Kind Of Phase Transition Research Articles

Bulk-boundary thermodynamic equivalence: a topology viewpoint

Setting the cosmological constant to be dynamical, we study the bulk and boundary thermodynamics of charged Anti-de Sitter black holes. We develop mass/energy formulas in terms of thermodynamic state functions for the extended thermodynamics, mixed thermodynamics, and boundary conformal field theory thermodynamics. We employ the residue method to study the topological properties of the phase transitions. Our analysis reveals that the bulk and boundary thermodynamics are topologically equivalent for both criticalities and first-order phase transitions in the canonical ensembles, as well as for the Hawking-Page(-like) phase transitions in the grand canonical ensembles. Additionally, those three kinds of phase transitions are shown to be distinguished by their unique topological charges. Our results exemplify the gravity-gauge duality in terms of topology.

Cryptocurrencies Are Becoming Part of the World Global Financial Market

In this study the cross-correlations between the cryptocurrency market represented by the two most liquid and highest-capitalized cryptocurrencies: bitcoin and ethereum, on the one side, and the instruments representing the traditional financial markets: stock indices, Forex, commodities, on the other side, are measured in the period: January 2020-October 2022. Our purpose is to address the question whether the cryptocurrency market still preserves its autonomy with respect to the traditional financial markets or it has already aligned with them in expense of its independence. We are motivated by the fact that some previous related studies gave mixed results. By calculating the q-dependent detrended cross-correlation coefficient based on the high frequency 10 s data in the rolling window, the dependence on various time scales, different fluctuation magnitudes, and different market periods are examined. There is a strong indication that the dynamics of the bitcoin and ethereum price changes since the March 2020 COVID-19 panic is no longer independent. Instead, it is related to the dynamics of the traditional financial markets, which is especially evident now in 2022, when the bitcoin and ethereum coupling to the US tech stocks is observed during the market bear phase. It is also worth emphasizing that the cryptocurrencies have begun to react to the economic data such as the Consumer Price Index readings in a similar way as traditional instruments. Such a spontaneous coupling of the so far independent degrees of freedom can be interpreted as a kind of phase transition that resembles the collective phenomena typical for the complex systems. Our results indicate that the cryptocurrencies cannot be considered as a safe haven for the financial investments.

100th Anniversary of Brillouin Scattering: Impact on Materials Science.

L. Brillouin predicted inelastic light scattering by thermally excited sound waves in 1922. Brillouin scattering is a non-contact and non-destructive method to measure sound velocity and attenuation. It is possible to investigate the elastic properties of gases, liquids, glasses, and crystals. Various kinds of phase transitions, i.e., liquid–glass transitions, crystallization, polymorphism, and denaturation have been studied by changing the temperature, pressure, time, and external fields such as the electric, magnetic, and stress fields. Nowadays, Brillouin scattering is extensively used to measure various elementary excitations and quasi-elastic scattering in the gigahertz range between 0.1 and 1000 GHz. A brief history, spectroscopic methods, and Brillouin scattering studies in materials science on ferroelectric materials, glasses, and proteins are reviewed.

Quantum Fisher information at finite temperatures and the critical properties in Ising-Heisenberg diamond chain

In this work we evaluate quantum Fisher information (QFI) of a two-qubit reduced state in the Ising-XXZ diamond structure at finite temperatures, which is applied to demonstrate quantum criticality and quantum phase transition in this model. Here we adopt the average QFI with respect to the local orthonormal observable bases [Phys. Rev. A. 88, 014,301 (2013)]. The results show that QFI around quantum critical points decreases or increases steeper when the system temperature is relatively lower. Meanwhile the singularity of QFI’ first-derivatives is becoming more and more obvious as the temperature is approaching zero. By the finite-temperature QFI and its scaling relation with temperature, quantum phase transitions can be well detected from the entangled state in ferrimagnetic phase to an unentangled state in ferrimagnetic phase or to an unentangled state in ferromagnetic phase. Moreover it is further found that the two kinds of phase transitions can be distinguished by the different scaling behaviors. It has been proved that QFI has enough capability to characterize quantum phase transition at finite temperature.

