Order Phase Transition Research Articles

The D3-D¯3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\overline{D}3 $$\\end{document}-brane inflation model revisited

Combining previous results, the D3-D¯3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\overline{D}3 $$\\end{document}-brane pair potential U(T, ϕ) is presented here, where the inflaton ϕ measures the separation between the D3-brane and the anti-D3-brane, and the complex scalar mode T becomes tachyonic when the annihilation of the branes happens as they collide. Besides the distinct form of the inflationary potential, this hybrid inflationary model differs from a typical hybrid model in 2 important aspects: (1) U(T, ϕ) becomes complex when T becomes tachyonic, where Im U(T, ϕ) plays an important role in the dynamics towards the end of the inflationary epoch; (2) tunnelling during the inflationary epoch can happen; this is particularly relevant if there are multiple D3-D¯3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\overline{D}3 $$\\end{document}-brane pairs in different warped throats. Besides the production of cosmic superstrings, the model offers the possibility of first order phase transition that may generate large enough density perturbation for the primordial black hole production. Stochastic gravitational wave background from these sources remain to be fully investigated.

Primordial black holes as dark matter: interferometric tests of phase transition origin

We show that primordial black holes — in the observationally allowed mass window with fPBH = 1 — formed from late nucleating patches in a first order phase transition imply upcoming gravitational wave interferometers will see a large stochastic background arising from the bubble collisions. As an example, we use a classically scale invariant B – L model, in which the right handed neutrinos explain the neutrino masses and leptogenesis, and the dark matter consists of primordial black holes. The conclusion regarding the gravitational waves is, however, expected to hold model independently for black holes coming from such late nucleating patches.

Studies on the Arrott plots of inhomogeneous first order magnetic phase transitions

First order ferromagnetic to paramagnetic phase transition is studied using the Bean-Rodbell model within the mean-field framework. The presence of sample inhomogeneities is modeled by considering distributions of the Bean-Rodbell parameter. The corresponding Arrott plots with and without distributions of the Bean-Rodbell parameter are generated and compared. Results indicate that in the presence of inhomogeneities, ferromagnetic to paramagnetic phase transition is broadened. The initial negative slopes in the Arrott plots due to first order phase transition changes to positive slopes for temperatures lying in the broadened tail region of the ferromagnetic to paramagnetic phase transitions. However, the initial negative slopes in the paramagnetic regime (for temperatures above the broadened tail region) are preserved even in the presence of sample inhomogeneities. Also, the effect of inhomogeneities on the magnetic entropy change near the first order transition is studied.

Applications of Domain Adversarial Neural Network in phase transition of 3D Potts model

Machine learning techniques exhibit significant performance in discriminating different phases of matter and provide a new avenue for studying phase transitions. We investigate the phase transitions of three dimensional q-state Potts model on cubic lattice by using a transfer learning approach, Domain Adversarial Neural Network (DANN). With the unique neural network architecture, it could evaluate the high-temperature (disordered) and low-temperature (ordered) phases, and identify the first and second order phase transitions. Meanwhile, by training the DANN with a few labeled configurations, the critical points for q=2,3,4 and 5 can be predicted with high accuracy, which are consistent with those of the Monte Carlo simulations. These findings would promote us to learn and explore the properties of phase transitions in high-dimensional systems.

Correlation of strontium anharmonicity with charge-lattice dynamics of the apical oxygens and their coupling to cuprate superconductivity

By means of Cu K edge x-ray absorption spectra of overdoped high-pressure oxygenated superconducting and , we demonstrate a remarkably strong three way correlation between the superconductivity and the local dynamics of their highly anharmonic Cu–Sr and Cu-apical O pairs. We model the latter as aspects of the Internal Quantum Tunneling Polarons (IQTPs) that give the two-site distributions in extended x-ray absorption fine structure and inelastic pair distribution function measurements. This finding obviates the common assumption that the universal Ba/Sr-apical O dielectric layer, far from only maintaining the separation of charges between the charge reservoir and the conducting domains, plays an unexpectedly active role in the unusual electronic properties of cuprate superconductors. Furthermore, we investigate the effects of the dynamic structure associated with these pairs by means of the exact diagonalization of a prototype Hamiltonian based on a six-atom cluster, with two neighboring Cu-apical O pairs bridged by an anharmonically coupled Sr atom and a planar O atom. In terms of the Kuramoto model for synchronization, these calculations show a first order phase transition, driven by anharmonicity, to a synchronized state of the IQTPs, in which a fraction of the charge originally confined to the apical O sites is transferred onto the planar O in the superconducting plane. This combination of experimental results and theory demonstrates that the Ba/Sr-apical O layer of cuprates most likely plays an important role in high temperature superconductivity via its collective charge dynamics.

