Directory of Open Access Journals (Sweden)
J.E. García-Ramos
2014-09-01
Full Text Available We introduce the basic concepts of catastrophe theory needed to derive analytically the phase diagram of the proton–neutron interacting boson model (IBM-2. Previous studies [1–3] were based on numerical solutions. We here explain the whole IBM-2 phase diagram including the precise order of the phase transitions in terms of the cusp catastrophe.
Energy Technology Data Exchange (ETDEWEB)
García-Ramos, J.E., E-mail: enrique.ramos@dfaie.uhu.es [Departamento de Física Aplicada, Universidad de Huelva, 21071 Huelva (Spain); Unidad Asociada de la Universidad de Huelva al IEM (CSIC), Madrid (Spain); Arias, J.M., E-mail: ariasc@us.es [Departamento de Física Atómica, Molecular y Nuclear, Universidad de Sevilla, Apdo 1065, 41080 Sevilla (Spain); Unidad Asociada de la Universidad de Sevilla al IEM (CSIC), Madrid (Spain); Dukelsky, J., E-mail: dukelsky@iem.cfmac.csic.es [Instituto de Estructura de la Materia, CSIC, Serrano 123, 28006 Madrid (Spain)
2014-09-07
We introduce the basic concepts of catastrophe theory needed to derive analytically the phase diagram of the proton–neutron interacting boson model (IBM-2). Previous studies [1–3] were based on numerical solutions. We here explain the whole IBM-2 phase diagram including the precise order of the phase transitions in terms of the cusp catastrophe.
Error catastrophe and phase transition in the empirical fitness landscape of HIV
Hart, Gregory R.; Ferguson, Andrew L.
2015-03-01
We have translated clinical sequence databases of the p6 HIV protein into an empirical fitness landscape quantifying viral replicative capacity as a function of the amino acid sequence. We show that the viral population resides close to a phase transition in sequence space corresponding to an "error catastrophe" beyond which there is lethal accumulation of mutations. Our model predicts that the phase transition may be induced by drug therapies that elevate the mutation rate, or by forcing mutations at particular amino acids. Applying immune pressure to any combination of killer T-cell targets cannot induce the transition, providing a rationale for why the viral protein can exist close to the error catastrophe without sustaining fatal fitness penalties due to adaptive immunity.
Appavoo, Kannatassen; Wang, Bin; Brady, Nathaniel F; Seo, Minah; Nag, Joyeeta; Prasankumar, Rohit P; Hilton, David J; Pantelides, Sokrates T; Haglund, Richard F
2014-03-12
Ultrafast photoinduced phase transitions could revolutionize data-storage and telecommunications technologies by modulating signals in integrated nanocircuits at terahertz speeds. In quantum phase-changing materials (PCMs), microscopic charge, lattice, and orbital degrees of freedom interact cooperatively to modify macroscopic electrical and optical properties. Although these interactions are well documented for bulk single crystals and thin films, little is known about the ultrafast dynamics of nanostructured PCMs when interfaced to another class of materials as in this case to active plasmonic elements. Here, we demonstrate how a mesh of gold nanoparticles, acting as a plasmonic photocathode, induces an ultrafast phase transition in nanostructured vanadium dioxide (VO2) when illuminated by a spectrally resonant femtosecond laser pulse. Hot electrons created by optical excitation of the surface-plasmon resonance in the gold nanomesh are injected ballistically across the Au/VO2 interface to induce a subpicosecond phase transformation in VO2. Density functional calculations show that a critical density of injected electrons leads to a catastrophic collapse of the 6 THz phonon mode, which has been linked in different experiments to VO2 phase transition. The demonstration of subpicosecond phase transformations that are triggered by optically induced electron injection opens the possibility of designing hybrid nanostructures with unique nonequilibrium properties as a critical step for all-optical nanophotonic devices with optimizable switching thresholds.
Energy Technology Data Exchange (ETDEWEB)
Fort, H [Complex Systems Group, Instituto de Fisica, Facultad de Ciencias, Universidad de la Republica, Igua 4225, 11400 Montevideo (Uruguay); Mazzeo, N [Depto. de EcologIa, Facultad de Ciencias, Universidad de la Republica, Igua 4225, 11400 Montevideo (Uruguay); Scheffer, M; Nes, E van, E-mail: hugo@fisica.edu.u [Wageningen Agricultural University, Aquatic Ecology and Water Quality Management Group, PO Box 47, 6700 AA Wageningen (Netherlands)
2010-09-01
Ecosystems are complex systems which can respond to gradual changes of their conditions by a sudden shift to a contrasting regime or alternative stable state (ASS). Predicting such critical points before they are reached is extremely difficult and providing early warnings is fundamental to design management protocols for ecosystems. Here we study different spatial versions of popular ecological models which are known to exhibit ASS. The spatial heterogeneity is introduced by a local parameter varying from cell to cell in a regular lattice. Transport of biomass among cells occurs by simple diffusion. We investigate whether different quantities from statistical mechanics -like the variance, the two-point correlation function and the patchiness-may serve as early warnings of catastrophic phase transitions between the ASS. In particular, we find that the patch-size distribution follows a power law when the system is close to the catastrophic transition. We also provide links between spatial and temporal indicators and analyze how the interplay between diffusion and spatial heterogeneity may affect the earliness of each of the observables. Finally, we comment on similarities and differences between these catastrophic shifts and paradigmatic thermodynamic phase transitions like the liquid-vapor change of state for a fluid like water.
Merli, Marcello; Sciascia, Luciana
2013-06-01
In this work, the Bader's topological analysis of the electron density, coupled with Thom's catastrophe theory, was used to characterize the pressure-induced transformations in α-quartz. In particular, ab initio calculations of the α-quartz structures in the range 0-105 Gpa have been performed at the HF/DFT exchange-correlation terms level, using Hamiltonians based on a WC1LYP hybrid scheme. The electron densities calculated throughout the ab initio wave functions have been analysed by means of the Bader's theory, seeking for some catastrophic mechanism in the sense of Thom's theory. The analysis mainly showed that there is a typical fold catastrophe feature involving an O-O interaction at the quartz-coesite transition pressure, while the amorphization of α-quartz is coincident with an average distribution of the gradient field of the electron density around the oxygen atom which is typically observed in the free atoms. This approach is addressed to depict a phase transition from a novel viewpoint, particularly useful in predicting the stability of a compound at extreme conditions, especially in the absence of experimental data.
Solé, Ricard V
2011-01-01
Phase transitions--changes between different states of organization in a complex system--have long helped to explain physics concepts, such as why water freezes into a solid or boils to become a gas. How might phase transitions shed light on important problems in biological and ecological complex systems? Exploring the origins and implications of sudden changes in nature and society, Phase Transitions examines different dynamical behaviors in a broad range of complex systems. Using a compelling set of examples, from gene networks and ant colonies to human language and the degradation o
Gitterman, Moshe
2014-09-01
In discussing phase transitions, the first thing that we have to do is to define a phase. This is a concept from thermodynamics and statistical mechanics, where a phase is defined as a homogeneous system. As a simple example, let us consider instant coffee. This consists of coffee powder dissolved in water, and after stirring it we have a homogeneous mixture, i.e., a single phase. If we add to a cup of coffee a spoonful of sugar and stir it well, we still have a single phase -- sweet coffee. However, if we add ten spoonfuls of sugar, then the contents of the cup will no longer be homogeneous, but rather a mixture of two homogeneous systems or phases, sweet liquid coffee on top and coffee-flavored wet sugar at the bottom...
Phase transitions in operational risk.
Anand, Kartik; Kühn, Reimer
2007-01-01
In this paper we explore the functional correlation approach to operational risk. We consider networks with heterogeneous a priori conditional and unconditional failure probability. In the limit of sparse connectivity, self-consistent expressions for the dynamical evolution of order parameters are obtained. Under equilibrium conditions, expressions for the stationary states are also obtained. Consequences of the analytical theory developed are analyzed using phase diagrams. We find coexistence of operational and nonoperational phases, much as in liquid-gas systems. Such systems are susceptible to discontinuous phase transitions from the operational to nonoperational phase via catastrophic breakdown. We find this feature to be robust against variation of the microscopic modeling assumptions.
Phase diagram of the two-fluid Lipkin model: A "butterfly" catastrophe
García-Ramos, J. E.; Pérez-Fernández, P.; Arias, J. M.; Freire, E.
2016-03-01
Background: In the past few decades quantum phase transitions have been of great interest in nuclear physics. In this context, two-fluid algebraic models are ideal systems to study how the concept of quantum phase transition evolves when moving into more complex systems, but the number of publications along this line has been scarce up to now. Purpose: We intend to determine the phase diagram of a two-fluid Lipkin model that resembles the nuclear proton-neutron interacting boson model Hamiltonian using both numerical results and analytic tools, i.e., catastrophe theory, and compare the mean-field results with exact diagonalizations for large systems. Method: The mean-field energy surface of a consistent-Q -like two-fluid Lipkin Hamiltonian is studied and compared with exact results coming from a direct diagonalization. The mean-field results are analyzed using the framework of catastrophe theory. Results: The phase diagram of the model is obtained and the order of the different phase-transition lines and surfaces is determined using a catastrophe theory analysis. Conclusions: There are two first-order surfaces in the phase diagram, one separating the spherical and the deformed shapes, while the other separates two different deformed phases. A second-order line, where the later surfaces merge, is found. This line finishes in a transition point with a divergence in the second-order derivative of the energy that corresponds to a tricritical point in the language of the Ginzburg-Landau theory for phase transitions.
Phase diagram of the two-fluid Lipkin model: a butterfly catastrophe
García-Ramos, J E; Arias, J M; Freire, E
2016-01-01
Background: In the last few decades quantum phase transitions have been of great interest in Nuclear Physics. In this context, two-fluid algebraic models are ideal systems to study how the concept of quantum phase transition evolves when moving into more complex systems, but the number of publications along this line has been scarce up to now. Purpose: We intend to determine the phase diagram of a two-fluid Lipkin model, that resembles the nuclear proton-neutron interacting boson model Hamiltonian, using both numerical results and analytic tools, i.e., catastrophe theory, and to compare the mean-field results with exact diagonalizations for large systems. Method: The mean-field energy surface of a consistent-Q-like two-fluid Lipkin Hamiltonian is studied and compared with exact results coming from a direct diagonalization. The mean-field results are analyzed using the framework of catastrophe theory. Results: The phase diagram of the model is obtained and the order of the different phase-transition lines and ...
Energy Technology Data Exchange (ETDEWEB)
Petry, W.; Neuhaus, J. [Techn. Universitaet Muenchen, Physik Department E13, Munich (Germany)
1996-11-01
Many elements transform from a high temperature bcc phase to a more dense packed temperature phase. The great majority of these transitions are of 1st order, displacive and reconstructive. The lattice potentials which govern these martensitic transitions can be probed by inelastic neutron scattering, thereby answering fundamental questions like : Will the transition be announced by dynamical or static fluctuations? What are the trajectories for the displacements needed for the transformation? Does the vibrational entropy stabilize the high temperature phase? Are the unusual transport properties in these materials related to their ability to transform? (author) 17 figs., 1 tab., 46 refs.
Phase transitions modern applications
Gitterman, Moshe
2014-01-01
This book provides a comprehensive review of the theory of phase transitions and its modern applications, based on the five pillars of the modern theory of phase transitions i.e. the Ising model, mean field, scaling, renormalization group and universality. This expanded second edition includes, along with a description of vortices and high temperature superconductivity, a discussion of phase transitions in chemical reaction and moving systems. The book covers a close connection between phase transitions and small world phenomena as well as scale-free systems such as the stock market and the Internet. Readership: Scientists working in different fields of physics, chemistry, biology and economics as well as teaching material for undergraduate and graduate courses.
Institute of Scientific and Technical Information of China (English)
许可; 李未
1999-01-01
Phase transition is an important feature of SAT problem. For random k-SAT model, it is proved that as r（ratio of clauses to variables） increases, the structure of solutions will undergo a sudden change like satisfiability phase transition when r reaches a threshold point (r=rcr). This phenomenon shows that the satisfying truth assignments suddenly shift from being relatively different from each other to being very similar to each other.##属性不符
The diamagnetic phase transition in Magnetars
Wang, Zhaojun; Zhu, Chunhua; Wu, Baoshan
2016-01-01
Neutron stars are ideal astrophysical laboratories for testing theories of the de Haas-van Alphen (dHvA) effect and diamagnetic phase transition which is associated with magnetic domain formation. The "magnetic interaction" between delocalized magnetic moments of electrons (the Shoenberg effect), can result in an effect of the diamagnetic phase transition into domains of alternating magnetization (Condon's domains). Associated with the domain formation are prominent magnetic field oscillation and anisotropic magnetic stress which may be large enough to fracture the crust of magnetar with a super-strong field. Even if the fracture is impossible as in "low-field" magnetar, the depinning phase transition of domain wall motion driven by low field rate (mainly due to the Hall effect) in the randomly perturbed crust can result in a catastrophically variation of magnetic field. This intermittent motion, similar to the avalanche process, makes the Hall effect be dissipative. These qualitative consequences about magne...
Kopaev, YuV
1992-01-01
Electronic Phase Transitions deals with topics, which are presently at the forefront of scientific research in modern solid-state theory. Anderson localization, which has fundamental implications in many areas of solid-state physics as well as spin glasses, with its influence on quite different research activities such as neural networks, are two examples that are reviewed in this book. The ab initio statistical mechanics of structural phase transitions is another prime example, where the interplay and connection of two unrelated disciplines of solid-state theory - first principle ele
Scaling law characterizing the dynamics of the transition of HIV-1 to error catastrophe
Gupta, Vipul; Dixit, Narendra M.
2015-10-01
Increasing the mutation rate, μ , of viruses above a threshold, {μ }c, has been predicted to trigger a catastrophic loss of viral genetic information and is being explored as a novel intervention strategy. Here, we examine the dynamics of this transition using stochastic simulations mimicking within-host HIV-1 evolution. We find a scaling law governing the characteristic time of the transition: τ ≈ 0.6/≤ft(μ -{μ }c\\right). The law is robust to variations in underlying evolutionary forces and presents guidelines for treatment of HIV-1 infection with mutagens. We estimate that many years of treatment would be required before HIV-1 can suffer an error catastrophe.
Photoinduced phase transitions
Nasu, K
2004-01-01
A new class of insulating solids was recently discovered. Whenirradiated by a few visible photons, these solids give rise to amacroscopic excited domain that has new structural and electronicorders quite different from the starting ground state. This occurrenceis called "photoinduced phase transition", and this multi-authoredbook reviews recent theoretical and experimental studies of this newphenomenon.
Understanding quantum phase transitions
Carr, Lincoln
2010-01-01
Quantum phase transitions (QPTs) offer wonderful examples of the radical macroscopic effects inherent in quantum physics: phase changes between different forms of matter driven by quantum rather than thermal fluctuations, typically at very low temperatures. QPTs provide new insight into outstanding problems such as high-temperature superconductivity and display fundamental aspects of quantum theory, such as strong correlations and entanglement. Over the last two decades, our understanding of QPTs has increased tremendously due to a plethora of experimental examples, powerful new numerical meth
A nonequilibrium phase transition in immune response
Institute of Scientific and Technical Information of China (English)
Zhang Wei; Qi An-Shen
2004-01-01
The dynamics of immune response correlated to signal transduction in immune thymic cells (T cells) is studied.In particular, the problem of the phosphorylation of the immune-receptor tyrosine-based activation motifs (ITAM) is explored. A nonlinear model is established on the basis of experimental observations. The behaviours of the model can be well analysed using the concepts of nonequilibrium phase transitions. In addition, the Riemann-Hugoniot cusp catastrophe is demonstrated by the model. Due to the application of the theory of nonequilibrium phase transitions,the biological phenomena can be clarified more precisely. The results can also be used to further explain the signal transduction and signal discrimination of an important type of immune T cell.
Fodor, Z
2000-01-01
Recent developments on the four dimensional (4d) lattice studies of the finite temperature electroweak phase transition (EWPT) are summarized. The phase diagram is given in the continuum limit. The finite temperature SU(2)-Higgs phase transition is of first order for Higgs-boson masses m/sub H/<66.5+or-1.4 GeV. Above this endpoint only a rapid cross-over can be seen. The full 4d result agrees completely with that of the dimensional reduction approximation. The Higgs-boson endpoint mass in the standard model (SM) would be 72.1+or-1. 4 GeV. Taking into account the LEP Higgs-boson mass lower bound excludes any EWPT in the SM. A one-loop calculation of the static potential in the SU(2)-Higgs model enables a precise comparison between lattice simulations and perturbative results. The most popular extension of the SM, the minimal supersymmetric SM (MSSM) is also studied on 4d lattices. (17 refs).
Mixed phases during the phase transitions
Tatsumi, Toshitaka; Maruyama, Toshiki
2011-01-01
Quest for a new form of matter inside compact stars compels us to examine the thermodynamical properties of the phase transitions. We closely consider the first-order phase transitions and the phase equilibrium on the basis of the Gibbs conditions, taking the liquid-gas phase transition in asymmetric nuclear matter as an example. Characteristic features of the mixed phase are figured out by solving the coupled equations for mean-fields and densities of constituent particles self-consistently within the Thomas-Fermi approximation. The mixed phase is inhomogeneous matter composed of two phases in equilibrium; it takes a crystalline structure with a unit of various geometrical shapes, inside of which one phase with a characteristic shape, called "pasta", is embedded in another phase by some volume fraction. This framework enables us to properly take into account the Coulomb interaction and the interface energy, and thereby sometimes we see the mechanical instability of the geometric structures of the mixed phase...
Learning phase transitions by confusion
van Nieuwenburg, Evert P L; Huber, Sebastian D
2016-01-01
Classifying phases of matter is a central problem in physics. For quantum mechanical systems, this task can be daunting owing to the exponentially large Hilbert space. Thanks to the available computing power and access to ever larger data sets, classification problems are now routinely solved using machine learning techniques. Here, we propose to use a neural network based approach to find phase transitions depending on the performance of the neural network after training it with deliberately incorrectly labelled data. We demonstrate the success of this method on the topological phase transition in the Kitaev chain, the thermal phase transition in the classical Ising model, and the many-body-localization transition in a disordered quantum spin chain. Our method does not depend on order parameters, knowledge of the topological content of the phases, or any other specifics of the transition at hand. It therefore paves the way to a generic tool to identify unexplored phase transitions.
A test of catastrophic transition mechanisms in the Chihuahuan Desert Grassland
Svejcar, L.; Bestelmeyer, B.; Duniway, M.
2012-12-01
Dryland ecosystems are known to undergo transitions from grassland or savanna states to shrub-dominated and/or eroded states with persistent loss of herbaceous vegetation. Theoretical models for predicting critical thresholds between states have been examined in drylands to search for early warning indicators, yet there is scant empirical evidence for the mechanisms. The models postulate that larger patches are favorable environments for plant growth in arid ecosystems due to short-range facilitation. The breakdown of large patches is thought to trigger catastrophic transitions. We tested assumptions underpinning these models using an experiment in black grama grassland (Bouteloua eriopoda Torr.) of the Chihuahuan Desert in which variable grazing intensities produced a wide range of patch sizes in plots with differing mesquite shrub (Prosopis glandulosa Torr.) densities. We tested the hypothesis that growth, reproductive capability, and reproductive success of black grama plants would be greater in larger plant patches than in smaller patches. From 2010-2012 we measured numbers of stolons, ramets, rooted ramets and young individual plants associated with focal black grama plants and fixed areas within each patch. We found that the largest patches did not always feature the highest rates of grass reproduction across years, suggesting that patch size does not consistently indicate the patch persistence mechanisms proposed in catastrophic transition models. Other factors, such as resource competition within patches, may play important roles in black grama grasslands. When assessing rangeland conditions in the Chihuahuan desert grasslands, theoretical models of critical thresholds and early warning indicators should be applied with caution.
Error and repair catastrophes: A two-dimensional phase diagram in the quasispecies model
Tannenbaum, Emmanuel; Shakhnovich, Eugene I.