Revisiting the phase transitions of the Dicke model

The Dicke model exhibits a variety of phase transitions. The quantum phase transition from the normal phase to the super-radiant phase is marked by a dramatic change in the scaling of the participation ratio. We find that the ground state in the super-radiant phase exhibits multifractality manifest in the participation ratio scaling as the square root of the full Hilbert space dimension. The thermal phase transition temperature, for which we obtain an exact analytical expression, is strikingly captured by the mutual information between two spins. In the excited state quantum phase transition within the super-radiant phase, we discover a new upper cut-off energy; the central energy band between the lower and upper cut-off energies shows distinctly different behaviour. This finding is corroborated with the aid of several eigenvector properties: von Neumann entanglement entropy between spins and bosons, the mean photon number, concurrence between two spins, and participation ratio. Thus we obtain a unified picture for the three different kinds of phase transitions.

Hypothesis of Cyclic Structures of Pre- and Consciousness as a Transition in Neuron-like Graphs to a Special Type of Symmetry

We study the proposed statistical kinetic model for describing the pre- and consciousness structures based on the cognitive neural networks. The method of statistics of the growth graph systems and a possible transition to symmetric structures (a kind of phase transition) is applied. With the complication of a random Erdőos-Rényi (ER) graph during the percolation transition from the tree structure to the large cluster structures is obtained. In the evolutionary model two classes of algorithms have been developed. The differences between the cycle parameters in the obtained neural network models can reach thousands or more times. This is due to the tree-like architecture of the neural graph, which mimics the columnar structures of the neocortex. These cluster and cyclic structures can be interpreted as the primary elements of consciousness and as a necessary condition for the effect of consciousness itself. The comparison with other known theoretical mainly statistical models of consciousness is discussed. The presented results are promising in neurocomputer interfaces, man-machine systems and artificial intelligence systems.

Polymorphic transition to metastable phases in hollow structured silicon anode in a Li-ions battery

In contrast to previous findings, a high-temperature phase Li4.1Si, rather than the commercial phase Li15Si4, was observed in the hollow-structured silicon anode of a Li-ions battery after lithiation. The formation of Li4.1Si, as well as other lithium silicides, could be ascribed by the polymorphic transition theory that promoted the formation of a metastable phase. The phase transition began with a nucleus composed of a specific octahedral, which led to the final phases containing similar short-range ordering. Due to the formation of the Li4.1Si, the hollow-structured silicon anode had an ultra-high capacity that remained at 2500 mAh/g after 250 cycles. This kind of phase transition may occur not only in hollow-structured silicon nanoparticles but also in other particles with specific morphologies if the requirements for polymorphic transition are satisfied.

Electron localization induced by intrinsic anion disorder in a transition metal oxynitride

Anderson localization derived from randomness plays a crucial role in various kinds of phase transitions. Although treated as a free variable parameter in theory, randomness in electronic materials is hard to control experimentally owing to the coexisting Coulomb interaction. Here we demonstrate that the intrinsic anion disorder in a mixed-anion system of SrNbO2N induces a significant random potential that overwhelms the Coulomb potential while maintaining the lattice structure. A metal-to-insulator transition is triggered by a chemical modulation of the electron density where the critical electron density is more than three orders of magnitude greater than that predicted by the well-known Mott criterion. The localized electrons show characteristic electrical properties such as temperature-dependent multiple crossovers of conduction mechanisms and a positive magnetoresistance above 50% at low temperature. The large magnetoresistance is attributed to wave-function shrinkage of the localized states and clearly visualizes the anisotropy in the band structure, which indicates a compatibility of the periodicity and randomness.

Recent progresses on QCD phases in a strong magnetic field: views from Nambu–Jona-Lasinio model

In this review, we summarize recent progress on the possible phases of quantum chromodynamics (QCD) in the presence of a strong magnetic field, mainly from the views of the chiral effective Nambu--Jona-Lasinio model. Four kinds of phase transitions are explored in detail: chiral symmetry breaking and restoration, neutral pseudoscalar superfluidity, charged pion superfluidity and charged rho superconductivity. In particular, we revisit the unsolved problems of inverse magnetic catalysis effect and competition between the chiral density wave and solitonic modulation phases. It is shown that useful results can be obtained by adopting self-consistent schemes.

