents on the dimensions of the lattices is the same as that of the Gaussian model with uniform interactions on translationally invariant lattices.

Critical Behavior of Gaussian Model on X Fractal Lattices in External Magnetic Fields

Using the renormalization group method, the critical behavior of Gaussian model is studied in external magnetic fields on X fractal lattices embedded in two-dimensional and -dimensional Euclidean spaces, respectively. Critical points and exponents are calculated. It is found that there is long-range order at finite temperature for this model, and that the critical points do not change with the space dimensionality (or the fractal dimensionality ). It is also found that the critical exponents are very different from results of Ising model on the same lattices, and that the exponents on X lattices are different from the exact results on translationally symmetric lattices.

Universal critical properties of the Eulerian bond-cubic model

We investigate the Eulerian bond-cubic model on the square lattice by means of Monte Carlo simulations, using an efficient cluster algorithm and a finite-size scaling analysis. The critical points and four critical exponents of the model are determined for several values of n. Two of the exponents are fractal dimensions, which are obtained numerically for the first time. Our results are consistent with the Coulomb gas predictions for the critical O（n） branch for n 〈 2 and the results obtained by previous transfer matrix calculations. For n = 2, we find that the thermal exponent, the magnetic exponent and the fractal dimension of the largest critical Eulerian bond component are different from those of the critical 0（2） loop model. These results confirm that the cubic anisotropy is marginal at n = 2 but irrelevant for n〈2.

A COMPARISON OF HIGH PRESSURE PHASE EQUILIBRIA AND ORITIOAL PHENOMENA FOR AQUEOUS C_4-ALKANE-SYSTEMS WITH OTHER ALKANES SYSTEMS

In an optical high--pressure autoclave with saphire windows and magnetic stirring, phase equilibria data in mixtures of water-n--butane and water-iso--butane were measured in a temperature range from 500K to 600K and at a pressure from 10MPa to 300MPa. The critical curves of these systems start at the critical point of pure water and tend to higher pressures and lower temperatures. These curves pass a temperature minima 624K and 625K respectively and then tend to a high temperature and pressure. Excess volumes on the phase equilibria surface were given. The results are discussed in view of the phase equilibria of other water--n--alkane systems.

Critical properties of XY model dimensional layered magnetic on two- films

Using Monte Carlo simulations, we have investigated the classical XY model on triangular lattices of ultra-thin film structures with middle ferromagnetic layers sandwiched between two antiferromagnetic layers. The internal energy, the specifc heat, the chirality and the chiral susceptibility are calculated in order to clarify phase transitions and critical phenomena. Prom the finite-size scaling analyses, the values of critical exponents are determined. In a range of interaction parameters, we find that the chirality steeply goes up as temperature increases in a temperature range; correspondingly the value of a critical exponent for this change is estimated.

Observation of lateral long range order in superconducting FeTe thin films

We find that the superconductivity in the thin films of the formerly believed non-superconducting parent compound FeTe is accompanied by an emergence of second order with a correlation length of 742 nm and 258 nm at 10 K and 300 K, respectively. The structural phase transition found in iron pnictide superconductors, in non-superconducting FeTe bulk samples, and in FeSe superconducting thin films is not observed in the superconducting FeTe thin films. The interplay between superconductivity and long range order may suggest the crucial role of competition between electronic localization and itinerancy which leads to strong quantum fluctuations in the FeTe system.

Characterization of Phase Transition in Heisenberg Fluids from Density Functional Theory

The phase transition of Heisenberg fluid has been investigated with the density functional theory in mean-field approximation （MF）. The matrix of the second derivatives of the grand canonical potential Ω with respect to the particle density fluctuations and the magnetization fluctuations has been investigated and diagonalized. The smallest eigenvalue being 0 signalizes the phase instability and the related eigenvector characterizes this phase transition. We find a Curie line where the order parameter is pure magnetization and a spinodal where the order parameter is a mixture of particle density and magnetization. Along the spinodal, the character of phase instability changes continuously from predominant condensation to predominant ferromagnetic phase transition with the decrease of total density. The spinodal meets the Curie line at the critical endpoint with the reduced density p＊=pσ3=0.224 and the reduced temperature T＊ =kT/ε=1.87 （σ is the diameter of Heisenberg hard sphere and e is the coupling constant）.

Effects of the trimodal random field on the magnetic properties of a spin-1 Ising nanotube

In this work, the hysteresis behavior of a nanotube, consisting of a ferromagnetic core of spin-1 atoms surrounded by a ferromagnetic shell of spin-1 atoms with ferro-or anti-ferromagnetic interracial coupling is studied in the presence of a random magnetic field. Based on a probability distribution method, the effective-field theory has been used to investigate the effects of the random magnetic field, the interfacial coupling constant, and the temperature on the hysteresis loops of the nanotube. Some characteristic behaviors have been found, such as the existence of double or triple hysteresis loops for appropriate values of the system parameters. The remanent magnetization and the coercive field, as functions of the temperature, are examined.