Status of the CBM experiment at FAIR

The CBM experiment will explore dense baryonic matter at moderate temperatures with rare observables that could not be investigated so far for this type of matter. Experiments will be performed at the future FAIR facility with beams from SIS 100 exploring a range in √SNN from 2.3 - 5.3 GeV at interaction rates up to 10 MHz. Within the first few years energy scans in particular for dilepton and fluctuation observables are planned in order to search for the predicted first order phase transition and critical point. The status of the experimental preparations is reviewed in this contribution.

Spinodal enhancement of fluctuations in nucleus-nucleus collisions

Subensemble Acceptance Method (SAM) [1, 2] is an essential link between measured event-by-event fluctuations and their grand canonical theoretical predictions such as lattice QCD. The method allows quantifying the global conservation law effects in fluctuations. In its basic formulation, SAM requires a sufficiently large system such as created in central nucleus-nucleus collisions and sufficient space-momentum correlations. Directly in the spinodal region of the First Order Phase Transition (FOPT) different approximations should be used that account for finite size effects. Thus, we present the generalization of SAM applicable in both the pure phases, metastable and unstable regions of the phase diagram [3]. Obtained analytic formulas indicate the enhancement of fluctuations due to crossing the spinodal region of FOPT and are tested using molecular dynamics simulations. A rather good agreement is observed. Using transport model calculations with interaction potential we show that the spinodal enhancement of fluctuations survives till the later stages of collision via the memory effect [4]. However, at low collision energies the space-momentum correlation is not strong enough for this signal to be transferred to second and third order cumulants measured in momentum subspace. This result agrees well with recent HADES data on proton number fluctuations at √SNN = 2.4 GeV which are found to be consistent with the binomial momentum space acceptance [5].

Non-equilibrium magnetic properties of a mixed spin (1/2, 1) Ising graphene nanoisland.

Based on Glauber-type stochastic dynamics intertwined with mean field theory, we have investigated a graphene nanoisland's out-of-equilibrium magnetic and thermomagnetic behaviors with a mixed ferrimagnetic spin (1/2, 1) configuration in the presence of an oscillating magnetic field. The influence of the oscillating external magnetic field, single-ion anisotropy and temperature on the dynamic magnetic properties (dynamic phase transitions, hysteresis loop areas, correlations, and phase diagrams) of the system is studied in detail. The results illustrate that single ion anisotropy and the magnetic field play important roles in the system's dynamic order parameters, phase transitions and phase diagrams. Dynamic phase diagrams display some dynamic special points such as dynamic tricritical points, quadruple points and some sort of reentrant phenomena, which strongly depend on interaction parameters. Our predicted results may provide a reference for future experimental and theoretical studies of the nanostructures.

Unraveling the atomic mechanism of the disorder–order phase transition from γ-Ga2O3 to β-Ga2O3

In this paper, we employ in situ transmission electron microscopy to study the disorder–order phase transition from amorphous Ga2O3 to γ-Ga2O3 and then to β-Ga2O3. The in situ studies are complemented by ex situ annealing experiments, of which the results are analyzed by x-ray diffraction and high resolution (scanning) transmission electron microscopy. Amorphous Ga2O3 deposited at 100 °C by molecular beam epitaxy crystallizes at 470 °C in the γ phase (Fd3̄m), which undergoes a phase transition to the β phase above 500 °C. Between 500° and 900 °C, we find a mixture of γ-Ga2O3 and β-Ga2O3 coexisting. Above 950 °C, we find only β-Ga2O3. Through our analyses and by considering symmetry relations, we have constructed a coincidence site lattice of both structures containing a common fcc-type sublattice occupied by oxygen atoms, the cation sites of β-Ga2O3 common to both phases, and partially occupied cation sites in the γ phase corresponding to the interstitial sites in the β phase. We assign the atomic displacements within this lattice responsible for transforming the initially disordered spinel structure with partially occupied cation sites into the well-ordered lattice of β-Ga2O3. We identify this transition as a reconstructive disorder-to-order phase transition, mediated by the exchange of cations to next nearest neighbor sites. Our model not only explains recent observations of the formation of γ-Ga2O3 during implantation for n-type doping and the subsequent recovery of β-Ga2O3 following annealing but also holds potential for inspiring understanding in other materials with similar phase transitions.