Edge-state influence on high-order harmonic generation in topological nanoribbons

The high-order harmonic generation in finite topological nanoribbons is investigated using a tight-binding approximation. The narrow, two-dimensional ribbons consist of hexagonal structures. A topological phase transition is defined by a sudden change of the topological invariant. In the bulk, this kind of phase transition might occur if an existing band gap closes and reopens again. Through the bulk-boundary correspondence, this is related to the emergence of topologically protected edge states in the respective finite systems. For the finite ribbons studied in this work, the variation of the tight-binding parameters leads to the emergence of two edge states after the closing of the band gap. The energies of those edge states as functions of the tight-binding parameters display crossings and avoided crossings, which influence the high-harmonic spectra.Graphic

Influence of distinct kinds of temporal disorder in discontinuous phase transitions.

Based on mean-field theory (MFT) arguments, a general description for discontinuous phase transitions in the presence of temporal disorder is considered. Our analysis extends the recent findings [C. E. Fiore etal., Phys. Rev. E 98, 032129 (2018)2470-004510.1103/PhysRevE.98.032129] by considering discontinuous phase transitions beyond those with a single absorbing state. The theory is exemplified in one of the simplest (nonequilibrium) order-disorder (discontinuous) phase transitions with "up-down" Z_{2} symmetry: the inertial majority vote model for two kinds of temporal disorder. As for absorbing phase transitions, the temporal disorder does not suppress the occurrence of discontinuous phase transitions, but remarkable differences emerge when compared with the pure (disorderless) case. A comparison between the distinct kinds of temporal disorder is also performed beyond the MFT for random-regular complex topologies. Our work paves the way for the study of a generic discontinuous phase transition under the influence of an arbitrary kind of temporal disorder.

Trimodal-random field Blume-Capel model

The external random magnetic field [Formula: see text] with three nodes, i.e. acting up and down along the [Formula: see text]-axis and zero, effective on the spins in the Blume-Capel model is analyzed on the Bethe lattice in terms of the exact recursion relations. All the nodes are assumed to have the same probability, [Formula: see text], so that the model could give various kinds of phase transitions. As a mapping of the phase transitions, the phase diagrams are constructed on two different planes which present very rich and interesting phase diagrams. In addition to the second- and first-order phase transitions, a few critical points, reentrant and double reentrant behaviors are also observed.

A REVIEW OF THE METHODS OF ECONOMIC AND MATHEMATICAL MODELING BASED ON THE PRINCIPLES OF ECONOPHYSICS. PART 2

A review of theoretical and applied results obtained in the framework of the scientific direction in econophysics at the Department of information systems and mathematical methods in economics is given. The first part gives the concept of a financial bubble and methods for finding them. At the beginning of the article, the development of econophysics is given. Therefore, using the research of physicists as a model, econophysics should begin its research not from the upper floors of an economic building (in the form of financial markets, distribution of returns on financial assets, etc.), but from its fundamental foundations or, in the words of physicists, from elementary economic objects and forms of their movement (labor, its productivity, etc.). Only in this way can econophysics find its subject of study and become a "new form of economic theory". Further, the main prerequisites of financial bubble models in the market are considered: the principle of the absence of arbitrage opportunities, the existence of rational agents, a risk-driven model, and a price-driven model. A well-known nonlinear LPPL model (log periodic power law model) was proposed. In the works of V.O. Arbuzov, it was proposed to use procedures for selecting models. Namely, basic selection, "stationarity" filtering, and spectral analysis were introduced. The results of the model were presented in the works of D. Sornette and his students. The second part gives the concept of percolation and its application in Economics. We will consider a mathematical model proposed by J.P. Bouchaud, D. Stauffer, and D. Sornette that recreates the behavior of an agent in the market and their interaction, geometrically describing a phase transition of the second kind. In this model, the price of an asset in a single time interval changes in proportion to the difference between supply and demand in this market. The results are published in the works of A.A. Byachkova, B.I. Myznikova and A.A. Simonov. There are two types of phase transition: the first and second kind. During the phase transition of the first kind, the most important, primary extensive parameters change abruptly: the specific volume, the amount of stored internal energy, the concentration of components, and other indicators. It should be noted that this refers to an abrupt change in these values with changes in temperature, pressure, and not a sudden change in time. The most common examples of phase transitions of the first kind are: melting and crystallization, evaporation and condensation. During the second kind of phase transition, the density and internal energy do not change. The jump is experienced by their temperature and pressure derivatives: heat capacity, coefficient of thermal expansion, or various susceptibilities. Phase transitions of the second kind occur when the symmetry of the structure of a substance changes: it can completely disappear or decrease. For quantitative characterization of symmetry in a second-order phase transition, an order parameter is introduced that runs through non-zero values in a phase with greater symmetry, and is identically equal to zero in an unordered phase. Thus, we can consider percolation as a phase transition of the second kind, by analogy with the transition of paramagnets to the state of ferromagnets. The percolation threshold or critical concentration separates two phases of the percolation grid: in one phase there are finite clusters, in the other phase there is one infinite cluster. The key situation to study is the moment of formation of an infinite cluster on the percolation grid, since this means the collapse of the market, when the overwhelming part of agents for this market has a similar opinion about their actions to buy or sell an asset. The main characteristics of the process are the threshold probability of market collapse, as well as the empirical distribution function of price changes in this market. Keywords: econophysics, behavior of agents in the market, market crash, second-order phase transition, percolation theory, model calibration, agent model calibration, percolation gratings, gradient percolation model, percolation threshold, clusters, fractal dimensions, phase transitions of the first and second kind.