2004-01-01
This paper develops a two-gene, single fitness peak model for determining the equilibrium distribution of genotypes in a unicellular population which is capable of genetic damage repair. The first gene, denoted by σvia, yields a viable organism with first-order growth rate constant k>1 if it is equal to some target “master” sequence σvia,0. The second gene, denoted by σrep, yields an organism capable of genetic repair if it is equal to some target “master” sequence σrep,0. This model is analytically solvable in the limit of infinite sequence length, and gives an equilibrium distribution which depends on μ≡Lɛ, the product of sequence length and per base pair replication error probability, and ɛr, the probability of repair failure per base pair. The equilibrium distribution is shown to exist in one of the three possible “phases.” In the first phase, the population is localized about the viability and repairing master sequences. As ɛr exceeds the fraction of deleterious mutations, the population undergoes a “repair” catastrophe, in which the equilibrium distribution is still localized about the viability master sequence, but is spread ergodically over the sequence subspace defined by the repair gene. Below the repair catastrophe, the distribution undergoes the error catastrophe when μ exceeds ln k/ɛr, while above the repair catastrophe, the distribution undergoes the error catastrophe when μ exceeds ln k/fdel, where fdel denotes the fraction of deleterious mutations.
Catastrophe,hysteresis and bifurcation of mode transition in scramjet engines and its model
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
This paper describes a class of nonlinear phenomena existing in the hypersonic flow and supersonic combustion process of scramjet engines:catastrophe,hysteresis and bifurcation,and further finds out the general rules(topological invariance)for the stability boundaries of mode transition in scramjet engines.With this topological invariance,a topological approach is put forward to model the stability boundaries,which may contribute to a complexity reduction of high-dimensional modeling when con-sidering more perturbation parameters,and help to explore the physical laws of the nonlinear phe-nomena.Accordingly,this paper interprets the characteristic of combustion mode transition based on the cusp topological model in singular theories,and observes the bifurcation characteristic in com-bustion mode transition.Moreover,a modeling approach is proposed to mathematically describe the stability boundaries of combustion mode transition in scramjet engines,and the model has high ac-curacy comparing to the simulation data,which proves the validation of the basic ideas proposed in this paper.Finally,future research directions are proposed.
Catastrophe, hysteresis and bifurcation of mode transition in scramjet engines and its model
Institute of Scientific and Technical Information of China (English)
YU DaRen; CUI Tao; BAO Wen
2009-01-01
This paper describes a class of nonlinear phenomena existing in the hypersonic flow and supersonic combustion process of scramjet engines: catastrophe, hysteresis and bifurcation, and further finds out the general rules (topological invariance) for the stability boundaries of mode transition in scramjet engines. With this topological invariance, a topological approach is put forward to model the stability boundaries, which may contribute to a complexity reduction of high-dimensional modeling when con-sidering more perturbation parameters, and help to explore the physical laws of the nonlinear phe-nomena. Accordingly, this paper interprets the characteristic of combustion mode transition based on the cusp topological model in singular theories, and observes the bifurcation characteristic in com-bustion mode transition. Moreover, a modeling approach is proposed to mathematically describe the stability boundaries of combustion mode transition in scramjet engines, and the model has high ac-curacy comparing to the simulation data, which proves the validation of the basic ideas proposed in this paper. Finally, future research directions are proposed.
Catastrophe and beauty: Ways of Dying, Zakes Mda’s novel of the transition
Directory of Open Access Journals (Sweden)
J. van Wyk
1997-05-01
Full Text Available This article explores Zakes Mda's novel, Ways of Dying (1995, as an example of transitional literature. Ways of Dying (1995 deals with the period between 1990, when negotiations for change in South Africa started, and 1994, when South Africa became a democratic country. The text portrays many recognisable aspects of life in this transitional period, but the focus is mainly on the multiple occurrences of violent death in a society where the State has lost control and legitimacy. The main character, Toloki, a professional mourner, lives through these apocalyptic times. He is, further, seeking an answer to the question of how it happened that the child of his homegirl, Noria, died at the hands of comrades. The text deals imaginatively with aspects such as the resurgence of group psychology that is a common characteristic of transitional periods with its resistance culture of mass meetings, oratory by political leaders and street processions. These are also elements of the carnivalesque. One of the interesting features of the text is its many references to dreams and its use of dream devices in its form. This article will argue that this is an integral part of a literature of a transitional period. Such a period implies the erosion of the reality principle. Reality itself in such a period takes on the features of fantasy; beauty combines with catastrophe and the apocalypse with rebirth.
Phase Transitions of Simple Systems
Berry, Stephen
2008-01-01
This monograph develops a unified microscopic basis for phases and phase changes of bulk matter and small systems in terms of classical physics. The origins of such phase changes are derived from simple but physically relevant models of how transitions between rigid crystalline, glassy and fluid states occur, how phase equilibria arise, and how bulk properties evolve from those of small systems.
Electroweak phase transition in technicolor
Jarvinen, Matti
2010-01-01
Several phenomenologically viable walking technicolor models have been proposed recently. I demonstrate that these models can have first order electroweak phase transitions, which are sufficiently strong for electroweak baryogenesis. Strong dynamics can also lead to several separate transitions at the electroweak scale, with the possibility of a temporary restoration and an extra breaking of the electroweak symmetry. First order phase transitions will produce gravitational waves, which may be detectable at future experiments.
Magnetic resonance of phase transitions
Owens, Frank J; Farach, Horacio A
1979-01-01
Magnetic Resonance of Phase Transitions shows how the effects of phase transitions are manifested in the magnetic resonance data. The book discusses the basic concepts of structural phase and magnetic resonance; various types of magnetic resonances and their underlying principles; and the radiofrequency methods of nuclear magnetic resonance. The text also describes quadrupole methods; the microwave technique of electron spin resonance; and the Mössbauer effect. Phase transitions in various systems such as fluids, liquid crystals, and crystals, including paramagnets and ferroelectrics, are also
Phase transition analogies in a laser with saturable absorber
Energy Technology Data Exchange (ETDEWEB)
Dembinski, S.T.; Kossakowski, A. (Uniwersytet Mikolaja Kopernika, Torun (Poland). Instytut Fizyki)
1976-01-01
The possible threshold behavior of a four-level laser in the presence of a saturable absorber is examined. In the parameter space of the absorber, regions where the threshold behavior resemble first or second order phase transitions are found. The analysis is based on the semi-classical approximation and makes use of some concepts taken from Thom's theory of catastrophes.
Multiobjective Optimization and Phase Transitions
Seoane, Luís F
2015-01-01
Many complex systems obey to optimality conditions that are usually not simple. Conflicting traits often interact making a Multi Objective Optimization (MOO) approach necessary. Recent MOO research on complex systems report about the Pareto front (optimal designs implementing the best trade-off) in a qualitative manner. Meanwhile, research on traditional Simple Objective Optimization (SOO) often finds phase transitions and critical points. We summarize a robust framework that accounts for phase transitions located through SOO techniques and indicates what MOO features resolutely lead to phase transitions. These appear determined by the shape of the Pareto front, which at the same time is deeply related to the thermodynamic Gibbs surface. Indeed, thermodynamics can be written as an MOO from where its phase transitions can be parsimoniously derived; suggesting that the similarities between transitions in MOO-SOO and Statistical Mechanics go beyond mere coincidence.
Non-equilibrium phase transitions
Henkel, Malte; Lübeck, Sven
2009-01-01
This book describes two main classes of non-equilibrium phase-transitions: (a) static and dynamics of transitions into an absorbing state, and (b) dynamical scaling in far-from-equilibrium relaxation behaviour and ageing. The first volume begins with an introductory chapter which recalls the main concepts of phase-transitions, set for the convenience of the reader in an equilibrium context. The extension to non-equilibrium systems is made by using directed percolation as the main paradigm of absorbing phase transitions and in view of the richness of the known results an entire chapter is devoted to it, including a discussion of recent experimental results. Scaling theories and a large set of both numerical and analytical methods for the study of non-equilibrium phase transitions are thoroughly discussed. The techniques used for directed percolation are then extended to other universality classes and many important results on model parameters are provided for easy reference.
Overfishing reduces resilience of kelp beds to climate-driven catastrophic phase shift.
Ling, S D; Johnson, C R; Frusher, S D; Ridgway, K R
2009-12-29
A key consideration in assessing impacts of climate change is the possibility of synergistic effects with other human-induced stressors. In the ocean realm, climate change and overfishing pose two of the greatest challenges to the structure and functioning of marine ecosystems. In eastern Tasmania, temperate coastal waters are warming at approximately four times the global ocean warming average, representing the fastest rate of warming in the Southern Hemisphere. This has driven range extension of the ecologically important long-spined sea urchin (Centrostephanus rodgersii), which has now commenced catastrophic overgrazing of productive Tasmanian kelp beds leading to loss of biodiversity and important rocky reef ecosystem services. Coincident with the overgrazing is heavy fishing of reef-based predators including the spiny lobster Jasus edwardsii. By conducting experiments inside and outside Marine Protected Areas we show that fishing, by removing large predatory lobsters, has reduced the resilience of kelp beds against the climate-driven threat of the sea urchin and thus increased risk of catastrophic shift to widespread sea urchin barrens. This shows that interactions between multiple human-induced stressors can exacerbate nonlinear responses of ecosystems to climate change and limit the adaptive capacity of these systems. Management actions focused on reducing the risk of catastrophic phase shift in ecosystems are particularly urgent in the face of ongoing warming and unprecedented levels of predator removal from the world's oceans.
Energy Technology Data Exchange (ETDEWEB)
Orange, N. B.; Chesny, D. L.; Oluseyi, H. M.; Hesterly, K.; Patel, M.; Champey, P. [Department of Physics and Space Sciences, Florida Institute of Technology, Melbourne, FL 32901 (United States)
2013-12-01
Minimal observational evidence exists for fast transition region (TR) upflows in the presence of cool loops. Observations of such occurrences challenge notions of standard solar atmospheric heating models as well as their description of bright TR emission. Using the EUV Imaging Spectrometer on board Hinode, we observe fast upflows (v {sub λ} ≤ –10 km s{sup –1}) over multiple TR temperatures (5.8 ≤log T ≤ 6.0) at the footpoint sites of a cool loop (log T ≤ 6.0). Prior to cool loop energizing, asymmetric flows of +5 km s{sup –1} and –60 km s{sup –1} are observed at footpoint sites. These flows, speeds, and patterns occur simultaneously with both magnetic flux cancellation (at the site of upflows only) derived from the Solar Dynamics Observatory's Helioseismic Magnetic Imager's line-of-sight magnetogram images, and a 30% mass influx at coronal heights. The incurred non-equilibrium structure of the cool loop leads to a catastrophic cooling event, with subsequent plasma evaporation indicating that the TR is the heating site. From the magnetic flux evolution, we conclude that magnetic reconnection between the footpoint and background field is responsible for the observed fast TR plasma upflows.
Catastrophic glacial multi-phase mass movements: a special type of glacial hazard
Directory of Open Access Journals (Sweden)
D. A. Petrakov
2008-04-01
Full Text Available Many glacier-related hazards are well typified and studied, but some events stand out from conventional classifications. The Kolka-Karmadon catastrophic event on 20 September 2002 in North Ossetia, North Caucasus, Russia is used as an example of a complex glacier failure exhibiting characteristics such as high mobility, long runout, ultrarapid movement and multiphase behaviour. We consider terminology protocol for glacier hazard classification and then, using the Kolka-Karmadon event and several other examples from around the world, we propose a new term for this family of events. Catastrophic glacier multi-phase mass movement (CGMM is described and further illustrated by eight major events from Russia, Georgia, Peru, Chile, and Canada. CGMM have a combination of specific features: extraordinary velocities and long-distance runout despite low path angle; progressive fluidisation along travel path; superelevation and run-up of the moving mass, air blast wave in the avalanche flow phase; entrainment of available materials in its path, and the repeated nature of the event. CGMM events may affect areas remote from glaciers which were previously considered as safe.
Somkotra, Tewarit; Lagrada, Leizel P
2008-12-01
Equitable health financing was embodied in the reform strategies of Thailand's health care system when the country moved towards implementing the Universal Coverage (UC) policy in 2001. This study aimed to measure the pattern of household out-of-pocket payments for health care and to examine the financial catastrophe and impoverishment due to such payments during the transitional period (pre- and post-Universal Coverage policy implementation) in Thailand. This study used the nationally representative Socioeconomic Surveys in 2000 (pre-UC), 2002, and 2004 (post-UC), which contained data from 24747, 34758 and 34843 individual households, respectively. The proportion of out-of-pocket payments for health care as a share of household living standards among Thai households shows a decreasing pattern during the observed period. Moreover, the incidence and intensity of catastrophic payments for health care decline from the pre-UC to post-UC period. The distribution of incidence and the intensity of catastrophic payments for health care across quintiles also indicate that the lower quintile group (1st and 2nd quintiles) incurs lower catastrophic health care payments compared to the higher quintile group. The UC policy is also effective in preventing impoverishment due to out-of-pocket payments for health care since both the poverty headcount and poverty gap decline from the pre-UC to post-UC period. This study provides important evidence that the UC policy implementation is a valuable social protection and safety net strategy that contributes to the prevention of financial catastrophe and impoverishment due to out-of-pocket payments for health care. In conclusion, the UC policy in Thailand achieves one of the goals of improving the health system through equitable health care financing by reducing financial catastrophe and impoverishment due to out-of-pocket payments for health care.
Incommensurate phase transitions
Energy Technology Data Exchange (ETDEWEB)
Currat, R. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)
1996-11-01
We review the characteristic aspects of modulated crystals from the point of view of inelastic neutron scattering. We discuss the phenomenological Landau theory of the normal-to-incommensurate displacive instability and its predictions concerning the fluctuation spectrum of the modulated phase. General results on the form of the normal-mode eigenvectors and on the inelastic scattering channels through which they couple to the probe are established using the superspace approach. We illustrate these results on a simple discrete model symmetry and we review available inelastic neutron scattering data on several displacively modulated compounds. (author) 21 figs., 73 refs.
Phase transitions in finite systems
Energy Technology Data Exchange (ETDEWEB)
Chomaz, Ph. [Grand Accelerateur National d' Ions Lourds (GANIL), DSM-CEA / IN2P3-CNRS, 14 - Caen (France); Gulminelli, F. [Caen Univ., 14 (France). Lab. de Physique Corpusculaire
2002-07-01
In this series of lectures we will first review the general theory of phase transition in the framework of information theory and briefly address some of the well known mean field solutions of three dimensional problems. The theory of phase transitions in finite systems will then be discussed, with a special emphasis to the conceptual problems linked to a thermodynamical description for small, short-lived, open systems as metal clusters and data samples coming from nuclear collisions. The concept of negative heat capacity developed in the early seventies in the context of self-gravitating systems will be reinterpreted in the general framework of convexity anomalies of thermo-statistical potentials. The connection with the distribution of the order parameter will lead us to a definition of first order phase transitions in finite systems based on topology anomalies of the event distribution in the space of observations. Finally a careful study of the thermodynamical limit will provide a bridge with the standard theory of phase transitions and show that in a wide class of physical situations the different statistical ensembles are irreducibly inequivalent. (authors)
Symmetry structure and phase transitions
Indian Academy of Sciences (India)
Ashok Goyal; Meenu Dahiya; Deepak Chandra
2003-05-01
We study chiral symmetry structure at ﬁnite density and temperature in the presence of external magnetic ﬁeld and gravity, a situation relevant in the early Universe and in the core of compact stars. We then investigate the dynamical evolution of phase transition in the expanding early Universe and possible formation of quark nuggets and their survival.
Phase transitions and critical phenomena
Domb, Cyril
2001-01-01
The field of phase transitions and critical phenomena continues to be active in research, producing a steady stream of interesting and fruitful results. It has moved into a central place in condensed matter studies.Statistical physics, and more specifically, the theory of transitions between states of matter, more or less defines what we know about 'everyday' matter and its transformations.The major aim of this serial is to provide review articles that can serve as standard references for research workers in the field, and for graduate students and others wishing to obtain reliable in
Perga, M. E.; Taranu, Z. E.; Gregory-Eaves, I.; Frossard, V.; Thomas, Z.; Legendre, P.; Anderson, N. J.; Leavitt, P.; Gell, P.
2015-12-01
The observation that managed ecosystems often fail to respond smoothly to changing external pressures has shed some light on their complex non-linear dynamics. The concept of critical transitions (i.e., ecosystem regime shifts), thresholds and alternative stable states has since spread to the ecological and environmental management literature. Most recently, however, reviews have raised some skepticism about whether these catastrophic transitions are the exceptions rather than the rule. Overall, a better understanding of the occurrence and processes of such critical transitions requires more empirical testing and evidence on the mechanistic links between pressures and consequent ecological change. Many of the changes observed, or modeled, by ecologists extend beyond the monitoring record. Palaeo-ecological records thus represent a unique opportunity to extend our temporal perspective to the relevancy of critical transitions. Yet, paleo-ecological records have their own biases and shortcomings, such as sediment focusing, irregular temporal integration and often studied in a semi-quantitative way. As such, palaeo-ecological time series are not strictly analogous to instrumental datasets. In this work, we aimed to test, using both modeled and actual records, how different properties that are common in palaeo-ecological records affect our ability to detect past non-linear dynamics, such as early-warning signals of catastrophic shifts.
Sliding Over a Phase Transition
Tosatti, Erio; Benassi, Andrea; Vanossi, Andrea; Santoro, Giuseppe E.
2011-03-01
The frictional response experienced by a stick-slip slider when a phase transition occurs in the underlying solid substrate is a potentially exciting, poorly explored problem. We show, based on 2-dimensional simulations modeling the sliding of a nanotip, that indeed friction may be heavily affected by a continuous structural transition. First, friction turns nonmonotonic as temperature crosses the transition, peaking at the critical temperature Tc where fluctuations are strongest. Second, below Tc friction depends upon order parameter directions, and is much larger for those where the frictional slip can cause a local flip. This may open a route towards control of atomic scale friction by switching the order parameter direction by an external field or strain, with possible application to e.g., displacive ferroelectrics such as BaTi O3 , as well as ferro- and antiferro-distortive materials. Supported by project ESF FANAS/AFRI sponsored by the Italian Research Council (CNR).
Electroweak phase transition recent results
Csikor, Ferenc
2000-01-01
Recent results of four-dimensional (4d) lattice simulations on the finite temperature electroweak phase transition (EWPT) are discussed. The phase transition is of first order in the SU(2)-Higgs model below the end point Higgs mass 66.5$\\pm$1.4 GeV. For larger masses a rapid cross-over appears. This result completely agrees with the results of the dimensional reduction approach. Including the full Standard Model (SM) perturbatively the end point is at 72.1$\\pm$1.4 GeV. Combined with recent LEP Higgs mass lower bounds, this excludes any EWPT in the SM. A one-loop calculation of the static potential makes possible a precise comparison of the lattice and perturbative results. Recent 4d lattice studies of the Minimal Supersymmetric SM (MSSM) are also mentioned.
Glonke, Sebastian; Sadowski, Gabriele; Brandenbusch, Christoph
2016-11-01
Biphasic whole-cell biotransformations are known to be efficient alternatives to common chemical synthesis routes, especially for the production of, e.g. apolar enantiopure organic compounds. They provide high stereoselectivity combined with high product concentrations owing to the presence of an organic phase serving as substrate reservoir and product sink. Industrial implementation suffers from the formation of stable Pickering emulsions caused by the presence of cells. State-of-the-art downstream processing includes inefficient strategies such as excessive centrifugation, use of de-emulsifiers or thermal stress. In contrast, using the catastrophic phase inversion (CPI) phenomenon (sudden switch of emulsion type caused by addition of dispersed phase), Pickering-type emulsions can be destabilized efficiently. Within this work a model system using bis(2-ethylhexyl) phthalate (BEHP) as organic phase in combination with E. coli, JM101 was successfully separated using a continuous mixer settler setup. Compared to the state-of-the-art centrifugal separations, this process allows complete phase separation with no detectable water content or cells in the organic phase with no utilities/additives required. Furthermore, the concentration of the product is not affected by the separation. It is therefore a simple applicable method that can be used for separation of stable Pickering-type emulsions based on the knowledge of the point of inversion.
Gibbs measures and phase transitions
Georgii, Hans-Otto
2011-01-01
From a review of the first edition: ""This book […] covers in depth a broad range of topics in the mathematical theory of phase transition in statistical mechanics. […] It is in fact one of the author's stated aims that this comprehensive monograph should serve both as an introductory text and as a reference for the expert."" (F. Papangelou, Zentralblatt MATH) The second edition has been extended by a new section on large deviations and some comments on the more recent developments in the area.