First and Continuous Order Phase Transition in the XY-Model in Two Orthogonal Fields

First and Continuous Order Phase Transition in the XY-Model in Two Orthogonal Fields

Improving Cycling Electrochemical Performance of P2-Type Na2/3Mn2/3Ni1/3O2 by Controlling Its Crystallinity

1. IntroductionNa2/3Mn2/3Ni1/3O2 with P2-type structure is a positive electrode material for the sodium ion battery with relatively high reversible capacity of 170 mAh/g and average potential of 3.6 V (vs. Na/Na+). On the other hand, it is known that there is a problem in cycle stability due to the P2-O2 phase transition associated with Na insertion/removal and the structural change caused by O2 desorption at the high state of charge. In this study, we focus on the crystallinity of the layered structure to improve the electrochemical property of P2-type Na2/3(Mn2/3Ni1/3)O2 .The effect of crystallinity on the electrochemical property of the P2-Na2/3(Mn2/3Ni1/3)O2 was explored using the ball milling approach. 2. ExperimentsThe Na2/3(Mn2/3Ni1/3)O2 was prepared by mixing NaOH, Mn2O3, and Ni(OH)2 in a molar ratio of 2 : 2 : 1 and firing at 950°C for 3 h in air (sintered sample). The sintered sample was ball-milled with 4 mmφ ZrO2 balls in an 80 ml ZrO2 vial using a planetary ball mill (Fritsch, P-6) at 500 rpm for 2 h to obtain a sample with low crystallinity (milled sample). The resulting samples was mixed with Ketjen black and PTFE at a weight ratio of 84:8:8, and the sheet was pressed onto an Al mesh to form an electrode. The electrodes were dried under vacuum at 220 °C for 5 hours, and then half-cells were assembled using Na foil as the counter electrode and 1M NaPF6/EC-DEC as the electrolyte to evaluate electrode characteristics. The cell was galvanostatically charged and discharged using a BLS5500 (Keisokuki Center) with a current density of 10 mA g−1, in which the denominator represents the mass of the active material in the positive electrode. The crystal structure of the samples was evaluated using XRD (Rigaku UltimaIV, Cu K-α), XAS (BL14B2 at SPring-8, BL-11, Ritsumeikan SR center), X-ray total scattering measurement (SPring-8, BL22XU, 70 keV) and TEM. In addition, the electronic structure was investigated using the first-principles calculation program (VASP) based on density functional theory.3. Results and DiscussionFig. 1 shows XRD of Na2/3(Mn2/3Ni1/3)O2 after calcination and ball milling. The sintered sample showed a diffraction pattern attributed to the P2 structure, but the milled sample showed a broad profile and the detailed crystal structure could not be identified. However, a peak in the 002 plane around 2θ = 16° could be confirmed, and from the results of TEM observation and PDF analysis, it is considered that the milled sample also has a layered structure.Fig. 2 shows a comparison of charge-discharge profiles and cycle characteristics. In the charge-discharge profile of the sintered sample, potential flat areas due to Na ordering and P2-O2 phase transition can be observed, but that for the milled sample, these potential flat areas are not observed and the profile is on a slope, which indicates that the crystallinity degradation due to milling suppresses structural changes during the charge-discharge process. The initial charge-discharge capacities of the milled samples were 146 and 141 mAh/g, respectively, which were smaller than those of the calcined samples (175 and 146 mAh/g, respectively), indicating that the milling process did not significantly affect the Na insertion/desorption characteristics. Comparing the cycle characteristics shown in Fig. 2, the discharge capacity of the milled sample maintained more than 80% while the sintered sample deteriorated to the 37% of the initial capacity after 50 cycles, confirming that the milling treatment was effective in improving cycle characteristics.Detailed mechanism of the milling effect and redox process will be discussed in the presentation. Figure 1

Study on phase transition critical phenomena in group movement based on eigen microstate theory

Group motion exists widely in nature. Physicists use abstract models, such as the Vicsek model, to simplify group motion to obtain universal laws. However, the order parameters and phase transition types that describe the characteristics of the Vicsek model system are still controversial. For example, how to characterize the order parameters and types of phase transitions that characterize the system. This paper starts with the eigen microstate method and studies the Vicsek model. First, the continuous phase transition in the system is deeply studied through scaling analysis, and two critical exponents about the noise are obtained. Second, considering the density effect, similar to the noise study, three eigen microstates in the Vicsek model are revealed through scaling analysis, showing discontinuous and continuous phase transitions. Moreover, it is proved that in the actual infinite system, continuous phase transition and discontinuous phase transition still exist. Finally, the experimental data under different noises and densities are obtained through a large number of numerical simulations, and the phase diagram of the Vicsek model is depicted.

