Entanglement Entropy Signature of Quantum Phase Transitions in a Multiple Spin Interactions Model

Through the Jordan-Wigner transformation, the entanglement entropy and ground state phase diagrams of exactly solvable spin model with alternating and multiple spin exchange interactions are investigated by means of Green's function theory. In the absence of four-spin interactions, the ground state presents plentiful quantum phases due to the multiple spin interactions and magnetic fields. It is shown that the two-site entanglement entropy is a good indicator of quantum phase transition (QPT). In addition, the alternating interactions can destroy the magnetization plateau and wash out the spin-gap of low-lying excitations. However, in the presence of four-spin interactions, apart from the second order QPTs, the system manifests the first order QPT at the tricritical point and an additional new phase called ``spin waves', which is due to the collapse of the continuous tower-like low-lying excitations modulated by the four-spin interactions for large three-spin couplings.     

QCD手征相变中的π介子增强(英文)

讨论了在LHC的Pb-Pb碰撞过程中,如果QGP SU(2)手征相变出现二级相变,那么系统将会有π弦产生,并且π弦最终将衰变为π介子。于是以上效应将导致在低动量区域（p~150—400 MeV）内的π介子增强。对应于不同的冷却温度T_f=130,120,110 MeV,产生于π弦衰变的π介子的数量分别是Nt≈270,150, 60. It is pointed out that if the QGP SU(2) chiral phase transition in the LHC Pb Pb collision process is taken place and the phase transition is in the second order, then pion strings will be formed, and decay. These phenomena lead to the pion enhancement in the low momentum region(p150—400 MeV) and the number of pions produced from pion string decay can be estimated about Nt≈270, 150, 60 for different freeze temperature Tf=130, 120, 110 MeV respectively.     

Phase Transitions for Uniformly Expanding Maps

Given a uniformly expanding map of two intervals we describe a large class of potentials admitting unique equilibrium measures. This class includes all Hölder continuous potentials but goes far beyond them. We also construct a family of continuous but not Hölder continuous potentials for which we observe phase transitions. This provides a version of the example in (9) for uniformly expanding maps.     

Quantum Phase Transitions and Dimerized Phases in Frustrated Spin Ladder

In this paper, we study the phase diagram of a frustrated spin ladder model by applying the bosonization technique and the density-matrix renormalization-group (DMRG) algorithm. Effect of the intra-chain next-nearest-neighbor (NNN) super-exchange interaction is investigated in detail and the order parameters are calculated to detect the emergence of the dimerized phases. We find that the intra-chain NNN interaction plays a key role in inducing dimerized phases.     

Local Field Corrections Effect on Equation of State in Dense Hydrogen Plasma: Plasma Phase Transition

We present calculations of Hydrogen plasma pressure including local field correction (LFC) effects modelled in the Singwi Tosi Land and Sjölander model extended to arbitrary temperature (ATSTLS), neutrals contributions are not included. We show that LFC induces thermodynamic instabilities (phase transition) in the vicinity of the maximum electron coupling parameter which corresponds to maximum departure of the ATSTLS electron polarizability from the Random Phase Approximation one. Comparison of our results to Monte‐Carlo calculations induced us to think that free electron coupling plays a dominant role in plasma phase transition. Critical temperature is estimated and compared to existing values (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

酯类铁电液晶的相变和构型研究(英文)

：本文对酯类铁电液晶的相变和构型进行了研究和评述。它包括固相 近晶Ｃ,近晶Ｃ 近晶Ａ相变的性质,一级、二级相变的判据,固相 近晶Ｃ相变的临界弛豫,顺式、反式的构型转变和新相分析。     

Peculiar Quantum Phase Transitions and Hidden Supersymmetry in a Lipkin-Meshkov-Glick Model

In this paper we theoretically report an unconventional quantum phase transition of a simple Lipkin- Meshkow-Glick model： an interacting collective spin system without external magnetic field. It is shown that this model with integer-spin can exhibit a flrst-order quantum phase transition between different disordered phases, and more intriguingly, possesses a hidden supersymmetry at the critical point. However, for half-integer spin we predict another flrst-order quantum phase transition between two different long-range-ordered phases with a vanishing energy gap, which is induced by the destructive topological quantum interference between the intanton and anti-instanton tunneling paths and accompanies spontaneously breaking of supersymmetry at the same critical point. We also show that, when the total spin-value varies from half-integer to integer this model can exhibit an abrupt variation of Berry phase from π to zero.     