Phase Transition in Tensor Models
Delepouve, Thibault
2015-01-01
Generalizing matrix models, tensor models generate dynamical triangulations in any dimension and support a $1/N$ expansion. Using the intermediate field representation we explicitly rewrite a quartic tensor model as a field theory for a fluctuation field around a vacuum state corresponding to the resummation of the entire leading order in $1/N$ (a resummation of the melonic family). We then prove that the critical regime in which the continuum limit in the sense of dynamical triangulations is reached is precisely a phase transition in the field theory sense for the fluctuation field.
Phase transitions and critical phenomena
Domb, Cyril
2000-01-01
The field of phase transitions and critical phenomena continues to be active in research, producing a steady stream of interesting and fruitful results. No longer an area of specialist interest, it has acquired a central focus in condensed matter studies. The major aim of this serial is to provide review articles that can serve as standard references for research workers in the field, and for graduate students and others wishing to obtain reliable information on important recent developments.The two review articles in this volume complement each other in a remarkable way. Both deal with what m
Light scattering near phase transitions
Cummins, HZ
1983-01-01
Since the development of the laser in the early 1960's, light scattering has played an increasingly crucial role in the investigation of many types of phase transitions and the published work in this field is now widely dispersed in a large number of books and journals.A comprehensive overview of contemporary theoretical and experimental research in this field is presented here. The reviews are written by authors who have actively contributed to the developments that have taken place in both Eastern and Western countries.
Second-Order Catalytic Quasispecies Yields First-Order Phase Transition
Wagner, Nathaniel; Tannenbaum, Emmanuel; Ashkenasy, Gonen
2009-01-01
The quasispecies model describes processes related to the origin of life and viral evolutionary dynamics. We discuss how the error catastrophe that reflects the transition from localized to delocalized quasispecies population is affected by catalytic replication of different reaction orders. Specifically, we find that 2nd order mechanisms lead to 1st order discontinuous phase transitions in the viable population fraction, and conclude that the "higher" the interaction the "lower" the transiti...
Quark Deconfinement Phase Transition in Neutron Stars
Alaverdyan, G B
2009-01-01
The hadron-quark phase transition in the interior of compact stars is investigated, when the transition proceeds through a mixed phase. The hadronic phase is described in the framework of relativistic mean-field theory, when also the scalar-isovector delta-meson mean-field is taken into account. The changes of the parameters of phase transition caused by the presence of delta-meson field are explored. The results of calculation of structure of the mixed phase (Glendenning construction) are compared with the results of usual first-order phase transition (Maxwell construction).
Interacting Weyl fermions: Phases, phase transitions and global phase diagram
Roy, Bitan; Juricic, Vladimir
2016-01-01
We study the effects of short-range interactions on a generalized three-dimensional Weyl semimetal, where the band touching points act as the (anti)monopoles of Abelian Berry curvature of strength $n$. We show that any local interaction has a \\emph{negative} scaling dimension $-2/n$. Consequently all Weyl semimetals are stable against weak short-range interactions. For sufficiently strong interactions, we demonstrate that the Weyl semimetal either undergoes a first order transition into a band insulator or a continuous transition into a symmetry breaking phase. A translational symmetry breaking axion insulator and a rotational symmetry breaking semimetal are two prominent candidates for the broken symmetry phase. At one loop level, the correlation length exponent for continuous transitions is $\
QCD Phase Transitions, Volume 15
Energy Technology Data Exchange (ETDEWEB)
Schaefer, T.; Shuryak, E.
1999-03-20
The title of the workshop, ''The QCD Phase Transitions'', in fact happened to be too narrow for its real contents. It would be more accurate to say that it was devoted to different phases of QCD and QCD-related gauge theories, with strong emphasis on discussion of the underlying non-perturbative mechanisms which manifest themselves as all those phases. Before we go to specifics, let us emphasize one important aspect of the present status of non-perturbative Quantum Field Theory in general. It remains true that its studies do not get attention proportional to the intellectual challenge they deserve, and that the theorists working on it remain very fragmented. The efforts to create Theory of Everything including Quantum Gravity have attracted the lion share of attention and young talent. Nevertheless, in the last few years there was also a tremendous progress and even some shift of attention toward emphasis on the unity of non-perturbative phenomena. For example, we have seen some efforts to connect the lessons from recent progress in Supersymmetric theories with that in QCD, as derived from phenomenology and lattice. Another example is Maldacena conjecture and related development, which connect three things together, string theory, super-gravity and the (N=4) supersymmetric gauge theory. Although the progress mentioned is remarkable by itself, if we would listen to each other more we may have chance to strengthen the field and reach better understanding of the spectacular non-perturbative physics.
The Structural Phase Transition in Solid DCN
DEFF Research Database (Denmark)
Dietrich, O. W.; Mackenzie, Gordon A.; Pawley, G. S.
1976-01-01
Neutron scattering measurements on deuterated hydrogen cyanide have shown that the structural phase transition from a tetragonal to an orthorhombic form at 160 K is a first order transition. A transverse acoustic phonon mode, which has the symmetry of the transition was observed at very low energ...... energies and showed “softening” as the transition was approached from above.......Neutron scattering measurements on deuterated hydrogen cyanide have shown that the structural phase transition from a tetragonal to an orthorhombic form at 160 K is a first order transition. A transverse acoustic phonon mode, which has the symmetry of the transition was observed at very low...
QGP phase transition and multiplicity fluctuations
Institute of Scientific and Technical Information of China (English)
杨纯斌; 王晓荣; 蔡勖
1997-01-01
The scaled factorial moments in QGP phase transitions are studied analytically by the extended Ginzburg-Landau model.The dependence of InFq on phase space interval is different for the first- and second-order QGP phase transitions.When lnFq are fitted to polynomials of X=δ1/3,the relative sign between the fitted coefficients of X and bq,l calculated theoretically can be used to judge the order of phase transitions.Two sets of experimental data are reanalysed and the phase transitions are the first order for one set of data but the second order for another.
Cosmological phase transitions from lattice field theory
Energy Technology Data Exchange (ETDEWEB)
Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2011-11-22
In this proceedings contribution we discuss the fate of the electroweak and the quantum chromodynamics phase transitions relevant for the early stage of the universe at non-zero temperature. These phase transitions are related to the Higgs mechanism and the breaking of chiral symmetry, respectively. We will review that non-perturbative lattice field theory simulations show that these phase transitions actually do not occur in nature and that physical observables show a completely smooth behaviour as a function of the temperature.
Holographic Phase Transition Probed by Nonlocal Observables
Directory of Open Access Journals (Sweden)
Xiao-Xiong Zeng
2016-01-01
Full Text Available From the viewpoint of holography, the phase structure of a 5-dimensional Reissner-Nordström-AdS black hole is probed by the two-point correlation function, Wilson loop, and entanglement entropy. As the case of thermal entropy, we find for all the probes that the black hole undergoes a Hawking-Page phase transition, a first-order phase transition, and a second-order phase transition successively before it reaches a stable phase. In addition, for these probes, we find that the equal area law for the first-order phase transition is valid always and the critical exponent of the heat capacity for the second-order phase transition coincides with that of the mean field theory regardless of the size of the boundary region.
Institute of Scientific and Technical Information of China (English)
黄定华; 段怡春; 李斌; 姚凌青; 张恒; 张凡; 王君慧; 郭浩; 殷鸿福
2002-01-01
On the centimeter scale of lithologic change,we conduct poly-statistic analysis on the sedimentary behavior and dynamic features of the stratigraphic sequence from upper Dalong formation to lower Daye formation,which across the Permian-Triassic boundary in East Hubei.From the perspective of stochastically dynamic system,the depositional process of upper Dalong formation can be regarded as a stable Markovian process with weakly stratigraphic correlation and randomly lithologic alteration.Compared to it,the depositional process of lower Daye formation was unstable Markovian process with much closer stratigraphic correlation and ordered lithologic change.As for the replacement style of the sedimental cycle,the former was chaotic,while the latter was periodical.Otherwise,although the overall depositional process of the two formations was continuous,their dynamic characteristics were obviously different.So this P-T sedimental boundary can also be regarded as a dynamic limit.It was a kind of depositional reaction in response to a catastrophic alteration when the geological environment was in continuous change but came over a certain threshold state.
The Diamagnetic Phase Transition of Dense Electron Gas: Astrophysical Applications
Wang, Zhaojun; Lü, Guoliang; Zhu, Chunhua; Wu, Baoshan
2016-10-01
Neutron stars are ideal astrophysical laboratories for testing theories of the de Haas-van Alphen effect and diamagnetic phase transition which is associated with magnetic domain formation. The “magnetic interaction” between delocalized magnetic moments of electrons (the Shoenberg effect), can result in an effect of the diamagnetic phase transition into domains of alternating magnetization (Condon's domains). Associated with the domain formation are prominent magnetic field oscillation and anisotropic magnetic stress which may be large enough to fracture the crust of magnetar with a super-strong field. Even if the fracture is impossible as in “low-field” magnetar, the depinning phase transition of domain wall (DW) motion driven by low field rate (mainly due to the Hall effect) in the randomly perturbed crust can result in a catastrophically variation of magnetic field. This intermittent motion, similar to the avalanche process, makes the Hall effect be dissipative. These qualitative consequences about magnetized electron gas are consistent with observations of magnetar emission, and especially the threshold critical dynamics of driven DW can partially overcome the difficulties of “low-field” magnetar bursts and the heating mechanism of transient, or “outbursting” magnetar.
Quantum Phase Transitions in a Finite System
Leviatan, A
2006-01-01
A general procedure for studying finite-N effects in quantum phase transitions of finite systems is presented and applied to the critical-point dynamics of nuclei undergoing a shape-phase transition of second-order (continuous), and of first-order with an arbitrary barrier.
The Structural Phase Transition in Solid DCN
DEFF Research Database (Denmark)
Dietrich, O. W.; Mackenzie, Gordon A.; Pawley, G. S.
1975-01-01
Neutron scattering measurements on deuterated hydrogen cyanide have shown that the structural phase change from a tetragonal to an orthorhombic form at 160K is a first-order transition. A transverse acoustic phonon mode, which has the symmetry of the phase change, was observed at very low energies...... and showed 'softening' as the transition temperature was approached from above....
Phase transitions in the web of science
Phillips, J. C.
2015-06-01
The Internet age is changing the structure of science, and affecting interdisciplinary interactions. Publication profiles connecting mathematics with molecular biology and condensed matter physics over the last 40 years exhibit common phase transitions indicative of the critical role played by specific interdisciplinary interactions. The strengths of the phase transitions quantify the importance of interdisciplinary interactions.
SUSY and the Electroweak Phase Transition
Farrar, Glennys R S; Farrar, Glennys R.; Losada, Marta
1996-01-01
We analyze the effective 3 dimensional theory previously constructed for the MSSM and multi-Higgs models to determine the regions of parameter space in which the electroweak phase transition is sufficiently strong for a $B+L$ asymmetry to survive in the low temperature phase. We find that the inclusion of all supersymmetric scalars and all 1-loop corrections has the effect of enhancing the strength of the phase transition. Without a light stop or extension of the MSSM the phase transition is sufficiently first order only if the lightest Higgs mass $M_{h}\\lsi 70$ GeV and $tan\\beta\\lsi 1.75$.
Chirality effects on 2D phase transitions
DEFF Research Database (Denmark)
Scalas, E.; Brezesinski, G.; Möhwald, H.
1996-01-01
-nearest neighbours (NNN) and an NNN-distorted lattice is observed. At 5 degrees C, the transition pressure is 15 mN m(-1), whereas at 20 degrees C it is 18 mN m(-1). Chirality destroys this transition: the pure enantiomer always exhibits an oblique lattice with tilted molecules, and the azimuths of tilt...... and distortion continuously vary from a direction close to NN to a direction close to NNN. The nature of the phase transition and the influence of chirality on it are discussed within the framework of Landau's theory of phase transitions....
Conductor-insulator quantum phase transitions
Trivedi, Nandini; Valles, James M
2012-01-01
When many particles come together how do they organise themselves? And what destroys this organisation? Combining experiments and theory, this book describes intriguing quantum phases - metals, superconductors and insulators - and transitions between them.
Magnetic Fields from the Electroweak Phase Transition
Törnkvist, O
1998-01-01
I review some of the mechanisms through which primordial magnetic fields may be created in the electroweak phase transition. I show that no magnetic fields are produced initially from two-bubble collisions in a first-order transition. The initial field produced in a three-bubble collision is computed. The evolution of fields at later times is discussed.
Molecular markers of phase transition in locusts
Institute of Scientific and Technical Information of China (English)
ARNOLD DE LOOF; ILSE CLAEYS; GERT SIMONET; PETER VERLEYEN; TIM VANDERSMISSEN; FILIP SAS; JURGEN HUYBRECHTS
2006-01-01
The changes accompanying the transition from the gregarious to the solitary phase state in locusts are so drastic that for a long time these phases were considered as distinct species. It was Boris Uvarov who introduced the concept of polyphenism. Decades of research revealed that phase transition implies changes in morphometry, the color of the cuticle, behavior and several aspects of physiology. In particular, in the recent decade, quite a number of molecular studies have been undertaken to uncover phase-related differences.They resulted in novel insights into the role of corazonin, neuroparsins, some protease inhibitors, phenylacetonitrile and so on. The advent of EST-databases of locusts (e.g. Kang et al., 2004) is a most encouraging novel development in physiological and behavioral locust research. Yet, the answer to the most intriguing question, namely whether or not there is a primordial molecular inducer of phase transition, is probably not within reach in the very near future.
Polymorphic phase transition in Superhydrous Phase B
Koch-Müller, M.; Dera, P.; Fei, Y.; Hellwig, H.; Liu, Z.; Orman, J. Van; Wirth, R.
2005-09-01
We synthesized superhydrous phase B (shy-B) at 22 GPa and two different temperatures: 1200°C (LT) and 1400°C (HT) using a multi-anvil apparatus. The samples were investigated by transmission electron microscopy (TEM), single crystal X-ray diffraction, Raman and IR spectroscopy. The IR spectra were collected on polycrystalline thin-films and single crystals using synchrotron radiation, as well as a conventional IR source at ambient conditions and in situ at various pressures (up to 15 GPa) and temperatures (down to -180°C). Our studies show that shy-B exists in two polymorphic forms. As expected from crystal chemistry, the LT polymorph crystallizes in a lower symmetry space group ( Pnn2), whereas the HT polymorph assumes a higher symmetry space group ( Pnnm). TEM shows that both modifications consist of nearly perfect crystals with almost no lattice defects or inclusions of additional phases. IR spectra taken on polycrystalline thin films exhibit just one symmetric OH band and 29 lattice modes for the HT polymorph in contrast to two intense but asymmetric OH stretching bands and at least 48 lattice modes for the LT sample. The IR spectra differ not only in the number of bands, but also in the response of the bands to changes in pressure. The pressure derivatives for the IR bands are higher for the HT polymorph indicating that the high symmetry form is more compressible than the low symmetry form. Polarized, low-temperature single-crystal IR spectra indicate that in the LT-polymorph extensive ordering occurs not only at the Mg sites but also at the hydrogen sites.
Polymorphic Phase Transition in Superhydrous Phase B
Energy Technology Data Exchange (ETDEWEB)
Koch-Muller,M.; Dera, P.; Fei, Y.; Hellwig, H.; Liu, Z.; Van Orman, J.; Wirth, R.
2005-01-01
We synthesized superhydrous phase B (shy-B) at 22 GPa and two different temperatures: 1200 C (LT) and 1400 C (HT) using a multi-anvil apparatus. The samples were investigated by transmission electron microscopy (TEM), single crystal X-ray diffraction, Raman and IR spectroscopy. The IR spectra were collected on polycrystalline thin-films and single crystals using synchrotron radiation, as well as a conventional IR source at ambient conditions and in situ at various pressures (up to 15 GPa) and temperatures (down to -180 C). Our studies show that shy-B exists in two polymorphic forms. As expected from crystal chemistry, the LT polymorph crystallizes in a lower symmetry space group (Pnn2), whereas the HT polymorph assumes a higher symmetry space group (Pnnm). TEM shows that both modifications consist of nearly perfect crystals with almost no lattice defects or inclusions of additional phases. IR spectra taken on polycrystalline thin films exhibit just one symmetric OH band and 29 lattice modes for the HT polymorph in contrast to two intense but asymmetric OH stretching bands and at least 48 lattice modes for the LT sample. The IR spectra differ not only in the number of bands, but also in the response of the bands to changes in pressure. The pressure derivatives for the IR bands are higher for the HT polymorph indicating that the high symmetry form is more compressible than the low symmetry form. Polarized, low-temperature single-crystal IR spectra indicate that in the LT-polymorph extensive ordering occurs not only at the Mg sites but also at the hydrogen sites.
Contemporary research of dynamically induced phase transitions
Hull, L. M.
2017-01-01
Dynamically induced phase transitions in metals, within the present discussion, are those that take place within a time scale characteristic of the shock waves and any reflections or rarefactions involved in the loading structure along with associated plastic flow. Contemporary topics of interest include the influence of loading wave shape, the effect of shear produced by directionality of the loading relative to the sample dimensions and initial velocity field, and the loading duration (kinetic effects, hysteresis) on the appearance and longevity of a transformed phase. These topics often arise while considering the loading of parts of various shapes with high explosives, are typically two or three-dimensional, and are often selected because of the potential of the transformed phase to significantly modify the motion. In this paper, we look at current work on phase transitions in metals influenced by shear reported in the literature, and relate recent work conducted at Los Alamos on iron's epsilon phase transition that indicates a significant response to shear produced by reflected elastic waves. A brief discussion of criteria for the occurrence of stress induced phase transitions is provided. Closing remarks regard certain physical processes, such as fragmentation and jet formation, which may be strongly influenced by phase transitions.
Magnetic phase transitions in layered intermetallic compounds
Mushnikov, N. V.; Gerasimov, E. G.; Rosenfeld, E. V.; Terent'ev, P. B.; Gaviko, V. S.
2012-10-01
Magnetic, magnetoelastic, and magnetotransport properties have been studied for the RMn2Si2 and RMn6Sn6 (R is a rare earth metal) intermetallic compounds with natural layered structure. The compounds exhibit wide variety of magnetic structures and magnetic phase transitions. Substitution of different R atoms allows us to modify the interatomic distances and interlayer exchange interactions thus providing the transition from antiferromagnetic to ferromagnetic state. Near the boundary of this transition the magnetic structures are very sensitive to the external field, temperature and pressure. The field-induced transitions are accompanied by considerable change in the sample size and resistivity. It has been shown that various magnetic structures and magnetic phase transitions observed in the layered compounds arise as a result of competition of the Mn-Mn and Mn-R exchange interactions.
An absorbing phase transition from a structured active particle phase
Energy Technology Data Exchange (ETDEWEB)
Lopez, Cristobal [Instituto Mediterraneo de Estudios Avanzados IMEDEA (CSIC-UIB), Campus de la Universidad de las Islas Baleares, E-07122 Palma de Mallorca (Spain); Ramos, Francisco [Departamento de Electromagnetismo y Fisica de la Materia and Instituto de Fisica Teorica y Computacional Carlos I, Facultad de Ciencias, Universidad de Granada, 18071 Granada (Spain); Hernandez-GarcIa, Emilio [Instituto Mediterraneo de Estudios Avanzados IMEDEA (CSIC-UIB), Campus de la Universidad de las Islas Baleares, E-07122 Palma de Mallorca (Spain)
2007-02-14
In this work we study the absorbing state phase transition of a recently introduced model for interacting particles with neighbourhood-dependent reproduction rates. The novelty of the transition is that as soon as the active phase is reached by increasing a control parameter a periodically arranged structure of particle clusters appears. A numerical study in one and two dimensions shows that the system falls into the directed percolation universality class.
Numerical Study of Phase Transition in Thermoviscoelasticity
Institute of Scientific and Technical Information of China (English)
ShaoqingTANG
1997-01-01
We study the spatially periodic problem of thermoviscoelasticity with nonmonotone structure relations.By pseudo-spectral method.we demosnstrate numerically phase transitions for certain symmetric initial data.Without symmetry,the simulations show that a translation occurs for the phase boundary.