Voltage-controlled Kosterlitz–Thouless transitions and various kinds of Kondo behaviors in a triple dot device

The transport property and phase transition for a parallel triple dot device are studied by adopting Wilson＇s numerical renormalization group technique, focusing on the effects of level spacings between neighboring dot sites. By keeping dot 2at the half-filled level and tuning the level differences, it is demonstrated that the system transits from local spin quadruplet to triplet and doublet sequently, and three kinds of Kondo peaks at the Fermi surface could be found, which are separated by two Kosterlitz–Thouless type quantum phase transitions and correspond to spin-3/2, spin-1, and spin-1/2 Kondo effect,respectively. To obtain a detailed understanding of these problems, the charge occupation, the spin–spin correlation, the transmission coefficient, and the temperature-dependent magnetic moment are shown, and necessary physical arguments are given.

Identifying the occurrence time of an impending mainshock:a very recent case

The procedure by means of which the occurrence time of an impending mainshock can be identified by analyzing in natural time the seismicity in the candidate area subsequent to the recording of a precursory seismic electric signals（SES） activity is reviewed. Here, we report the application of this procedure to an MW5.4 mainshock that occurred in Greece on 17 November 2014. This mainshock（which is pretty rare since it is the strongest in that area for more than half a century） was preceded by an SES activity recorded on 27 July 2014, and the results of the natural time analysis reveal that the system approached the critical point（mainshock occurrence） early in the morning on 15 November 2014.

Critical behaviors of a(2+1)-dimensional black hole with a nonlinear electrodynamics source

On the basis of a charged BTZ black hole,we add an extra term in the metric function to describe the contribution from nonlinear electrodynamics.In this way we artificially construct a(2+1)-dimensional black hole in general relativity coupled with a nonlinear electrodynamics source.The thermodynamic quantities and Smarr formula are derived.It is found that this black hole has T-S criticality like that of an RN-Ad S black hole.Further modifying the metric function,we obtain a(2+1)-dimensional black hole possessing P-V critical behaviors similar to that of van der Waals fluid.To our knowledge,this is the first example of(2+1)-dimensional black holes having this kind of critical behavior.

Critical Behaviors and Finite-Size Scaling of Principal Fluctuation Modes in Complex Systems

Complex systems consisting of N agents can be investigated from the aspect of principal fluctuation modes of agents. From the correlations between agents, an N × N correlation matrix C can be obtained. The principal fluctuation modes are defined by the eigenvectors of C. Near the critical point of a complex system, we anticipate that the principal fluctuation modes have the critical behaviors similar to that of the susceptibity. With the Ising model on a two-dimensional square lattice as an example, the critical behaviors of principal fluctuation modes have been studied. The eigenvalues of the first 9 principal fluctuation modes have been invesitigated. Our Monte Carlo data demonstrate that these eigenvalues of the system with size L and the reduced temperature t follow a finite-size scaling form λn(L, t) = Lγ/νf n(t L^(1/ν)), where γ is critical exponent of susceptibility and ν is the critical exponent of the correlation length. Using eigenvalues λ1, λ2 and λ6, we get the finite-size scaling form of the second moment correlation length ξ(L, t) = Lξ(tL^(1/ν)).It is shown that the second moment correlation length in the two-dimensional square lattice is anisotropic.

Reaction mechanism,insensitivity and mechanical property of PTFE-Mg-W composites with magnesium particles surface modification

This paper aims at enhancing impact insensitivity of polytetrafluoroethylene(PTFE)-Mg-W without sacrificing bulk of energy released in the reaction and optimizing mechanical properties of PTFE-Mg-W by magnesium surface treatment.The reaction energy results indicate that the reaction energy of PTFE-Mg-W(modified 1 min)in oxygen decreases slightly to 7905 J·g^(-1)compared with that of PTFE-Mg-W(unmodified)which is8533 J·g^(-1).Under impact condition(impact velocity between 16.232 and 17.726 m·s^(-1)),compared with PTFEMg-W(unmodified),the initiation time before ignition of PTFE-Mg-W(modified 1 min)delays 50μs;the absorbed energy needed for ignition of PTFE-Mg-W(modified1 min)increases by 67.9%.This increase in impact insensitivity of PTFE-Mg-W can be contributed to the formation of passivated layers of magnesium particles after modification which effectively weakens the total interface area among reactive components and partly contributes to the loss of released energy of PTFE-Mg-W after magnesium modification.The quasi-static and dynamic compression results show that PTFE-Mg-W(modified 1 min)possess the highest strength and the best ductility.

Ronald Egan's Research on the History of the Northern Song Ci Poetry from a GenderPerspective

Ronald C.Egan,a renowned American sinologist,is best known for his accurate English translations,exquisite readings,and innovative perspectives on the aesthetic ideas and pursuits of ci poets such as Ouyang Xiu,Su Shi,and Li Qingzhao,as well as the scholarofficial group of the Northern Song dynasty.However,through his longitudinal study of specific ci poets,he also shows a unique understanding of the development and evolution of ci lyric poetry in the Northern Song.An integrated analysis of Egan's scattered articles on Northern Song ci poetry indicates that gender is key to his understanding of the evolution of ci in the Northern Song.On this basis,Egan has conducted in-depth research on three aspects:the gender perspective of the lyrical protagonists described by ci poets;changes in the form,content,and patterns of writing ci poetry;and new phenomena in ci criticism.His research further enriches the details of the evolution of Northern Song ci poetry and expands its historical research horizon.