SD对壳模型下原子核形状相变（英文）

在SD 对壳模型的理论框架下讨论了原子核形状相变模式。研究结果表明,该理论模型可以把相互作用玻色子模型中U（5）-SU（3）以及U（5）-SO（6） 形状相变模式再现出来,相互作用玻色子模型中有关临界点对称性的特征也可以很好地描述。本文同时也发现原子核从振动到转动的形状相变可以通过改变相互作用强度来实现。The nuclear shape phase transitional patterns were studied in the SD-pair shell model. The results show that the transitional patterns similar to the U(5)-SU(3) and U(5)-SO(6) transitions in the interacting boson model can be produced. The signatures of the critical point symmetry in the interacting boson model are also produced approximately. It is also found that the shape phase transitional pattern between vibration and rotation can also be produced by changing the interactional strength.     

Phase Transitions in Nonideal Alkali- and Noble Gas Plasmas

In this paper the plasma composition of Cs- and Xe-plasmas was determined for temperatures between 3000 K (Cs) or 8000 K (Xe) and 25000 K and for free charge carrier densities between 10²³ m^?3 and 5. 10²⁸ m^?3. Besides the Coulomb forces we took into account also short range forces between the charged particles and between the atoms. Effects of degeneration were neglected. The thermodynamic stability is discussed, and the influence of the different interaction contributions between the particles on the border of the instability region is considered. Especially the Mott transition is dealt with.     

Composition and Thermodynamic Properties of Dense Alkali Metal Plasmas

In this work composition and thermodynamic properties of dense alkali metal plasmas (Li, Na) were investigated. Composition was derived by solving the Saha equations with corrections due to nonideality. The lowering of the ionization potentials was calculated on the basis of pseudopotentials by taking screening and quantum effects into account (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Phase Transitions in a Mixture of Hard-Sphere Dipoles and Neutral Hard Spheres

Using the reference hypernetted chain （RHNC） integral equation theory and a rigorous stability analysis method, we investigate the phase behavior of a mixture of hard-sphere dipoles and neutral hard spheres based on the correlations of the homogeneous isotropic phase. Lowering the temperature down to the points where the RHNC equations fail to have a solution, several ttuctuations strongly increase. At low densities our results indicate the onset of ／ chain formation, which is similar with the pure DHS system. At high densities, the results indicate the appearance of isotropic-to-ferroelectric transitions （small neutral hard spheres concentrations） and demixing transitions （large neutral hard spheres concentrations）.     

Phase Transitions Induced by Top-Priority of Randomization

We study the characteristics of phase transition to take the top-priority of randomization in the rules of NaSch model (i.e.noise-first model) into account via computing the relaxation time and the order parameter.The scaling exponents of the relaxation time and the scaling relation of order parameter,respectively,axe obtained.     

Equilibrium Phase Transitions in Coupled Map Lattices: A Pedestrian Approach

A class of piecewise linear coupled map lattices with simple symbolic dynamics is constructed. It can be solved analytically in terms of the statistical mechanics of spin lattices. The corresponding Hamiltonian is written down explicitly in terms of the parameters of the map. The approach follows the line of recent mathematical investigations. But the presentation is kept elementary so that phase transitions in the dynamical model can be studied in detail. Although the method works only for map lattices with repelling invariant sets some of the conclusions, i.e., the role of local curvature of the single site map and properties of the nearest neighbour coupling might play an important role for phase transitions in general dynamical systems.     

Phase Transitions for the Growth Rate of Linear Stochastic Evolutions

We consider a discrete-time stochastic growth model on d-dimensional lattice. The growth model describes various interesting examples such as oriented site/bond percolation, directed polymers in random environment, time discretizations of binary contact path process and the voter model. We study the phase transition for the growth rate of the “total number of particles” in this framework. The main results are roughly as follows: If d≥3 and the system is “not too random”, then, with positive probability, the growth rate of the total number of particles is of the same order as its expectation. If on the other hand, d=1,2, or the system is “random enough”, then the growth rate is slower than its expectation. We also discuss the above phase transition for the dual processes and its connection to the structure of invariant measures for the model with proper normalization. Supported in part by JSPS Grant-in-Aid for Scientific Research, Kiban (C) 17540112.     

Phase Transitions in a Mixture of Hard-Sphere Dipoles and Neutral Hard Spheres

Using the reference hypernetted chain (RHNC) integral equation theory and a rigorous stability analysis method, we investigate the phase behavior of a mixture of hard-sphere dipoles and neutral hard spheres based on the correlations of the homogeneous isotropic phase. Lowering the temperature down to the points where the RHNC equations fail to have a solution, several fluctuations strongly increase. At low densities our results indicate the onset of chain formation, which is similar with the pure DHS system. At highdensities, the results indicate the appearance of isotropic-to-ferroelectric transitions (small neutral hard spheres concentrations) and demixing transitions (large neutral hard spheres concentrations).     