Phase Transition in the Simplest Plasma Model
Iosilevskiy, Igor
2009-01-01
We have investigated the phase transition of the gas-liquid type, with an upper critical point, in a variant of the One Component Plasma model (OCP) that has a uniform but compressible compensating background. We have calculated the parameters of the critical and triple points, spinodals, and two-phase coexistence curves (binodals). We have analyzed the connection of this simplest plasma phase transition with anomalies in the spatial charge profiles of equilibrium non-uniform plasma in the local-density approximations of Thomas-Fermi or Poisson-Boltzmann-type.
End point of the electroweak phase transition
Csikor, Ferenc; Heitger, J; Aoki, Y; Ukawa, A
1999-01-01
We study the hot electroweak phase transition (EWPT) by 4-dimensional lattice simulations on lattices with symmetric and asymmetric lattice spacings and give the phase diagram. A continuum extrapolation is done. We find first order phase transition for Higgs-boson masses $m_H<66.5 \\pm 1.4$ GeV. Above this end point a rapid cross-over occurs. Our result agrees with that of the dimensional reduction approach. It also indicates that the fermionic sector of the Standard Model (SM) may be included perturbatively. We get for the SM end point $72.4 the SM.
Phase Transition Induced Fission in Lipid Vesicles
Leirer, C; Myles, V M; Schneider, M F
2010-01-01
In this work we demonstrate how the first order phase transition in giant unilamellar vesicles (GUVs) can function as a trigger for membrane fission. When driven through their gel-fluid phase transition GUVs exhibit budding or pearl formation. These buds remain connected to the mother vesicle presumably by a small neck. Cooling these vesicles from the fluid phase (T>Tm) through the phase transition into the gel state (T
Microgravity Two-Phase Flow Transition
Parang, M.; Chao, D.
1999-01-01
Two-phase flows under microgravity condition find a large number of important applications in fluid handling and storage, and spacecraft thermal management. Specifically, under microgravity condition heat transfer between heat exchanger surfaces and fluids depend critically on the distribution and interaction between different fluid phases which are often qualitatively different from the gravity-based systems. Heat transfer and flow analysis in two-phase flows under these conditions require a clear understanding of the flow pattern transition and development of appropriate dimensionless scales for its modeling and prediction. The physics of this flow is however very complex and remains poorly understood. This has led to various inadequacies in flow and heat transfer modeling and has made prediction of flow transition difficult in engineering design of efficient thermal and flow systems. In the present study the available published data for flow transition under microgravity condition are considered for mapping. The transition from slug to annular flow and from bubbly to slug flow are mapped using dimensionless variable combination developed in a previous study by the authors. The result indicate that the new maps describe the flow transitions reasonably well over the range of the data available. The transition maps are examined and the results are discussed in relation to the presumed balance of forces and flow dynamics. It is suggested that further evaluation of the proposed flow and transition mapping will require a wider range of microgravity data expected to be made available in future studies.
PT phase transition in multidimensional quantum systems
Bender, Carl M
2012-01-01
Non-Hermitian PT-symmetric quantum-mechanical Hamiltonians generally exhibit a phase transition that separates two parametric regions, (i) a region of unbroken PT symmetry in which the eigenvalues are all real, and (ii) a region of broken PT symmetry in which some of the eigenvalues are complex. This transition has recently been observed experimentally in a variety of physical systems. Until now, theoretical studies of the PT phase transition have generally been limited to one-dimensional models. Here, four nontrivial coupled PT-symmetric Hamiltonians, $H=p^2/2+x^2/2+q^2/2+y^2/2+igx^2y$, $H=p^2/2+x^2/2+q^2/2+y^2+igx^2y$, $H=p^2/2+x^2/2+q^2/2+y^2/2+r^2/2+z^2/2+igxyz$, and $H=p^2/2+x^2/2+q^2/2+y^2+r^2/2+3z^2/2+igxyz$ are examined. Based on extensive numerical studies, this paper conjectures that all four models exhibit a phase transition. The transitions are found to occur at $g\\approx 0.1$, $g\\approx 0.04$, $g\\approx 0.1$, and $g\\approx 0.05$. These results suggest that the PT phase transition is a robust phen...
Quantum critical phase and Lifshitz transition in an extended periodic Anderson model.
Laad, M S; Koley, S; Taraphder, A
2012-06-13
We study the quantum phase transition in f-electron systems as a quantum Lifshitz transition driven by selective-Mott localization in a realistic extended Anderson lattice model. Using dynamical mean-field theory (DMFT), we find that a quantum critical phase with anomalous ω/T scaling separates a heavy Landau-Fermi liquid from ordered phase(s). This non-Fermi liquid state arises from a lattice orthogonality catastrophe originating from orbital-selective Mott localization. Fermi surface reconstruction occurs via the interplay between and penetration of the Green function zeros to the poles, leading to violation of Luttinger's theorem in the strange metal. We show how this naturally leads to scale-invariant responses in transport. Thus, our work represents a specific DMFT realization of the hidden-FL and FL* theories, and holds promise for the study of 'strange' metal phases in quantum matter.
Quantum phase transitions with dynamical flavors
Bea, Yago; Ramallo, Alfonso V
2016-01-01
We study the properties of a D6-brane probe in the ABJM background with smeared massless dynamical quarks in the Veneziano limit. Working at zero temperature and non-vanishing charge density, we show that the system undergoes a quantum phase transition in which the topology of the brane embedding changes from a black hole to a Minkowski embedding. In the unflavored background the phase transition is of second order and takes place when the charge density vanishes. We determine the corresponding critical exponents and show that the scaling behavior near the quantum critical point has multiplicative logarithmic corrections. In the background with dynamical quarks the phase transition is of first order and occurs at non-zero charge density. In this case we compute the discontinuity of several physical quantities as functions of the number $N_f$ of unquenched quarks of the background.
Thermogeometric phase transition in a unified framework
Banerjee, Rabin; Samanta, Saurav
2016-01-01
Using geomterothermodynamics (GTD), we investigate the phase transition of black hole in a metric independent way. We show that for any black hole, curvature scalar (of equilibrium state space geometry) is singular at the point where specific heat diverges. Previously such a result could only be shown by taking specific examples on a case by case basis. A different type of phase transition, where inverse specific heat diverges, is also studied within this framework. We show that in the latter case, metric (of equilibrium state space geometry) is singular instead of curvature scalar. Since a metric singularity may be a coordinate artifact, we propose that GTD indicates that it is the singularity of specific heat and not inverse specific heat which indicates a phase transition of black holes.
Quantum phase transitions with dynamical flavors
Bea, Yago; Jokela, Niko; Ramallo, Alfonso V.
2016-07-01
We study the properties of a D6-brane probe in the Aharony-Bergman-Jafferis-Maldacena (ABJM) background with smeared massless dynamical quarks in the Veneziano limit. Working at zero temperature and nonvanishing charge density, we show that the system undergoes a quantum phase transition in which the topology of the brane embedding changes from a black hole to a Minkowski embedding. In the unflavored background the phase transition is of second order and takes place when the charge density vanishes. We determine the corresponding critical exponents and show that the scaling behavior near the quantum critical point has multiplicative logarithmic corrections. In the background with dynamical quarks the phase transition is of first order and occurs at nonzero charge density. In this case we compute the discontinuity of several physical quantities as functions of the number Nf of unquenched quarks of the background.
Late-time cosmological phase transitions
Energy Technology Data Exchange (ETDEWEB)
Schramm, D.N. (Chicago Univ., IL (USA) Fermi National Accelerator Lab., Batavia, IL (USA))
1990-11-01
It is shown that the potential galaxy formation and large-scale structure problems of objects existing at high redshifts (Z {approx gt} 5), structures existing on scales of 100M pc as well as velocity flows on such scales, and minimal microwave anisotropies ({Delta}T/T) {approx lt} 10{sup {minus}5} can be solved if the seeds needed to generate structure form in a vacuum phase transition after decoupling. It is argued that the basic physics of such a phase transition is no more exotic than that utilized in the more traditional GUT scale phase transitions, and that, just as in the GUT case, significant random gaussian fluctuations and/or topological defects can form. Scale lengths of {approximately}100M pc for large-scale structure as well as {approximately}1 M pc for galaxy formation occur naturally. Possible support for new physics that might be associated with such a late-time transition comes from the preliminary results of the SAGE solar neutrino experiment, implying neutrino flavor mixing with values similar to those required for a late-time transition. It is also noted that a see-saw model for the neutrino masses might also imply a tau neutrino mass that is an ideal hot dark matter candidate. However, in general either hot or cold dark matter can be consistent with a late-time transition. 47 refs., 2 figs.
Exceptional Points and Dynamical Phase Transitions
Directory of Open Access Journals (Sweden)
I. Rotter
2010-01-01
Full Text Available In the framework of non-Hermitian quantum physics, the relation between exceptional points,dynamical phase transitions and the counter intuitive behavior of quantum systems at high level density is considered. The theoretical results obtained for open quantum systems and proven experimentally some years ago on a microwave cavity, may explain environmentally induce deffects (including dynamical phase transitions, which have been observed in various experimental studies. They also agree(qualitatively with the experimental results reported recently in PT symmetric optical lattices.
Scaling Concepts in Describing Continuous Phase Transitions
Indian Academy of Sciences (India)
2016-10-01
Phase transitions, like the boiling of water upon increasingtemperature, are a part of everyday experience and are yet,upon closer inspection, unusual phenomena, and reveal a hostof fascinating features. Comprehending key aspects of phasetransitions has lead to the uncovering of new ways of describingmatter composed of large numbers of interacting elements,which form a dominant way of analysis in contemporarystatistical mechanics and much else. An introductorydiscussion is presented here of the concepts of scaling, universalityand renormalization, which forms the foundation ofthe study of continuous phase transitions, such as the spontaneousmagnetization of ferromagnetic substances.
Phase Transition in Loop Quantum Gravity
Mäkelä, Jarmo
2016-01-01
We point out that with a specific counting of states loop quantum gravity implies that black holes perform a phase transition at a certain characteristic temperature $T_C$. In this phase transition the punctures of the spin network on the stretched horizon of the black hole jump, in effect, from the vacuum to the excited states. The characteristic temperature $T_C$ may be regarded as the lowest possible temperature of the hole. From the point of view of a distant observer at rest with respect to the hole the characteristic temperature $T_C$ corresponds to the Hawking temperature of the hole.
Queueing phase transition: theory of translation.
Romano, M Carmen; Thiel, Marco; Stansfield, Ian; Grebogi, Celso
2009-05-15
We study the current of particles on a lattice, where to each site a different hopping probability has been associated and the particles can move only in one direction. We show that the queueing of the particles behind a slow site can lead to a first-order phase transition, and derive analytical expressions for the configuration of slow sites for this to happen. We apply this stochastic model to describe the translation of mRNAs. We show that the first-order phase transition, uncovered in this work, is the process responsible for the classification of the proteins having different biological functions.
Fluctuations near the deconfinement phase transition boundary
Mishustin, I N
2005-01-01
In this talk I discuss how a first order phase transition may proceed in rapidly expanding partonic matter produced in a relativistic heavy-ion collision. The resulting picture is that a strong collective flow of matter will lead to the fragmentation of a metastable phase into droplets. If the transition from quark-gluon plasma to hadron gas is of the first order, it will manifest itself by strong nonstatistical fluctuations in observable hadron distributions. I discuss shortly existing experimental data on the multiplicity fluctuations.
Endpoint of the hot electroweak phase transition
Csikor, Ferenc; Heitger, J
1999-01-01
We give the nonperturbative phase diagram of the four-dimensional hot electroweak phase transition. The Monte-Carlo analysis is done on lattices with different lattice spacings ($a$). A systematic extrapolation $a \\to 0$ is done. Our results show that the finite temperature SU(2)-Higgs phase transition is of first order for Higgs-boson masses $m_H<66.5 \\pm 1.4$ GeV. At this endpoint the phase transition is of second order, whereas above it only a rapid cross-over can be seen. The full four-dimensional result agrees completely with that of the dimensional reduction approximation. This fact is of particular importance, because it indicates that the fermionic sector of the Standard Model can be included perturbatively. We obtain that the Higgs-boson endpoint mass in the Standard Model is $72.4 \\pm 1.7$ GeV. Taking into account the LEP Higgs-boson mass lower bound excludes any electroweak phase transition in the Standard Model.
Transition to turbulence in pipe flow as a phase transition
Vasudevan, Mukund; Hof, Björn
2015-11-01
In pipe flow, turbulence first arises in the form of localized turbulent patches called puffs. The flow undergoes a transition to sustained turbulence via spatio-temporal intermittency, with puffs splitting, decaying and merging in the background laminar flow. However, the due to mean advection of the puffs and the long timescales involved (~107 advective time units), it is not possible to study the transition in typical laboratory set-ups. So far, it has only been possible to indirectly estimate the critical point for the transition. Here, we exploit the stochastic memoryless nature of the puff decay and splitting processes to construct a pipe flow set-up, that is periodic in a statistical sense. It then becomes possible to study the flow for sufficiently long times and characterize the transition in detail. We present measurements of the turbulent fraction as a function of Reynolds number which in turn allows a direct estimate of the critical point. We present evidence that the transition has features of a phase transition of second order.
Deconfinement phase transition in neutron star matter
Institute of Scientific and Technical Information of China (English)
LI Ang; PENG Guang-Xiong; Lombardo U
2009-01-01
The transition from hadron phase to strange quark phase in dense matter is investigated. Instead of using the conventional bag model in quark sect, we achieve the confinement by a density-dependent quark mass derived from in-medium chiral condensates, with a thermodynamic problem improved. In nuclear slot,we adopt the equation of state from Brueckner-Bethe-Goldstone approach with three-body force. It is found that the mixed phase can occur, for reasonable confinement parameter, near the normal saturation density,and transit to pure quark matter at 4-5 times the saturation, which is quite different from the previous results from other quark models that pure quark phase can not appear at neutron-star densities.
Liquid gas phase transition in hypernuclei
Mallik, S
2016-01-01
The fragmentation of excited hypernuclear system formed in heavy ion collisions has been described by the canonical thermodynamical model extended to three component systems. The multiplicity distribution of the fragments has been analyzed in detail and it has been observed that the hyperons have the tendency to get attached to the heavier fragments. Another important observation is the phase coexistence of the hyperons, a phenomenon which is linked to liquid gas phase transition in strange matter.
Chaos: Butterflies also Generate Phase Transitions
Leplaideur, Renaud
2015-10-01
We exhibit examples of mixing subshifts of finite type and of continuous potentials such that there are phase transitions but the pressure is always strictly convex. More surprisingly, we show that the pressure can be analytic on some interval although there exist several equilibrium states.
The Structural Phase Transition in Octaflournaphtalene
DEFF Research Database (Denmark)
Mackenzie, Gordon A.; Arthur, J. W.; Pawley, G. S.
1977-01-01
The phase transition in octafluoronaphthalene has been investigated by Raman scattering and neutron powder diffraction. The weight of the experimental evidence points to a unit cell doubling in the a direction, but with no change in space group symmetry. Lattice dynamics calculations support...
Problem of phase transitions in nuclear structure
Energy Technology Data Exchange (ETDEWEB)
Scharff-Goldhaber, G
1980-01-01
Phase transitions between rotational and vibrational nuclei are discussed from the point of view of the variable moment of inertia model. A three-dimensional plot of the ground-state moments of inertia of even-even nuclei vs N and Z is shown. 3 figures. (RWR)
Caloric materials near ferroic phase transitions
Moya, X.; Kar-Narayan, S.; Mathur, N. D.
2014-05-01
A magnetically, electrically or mechanically responsive material can undergo significant thermal changes near a ferroic phase transition when its order parameter is modified by the conjugate applied field. The resulting magnetocaloric, electrocaloric and mechanocaloric (elastocaloric or barocaloric) effects are compared here in terms of history, experimental method, performance and prospective cooling applications.
Neutrino Oscillation Induced by Chiral Phase Transition
Institute of Scientific and Technical Information of China (English)
MU Cheng-Fu; SUN Gao-Feng; ZHUANG Peng-Fei
2009-01-01
Electric charge neutrality provides a relationship between chiral dynamics and neutrino propagation in compact stars.Due to the sudden drop of the electron density at the first-order chiral phase transition,the oscillation for low energy neutrinos is significant and can be regarded as a signature of chiral symmetry restoration in the core of compact stars.
Higgs Couplings and Electroweak Phase Transition
Katz, Andrey
2014-01-01
We argue that extensions of the Standard Model (SM) with a strongly first-order electroweak phase transition generically predict significant deviations of the Higgs couplings to gluons, photons, and Z bosons from their SM values. Precise experimental measurements of the Higgs couplings at the LHC and at the proposed next-generation facilities will allow for a robust test of the phase transition dynamics. To illustrate this point, in this paper we focus on the scenario in which loops of a new scalar field are responsible for the first-order phase transition, and study a selection of benchmark models with various SM gauge quantum numbers of the new scalar. We find that the current LHC measurement of the Higgs coupling to gluons already excludes the possibility of a first-order phase transition induced by a scalar in a sextet, or larger, representation of the SU(3)_c. Future LHC experiments (including HL-LHC) will be able to definitively probe the case when the new scalar is a color triplet. If the new scalar is...
Passive Supporters of Terrorism and Phase Transitions
August, Friedrich; Delitzscher, Sascha; Hiller, Gerald; Krueger, Tyll
2010-01-01
We discuss some social contagion processes to describe the formation and spread of radical opinions. The dynamics of opinion spread involves local threshold processes as well as mean field effects. We calculate and observe phase transitions in the dynamical variables resulting in a rapidly increasing number of passive supporters. This strongly indicates that military solutions are inappropriate.
Hysteresis in the phase transition of chocolate
Ren, Ruilong; Lu, Qunfeng; Lin, Sihua; Dong, Xiaoyan; Fu, Hao; Wu, Shaoyi; Wu, Minghe; Teng, Baohua
2016-01-01
We designed an experiment to reproduce the hysteresis phenomenon of chocolate appearing in the heating and cooling process, and then established a model to relate the solidification degree to the order parameter. Based on the Landau-Devonshire theory, our model gave a description of the hysteresis phenomenon in chocolate, which lays the foundations for the study of the phase transition behavior of chocolate.
The transition to chaotic phase synchronization
DEFF Research Database (Denmark)
Mosekilde, E.; Laugesen, J. L.; Zhusubaliyev, Zh. T.
2012-01-01
The transition to chaotic phase synchronization for a periodically driven spiral-type chaotic oscillator is known to involve a dense set of saddle-node bifurcations. By following the synchronization transition through the cascade of period-doubling bifurcations in a forced Ro¨ssler system......, this paper describes how these saddle-node bifurcations arise and how their characteristic cyclic organisation develops. We identify the cycles that are involved in the various saddle-node bifurcations and describe how the formation of multi-layered resonance cycles in the synchronization domain is related...... varying arterial blood pressure. The paper finally discusses how an alternative transition to chaotic phase synchronization may occur in the mutual synchronization of two chaotically oscillating period-doubling systems....
Dimensional phase transitions in small Yukawa clusters
Sheridan, T E
2009-01-01
We investigate the one- to two-dimensional zigzag transition in clusters consisting of a small number of particles interacting through a Yukawa (Debye) potential and confined in a two-dimensional biharmonic potential well. Dusty (complex) plasma clusters with $n \\le 19$ monodisperse particles are characterized experimentally for two different confining wells. The well anisotropy is accurately measured, and the Debye shielding parameter is determined from the longitudinal breathing frequency. Debye shielding is shown to be important. A model for this system is used to predict equilibrium particle configurations. The experiment and model exhibit excellent agreement. The critical value of $n$ for the zigzag transition is found to be less than that predicted for an unshielded Coulomb interaction. The zigzag transition is shown to behave as a continuous phase transition from a one-dimensional to a two-dimensional state, where the state variables are the number of particles, the well anisotropy and the Debye shield...
Statistical physics of non-thermal phase transitions from foundations to applications
Abaimov, Sergey G
2015-01-01
Statistical physics can be used to better understand non-thermal complex systems—phenomena such as stock-market crashes, revolutions in society and in science, fractures in engineered materials and in the Earth’s crust, catastrophes, traffic jams, petroleum clusters, polymerization, self-organized criticality and many others exhibit behaviors resembling those of thermodynamic systems. In particular, many of these systems possess phase transitions identical to critical or spinodal phenomena in statistical physics. The application of the well-developed formalism of statistical physics to non-thermal complex systems may help to predict and prevent such catastrophes as earthquakes, snow-avalanches and landslides, failure of engineering structures, or economical crises. This book addresses the issue step-by-step, from phenomenological analogies between complex systems and statistical physics to more complex aspects, such as correlations, fluctuation-dissipation theorem, susceptibility, the concept of free ener...