Tuning magnetic properties based on FeCoNiSi0.4Al0.4 with dual-phase nano-crystal and nano-amorphous microstructure

The idea of adjusting the crystallinity of powders via controlling the phase composition of milling precursor (ribbons) has been used to prepare FeCoNiSi0.4Al0.4 high entropy alloy powders (HEAPs) with dual-phase nano-crystal (NC) and nano-amorphous (NA) microstructure. The crystallinity of HEAPs are related to the FCC phase proportion of milling precursor: within 60%, positive correlation; beyond 60%, negative correlation. Different phase structure for ribbons can be obtained by taking advantage of the difference in phase stability, as an extension of annealing time induces the increment of FCC phase content. The introduction of nano-scale phase separation in HEA ribbons provides a prerequisite. Multiphase NCs distribute randomly in matrix, while NCs with FCC phase are aggregated into about 50 nm regions embedded in matrix. Three kinds of phase transition are co-existed during the dry-milling process, generating the coexistence of NCs and NAs. Due to the unique microstructure, in especial NCs doped by NAs, and the skillful preparation technology, a small Hc, varying from 12.97 Oe (C0) to 28.33 Oe (C50), and a large complex permeability (μ′), varying from 2.60 (C0) to 2.30 (C50), can be obtained.

Tricritical point and solid/liquid/gas phase transition of higher dimensional AdS black hole in massive gravity

By considering the fifth order graviton term in massive gravity theory, we study the P–V critical behaviors of AdS black hole in d≥7 dimensional space–time, and find the solid/liquid/gas phase transition with the “common” tricritical point, which does not exist in absence of higher graviton terms. Moreover, we also find the number of positive real roots of critical radius equation plays a key role in classifying different kinds of phase transitions. If there is only one positive root of equation, the first order Van der Waals-like phase transition emerges. For two roots, the system could experience a zero-order reentrant phase transition. Notably, for three roots, the solid/liquid/gas phase transition can occur. In addition, because the critical radius equation is a (n−2)-order polynomial equation associated with the graviton terms, the critical phenomena of black holes in extended phase space depend crucially on the number n of the graviton terms in high dimensional massive gravity.

Equation of state, ionic structure, and phase diagram of warm dense krypton

Extensive quantum molecular dynamics (QMD) simulations are performed to determine the equation of state, sound velocity, and phase diagram of middle-Z krypton in a warm dense regime where the pressure (P) is up to 300GPa and the temperature is up to 60 kK. The shock wave experimental data are used to validate the present theoretical models. It is found that, within the regime of the current density (ρ) and temperature (T), sound velocity can effectively discriminate differences between different theoretical models, and therefore it is more suitable as a benchmark to verify the practicability of models. The QMD-simulated results of the ionic structures and electronic properties imply the occurrence of two kinds of phase transitions, including transition from a solidlike to fluid state and that from an insulator to conductive fluid in this T-P regime. The calculated electrical conductivities confirm that the metallization transition occurs at about 60GPa and 17.5 kK along the principal Hugoniot. With the help of simulation results and experimental data, a comprehensive phase diagram for krypton is constructed by using the solid-fluid and insulator-metal fluid phase boundaries, which fills the gap of the experimental work [Proc. Natl. Acad. Sci. USA 112, 7925 (2015)PNASA60027-842410.1073/pnas.1421801112]. These results will provide an instructive basis for the experimental investigations of rare gases over a wide T-P range.