A comprehensive study of dielectric, magnetic and anticancerous properties of lanthanum manganite perovskite nanoparticles

Present study reports the combustion synthesis of lanthanum manganite (LaMnO3) perovskites with rhombohedral structure having R-3 C space group. The structural and morphological evaluations of synthesized nanoparticles were done by XRD, FTIR, SEM and XPS. The BDS analysis reveals different types of polarization associated with dielectric properties. Frequency-dependent dielectric properties such as dielectric constant, dielectric loss, ac conductivity and capacitance were analyzed at room temperature. BDS analysis explain Maxwell-Wagner effect and Jhonscher universal power law. Room temperature and low temperature magnetic properties were investigated using VSM. M(T) measurements shows second order phase transition from ferromagnetic (FM) to paramagnetic (PM) at 230 K Curie temperature. The detailed magnetic characteristics of lanthanum manganite perovskites were clearly explained by Curie – Wiess and Arrott’s plot. The hyperthermial behavior were studied with normal and pre-heated LaMnO3. The in - vitro anticancerous analysis were explained by MTT assay. The LC50 values of normal and preheated specimens are 124.145 µg/ml and 86.159 µg/ml, respectively. The reduction in LC50 value of preheated sample underscores its superior anticancer efficacy compared to normal sample.

Q-state Potts model from the nonperturbative renormalization group.

We study the q-state Potts model for q and the space dimension d arbitrary real numbers using the derivative expansion of the nonperturbative renormalization group at its leading order, the local potential approximation (LPA and LPA^{'}). We determine the curve q_{c}(d) separating the first [q>q_{c}(d)] and second [q<q_{c}(d)] -order phase transition regions for 2.8<d≤4. At small ε=4-d and δ=q-2 the calculation is performed in a double expansion in these parameters, and we find q_{c}(d)=2+aε^{2} with a≃0.1. For finite values of ε and δ, we obtain this curve by integrating the LPA and LPA^{'} flow equations. We find that q_{c}(d=3)=2.11(7), which confirms that the transition is of first order in d=3 for the three-state Potts model.

Spin-liquid behavior in the classical antiferromagnetic [formula omitted] spin system on the square-kagome lattice: Exact analysis within recursive-lattice approach

Magnetic and thermodynamic properties of the antiferromagnetic J1−J2−J3 spin system, i.e., the spin system with three different nearest-neighbor antiferromagnetic interactions, on the square-kagome lattice is investigated in the framework of the corresponding exactly solvable spin-1/2 Ising model on the recursive square-kagome lattice. The phase diagram of the model is found and it is shown that, depending on the model parameters, the model exhibits the existence of three long-range order (antiferromagnetic) phases, which are separated from the paramagnetic phase by the second order phase transitions. It is also shown that, in the zero temperature limit, the paramagnetic phase splits into three different ground states realized on the lines that separate antiferromagnetic ground states of the model. Due to the frustration, all these “paramagnetic” ground states are highly macroscopically degenerated with strict hierarchy of their residual entropies. Moreover, the high macroscopic degeneracy of the paramagnetic phase in the vicinity of these ground states together with the presence of strong correlations (given by the proximity of the second order phase transitions) allow one to consider the paramagnetic ground states as well as their immediate paramagnetic surroundings as regions with the classical spin-liquid behavior. It is also shown that the presence of the second order phase transitions in the vicinity of the paramagnetic ground states suppresses expected anomalous (Schottky-type) behavior of the specific heat related to the rapid entropy changes caused by the frustration.

Scale-Free Chaos in the 2D Harmonically Confined Vicsek Model.