Phase transition to QGP matter : confined vs deconfined matter
Maire, Antonin
2015-01-01
Simplified phase diagram of the nuclear phase transition, from the regular hadronic matter to the QGP phase. The sketch is meant to describe the transition foreseen along the temperature axis, at low baryochemical potential, µB.
Phase transitions in Pareto optimal complex networks
Seoane, Luís F
2015-01-01
The organization of interactions in complex systems can be described by networks connecting different units. These graphs are useful representations of the local and global complexity of the underlying systems. The origin of their topological structure can be diverse, resulting from different mechanisms including multiplicative processes and optimization. In spatial networks or in graphs where cost constraints are at work, as it occurs in a plethora of situations from power grids to the wiring of neurons in the brain, optimization plays an important part in shaping their organization. In this paper we study network designs resulting from a Pareto optimization process, where different simultaneous constraints are the targets of selection. We analyze three variations on a problem finding phase transitions of different kinds. Distinct phases are associated to different arrangements of the connections; but the need of drastic topological changes does not determine the presence, nor the nature of the phase transit...
Phase transition – Break down the walls
DEFF Research Database (Denmark)
Wandahl, Søren
2012-01-01
-phase issues of the construction process. This research first identifies the problems theoretically, and looks into which framework to be used in understanding of the phase transition problem. This combined with data from interviews reveal 8 major issues in phase transition, which decrease the value....... In a popular term this problem is often called “over the wall syndrome”. The manufacturing industry has worked with this for many years, in e.g. integrated product development, concurrent engineering, supply chain management, etc. Now the construction industry needs to focus more on these crucial inter...... tender often is limited due to regulations. Therefore, contractors miss a large amount of non-operational information, and the client and his consulting engineers never mange to share their tacit knowledge of project preconditions....
Phase diagrams and kinetics of phase transitions in protein solutions.
Vekilov, Peter G
2012-05-16
The phase behavior of proteins is of interest for fundamental and practical reasons. The nucleation of new phases is one of the last major unresolved problems of nature. The formation of protein condensed phases (crystals, polymers, and other solid aggregates, as well as dense liquids and gels) underlies pathological conditions, plays a crucial role in the biological function of the respective protein, or is an essential part of laboratory and industrial processes. In this review, we focus on phase transitions of proteins in their properly folded state. We first summarize the recently acquired understanding of physical processes underlying the phase diagrams of the protein solutions and the thermodynamics of protein phase transitions. Then we review recent findings on the kinetics of nucleation of dense liquid droplets and crystals. We explore the transition from nucleation to spinodal decomposition for liquid-liquid separation and introduce the new concept of solution-to-crystal spinodal. We review the two-step mechanism of protein crystal nucleation, in which mesoscopic metastable protein clusters serve as precursors to the ordered crystal nuclei. The concepts and mechanisms reviewed here provide powerful tools for control of the nucleation process by varying the solution thermodynamic parameters.
The comfortable driving model revisited: Traffic phases and phase transitions
Knorr, Florian
2013-01-01
We study the spatiotemporal patterns resulting from different boundary conditions for a microscopic traffic model and contrast it with empirical results. By evaluating the time series of local measurements, the local traffic states are assigned to the different traffic phases of Kerner's three-phase traffic theory. For this classification we use the rule-based FOTO-method, which provides `hard' rules for this assignment. Using this approach, our analysis shows that the model is indeed able to reproduce three qualitatively different traffic phases: free flow (F), synchronized traffic (S), and wide moving jams (J). In addition, we investigate the likelihood of transitions between the three traffic phases. We show that a transition from free flow (F) to a wide moving jam (J) often involves an intermediate transition; first from free flow F to synchronized flow S and then from synchronized flow to a wide moving jam. This is supported by the fact that the so called F->S transition (from free flow to synchronized t...
Dynamics of the chiral phase transition
van Hees, H; Meistrenko, A; Greiner, C
2013-01-01
The intention of this study is the search for signatures of the chiral phase transition in heavy-ion collisions. To investigate the impact of fluctuations, e.g., of the baryon number, at the transition or at a critical point, the linear sigma model is treated in a dynamical (3+1)-dimensional numerical simulation. Chiral fields are approximated as classical mean fields, and quarks are described as quasi particles in a Vlasov equation. Additional dynamics is implemented by quark-quark and quark-sigma-field interactions. For a consistent description of field-particle interactions, a new Monte-Carlo-Langevin-like formalism has been developed and is discussed.
Phase transitions in Pareto optimal complex networks.
Seoane, Luís F; Solé, Ricard
2015-09-01
The organization of interactions in complex systems can be described by networks connecting different units. These graphs are useful representations of the local and global complexity of the underlying systems. The origin of their topological structure can be diverse, resulting from different mechanisms including multiplicative processes and optimization. In spatial networks or in graphs where cost constraints are at work, as it occurs in a plethora of situations from power grids to the wiring of neurons in the brain, optimization plays an important part in shaping their organization. In this paper we study network designs resulting from a Pareto optimization process, where different simultaneous constraints are the targets of selection. We analyze three variations on a problem, finding phase transitions of different kinds. Distinct phases are associated with different arrangements of the connections, but the need of drastic topological changes does not determine the presence or the nature of the phase transitions encountered. Instead, the functions under optimization do play a determinant role. This reinforces the view that phase transitions do not arise from intrinsic properties of a system alone, but from the interplay of that system with its external constraints.
A mesoscopic approach on stability and phase transition between different traffic flow states
Qian, Wei-Liang; Lin, Kai; Machado, Romuel F; Hama, Yogiro
2015-01-01
It is understood that congestion in traffic can be interpreted in terms of the instability of the equation of dynamic motion. The evoltuion of a traffic system from an unstable or metastable state to a globally stable state bears a strong resemblance to the phase transition in thermodynamics. In this work, we explore the underlying physics of the traffic system, by examing closely the physical properties and mathematical constraints of the phase transitons therein. By using a mesoscopic approach, one entitles the catastrophe model the same physical content as in the Landau's theory, and uncovers its close connection to the instability and phase transitions. In addition to the one-dimensional configuration space, we generalize our discussion to the higher-dimensional case, where the observed temporal oscillation in traffic flow data is attributed to the curl of a vector field. We exhibit that our model can reproduce main features of the observed fundamental diagram including the inverse-$\\lambda$ shape and the...
The Next Generation Transit Survey - Prototyping Phase
McCormac, James; Wheatley, Peter; West, Richard; Walker, Simon; Bento, Joao; Skillen, Ian; Faedi, Francesca; Burleigh, Matt; Casewell, Sarah; Chazelas, Bruno; Genolet, Ludovic; Gibson, Neale; Goad, Mike; Lawrie, Katherine; Ryans, Robert; Todd, Ian; Udry, Stephan; Watson, Christopher
2016-01-01
We present the prototype telescope for the Next Generation Transit Survey, which was built in the UK in 2008/09 and tested on La Palma in the Canary Islands in 2010. The goals for the prototype system were severalfold: to determine the level of systematic noise in an NGTS-like system; demonstrate that we can perform photometry at the (sub) millimagnitude level on transit timescales across a wide field; show that it is possible to detect transiting super-Earth and Neptune-sized exoplanets and prove the technical feasibility of the proposed planet survey. We tested the system for around 100 nights and met each of the goals above. Several key areas for improvement were highlighted during the prototyping phase. They have been subsequently addressed in the final NGTS facility which was recently commissioned at ESO Cerro Paranal, Chile.
Phase transition in the countdown problem
Lacasa, Lucas; Luque, Bartolo
2012-07-01
We present a combinatorial decision problem, inspired by the celebrated quiz show called Countdown, that involves the computation of a given target number T from a set of k randomly chosen integers along with a set of arithmetic operations. We find that the probability of winning the game evidences a threshold phenomenon that can be understood in the terms of an algorithmic phase transition as a function of the set size k. Numerical simulations show that such probability sharply transitions from zero to one at some critical value of the control parameter, hence separating the algorithm's parameter space in different phases. We also find that the system is maximally efficient close to the critical point. We derive analytical expressions that match the numerical results for finite size and permit us to extrapolate the behavior in the thermodynamic limit.
Holographic phase transitions at finite chemical potential
Mateos, David; Matsuura, Shunji; Myers, Robert C.; Thomson, Rowan M.
2007-11-01
Recently, holographic techniques have been used to study the thermal properties of Script N = 2 super-Yang-Mills theory, with gauge group SU(Nc) and coupled to Nf coupling. Here we consider the phase diagram as a function of temperature and baryon chemical potential μb. For fixed μb transitions separating a region with vanishing baryon density and one with nonzero density. For fixed μb>Nc Mq there is no phase transition as a function of the temperature and the baryon density is always nonzero. We also compare the present results for the grand canonical ensemble with those for canonical ensemble in which the baryon density is held fixed [1].
Nonequilibrium phase transitions in biomolecular signal transduction
Smith, Eric; Krishnamurthy, Supriya; Fontana, Walter; Krakauer, David
2011-11-01
We study a mechanism for reliable switching in biomolecular signal-transduction cascades. Steady bistable states are created by system-size cooperative effects in populations of proteins, in spite of the fact that the phosphorylation-state transitions of any molecule, by means of which the switch is implemented, are highly stochastic. The emergence of switching is a nonequilibrium phase transition in an energetically driven, dissipative system described by a master equation. We use operator and functional integral methods from reaction-diffusion theory to solve for the phase structure, noise spectrum, and escape trajectories and first-passage times of a class of minimal models of switches, showing how all critical properties for switch behavior can be computed within a unified framework.
Extracellular ice phase transitions in insects.
Hawes, T C
2014-01-01
At temperatures below their temperature of crystallization (Tc), the extracellular body fluids of insects undergo a phase transition from liquid to solid. Insects that survive the transition to equilibrium (complete freezing of the body fluids) are designated as freeze tolerant. Although this phenomenon has been reported and described in many Insecta, current nomenclature and theory does not clearly delineate between the process of transition (freezing) and the final solid phase itself (the frozen state). Thus freeze tolerant insects are currently, by convention, described in terms of the temperature at which the crystallization of their body fluids is initiated, Tc. In fact, the correct descriptor for insects that tolerate freezing is the temperature of equilibrium freezing, Tef. The process of freezing is itself a separate physical event with unique physiological stresses that are associated with ice growth. Correspondingly there are a number of insects whose physiological cryo-limits are very specifically delineated by this transitional envelope. The distinction also has considerable significance for our understanding of insect cryobiology: firstly, because the ability to manage endogenous ice growth is a fundamental segregator of cryotype; and secondly, because our understanding of internal ice management is still largely nascent.
Seiler, Christian A
2011-08-01
Patients with an abdominal catastrophe are in urgent need of early, interdisciplinary medical help. The treatment plan should be based on medical priorities and clear leadership. First priority should be given to achieve optimal oxygenation of blood and stabilization of circulation during all treatment-phases. The sicker the patient, the less invasive the (surgical) treatment should to be, which means "damage control only". This short article describes 7 important, pragmatic rules that will help to increase the survival of a patient with an abdominal catastrophe. Preexisting morbidity and risk factors must be included in the overall risk-evaluation for every therapeutic intervention. The challenge in patients with an abdominal catastrophe is to carefully balance the therapeutic stress and the existing resistance of the individual patient. The best way to avoid abdominal disaster, however, is its prevention.
Holographic phase transitions at finite chemical potential
Mateos, David; Myers, Robert C; Thomson, Rowan M
2007-01-01
Recently holographic techniques have been used to study the thermal properties of N=2 SYM theory, with gauge group SU(Nc) and coupled to Nf Nc Mq there is no phase transition as a function of the temperature and the baryon density is always nonzero. We also compare the present results for the grand canonical ensemble with those for canonical ensemble in which the baryon density is held fixed [1].
Quantum phase transitions in constrained Bose systems
Bonnes, Lars
2011-01-01
This doctoral thesis studies low dimensional quantum systems that can be realized in recent cold atom experiments. From the viewpoint of quantum statistical mechanics, the main emphasis is on the detailed study of the different quantum and thermal phases and their transitions using numerical methods, such as quantum Monte Carlo and the Tensor Network Renormalization Group. The first part of this work deals with a lattice Boson model subject to strong three-body losses. In a quantum-Zeno li...
Recent theoretical advances on superradiant phase transitions
Baksic, Alexandre; Nataf, Pierre; Ciuti, Cristiano
2013-03-01
The Dicke model describing a single-mode boson field coupled to two-level systems is an important paradigm in quantum optics. In particular, the physics of ``superradiant phase transitions'' in the ultrastrong coupling regime is the subject of a vigorous research activity in both cavity and circuit QED. Recently, we explored the rich physics of two interesting generalizations of the Dicke model: (i) A model describing the coupling of a boson mode to two independent chains A and B of two-level systems, where chain A is coupled to one quadrature of the boson field and chain B to the orthogonal quadrature. This original model leads to a quantum phase transition with a double symmetry breaking and a fourfold ground state degeneracy. (ii) A generalized Dicke model with three-level systems including the diamagnetic term. In contrast to the case of two-level atoms for which no-go theorems exist, in the case of three-level system we prove that the Thomas-Reich-Kuhn sum rule does not always prevent a superradiant phase transition.
Superconducting phase transition in STM tips
Energy Technology Data Exchange (ETDEWEB)
Eltschka, Matthias; Jaeck, Berthold; Assig, Maximilian; Etzkorn, Markus; Ast, Christian R. [Max Planck Institute for Solid State Research, Stuttgart (Germany); Kern, Klaus [Max Planck Institute for Solid State Research, Stuttgart (Germany); Ecole Polytechnique Federale de Lausanne (Switzerland)
2015-07-01
The superconducting properties of systems with dimensions comparable to the London penetration depth considerably differ from macroscopic systems. We have studied the superconducting phase transition of vanadium STM tips in external magnetic fields. Employing Maki's theory we extract the superconducting parameters such as the gap or the Zeeman splitting from differential conductance spectra. While the Zeeman splitting follows the theoretical description of a system with s=1/2 and g=2, the superconducting gaps as well as the critical fields depend on the specific tip. For a better understanding of the experimental results, we solve a one dimensional Usadel equation modeling the superconducting tip as a cone with the opening angle α in an external magnetic field. We find that only a small region at the apex of the tip is superconducting in high magnetic fields and that the order of the phase transition is directly determined by α. Further, the spectral broadening increases with α indicating an intrinsic broadening mechanism due to the conical shape of the tip. Comparing these calculations to our experimental results reveals the order of the superconducting phase transition of the STM tips.
Dynamical quantum phase transitions (Review Article)
Zvyagin, A. A.
2016-11-01
During recent years the interest to dynamics of quantum systems has grown considerably. Quantum many body systems out of equilibrium often manifest behavior, different from the one predicted by standard statistical mechanics and thermodynamics in equilibrium. Since the dynamics of a many-body quantum system typically involve many excited eigenstates, with a non-thermal distribution, the time evolution of such a system provides an unique way for investigation of non-equilibrium quantum statistical mechanics. Last decade such new subjects like quantum quenches, thermalization, pre-thermalization, equilibration, generalized Gibbs ensemble, etc. are among the most attractive topics of investigation in modern quantum physics. One of the most interesting themes in the study of dynamics of quantum many-body systems out of equilibrium is connected with the recently proposed important concept of dynamical quantum phase transitions. During the last few years a great progress has been achieved in studying of those singularities in the time dependence of characteristics of quantum mechanical systems, in particular, in understanding how the quantum critical points of equilibrium thermodynamics affect their dynamical properties. Dynamical quantum phase transitions reveal universality, scaling, connection to the topology, and many other interesting features. Here we review the recent achievements of this quickly developing part of low-temperature quantum physics. The study of dynamical quantum phase transitions is especially important in context of their connection to the problem of the modern theory of quantum information, where namely non-equilibrium dynamics of many-body quantum system plays the major role.
Stability and Existence of Multidimensional Subsonic Phase Transitions
Institute of Scientific and Technical Information of China (English)
Ya-Guang Wang; Zhouping Xin
2003-01-01
The purpose of this paper is to prove the uniform stability of multidimensional subsonic phase transitions satisfying the viscosity-capillarity criterion in a van der Waals fluid, and further to establish the local existence of phase transition solutions.
Phase transitions of ε-HNIW in compound systems
Directory of Open Access Journals (Sweden)
Jing-yuan Zhang
2016-05-01
Full Text Available The heat-induced phase transitions of ε-HNIW, both neat and coated with various additives used in plastic bonded explosives, were investigated using powder X-ray diffraction and differential scanning calorimetry. It was found that ε-HNIW, after being held at 70°C for 60h, remained in the ε-phase. Applying other conditions, various phase transition parameters were determined, including Tc (the critical phase transition temperature, T50 (the temperature at which 50% of the phase transition is complete and T180 (the percentage of γ-HNIW present in samples heated to 180°C. According to the above three parameters, additives were divided into three categories: those that delay phase transition, those that raise the critical temperature and the transition rate, and those that promote the phase transition. Based on the above data, a phase transition mechanism is proposed.
Holography and the Electroweak Phase Transition
Creminelli, P; Rattazzi, Riccardo; Creminelli, Paolo; Nicolis, Alberto; Rattazzi, Riccardo
2002-01-01
We study through holography the compact Randall-Sundrum (RS) model at finite temperature. In the presence of radius stabilization, the system is described at low enough temperature by the RS solution. At high temperature it is described by the AdS-Schwarzshild solution with an event horizon replacing the TeV brane. We calculate the transition temperature T_c between the two phases and we find it to be somewhat smaller than the TeV scale. Assuming that the Universe starts out at T >> T_c and cools down by expansion, we study the rate of the transition to the RS phase. We find that the transition is too slow and the Universe ends up in an old inflation scenario unless tight bounds are satisfied by the model parameters. In particular we find that the AdS curvature must be comparable to the 5D Planck mass and that the radius stabilization mechanism must lead to a sizeable distortion of the basic RS metric.
Second-order phase transitions of pure substances
Schaftenaar, H.P.C.
2009-01-01
In this report we are dealing with the thermodynamic theory of second-order phase transitions or continuous transitions of unary systems. The first classification of these phase transitions is due to Ehrenfest (1933), based on chemical potentials. First-order transitions are changes in which the der
Catastrophe medicine; Medecine de catastrophe
Energy Technology Data Exchange (ETDEWEB)
Lebreton, A. [Service Technique de l`Energie Electrique et des Grands Barrages (STEEGB), (France)
1996-12-31
The `Catastrophe Medicine` congress which took place in Amiens (France) in December 5 to 7 1996 was devoted to the assessment and management of risks and hazards in natural and artificial systems. The methods of risk evaluation and prevision were discussed in the context of dams accidents with the analysis of experience feedbacks and lessons gained from the organisation of emergency plans. Three round table conferences were devoted to the importance of psychological aspects during such major crises. (J.S.)
Landau Theory in the Region of First Order Phase Transitions
Directory of Open Access Journals (Sweden)
O.G. Medvedovskaya
2014-04-01
Full Text Available For the case when the line of the first order phase transitions does not transform into the line of the second order phase transitions, i.e. not as ends with the tricritical point but not with a critical one: critical lines, limiting the region of metastable states, by using the Landau theory of phase transitions were determined.
Locating phase transitions in computationally hard problems
Indian Academy of Sciences (India)
B Ashok; T K Patra
2010-09-01
We discuss how phase-transitions may be detected in computationally hard problems in the context of anytime algorithms. Treating the computational time, value and utility functions involved in the search results in analogy with quantities in statistical physics, we indicate how the onset of a computationally hard regime can be detected and the transit to higher quality solutions be quantified by an appropriate response function. The existence of a dynamical critical exponent is shown, enabling one to predict the onset of critical slowing down, rather than finding it after the event, in the specific case of a travelling salesman problem (TSP). This can be used as a means of improving efficiency and speed in searches, and avoiding needless computations.