Topological bound modes in anti-PT-symmetric optical waveguide arrays.

We investigate the topological bound modes in a binary optical waveguide array with anti-parity-time (PT) symmetry. The anti-PT-symmetric arrays are realized by incorporating additional waveguides to the bare arrays, such that the effective coupling coefficients are imaginary. The systems experience two kinds of phase transition, including global topological order transition and quantum phase transition. As a result, the system supports two kinds of robust bound modes, which are protected by the global topological order and the quantum phase, respectively. The study provides a promising approach to realizing robust light transport by utilizing mediating components.

Cooperation percolation in spatial evolutionary games

It has been known that the formation of cooperator clusters plays an important role in spatial evolutionary games. By gathering together, cooperators assist each other and the benefits of mutual cooperation can outweigh the losses against the defector. In this letter, we study the dynamical organization of cooperator clusters in the spatial Stag Hunt game, the Prisoner's Dilemma game and the Snowdrift game. For the above games in square lattices, there exists a continuous phase transition characterized by the emergence of a large spanning cooperator cluster which occurs when the initial fraction of the cooperators exceeds a certain threshold. For games in random graphs, there exist two different kinds of phase transitions. At the first the normalized size of the giant cooperator cluster increases continuously from zero, and at the second the normalized size of the giant cooperator cluster jumps from a low value to a very high value.

Construction of a thermal conductivity measurement system for small single crystals of organic conductors

We newly constructed a thermal conductivity measurement system for single crystals of molecular compounds. This system enables us to measure the thermal conductivity of samples with the length of less than 1.0 mm. In order to evaluate the capability of detection of phase transitions occurred in molecule-based materials, we performed the thermal conductivity measurement of single crystals of organic conductors α-(BEDT-TTF)2I3 and κ-(BEDT-TTF)2Cu[N(CN)2]Br, where BEDT-TTF denotes bis(ethylenedithio)tetrathiafulvalene. From the temperature dependence of the thermal conductivity of α-(BEDT-TTF)2I3, we succeeded in observing the metal–insulator transition as a sudden drop of κ(T) at 135 K. In the temperature dependence of thermal conductivity of κ-(BEDT-TTF)2Cu[N(CN)2]Br, we could observe the increment of κ(T) at the metal-superconducting transition (Tc = 11.4 K). These results show that the newly developed system has high performance enough to detect various kinds of phase transitions in small crystals of molecular compounds.

Investigation of the crystal structure, magnetic phase transition and magnetocaloric effect in RE5Ni2In4 (RE = Dy, Ho and Er) compounds

The structure, magnetic phase transition and magnetocaloric properties of ternary intermetallic RE5Ni2In4 (RE = Dy, Ho and Er) compounds are investigated. The results of XRD and Rietveld refinement confirm that all the samples crystallized in the orthorhombic Lu5Ni2In4-type structure belonging to the space group of Pbam. The RE5Ni2In4 compounds show various magnetic phase transition behaviors, i.e. a ferromagnetic to paramagnetic (FM-PM) phase transition at TC = 105 K together with an antiferromagnetic to ferromagnetic (AFM-FM) at low temperature TN = 20 K for the Dy5Ni2In4, the Ho5Ni2In4 reveals two different kinds of phase transitions at TN = 31 K and TC = 19 K which are corresponding to the second order PM-AFM and the first order AFM-FM phase transitions, and a PM-FM phase transition exists in the Er5Ni2In4 at TC = 21 K. In addition, a large hysteresis loop with particular shape and a high coercive field (HC = 4 T) are observed at 3 K for the Dy5Ni2In4 compound. The corresponding isothermal magnetization curves change into the state of reversibility when the temperature is 60 K, and the coercivity is reduced to zero. The maximum values of −ΔSMmax are determined to be 4.7, 10.1 and 10.2 J/kg K around TC for the RE5Ni2In4 (RE = Dy, Ho and Er) compounds in a field of 7 T, respectively.