Quantum Phase Transitions in Anisotropic Spin Ladders with Antiferromagnetic Rungs

We apply perturbation theory to study quantum phase transitions in anisotropic two-leg spin ladders with antiferromagnetic rungs in the strong interchain coupling limit. The energy gap is expanded up to the fourth order in the ratio of the intrachain to interchain couplings. The transition point is determined by examing the disappearance of the energy gap. Present results for the anisotropic ferromagnetic-leg spin ladder are consistent qualitatively with the nonlinear σ-model analysis and in good agreement with the numerical results by the diagonalization method.     

Dynamic Opalescence upon Phase Transitions and in Inhomogeneous Systems

The temperature isofrequency dependences of Raman intensities are studied in a number of crystals (lithium tantalate, barium sodium niobate, barium titanate, and quartz) in the low-frequency range near the structural phase-transition points. In the case of ferroelectrics, poly- and single-domain single crystals are studied with a stationary electric field applied to the sample. A drastic increase in the intensity of the quasielastic (low-frequency) light scattering is found when approaching the phase-transition point. The studies are carried out for the 90° scattering geometry as well as at angles close to 180° (backscattering geometry). The anomalies of the quasielastic light scattering near the points of phase transition are observed in the latter case. The position of the maximum intensity of the isofrequency dependence on the temperature scale is found to be dependent on the frequency value = ₀ – (₀ and are the frequency of exciting radiation and the frequency to which the monochromator is tuned, respectively). A theory explaining satisfactorily the observed effect of dynamic opalescence near the phase-transition points in crystals is developed. The specific features of light scattering in an inhomogeneous medium as well as the dynamic properties of the model of such a medium in the form of periodically arranged microresonators are studied. Additional vibrational branches (superlattice vibrations) are shown to be formed in such a medium under certain conditions. These branches give rise to a central peak and strongly affect the characteristics of the structural phase transition depending on the microresonator dimensions. The observing conditions of the dynamic opalescence in inhomogeneous media by the isochronous spectroscopy technique upon pulsed laser excitation are analyzed.     

Critical Behaviors and Universality Classes of Percolation Phase Transitions on Two-Dimensional Square Lattice

We have investigated both site and bond percolation on two-dimensional lattice under the random rule and the product rule respectively. With the random rule, sites or bonds are added randomly into the lattice. From two candidates picked randomly, the site or bond with the smaller size product of two connected clusters is added when the product rule is taken. Not only the size of the largest cluster but also its size jump are studied to characterize the universality class of percolation. The finite-size scaling forms of giant cluster size and size jump are proposed and used to determine the critical exponents of percolation from Monte Carlo data. It is found that the critical exponents of both size and size jump in random site percolation are equal to that in random bond percolation. With the random rule, site and bond percolation belong to the same universality class. We obtain the critical exponents of the site percolation under the product rule, which are different from that of both random percolation and the bond percolation under the product rule. The universality class of site percolation differs different from that of bond percolation when the product rule is used.     

Ionization Potential Depression in Hot Dense Plasmas Through a Pure Classical Model

The ionization potential of an ion embedded in a plasma, lowered due to the whole of the charged particles (ions and electrons) interacting with this ion, is the so‐called plasma effect. A numerical plasma model based on classical molecular dynamics has been developed recently. It is capable to describe a neutral plasma at equilibrium involving ions of various charge states of the same atom together with electrons. This code is used here to investigate the ionization potential depression (IPD). The study of the IPD is illustrated and discussed for aluminum plasmas at mid and solid density and electron temperatures varying from 50eV to 190eV. The method relies on a sampling of the total potential energy of the electron located at an ion being ionized. The potential energy of such electron results from all of the interacting charged particles interacting with it. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

有限玻色子系统中的激发态量子相变

为了探讨原子核系统中存在激发态量子相变的可能性,在相互作用玻色子模型框架下对有限玻色子系统中的激发态量子相变现象进行唯象分析,特别是针对角动量和有限N效应如何影响U（5）-SU（3）和SU（3）-O（6）过渡区中的激发态量子相变行为进行了系统研究。结果表明,低角动量振动谱中的激发态量子相变特征在现实玻色子数情况下可以很好地保持,但随着角动量增加相变特征逐渐消失。In this work, a phenomenological analysis of the excited-state quantum phase transitions (ESQPTs) in the finite-N boson system has been carried out within the interacting boson model in order to reveal the possibility of finding ESQPTs in nuclear systems. Particularly, the angular momentum and finite-N effects on the ESQPTs in the U(5)-SU(3) and SU(3)-O(6) transitional regions have been systematically investigated. The results indicate that the main features of ESQPTs can be well preserved even at a realistic boson number for small angular momentum but will gradually disappear as the angular momentum increases.