Scale invariance from phase transitions to turbulence
Lesne, Annick
2012-01-01
During a century, from the Van der Waals mean field description (1874) of gases to the introduction of renormalization group (RG techniques 1970), thermodynamics and statistical physics were just unable to account for the incredible universality which was observed in numerous critical phenomena. The great success of RG techniques is not only to solve perfectly this challenge of critical behaviour in thermal transitions but to introduce extremely useful tools in a wide field of daily situations where a system exhibits scale invariance. The introduction of scaling, scale invariance and universality concepts has been a significant turn in modern physics and more generally in natural sciences. Since then, a new "physics of scaling laws and critical exponents", rooted in scaling approaches, allows quantitative descriptions of numerous phenomena, ranging from phase transitions to earthquakes, polymer conformations, heartbeat rhythm, diffusion, interface growth and roughening, DNA sequence, dynamical systems, chaos ...
Phase transition in SONFIS&SORST
Owladeghaffari, Hamed
2008-01-01
In this study, we introduce general frame of MAny Connected Intelligent Particles Systems (MACIPS). Connections and interconnections between particles get a complex behavior of such merely simple system (system in system).Contribution of natural computing, under information granulation theory, are the main topics of this spacious skeleton. Upon this clue, we organize two algorithms involved a few prominent intelligent computing and approximate reasoning methods: self organizing feature map (SOM), Neuro- Fuzzy Inference System and Rough Set Theory (RST). Over this, we show how our algorithms can be taken as a linkage of government-society interaction, where government catches various fashions of behavior: solid (absolute) or flexible. So, transition of such society, by changing of connectivity parameters (noise) from order to disorder is inferred. Add to this, one may find an indirect mapping among finical systems and eventual market fluctuations with MACIPS. Keywords: phase transition, SONFIS, SORST, many con...
Dynamical phase transitions in quantum mechanics
Directory of Open Access Journals (Sweden)
Rotter Ingrid
2012-02-01
Full Text Available The nucleus is described as an open many-body quantum system with a non-Hermitian Hamilton operator the eigenvalues of which are complex, in general. The eigenvalues may cross in the complex plane (exceptional points, the phases of the eigenfunctions are not rigid in approaching the crossing points and the widths bifurcate. By varying only one parameter, the eigenvalue trajectories usually avoid crossing and width bifurcation occurs at the critical value of avoided crossing. An analog spectroscopic redistribution takes place for discrete states below the particle decay threshold. By this means, a dynamical phase transition occurs in the many-level system starting at a critical value of the level density. Hence the properties of the low-lying nuclear states (described well by the shell model and those of highly excited nuclear states (described by random ensembles differ fundamentally from one another. The statement of Niels Bohr on the collective features of compound nucleus states at high level density is therefore not in contradiction to the shell-model description of nuclear (and atomic states at low level density. Dynamical phase transitions are observed experimentally in different quantum mechanical systems by varying one or two parameters.
Phases and phase transitions in the algebraic microscopic shell model
Directory of Open Access Journals (Sweden)
Georgieva A. I.
2016-01-01
Full Text Available We explore the dynamical symmetries of the shell model number conserving algebra, which define three types of pairing and quadrupole phases, with the aim to obtain the prevailing phase or phase transition for the real nuclear systems in a single shell. This is achieved by establishing a correspondence between each of the pairing bases with the Elliott’s SU(3 basis that describes collective rotation of nuclear systems. This allows for a complete classification of the basis states of different number of particles in all the limiting cases. The probability distribution of the SU(3 basis states within theirs corresponding pairing states is also obtained. The relative strengths of dynamically symmetric quadrupole-quadrupole interaction in respect to the isoscalar, isovector and total pairing interactions define a control parameter, which estimates the importance of each term of the Hamiltonian in the correct reproduction of the experimental data for the considered nuclei.
Wheeler, J. Craig
2014-08-01
Preface; 1. Setting the stage: star formation and hydrogen burning in single stars; 2. Stellar death: the inexorable grip of gravity; 3. Dancing with stars: binary stellar evolution; 4. Accretion disks: flat stars; 5. White Dwarfs: quantum dots; 6. Supernovae: stellar catastrophes; 7. Supernova 1987A: lessons and enigmas; 8. Neutron stars: atoms with attitude; 9. Black holes in theory: into the abyss; 10. Black holes in fact: exploring the reality; 11. Gamma-ray bursts, black holes and the universe: long, long ago and far, far away; 12. Supernovae and the universe; 13. Worm holes and time machines: tunnels in space and time; 14. Beyond: the frontiers; Index.
Early Work on Defect Driven Phase Transitions
Kosterlitz, J. Michael; Thouless, David J.
2016-12-01
This article summarizes the early history of the theory of phase transitions driven by topological defects, such as vortices in superfluid helium films or dislocations and disclinations in two-dimensional solids. We start with a review of our two earliest papers, pointing out their errors and omissions as well as their insights. We then describe the work, partly done by Kosterlitz but mostly done by other people, which corrected these oversights, and applied these ideas to experimental systems, and to numerical and experimental simulations.
Melonic phase transition in group field theory
Baratin, Aristide; Oriti, Daniele; Ryan, James P; Smerlak, Matteo
2013-01-01
Group field theories have recently been shown to admit a 1/N expansion dominated by so-called `melonic graphs', dual to triangulated spheres. In this note, we deepen the analysis of this melonic sector. We obtain a combinatorial formula for the melonic amplitudes in terms of a graph polynomial related to a higher dimensional generalization of the Kirchhoff tree-matrix theorem. Simple bounds on these amplitudes show the existence of a phase transition driven by melonic interaction processes. We restrict our study to the Boulatov-Ooguri models, which describe topological BF theories and are the basis for the construction of four dimensional models of quantum gravity.
Detonations and deflagrations in cosmological phase transitions
Megevand, Ariel
2009-01-01
We study the steady state motion of bubble walls in cosmological phase transitions. Taking into account the boundary and continuity conditions for the fluid variables, we calculate numerically the wall velocity as a function of the nucleation temperature, the latent heat, and a friction parameter. We determine regions in the space of these parameters in which detonations and/or deflagrations are allowed. In order to apply the results to a physical case, we calculate these quantities in a specific model, which consists of an extension of the Standard Model with singlet scalar fields. We also obtain analytic approximations for deflagrations and detonations.
Observables of non-equilibrium phase transition
Tomasik, Boris; Melo, Ivan; Kopecna, Renata
2015-01-01
Rapidly expanding fireball which undergoes first-order phase transition will supercool and proceed via spinodal decomposition. Hadrons are produced from the individual fragments as well as leftover matter filling the space between them. Emission from fragments should be visible in rapidity correlations, particularly of protons. Also, even within narrow centrality classes, rapidity distributions will be fluctuating from one event to another in case of fragmentation. This can be identified with the help of Kolmogorov-Smirnov test. Finally, a method is presented which allows to sort events with varying rapidity distributions in such a way, that events with similar rapidity histograms are grouped together.
Chiral phase transition from string theory.
Parnachev, Andrei; Sahakyan, David A
2006-09-15
The low energy dynamics of a certain D-brane configuration in string theory is described at weak t'Hooft coupling by a nonlocal version of the Nambu-Jona-Lasinio model. We study this system at finite temperature and strong t'Hooft coupling, using the string theory dual. We show that for sufficiently low temperatures chiral symmetry is broken, while for temperatures larger then the critical value, it gets restored. We compute the latent heat and observe that the phase transition is of the first order.
Berry phase transition in twisted bilayer graphene
Rode, Johannes C.; Smirnov, Dmitri; Schmidt, Hennrik; Haug, Rolf J.
2016-09-01
The electronic dispersion of a graphene bilayer is highly dependent on rotational mismatch between layers and can be further manipulated by electrical gating. This allows for an unprecedented control over electronic properties and opens up the possibility of flexible band structure engineering. Here we present novel magnetotransport data in a twisted bilayer, crossing the energetic border between decoupled monolayers and coupled bilayer. In addition a transition in Berry phase between π and 2π is observed at intermediate magnetic fields. Analysis of Fermi velocities and gate induced charge carrier densities suggests an important role of strong layer asymmetry for the observed phenomena.
Adiabatic quantum computation and quantum phase transitions
Latorre, J I; Latorre, Jose Ignacio; Orus, Roman
2003-01-01
We analyze the ground state entanglement in a quantum adiabatic evolution algorithm designed to solve the NP-complete Exact Cover problem. The entropy of entanglement seems to obey linear and universal scaling at the point where the mass gap becomes small, suggesting that the system passes near a quantum phase transition. Such a large scaling of entanglement suggests that the effective connectivity of the system diverges as the number of qubits goes to infinity and that this algorithm cannot be efficiently simulated by classical means. On the other hand, entanglement in Grover's algorithm is bounded by a constant.
Phase transition equilibrium of terthiophene isomers
Energy Technology Data Exchange (ETDEWEB)
Costa, Jose C.S.; Lima, Carlos F.R.A.C.; Rocha, Marisa A.A. [Centro de Investigacao em Quimica, Departamento de Quimica e Bioquimica, Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal); Gomes, Ligia R. [CIAGEB, Faculdade de Ciencias de Saude Escola Superior de Saude da UFP, Universidade Fernando Pessoa, Rua Carlos da Maia, 296, P-4200-150 Porto (Portugal); REQUIMTE, Departamento de Quimica e Bioquimica, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal); Santos, Luis M.N.B.F., E-mail: lbsantos@fc.up.p [Centro de Investigacao em Quimica, Departamento de Quimica e Bioquimica, Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal)
2011-02-15
The thermodynamic study of the phase transition (fusion and sublimation) of 2,2':5',2''-terthiophene and 3,2':5',3''-terthiophene is presented. The obtained data is used to evaluate the (solid + liquid) and (solid + gas) phase equilibrium, and draw the phase diagrams of the pure compounds near the triple point coordinates. For each compound the vapour pressures at different temperatures were measured by a combined Knudsen effusion method with a vacuum quartz crystal microbalance. Based on the previous results, the standard molar enthalpies, entropies and Gibbs energies of sublimation were derived at T = 298.15 K. For the two terthiophenes and for 3,3'-bithiophene, the temperature, and the molar enthalpies of fusion were measured in a power compensated differential scanning calorimetry. The relationship between structure and energetics is discussed based on the experimental results, ab initio calculations and previous literature data for 2,2'-bithiophene and 3,3'-bithiophene. The 3,2':5',3''-terthiophene shows a higher solid phase stability than the 2,2':5',2''-terthiophene isomer arising from the higher cohesive energy due to positioning of the sulphur atom in the thiophene ring. The higher phase stability of 3,3'-bithiophene relative to 2,2'-bithiophene isomer is also related to its higher absolute entropy in the solid phase associated with the ring positional degeneracy observed in the crystal structure of this isomer. A significant differentiation in the crystal phase stability between isomers was found.
Transitional Phenomena on Phase Change Materials
Directory of Open Access Journals (Sweden)
Wójcik Tadeusz M.
2014-03-01
Full Text Available One of the most significant problem with technology development is transferring of large heat fluxes, which requires constant heat transfer temperature (in the specified temperature range. This problem concern mainly the nuclear energetics, space technologies, military technologies and most of all electronics containing integrated circuits with very large scale of integrations. Intensive heat transfer and thermal energy storage are possible by the use of phase change materials (PCMs. In the paper there are presented preliminary results of research on the use of liquid-gas (L-G PCMs and solid-solid phase change materials (S-S PCMs. For L-G PCMs the boiling characteristics were determined by increasing and decreasing the heat flux, which for certain sets of structural parameters of the heating surface and the physical properties of the liquid induce a variety of forms of transitional phenomena. Thermal energy storage is much more effective when using PCMs than sensible heat.
Topological phase transitions in superradiance lattices
Wang, Da-Wei; Yuan, Luqi; Liu, Ren-Bao; Zhu, Shi-Yao
2015-01-01
The discovery of the quantum Hall effect (QHE) reveals a new class of matter phases, topological insulators (TI's), which have been extensively studied in solid-state materials and recently in photonic structures, time-periodic systems and optical lattices of cold atoms. All these topological systems are lattices in real space. Our recent study shows that Scully's timed Dicke states (TDS) can form a superradiance lattice (SL) in momentum space. Here we report the discovery of topological phase transitions in a two-dimensional SL in electromagnetically induced transparency (EIT). By periodically modulating the three EIT coupling fields, we can create a Haldane model with in-situ tunable topological properties. The Chern numbers of the energy bands and hence the topological properties of the SL manifest themselves in the contrast between diffraction signals emitted by superradiant TDS. The topological superradiance lattices (TSL) provide a controllable platform for simulating exotic phenomena in condensed matte...
Phase transitions in fluids and biological systems
Sipos, Maksim
metric to 16S rRNA metagenomic studies of 6 vertebrate gastrointestinal microbiomes and find that they assembled through a highly non-neutral process. I then consider a phase transition that may occur in nutrient-poor environments such as ocean surface waters. In these systems, I find that the experimentally observed genome streamlining, specialization and opportunism may well be generic statistical phenomena.
On Phase Transition of Compressed Sensing in the Complex Domain
Yang, Zai; Xie, Lihua
2011-01-01
The phase transition is a performance measure of the sparsity-undersampling tradeoff in compressed sensing (CS). This letter reports, for the first time, the existence of an exact phase transition for the $\\ell_1$ minimization approach to the complex valued CS problem. This discovery is not only a complementary result to the known phase transition of the real valued CS but also shows considerable superiority of the phase transition of complex valued CS over that of the real valued CS. The results are obtained by extending the recently developed ONE-L1 algorithms to complex valued CS and applying their optimal and iterative solutions to empirically evaluate the phase transition.
Nuclear binding near a quantum phase transition
Elhatisari, Serdar; Rokash, Alexander; Alarcón, Jose Manuel; Du, Dechuan; Klein, Nico; Lu, Bing-nan; Meißner, Ulf-G; Epelbaum, Evgeny; Krebs, Hermann; Lähde, Timo A; Lee, Dean; Rupak, Gautam
2016-01-01
How do protons and neutrons bind to form nuclei? This is the central question of ab initio nuclear structure theory. While the answer may seem as simple as the fact that nuclear forces are attractive, the full story is more complex and interesting. In this work we present numerical evidence from ab initio lattice simulations showing that nature is near a quantum phase transition, a zero-temperature transition driven by quantum fluctuations. Using lattice effective field theory, we perform Monte Carlo simulations for systems with up to twenty nucleons. For even and equal numbers of protons and neutrons, we discover a first-order transition at zero temperature from a Bose-condensed gas of alpha particles (4He nuclei) to a nuclear liquid. Whether one has an alpha-particle gas or nuclear liquid is determined by the strength of the alpha-alpha interactions, and we show that the alpha-alpha interactions depend on the strength and locality of the nucleon-nucleon interactions. The existence of the nearby first-order ...
Nuclear Binding Near a Quantum Phase Transition
Elhatisari, Serdar; Li, Ning; Rokash, Alexander; Alarcón, Jose Manuel; Du, Dechuan; Klein, Nico; Lu, Bing-nan; Meißner, Ulf-G.; Epelbaum, Evgeny; Krebs, Hermann; Lähde, Timo A.; Lee, Dean; Rupak, Gautam
2016-09-01
How do protons and neutrons bind to form nuclei? This is the central question of ab initio nuclear structure theory. While the answer may seem as simple as the fact that nuclear forces are attractive, the full story is more complex and interesting. In this work we present numerical evidence from ab initio lattice simulations showing that nature is near a quantum phase transition, a zero-temperature transition driven by quantum fluctuations. Using lattice effective field theory, we perform Monte Carlo simulations for systems with up to twenty nucleons. For even and equal numbers of protons and neutrons, we discover a first-order transition at zero temperature from a Bose-condensed gas of alpha particles (4He nuclei) to a nuclear liquid. Whether one has an alpha-particle gas or nuclear liquid is determined by the strength of the alpha-alpha interactions, and we show that the alpha-alpha interactions depend on the strength and locality of the nucleon-nucleon interactions. This insight should be useful in improving calculations of nuclear structure and important astrophysical reactions involving alpha capture on nuclei. Our findings also provide a tool to probe the structure of alpha cluster states such as the Hoyle state responsible for the production of carbon in red giant stars and point to a connection between nuclear states and the universal physics of bosons at large scattering length.
Phase transitions in Thirring’s model
Campa, Alessandro; Casetti, Lapo; Latella, Ivan; Pérez-Madrid, Agustín; Ruffo, Stefano
2016-07-01
In his pioneering work on negative specific heat, Walter Thirring introduced a model that is solvable in the microcanonical ensemble. Here, we give a complete description of the phase-diagram of this model in both the microcanonical and the canonical ensemble, highlighting the main features of ensemble inequivalence. In both ensembles, we find a line of first-order phase transitions which ends in a critical point. However, neither the line nor the point have the same location in the phase-diagram of the two ensembles. We also show that the microcanonical and canonical critical points can be analytically related to each other using a Landau expansion of entropy and free energy, respectively, in analogy with what has been done in (Cohen and Mukamel 2012 J. Stat. Mech. P12017). Examples of systems with certain symmetries restricting the Landau expansion have been considered in this reference, while no such restrictions are present in Thirring’s model. This leads to a phase diagram that can be seen as a prototype for what happens in systems of particles with kinematic degrees of freedom dominated by long-range interactions.
Multifractality and Network Analysis of Phase Transition
Li, Wei; Yang, Chunbin; Han, Jihui; Su, Zhu; Zou, Yijiang
2017-01-01
Many models and real complex systems possess critical thresholds at which the systems shift dramatically from one sate to another. The discovery of early-warnings in the vicinity of critical points are of great importance to estimate how far the systems are away from the critical states. Multifractal Detrended Fluctuation analysis (MF-DFA) and visibility graph method have been employed to investigate the multifractal and geometrical properties of the magnetization time series of the two-dimensional Ising model. Multifractality of the time series near the critical point has been uncovered from the generalized Hurst exponents and singularity spectrum. Both long-term correlation and broad probability density function are identified to be the sources of multifractality. Heterogeneous nature of the networks constructed from magnetization time series have validated the fractal properties. Evolution of the topological quantities of the visibility graph, along with the variation of multifractality, serve as new early-warnings of phase transition. Those methods and results may provide new insights about the analysis of phase transition problems and can be used as early-warnings for a variety of complex systems. PMID:28107414
Preon model and cosmological quantum-hyperchromodynamic phase transition
Nishimura, H.; Hayashi, Y.
1987-05-01
From the cosmological viewpoint, we investigate whether or not recent preon models are compatible with the picture of the first-order phase transition from the preon phase to the composite quark-lepton phase. It is shown that the current models accepting the 't Hooft anomaly-matching condition together with quantum hyperchromodynamics are consistent with the cosmological first-order phase transition.
Stress induced phase transitions in silicon
Budnitzki, M.; Kuna, M.
2016-10-01
Silicon has a tremendous importance as an electronic, structural and optical material. Modeling the interaction of a silicon surface with a pointed asperity at room temperature is a major step towards the understanding of various phenomena related to brittle as well as ductile regime machining of this semiconductor. If subjected to pressure or contact loading, silicon undergoes a series of stress-driven phase transitions accompanied by large volume changes. In order to understand the material's response for complex non-hydrostatic loading situations, dedicated constitutive models are required. While a significant body of literature exists for the dislocation dominated high-temperature deformation regime, the constitutive laws used for the technologically relevant rapid low-temperature loading have severe limitations, as they do not account for the relevant phase transitions. We developed a novel finite deformation constitutive model set within the framework of thermodynamics with internal variables that captures the stress induced semiconductor-to-metal (cd-Si → β-Si), metal-to-amorphous (β-Si → a-Si) as well as amorphous-to-amorphous (a-Si → hda-Si, hda-Si → a-Si) transitions. The model parameters were identified in part directly from diamond anvil cell data and in part from instrumented indentation by the solution of an inverse problem. The constitutive model was verified by successfully predicting the transformation stress under uniaxial compression and load-displacement curves for different indenters for single loading-unloading cycles as well as repeated indentation. To the authors' knowledge this is the first constitutive model that is able to adequately describe cyclic indentation in silicon.
Quark-hadron phase transition in massive gravity
Atazadeh, K.
2016-11-01
We study the quark-hadron phase transition in the framework of massive gravity. We show that the modification of the FRW cosmological equations leads to the quark-hadron phase transition in the early massive Universe. Using numerical analysis, we consider that a phase transition based on the chiral symmetry breaking after the electroweak transition, occurred at approximately 10 μs after the Big Bang to convert a plasma of free quarks and gluons into hadrons.