Eigen microstates and their evolutions in complex systems

Emergence refers to the existence or formation of collective behaviors in complex systems.Here,we develop a theoretical framework based on the eigen microstate theory to analyze the emerging phenomena and dynamic evolution of complex system.In this framework,the statistical ensemble composed of M microstates of a complex system with N agents is defined by the normalized N×M matrix A,whose columns represent microstates and order of row is consist with the time.The ensemble matrix A can be decomposed as■,where r=min(N,M),eigenvalueσIbehaves as the probability amplitude of the eigen microstate U_I so that■and U_I evolves following V_I.In a disorder complex system,there is no dominant eigenvalue and eigen microstate.When a probability amplitudeσIbecomes finite in the thermodynamic limit,there is a condensation of the eigen microstate UIin analogy to the Bose–Einstein condensation of Bose gases.This indicates the emergence of U_I and a phase transition in complex system.Our framework has been applied successfully to equilibrium threedimensional Ising model,climate system and stock markets.We anticipate that our eigen microstate method can be used to study non-equilibrium complex systems with unknown orderparameters,such as phase transitions of collective motion and tipping points in climate systems and ecosystems.

Mechanical, vibrational, and amorphous systems dynamical properties of near jamming

Amorphous systems undergo the jamming transition when the density increases, temperature drops, or external shear stress decreases, as described by the jamming phase diagram which was proposed to unify different processes such as the glass transition, random close packing, and yielding under shear stress. At zero temperature and shear stress, the jamming transition occurs at a critical density at Point J. In this paper, we review recent studies of the material properties of marginally jammed solids and the glassy dynamics in the vicinity of Point J. As the only singular point in the jamming phase diagram, Point J exhibits special criticality in both mechanical and vibrational quantities. Dynamics approaching the glass transition in the vicinity of Point J show critical scalings, suggesting that the molecular glass transition and the colloidal glass transition are equivalent in the hard sphere limit. All these studies shed light on the long-standing puzzles of the glass transition arid unusual properties of amorphous solids.

Research trends in electron-doped cuprate superconductors

In this review, we look back on some intriguing and puzzling issues in electron-doped cuprate superconductors, such as electron-hole asymmetry, two types of carriers, quantum critical points, order-parameter symmetry, etc. The necessity of study on this family is invoked in comparison with the hole-doped counterparts from several aspects. The related progress, especially in last few years, has been outlined point to point, as well as other hot topics like the discovery of ambipolar superconductors, the applications in superconducting electronics, and the emergency of superconductivity in parent compounds. In perspective, the utilization of blooming advanced techniques, electric double layer transistor and combinatorial film deposition, will bring some new insights into the mechanism such as electron-doped cuprate superconductors.

The Damage Spreading Method in Monte Carlo Simulations:A Brief Overview and Applications to Confined Magnetic Materials

The Damage Spreading(DS)method allows the investigation of the effect caused by tiny perturbations,in the initial conditions of physical systems,on their final stationary or equilibrium states.The damage(D(t))is determined during the dynamic evolution of a physical system and measures the time dependence of the difference between a reference(unperturbed)configuration and an initially perturbed one.In this paper we first give a brief overview of Monte Carlo simulation results obtained by applying the DS method.Different model systems under study often exhibit a transition between a state where the damage becomes healed(the frozen phase)and a regime where the damage spreads arriving at a finite(stationary)value(the damaged phase),when a control parameter is finely tuned.These kinds of transitions are actually true irreversible phase transitions themselves,and the issue of their universality class is also discussed.Subsequently,the attention is focused on the propagation of damage in magnetic systems placed in confined geometries.The influence of interfaces between magnetic domains of different orientation on the spreading of the perturbation is also discussed,showing that the presence of interfaces enhances the propagation of the damage.Furthermore,the critical transition between propagation and nonpropagation of the damage is discussed.In all cases,the determined critical exponents suggest that the DS transition does not belong to the universality class of Directed Percolation,unlike many other systems exhibiting irreversible phase transitions.This result reflects the dramatic influence of interfaces on the propagation of perturbations in magnetic systems.

Metastability in the Spin-1 Blume–Emery–Griffiths Model within Constant Coupling Approximation

In this paper, the equilibrium properties of spin-1 Blume–Emery–Griffiths model are studied by using constant-coupling approximation. The dipolar and quadrupolar order parameters, the stable, metastable and unstable states and free energy of the model are investigated. The states are defined in terms of local minima of the free energy of system. The numerical calculations are presented for several values of exchange interactions on the simple cubic lattice with q = 6.