Animal motion and flocking are ubiquitous nonequilibrium phenomena that are often studied within active matter. In examples such as insect swarms, macroscopic quantities exhibit power laws with measurable critical exponents and ideas from phase transitions and statistical mechanics have been explored to explain them. The widely used Vicsek model with periodic boundary conditions has an ordering phase transition but the corresponding homogeneous ordered or disordered phases are different from observations of natural swarms. If a harmonic potential (instead of a periodic box) is used to confine particles, then the numerical simulations of the Vicsek model display periodic, quasiperiodic, and chaotic attractors. The latter are scale-free on critical curves that produce power laws and critical exponents. Here, we investigate the scale-free chaos phase transition in two space dimensions. We show that the shape of the chaotic swarm on the critical curve reflects the split between the core and the vapor of insects observed in midge swarms and that the dynamic correlation function collapses only for a finite interval of small scaled times. We explain the algorithms used to calculate the largest Lyapunov exponents, the static and dynamic critical exponents, and compare them to those of the three-dimensional model.

Holographic model for the first order phase transition in the composite Higgs boson scenario

Holographic model for the first order phase transition in the composite Higgs boson scenario

Probing electroweak phase transition in the singlet Standard Model via bbγγ and 4l channels

We investigate the prospects for resonant di-Higgs and heavy Higgs production searches at the 14 TeV HL-LHC in the combination of bbγγ and 4l channels, as a probe of a possible first order electroweak phase transition in real singlet scalar extension of the Standard Model. Event selection follows those utilized in the bbγγ and 4l searches by the ATLAS Collaboration, applied to simulation using benchmark parameters that realize a strong first order electroweak phase transition. The output of discriminant analysis is implemented by numerical calculation, optimised by the joint restriction from the two channels. The prospective reach for bbγγ/4l channel could be more competitive in probing the electroweak phase transition at lower/higher resonance masses. With 3 ab−1 integrated luminosity, the combination of the bbγγ and 4l channels can discover/exclude a significant portion of the viable parameter space that realizes a strong first order phase transition when the resonance mass is heavier than 500 GeV.

Shallow relic gravitational wave spectrum with acoustic peak

We study the gravitational wave (GW) spectrum produced by acoustic waves in the early universe, such as would be produced by a first order phase transition, focusing on the low-frequency side of the peak. We confirm with numerical simulations the Sound Shell model prediction of a steep rise with wave number k of k 9 to a peak whose magnitude grows at a rate (H/k p)H, where H is the Hubble rate and k p the peak wave number, set by the peak wave number of the fluid velocity power spectrum. We also show that hitherto neglected terms give a shallower part with amplitude (H/k p)2 in the range H ≲ k ≲ k p, which in the limit of small H/k rises as k. This linear rise has been seen in other modelling and also in direct numerical simulations. The relative amplitude between the linearly rising part and the peak therefore depends on the peak wave number of the velocity spectrum and the lifetime of the source, which in an expanding background is bounded above by the Hubble time H -1. For slow phase transitions, which have the lowest peak wave number and the loudest signals, the acoustic GW peak appears as a localized enhancement of the spectrum, with a rise to the peak less steep than k 9. The shape of the peak, absent in vortical turbulence, may help to lift degeneracies in phase transition parameter estimation at future GW observatories.

Exploring complex magnetic phase transitions and magnetocaloric effect in the nanocrystalline Nd0.5Ca0.5MnO[formula omitted] compound

In this article, we have investigated the temperature and magnetic field-induced complex magnetic phases and magnetocaloric properties of the nanocrystalline Nd0.5Ca0.5MnO3 (NCMO) compound in detail. The compound exhibits charge-ordered antiferromagnetic (CO-AFM) and charge-orbital-ordered antiferromagnetic (AFM) phases at TCO≃ 225 K and TN= 160 K respectively. At the intermediate temperature range, i.e. TN≤ T ≤ TCO, an unfamiliar magnetic state is present where the orbital ordering of manganese ions sets progressively. Both the short-range and zig-zag ordered ferromagnetic (FM) chains and an AFM phase coexist within this temperature window. The effect of magnetic field and temperature drastically modifies the fragile magnetic ground state and this change is also reflected in the magnetocaloric properties of the studied compound. At the low-temperature region, an inverse magnetocaloric effect (MCE) is noticed due to the kinetically arrested magnetic moments of the AFM phase. However, a conventional MCE is noticed in the high-temperature regime. The anomalous behavior of the MCE in the nanocrystalline NCMO compound is analyzed by considering the effect of the reduction of particle size and the meta-stable nature of the magnetic ground state. In addition, we have paid attention to the hysteretic losses associated with the first-order phase transition (FOPT) in order to estimate the magnetic cooling capacity for the material. These studies carry notable importance for the usefulness of nanocrystalline half-doped manganite compounds not only for basic scientific research purpose, but also having possible practical utilization in the magnetic refrigeration industries.