Exotic quantum phase transitions of strongly interacting topological insulators
Slagle, Kevin; You, Yi-Zhuang; Xu, Cenke
2015-03-01
Using determinant quantum Monte Carlo simulations, we demonstrate that an extended Hubbard model on a bilayer honeycomb lattice has two novel quantum phase transitions. The first is a quantum phase transition between the weakly interacting gapless Dirac fermion phase and a strongly interacting fully gapped and symmetric trivial phase, which cannot be described by the standard Gross-Neveu model. The second is a quantum critical point between a quantum spin Hall insulator with spin Sz conservation and the previously mentioned strongly interacting fully gapped phase. At the latter quantum critical point the single-particle excitations remain gapped, while spin and charge gaps both close. We argue that the first quantum phase transition is related to the Z16 classification of the topological superconductor 3He-B phase with interactions, while the second quantum phase transition is a topological phase transition described by a bosonic O (4 ) nonlinear sigma model field theory with a Θ term.
Information Dynamics at a Phase Transition
Sowinski, Damian; Gleiser, Marcelo
2017-03-01
We propose a new way of investigating phase transitions in the context of information theory. We use an information-entropic measure of spatial complexity known as configurational entropy (CE) to quantify both the storage and exchange of information in a lattice simulation of a Ginzburg-Landau model with a scalar order parameter coupled to a heat bath. The CE is built from the Fourier spectrum of fluctuations around the mean-field and reaches a minimum at criticality. In particular, we investigate the behavior of CE near and at criticality, exploring the relation between information and the emergence of ordered domains. We show that as the temperature is increased from below, the CE displays three essential scaling regimes at different spatial scales: scale free, turbulent, and critical. Together, they offer an information-entropic characterization of critical behavior where the storage and fidelity of information processing is maximized at criticality.
The phase transition of Axelrod's model revisited
Reia, Sandro M
2016-01-01
Axelrod's model with $F=2$ cultural features, where each feature can assume $k$ states drawn from a Poisson distribution of parameter $q$, exhibits a continuous nonequilibrium phase transition in the square lattice. Here we use extensive Monte Carlo simulations and finite size scaling to study the critical behavior of the order parameter $\\rho$, which is the fraction of sites that belong to the largest domain of an absorbing configuration averaged over many runs. We find that it vanishes as $\\rho \\sim \\left (q_c^0 - q \\right)^\\beta$ with $\\beta \\approx 0.25$ at the critical point $q_c^0 \\approx 3.10$ and that the exponent that measures the width of the critical region is $\
Magnetocaloric materials and first order phase transitions
DEFF Research Database (Denmark)
Neves Bez, Henrique
of the properties of such materials.The experimental characterization of these materials is done through various different methods, such as X-ray diffraction, magnetometry, calorimetry, direct measurements of entropy change, capacitance dilatometry, scanning electron microscopy,energy-dispersive X-ray spectrometry......This thesis studies the first order phase transitions of the magnetocaloric materials La0.67Ca0.33MnO3 and La(Fe,Mn,Si)13Hz trying to overcome challenges that these materials face when applied in active magnetic regenerators. The study is done through experimental characterization and modelling...... and magnetocaloric regenerative tests. The magnetic, thermal and structural properties obtained from such measurements are then evaluated through different models, i.e. the Curie-Weiss law, the Bean-Rodbell model, the free electron model and the Debye model.The measured magnetocaloric properties of La0.67Ca0.33MnO3...
Phase transitions in open quantum systems
Jung, C; Rotter, I
1999-01-01
We consider the behaviour of open quantum systems in dependence on the coupling to one decay channel by introducing the coupling parameter $\\alpha$ being proportional to the average degree of overlapping. Under critical conditions, a reorganization of the spectrum takes place which creates a bifurcation of the time scales with respect to the lifetimes of the resonance states. We derive analytically the conditions under which the reorganization process can be understood as a second-order phase transition and illustrate our results by numerical investigations. The conditions are fulfilled e.g. for a picket fence with equal coupling of the states to the continuum. Energy dependencies within the system are included. We consider also the generic case of an unfolded Gaussian Orthogonal Ensemble. In all these cases, the reorganization of the spectrum occurs at the critical value $\\alpha_{crit}$ of the control parameter globally over the whole energy range of the spectrum. All states act cooperatively.
Scaling theory of topological phase transitions
Chen, Wei
2016-02-01
Topologically ordered systems are characterized by topological invariants that are often calculated from the momentum space integration of a certain function that represents the curvature of the many-body state. The curvature function may be Berry curvature, Berry connection, or other quantities depending on the system. Akin to stretching a messy string to reveal the number of knots it contains, a scaling procedure is proposed for the curvature function in inversion symmetric systems, from which the topological phase transition can be identified from the flow of the driving energy parameters that control the topology (hopping, chemical potential, etc) under scaling. At an infinitesimal operation, one obtains the renormalization group (RG) equations for the driving energy parameters. A length scale defined from the curvature function near the gap-closing momentum is suggested to characterize the scale invariance at critical points and fixed points, and displays a universal critical behavior in a variety of systems examined.
Observables of non-equilibrium phase transition
Energy Technology Data Exchange (ETDEWEB)
Tomasik, Boris [Univerzita Mateja Bela, FPV, Banska Bystrica (Slovakia); Ceske vysoke uceni technicke v Praze, FJFI, Prague (Czech Republic); Schulc, Martin; Kopecna, Renata [Ceske vysoke uceni technicke v Praze, FJFI, Prague (Czech Republic); Melo, Ivan [Univerzita Mateja Bela, FPV, Banska Bystrica (Slovakia); Zilinska univerzita, Elektrotechnicka fakulta, Zilina (Slovakia)
2016-08-15
A rapidly expanding fireball which undergoes first-order phase transition will supercool and proceed via spinodal decomposition. Hadrons are produced from the individual fragments as well as the left-over matter filling the space between them. Emission from fragments should be visible in rapidity correlations, particularly of protons. In addition to that, even within narrow centrality classes, rapidity distributions will be fluctuating from one event to another in case of fragmentation. This can be identified with the help of the Kolmogorov-Smirnov test. Finally, we present a method which allows to sort events with varying rapidity distributions, in such a way that events with similar rapidity histograms are grouped together. (orig.)
Information Dynamics at a Phase Transition
Sowinski, Damian
2016-01-01
We propose a new way of investigating phase transitions in the context of information theory. We use an information-entropic measure of spatial complexity known as configurational entropy (CE) to quantify both the storage and exchange of information in a lattice simulation of a Ginzburg-Landau model with a scalar order parameter coupled to a heat bath. The CE is built from the Fourier spectrum of fluctuations around the mean-field and reaches a minimum at criticality. In particular, we investigate the behavior of CE near and at criticality, exploring the relation between information and the emergence of ordered domains. We show that as the temperature is increased from below, the CE displays three essential scaling regimes at different spatial scales: scale free, turbulent, and critical. Together, they offer an information-entropic characterization of critical behavior where the storage and processing of information is maximized at criticality.
Valleytronics and phase transition in silicene
Aftab, Tayyaba
2017-03-01
Magnetic and transport properties of silicene in the presence of perpendicular electromagnetic fields and a ferromagnetic material are studied. It is shown that for small exchange field, the magnetic moment associated with each valley is opposite for the other and it gives a shift in band energy, by a Zeeman-like coupling term. Thus opening a new horizon for valley-orbit coupling. Magnetic proximity effect is seen to adjust the spintronics of each valley. Valley polarization is calculated using the semi classical formulation of electron dynamics. It can be modified and measured due to its contribution in Hall conductivity. Quantum phase transitions are observed in silicene, providing a tool to control the topological state experimentally. The strong dependence of the physical properties on valley degree of freedom is an important step towards valleytronics.
Modeling the competing phase transition pathways in nanoscale olivine electrodes
Energy Technology Data Exchange (ETDEWEB)
Tang Ming, E-mail: tang25@llnl.go [Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Carter, W. Craig [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Belak, James F. [Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Chiang, Yet-Ming [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)
2010-12-30
Recent experimental developments reveal that nanoscale lithium iron phosphate (LiFePO{sub 4}) olivine particles exhibit very different phase transition behavior from the bulk olivine phase. A crystalline-to-amorphous phase transition has been observed in nanosized particles in competition with the equilibrium phase transition between the lithium-rich and lithium-poor olivine phases. Here we apply a diffuse-interface (phase-field) model to study the kinetics of the different phase transition pathways in nanosized LiFePO{sub 4} particles upon delithiation. We find that the nucleation and growth kinetics of the crystalline-to-crystalline and crystalline-to-amorphous phase transformations are sensitive to the applied electrical overpotential and particle size, which collectively determine the preferred phase transition pathway. While the crystalline-to-crystalline phase transition is favored by either faster nucleation or growth kinetics at low or high overpotentials, particle amorphization dominates at intermediate overpotentials. Decreasing particle size expands the overpotential region in which amorphization is preferred. The asymmetry in the nucleation energy barriers for amorphization and recrystallization results in a phase transition hysteresis that should promote the accumulation of the amorphous phase in electrodes after repeated electrochemical cycling. The predicted overpotential- and size-dependent phase transition behavior of nanoscale LiFePO{sub 4} particles is consistent with experimental observations.
Phase Transitions in Living Neural Networks
Williams-Garcia, Rashid Vladimir
Our nervous systems are composed of intricate webs of interconnected neurons interacting in complex ways. These complex interactions result in a wide range of collective behaviors with implications for features of brain function, e.g., information processing. Under certain conditions, such interactions can drive neural network dynamics towards critical phase transitions, where power-law scaling is conjectured to allow optimal behavior. Recent experimental evidence is consistent with this idea and it seems plausible that healthy neural networks would tend towards optimality. This hypothesis, however, is based on two problematic assumptions, which I describe and for which I present alternatives in this thesis. First, critical transitions may vanish due to the influence of an environment, e.g., a sensory stimulus, and so living neural networks may be incapable of achieving "critical" optimality. I develop a framework known as quasicriticality, in which a relative optimality can be achieved depending on the strength of the environmental influence. Second, the power-law scaling supporting this hypothesis is based on statistical analysis of cascades of activity known as neuronal avalanches, which conflate causal and non-causal activity, thus confounding important dynamical information. In this thesis, I present a new method to unveil causal links, known as causal webs, between neuronal activations, thus allowing for experimental tests of the quasicriticality hypothesis and other practical applications.
Phase Transitions in Networks of Memristive Elements
Sheldon, Forrest; di Ventra, Massimiliano
The memory features of memristive elements (resistors with memory), analogous to those found in biological synapses, have spurred the development of neuromorphic systems based on them (see, e.g.,). In turn, this requires a fundamental understanding of the collective dynamics of networks of memristive systems. Here, we study an experimentally-inspired model of disordered memristive networks in the limit of a slowly ramped voltage and show through simulations that these networks undergo a first-order phase transition in the conductivity for sufficiently high values of memory, as quantified by the memristive ON/OFF ratio. We provide also a mean-field theory that reproduces many features of the transition and particularly examine the role of boundary conditions and current- vs. voltage-controlled networks. The dynamics of the mean-field theory suggest a distribution of conductance jumps which may be accessible experimentally. We finally discuss the ability of these networks to support massively-parallel computation. Work supported in part by the Center for Memory and Recording Research at UCSD.
Topological and geometrical aspects of phase transitions
Santos, F. A. N.; Rehn, J. A.; Coutinho-Filho, M. D.
2014-03-01
In the first part of this review, we use a topological approach to describe the frustration- and field-induced phase transitions exhibited by the infinite-range XY model on the AB2 chain, including noncollinear spin structures. For this purpose, we have computed the Euler characteristic, χ, as well as other topological invariants, which are found to behave similarly as a function of the energy level in the context of Morse theory. Our findings and those available in the literature suggest that the cusp-like singularity exhibited by χ at the critical energy, Ec, put together with the divergence of the density of Jacobian's critical points emerge as necessary and sufficient conditions for the occurrence of finite-temperature topology-induced phase transitions. In the second part, we present an alternative solution of the Ising chain in a field under free and periodic boundary conditions, in the microcanonical, canonical, and grand canonical ensembles, from a unified combinatorial and topological perspective. In particular, the computation of the per-site entropy as a function of the energy unveils a residual value for critical values of the magnetic field, a phenomenon for which we provide a topological interpretation and a connection with the Fibonacci sequence. We also show that, in the thermodynamic limit, the per-site microcanonical entropy is equal to the logarithm of the per-site Euler characteristic. Finally, we emphasize that our combinatorial approach to the canonical ensemble allows exact computation of the thermally averaged value (T) of the Euler characteristic; our results show that the conjecture (Tc)= 0, where Tc is the critical temperature, is valid for the Ising chain.
The Deconfinement Phase Transition in the Interior of Neutron Stars
Zhou, Xia
2010-01-01
The decon?nement phase transition which happens in the interior of neutron stars are investigated. Coupled with the spin evolution of the stars, the effect of entropy production and deconfinement heat generation during the deconfinement phase transition in the mixed phase of the neutron stars are discussed. The entropy production of deconfinement phase transition can be act as a signature of phase transition, but less important and does not significantly change the thermal evolution of neutron stars. The deconfinement heat can change the thermal evolution of neutron star distinctly.
Eichelberger, J. C.
2003-12-01
The big news from 20th century geophysics may not be plate tectonics but rather the surprise return of catastrophism, following its apparent 19th century defeat to uniformitarianism. Divine miracles and plagues had yielded to the logic of integrating observations of everyday change over time. Yet the brilliant interpretation of the Cretaceous-Tertiary Boundary iridium anomaly introduced an empirically based catastrophism. Undoubtedly, decades of contemplating our own nuclear self-destruction played a role in this. Concepts of nuclear winter, volcanic winter, and meteor impact winter are closely allied. And once the veil of threat of all-out nuclear exchange began to lift, we could begin to imagine slower routes to destruction as "global change". As a way to end our world, fire is a good one. Three-dimensional magma chambers do not have as severe a magnitude limitation as essentially two-dimensional faults. Thus, while we have experienced earthquakes that are as big as they get, we have not experienced volcanic eruptions nearly as great as those preserved in the geologic record. The range extends to events almost three orders of magnitude greater than any eruptions of the 20th century. Such a calamity now would at the very least bring society to a temporary halt globally, and cause death and destruction on a continental scale. At maximum, there is the possibility of hindering photosynthesis and threatening life more generally. It has even been speculated that the relative genetic homogeneity of humankind derives from an evolutionary "bottleneck" from near-extinction in a volcanic cataclysm. This is somewhat more palatable to contemplate than a return to a form of Original Sin, in which we arrived at homogeneity by a sort of "ethnic cleansing". Lacking a written record of truly great eruptions, our sense of human impact must necessarily be aided by archeological and anthropological investigations. For example, there is much to be learned about the influence of
Non-equilibrium phase transitions in complex plasma
Sutterlin, K. R.; Wysocki, A.; Rath, C.; Ivlev, A. V.; Thomas, H. M.; Khrapak, S.; Zhdanov, S.; Rubin-Zuzic, M.; W. J. Goedheer,; Fortov, V. E.; Lipaev, A. M.; Molotkov, V. I.; Petrov, O. F.; Morfill, G. E.; Lowen, H.
2010-01-01
Complex plasma being the 'plasma state of soft matter' is especially suitable for investigations of non-equilibrium phase transitions. Non-equilibrium phase transitions can manifest in dissipative structures or self-organization. Two specific examples are lane formation and phase separatio
Phase transitions in a gas of anyons
MacKenzie, R; Paranjape, M B; Richer, J
2010-01-01
We continue our numerical Monte Carlo simulation of a gas of closed loops on a 3 dimensional lattice, however now in the presence of a topological term added to the action corresponding to the total linking number between the loops. We compute the linking number using certain notions from knot theory. Adding the topological term converts the particles into anyons. Using the correspondence that the model is an effective theory that describes the 2+1-dimensional Abelian Higgs model in the asymptotic strong coupling regime, the topological linking number simply corresponds to the addition to the action of the Chern-Simons term. We find the following new results. The system continues to exhibit a phase transition as a function of the anyon mass as it becomes small \\cite{mnp}, although the phases do not change the manifestation of the symmetry. The Chern-Simons term has no effect on the Wilson loop, but it does affect the {\\rm '}t Hooft loop. For a given configuration it adds the linking number of the 't Hooft loo...
Energy Technology Data Exchange (ETDEWEB)
Lopez-Moreno, Enrique; Grether, M; Velazquez, Victor, E-mail: elm@hp.fciencias.unam.mx [Facultad de Ciencias, Departamento de Fisica, Universidad Nacional Autonoma de Mexico, Cd. Universitaria, Circuito Exterior, 04510 Mexico DF (Mexico)
2011-11-25
A general spin system with a nonaxially symmetric Hamiltonian containing J{sub x}, J{sub z}-linear and J{sub z}-quadratic terms, widely used in many-body fermionic and bosonic systems and in molecular magnetism, is considered for the variations of general parameters describing intensity interaction changes of each of its terms. For this model Hamiltonian, a semiclassical energy surface (ES) is obtained by means of the coherent-state formalism. An analysis of this ES function, based on catastrophe theory, determines the separatrix in the control parameter space of the system Hamiltonian: the loci of singularities representing semiclassical phase transitions. Here we show that distinct regions of qualitatively different spectrum structures, as well as a singular behavior of quantum states, are ruled by this separatrix: here we show that the separatrix not only describes ground-state singularities, which have been associated with quantum phase transitions, but also reveals the structure of the excited spectrum, distinguishing different quantum phases within the parameter space. Finally, we consider magnetic susceptibility and heat capacity of the system at finite temperature, in order to study thermal properties and thermodynamical phase transitions in the perspective of the separatrix of this Hamiltonian system. (paper)
Bubble nucleation and growth in very strong cosmological phase transitions
Megevand, Ariel
2016-01-01
Strongly first-order phase transitions, i.e., those with a large order parameter, are characterized by a considerable supercooling and high velocities of phase transition fronts. A very strong phase transition may have important cosmological consequences due to the departures from equilibrium caused in the plasma. In general, there is a limit to the strength, since the metastability of the old phase may prevent the transition to complete. Near this limit, the bubble nucleation rate achieves a maximum and thus departs from the widely assumed behavior in which it grows exponentially with time. We study the dynamics of this kind of phase transitions. We show that in some cases a gaussian approximation for the nucleation rate is more suitable, and in such a case we solve analytically the evolution of the phase transition. We compare the gaussian and exponential approximations with realistic cases and we determine their ranges of validity. We also discuss the implications for cosmic remnants such as gravitational ...
Pressure-induced phase transition in CrO2.
Alptekin, Sebahaddin
2015-12-01
The ab initio constant pressure molecular dynamics technique and density functional theory with generalized gradient approximation (GGA) was used to study the pressure-induced phase transition of CrO2. The phase transition of the rutile (P42/mnm) to the orthorhombic CaCl2 (Pnnm) structure at 30 GPa was determined successfully in a constant pressure simulation. This phase transition was analyzed from total energy calculations and, from the enthalpy calculation, occurred at around 17 GPa. Structural properties such as bulk modules, lattice parameters and phase transition were compared with experimental results. The phase transition at 12 ± 3 GPa was in good agreement with experimental results, as was the phase transition from the orthorhombic CaCl2 (Pnnm) to the monoclinic (P21/c) structure also found at 35 GPa.
Quantum phase transition and entanglement in Li atom system
Institute of Scientific and Technical Information of China (English)
2008-01-01
By use of the exact diagonalization method, the quantum phase transition and en- tanglement in a 6-Li atom system are studied. It is found that entanglement appears before the quantum phase transition and disappears after it in this exactly solvable quantum system. The present results show that the von Neumann entropy, as a measure of entanglement, may reveal the quantum phase transition in this model.
Discord under the influence of a quantum phase transition
Institute of Scientific and Technical Information of China (English)
Wang Lin-cheng; Shen Jian; Yi Xue-Xi
2011-01-01
This paper studies the discord of a bipartite two-level system coupling to an XY spin-chain environment in a transverse field and investigates the relationship between the discord property and the environment's quantum phase transition. The results show that the quantum discord is also able to characterize the quantum phase transitions. We also discuss the difference between discord and entanglement, and show that quantum discord may reveal more general information than quantum entanglement for characterizing the environment's quantum phase transition.
Gravitational waves from global second order phase transitions
Energy Technology Data Exchange (ETDEWEB)
Jr, John T. Giblin [Department of Physics, Kenyon College, 201 North College Rd, Gambier, OH 43022 (United States); Price, Larry R.; Siemens, Xavier; Vlcek, Brian, E-mail: giblinj@kenyon.edu, E-mail: larryp@caltech.edu, E-mail: siemens@gravity.phys.uwm.edu, E-mail: bvlcek@uwm.edu [Center for Gravitation and Cosmology, Department of Physics, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, WI 53201 (United States)
2012-11-01
Global second-order phase transitions are expected to produce scale-invariant gravitational wave spectra. In this manuscript we explore the dynamics of a symmetry-breaking phase transition using lattice simulations. We explicitly calculate the stochastic gravitational wave background produced during the transition and subsequent self-ordering phase. We comment on this signal as it compares to the scale-invariant spectrum produced during inflation.
Holographic phase transition probed by non-local observables
Zeng, Xiao-Xiong
2016-01-01
From the viewpoint of holography, the phase structure of a 5-dimensional Reissner-Nordstr\\"{o}m-AdS black hole is probed by the two point correlation function, Wilson loop, and entanglement entropy. As the case of thermal entropy, we find for all the probes, the black hole undergos a Hawking-Page phase transition, a first order phase transition and a second order phase transition successively before it reaches to a stable phase. In addition, for these probes, we find the equal area law for the first order phase transition is valid always and the critical exponent of the heat capacity for the second order phase transition coincides with that of the mean field theory regardless of the size of the boundary region.
Kinetics of shock-induced polymorphic phase transitions
Energy Technology Data Exchange (ETDEWEB)
Hayes, D.B.
1976-01-01
Shock-loading induces polymorphic phase transitions in some solids if the pressure exceeds that at which phase transition occurs under quasi-static compression. Volume changes in shock-induced transitions must occur very rapidly to produce the structured shock waves observed, so transition rates are large under these dynamic conditions. By contrast, the same transition might require minutes or hours under quasi-static loading. If shock-induced transition is so rapid that kinetic effects can be ignored, a steady two-wave structure is propagated. The first wave, of amplitude equal to the transition pressure, shocks the material to the phase boundary but produces no transition; the second, slower wave produces the transformed phase. When kinetic effects are important, this two-wave structure does not form immediately but by an evolutionary process which produces transients in the amplitudes and rise times of the stress waves. By measuring these transient effects, some facts about the kinetics of phase transitions have been inferred. Comprehensive studies on phase-transition kinetics in antimony, iron, and potassium chloride are described, with emphasis on a thermodynamic description of the intermediate states during transition. Complicating effects such as shear strength and wave perturbations due to free surfaces are discussed.
Elastic phase transitions in metals at high pressures.
Krasilnikov, O M; Vekilov, Yu Kh; Mosyagin, I Yu; Isaev, E I; Bondarenko, N G
2012-04-19
The elastic phase transitions of cubic metals at high pressures are investigated within the framework of Landau theory. It is shown that at pressures comparable with the magnitude of the bulk modulus the phase transition is connected with the loss of stability relative to uniform deformation of the crystalline lattice. Discontinuity of the order parameter at the transition point and its equilibrium value are expressed through the second- to fourth-order elastic constants. The second-,third- and fourth-order elastic constants and phonon dispersion curves of vanadium under hydrostatic pressure are obtained by first-principles calculations. Structural transformation in vanadium under pressure is studied using the obtained results. It is shown that the experimentally observed at P ≈ 69 GPa phase transition in vanadium is the first-order phase transition close to a second-order phase transition.
Pressure induced phase transitions in ceramic compounds containing tetragonal zirconia
Energy Technology Data Exchange (ETDEWEB)
Sparks, R.G.; Pfeiffer, G.; Paesler, M.A.
1988-12-01
Stabilized tetragonal zirconia compounds exhibit a transformation toughening process in which stress applied to the material induces a crystallographic phase transition. The phase transition is accompanied by a volume expansion in the stressed region thereby dissipating stress and increasing the fracture strength of the material. The hydrostatic component of the stress required to induce the phase transition can be investigated by the use of a high pressure technique in combination with Micro-Raman spectroscopy. The intensity of Raman lines characteristic for the crystallographic phases can be used to calculate the amount of material that has undergone the transition as a function of pressure. It was found that pressures on the order of 2-5 kBar were sufficient to produce an almost complete transition from the original tetragonal to the less dense monoclinic phase; while a further increase in pressure caused a gradual reversal of the transition back to the original tetragonal structure.
Van der Waals phase transition in the framework of holography
Zeng, Xiao-Xiong
2015-01-01
Phase structure of the quintessence Reissner-Nordstr\\"{o}m-AdS black hole is probed with the nonlocal observables such as holographic entanglement entropy and two point correlation function. Our result shows that, as the case of the thermal entropy, both the observables exhibit the similar Van der Waals-like phase transition. To reinforce the conclusion, we further check the equal area law for the first order phase transition and critical exponent of the heat capacity for the second order phase transition. We also discuss the effect of the state parameter on the phase structure of the nonlocal observables.
ATLAS Transition Region Upgrade at Phase-1
Song, H; The ATLAS collaboration
2014-01-01
This report presents the L1 Muon trigger transition region (1.0<|ƞ|<1.3) upgrade of ATLAS Detector at phase-1. The high fake trigger rate in the Endcap region 1.0<|ƞ|<2.4 would become a serious problem for the ATLAS L1 Muon trigger system at high luminosity. For the region 1.3<|ƞ|<2.4, covered by the Small Wheel, ATLAS is enhancing the present muon trigger by adding local fake rejection and track angle measurement capabilities. To reduce the rate in the remaining ƞ interval it has been proposed a similar enhancement by adding at the edge of the inner barrel a structure of 3-layers RPCs of a new generation. These RPCs will be based on a thinner gas gap and electrodes with respect to the ATLAS standards, a new high performance Front End, integrating fast TDC capabilities, and a new low profile and light mechanical structure allowing the installation in the tiny space available.This design effectively suppresses fake triggers by making the coincidence with both end-cap and interaction point...
Phase transitions in models of human cooperation
Perc, Matjaž
2016-08-01
If only the fittest survive, why should one cooperate? Why should one sacrifice personal benefits for the common good? Recent research indicates that a comprehensive answer to such questions requires that we look beyond the individual and focus on the collective behavior that emerges as a result of the interactions among individuals, groups, and societies. Although undoubtedly driven also by culture and cognition, human cooperation is just as well an emergent, collective phenomenon in a complex system. Nonequilibrium statistical physics, in particular the collective behavior of interacting particles near phase transitions, has already been recognized as very valuable for understanding counterintuitive evolutionary outcomes. However, unlike pairwise interactions among particles that typically govern solid-state physics systems, interactions among humans often involve group interactions, and they also involve a larger number of possible states even for the most simplified description of reality. Here we briefly review research done in the realm of the public goods game, and we outline future research directions with an emphasis on merging the most recent advances in the social sciences with methods of nonequilibrium statistical physics. By having a firm theoretical grip on human cooperation, we can hope to engineer better social systems and develop more efficient policies for a sustainable and better future.
Swarms, Phase Transitions, and Collective Intelligence
Millonas, M M
1993-01-01
A spacially extended model of the collective behavior of a large number of locally acting organisms is proposed in which organisms move probabilistically between local cells in space, but with weights dependent on local morphogenetic substances, or morphogens. The morphogens are in turn are effected by the passage of an organism. The evolution of the morphogens, and the corresponding flow of the organisms constitutes the collective behavior of the group. Such models have various types of phase transitions and self-organizing properties controlled both by the level of the noise, and other parameters. The model is then applied to the specific case of ants moving on a lattice. The local behavior of the ants is inspired by the actual behavior observed in the laboratory, and analytic results for the collective behavior are compared to the corresponding laboratory results. It is hoped that the present model might serve as a paradigmatic example of a complex cooperative system in nature. In particular swarm models c...
Entanglement, quantum phase transitions and quantum algorithms
Orus, R
2006-01-01
The work that we present in this thesis tries to be at the crossover of quantum information science, quantum many-body physics, and quantum field theory. We use tools from these three fields to analyze problems that arise in the interdisciplinary intersection. More concretely, in Chapter 1 we consider the irreversibility of renormalization group flows from a quantum information perspective by using majorization theory and conformal field theory. In Chapter 2 we compute the entanglement of a single copy of a bipartite quantum system for a variety of models by using techniques from conformal field theory and Toeplitz matrices. The entanglement entropy of the so-called Lipkin-Meshkov-Glick model is computed in Chapter 3, showing analogies with that of (1+1)-dimensional quantum systems. In Chapter 4 we apply the ideas of scaling of quantum correlations in quantum phase transitions to the study of quantum algorithms, focusing on Shor's factorization algorithm and quantum algorithms by adiabatic evolution solving a...
Phase Transitions in Two-Dimensional Traffic Flow Models
Cuesta, J A; Molera, J M; Cuesta, José A; Martinez, Froilán C; Molera, Juan M
1993-01-01
Abstract: We introduce two simple two-dimensional lattice models to study traffic flow in cities. We have found that a few basic elements give rise to the characteristic phase diagram of a first-order phase transition from a freely moving phase to a jammed state, with a critical point. The jammed phase presents new transitions corresponding to structural transformations of the jam. We discuss their relevance in the infinite size limit.
Phase Transitions in Two-Dimensional Traffic Flow Models
Cuesta, José A; Molera, Juan M; Escuela, Angel Sánchez; 10.1103/PhysRevE.48.R4175
2009-01-01
We introduce two simple two-dimensional lattice models to study traffic flow in cities. We have found that a few basic elements give rise to the characteristic phase diagram of a first-order phase transition from a freely moving phase to a jammed state, with a critical point. The jammed phase presents new transitions corresponding to structural transformations of the jam. We discuss their relevance in the infinite size limit.
Cosmological Consequences of QCD Phase Transition(s) in Early Universe
Tawfik, A
2008-01-01
We discuss the cosmological consequences of QCD phase transition(s) on the early universe. We argue that our recent knowledge about the transport properties of quark-gluon plasma (QGP) should throw additional lights on the actual time evolution of our universe. Understanding the nature of QCD phase transition(s), which can be studied in lattice gauge theory and verified in heavy ion experiments, provides an explanation for cosmological phenomenon stem from early universe.
Fast phase transitions induced by picosecond electrical pulses on phase change memory cells
Wang, W. J.; Shi, L. P.; Zhao, R.; Lim, K. G.; Lee, H. K.; Chong, T. C.; Wu, Y. H.
2008-07-01
The reversible and fast phase transitions induced by picosecond electrical pulses are observed in the nanostructured GeSbTe materials, which provide opportunities in the application of high speed nonvolatile random access memory devices. The mechanisms for fast phase transition are discussed based on the investigation of the correlation between phase transition speed and material size. With the shrinkage of material dimensions, the size effects play increasingly important roles in enabling the ultrafast phase transition under electrical activation. The understanding of how the size effects contribute to the phase transition speed is of great importance for ultrafast phenomena and applications.
Liquid-liquid phase transition in Stillinger-Weber silicon
Energy Technology Data Exchange (ETDEWEB)
Beaucage, Philippe; Mousseau, Normand [Departement de Physique and Regroupement Quebecois sur les Materiaux de Pointe, Universite de Montreal, CP 6128, Succursale Centre-ville, Montreal, QC, H3C 3J7 (Canada)
2005-04-20
It was recently demonstrated that Stillinger-Weber silicon undergoes a liquid-liquid first-order phase transition deep into the supercooled region (Sastry and Angell 2003 Nat. Mater. 2 739). Here we study the effects of perturbations on this phase transition. We show that the order of the liquid-liquid transition changes with negative pressure. We also find that the liquid-liquid transition disappears when the three-body term of the potential is strengthened by as little as 5%. This implies that the details of the potential could affect strongly the nature and even the existence of the liquid-liquid phase.
Quantum phase transitions in Bose-Fermi systems
Petrellis, D; Iachello, F
2011-01-01
Quantum phase transitions in a system of N bosons with angular momentum L=0,2 (s,d) and a single fermion with angular momentum j are investigated both classically and quantum mechanically. It is shown that the presence of the odd fermion strongly influences the location and nature of the phase transition, especially the critical value of the control parameter at which the phase transition occurs. Experimental evidence for the U(5)-SU(3) (spherical to axially-deformed) transition in odd-even nuclei is presented.
Liquid-Gas Phase Transition in Nuclear Equation of State
Lee, S J
1997-01-01
A canonical ensemble model is used to describe a caloric curve of nuclear liquid-gas phase transition. Allowing a discontinuity in the freeze out density from one spinodal density to another for a given initial temperature, the nuclear liquid-gas phase transition can be described as first order. Averaging over various freeze out densities of all the possible initial temperatures for a given total reaction energy, the first order characteristics of liquid-gas phase transition is smeared out to a smooth transition. Two experiments, one at low beam energy and one at high beam energy show different caloric behaviors and are discussed.
Diamagnetic phase transitions in two-dimensional conductors
Bakaleinikov, L. A.; Gordon, A.
2014-11-01
A theory describing the susceptibility amplitude and the magnetic induction bifurcation near the dHvA driven diamagnetic phase transitions in quasi two-dimensional (2D) organic conductors of the (ET)2X with X=Cu(NCS)2, KHg(SCN)4, I3, AuBr2, IBr2, etc. is presented. We show that there is a drastic increase in the temperature and magnetic field dependence of the susceptibility amplitude on approaching the diamagnetic phase transition point. Near the phase transition point the temperature and magnetic field dependences are fitted by the ones typical of the mean-field phase transition theory. These dependences confirm the long-range character of the magnetic interactions among the conduction electrons leading to diamagnetic phase transitions. We demonstrate that the magnetic induction splitting of nuclear magnetic resonance (NMR) and muon spin-rotation spectroscopy (μSR) lines due to two Condon domains decreases tending to zero on approaching the diamagnetic phase transition. This decrease is fitted by the temperature and magnetic field dependence of the susceptibility characteristic of the mean-field theory of phase transitions. Performing new susceptibility, NMR and μSR experiments will enable to detect diamagnetic phase transitions and Condon domains in quasi 2D metals.
Quantum Monte Carlo simulation of topological phase transitions
Yamamoto, Arata; Kimura, Taro
2016-12-01
We study the electron-electron interaction effects on topological phase transitions by the ab initio quantum Monte Carlo simulation. We analyze two-dimensional class A topological insulators and three-dimensional Weyl semimetals with the long-range Coulomb interaction. The direct computation of the Chern number shows the electron-electron interaction modifies or extinguishes topological phase transitions.
Experimental and theoretical investigations on shock wave induced phase transitions
Gupta, Satish C.; Sikka, S. K.
2001-06-01
Shock wave loading of a material can cause variety of phase transitions, like polymorphism, amorphization, metallization and molecular dissociations. As the shocked state lasts only for a very short duration (about a few microseconds or less), in-situ microscopic measurements are very difficult. Although such studies are beginning to be possible, most of the shock-induced phase transitions are detected using macroscopic measurements. The microscopic nature of the transition is then inferred from comparison with static pressure data or interpreted by theoretical methods. For irreversible phase transitions, microscopic measurements on recovered samples, together with orientation relations determined from selected area electron diffraction and examination of the morphology of growth of the new phase can provide insight into mechanism of phase transitions. On theoretical side, the current ab initio band structure techniques based on density functional formalism provide capability for accurate computation of the small energy differences (a few mRy or smaller) between different plausible structures. Total energy calculation along the path of a phase transition can furnish estimates of activation barrier, which has implications for understanding kinetics of phase transitions. Molecular dynamics calculations, where the new structure evolves naturally, are becoming increasingly popular especially for understanding crystal to amorphous phase transitions. Illustrations from work at our laboratory will be presented.
Quantum Monte Carlo simulation of topological phase transitions
Yamamoto, Arata
2016-01-01
We study the electron-electron interaction effects on topological phase transitions by the ab-initio quantum Monte Carlo simulation. We analyze two-dimensional class A topological insulators and three-dimensional Weyl semimetals with the long-range Coulomb interaction. The direct computation of the Chern number shows the electron-electron interaction modifies or extinguishes topological phase transitions.
Nuclear Liquid-Gas Phase Transition: Experimental Signals
D'Agostino, M.; Bruno, M.; Gulminelli, F.; Cannata, F.; Chomaz, Ph.; Casini, G.; Geraci, E.; Gramegna, F.; Moroni, A.; Vannini, G.
2005-03-01
The connection between the thermodynamics of charged finite nuclear systems and the asymptotically measured partitions in heavy ion collisions is discussed. Different independent signals compatible with a liquid-to-gas-like phase transition are reported. In particular abnormally large fluctuations in the measured observables are presented as a strong evidence of a first order phase transition with negative heat capacity.
Nuclear liquid-gas phase transition: Experimental signals
Energy Technology Data Exchange (ETDEWEB)
D' Agostino, M. [Dipartimento di Fisica and INFN, Bologna (Italy); Bruno, M. [Dipartimento di Fisica and INFN, Bologna (Italy); Gulminelli, F. [LPC Caen (IN2P3-CNRS/ISMRA et Universite), F-14050 Caen Cedex (France); Cannata, F. [Dipartimento di Fisica and INFN, Bologna (Italy); Chomaz, Ph. [GANIL, DSM-CEA/IN2P3-CNRS (France); Casini, G. [INFN Sezione di Firenze (Italy); Geraci, E. [Dipartimento di Fisica and INFN, Bologna (Italy); Gramegna, F. [INFN Laboratorio Nazionale di Legnaro (Italy); Moroni, A. [Dipartimento di Fisica and INFN, Milano (Italy); Vannini, G. [Dipartimento di Fisica and INFN, Bologna (Italy)
2005-03-07
The connection between the thermodynamics of charged finite nuclear systems and the asymptotically measured partitions in heavy ion collisions is discussed. Different independent signals compatible with a liquid-to-gas-like phase transition are reported. In particular abnormally large fluctuations in the measured observables are presented as a strong evidence of a first order phase transition with negative heat capacity.
Two kinds of Phase transitions in a Voting model
Hisakado, Masato
2012-01-01
In this paper, we discuss a voting model with two candidates, C_1 and C_2. We consider two types of voters--herders and independents. The voting of independents is based on their fundamental values; on the other hand, the voting of herders is based on the number of previous votes. We can identify two kinds of phase transitions. One is information cascade transition similar to a phase transition seen in Ising model. The other is a transition of super and normal diffusions. These phase transitions coexist together. We compared our results to the conclusions of experiments and identified the phase transitions in the upper t limit using analysis of human behavior obtained from experiments.
Quantum Phase Transitions in Odd-Mass Nuclei
Leviatan, A; Iachello, F
2011-01-01
Quantum shape-phase transitions in odd-even nuclei are investigated in the framework of the interacting boson-fermion model. Classical and quantum analysis show that the presence of the odd fermion strongly influences the location and nature of the phase transition, especially near the critical point. Experimental evidence for the occurrence of spherical to axially-deformed transitions in odd-proton nuclei Pm, Eu and Tb (Z=61, 63, 65) is presented.
Deconfinement Phase Transition Heating and Thermal Evolution of Neutron Stars
Kang, Miao; Wang, Xiaodong
2007-01-01
The deconfinement phase transition will lead to the release of latent heat during spins down of neutron stars if the transition is the first-order one.We have investigated the thermal evolution of neutron stars undergoing such deconfinement phase transition. The results show that neutron stars may be heated to higher temperature.This feature could be particularly interesting for high temperature of low-magnetic field millisecond pulsar at late stage.
High pressure phase transitions for CdSe
Indian Academy of Sciences (India)
Bo Kong; Ti-Xian Zeng; Zhu-Wen Zhou; De-Liang Chen; Xiao-Wei Sun
2014-05-01
The structure and pressure-induced phase transitions for CdSe are investigated using first-principles calculations. The pressure-induced phase transition sequence WZ/ZB $\\to$ Rs $\\to$ $\\to$ CsCl for CdSe is drawn reasonably for the fist time, the corresponding transition pressures are 3.8, 29 and 107 GPa, respectively and the intermediate states between the structure and the CsCl structure should exist.
Chiral phase transition in QED3 at finite temperature
Yin, Pei-Lin; Xiao, Hai-Xiao; Wei, Wei; Feng, Hong-Tao; Zong, Hong-Shi
2016-12-01
In the framework of Dyson-Schwinger equations, we employ two kinds of criteria (one kind is the chiral condensate, the other kind is thermodynamic quantities, such as the pressure, the entropy, and the specific heat) to investigate the nature of chiral phase transitions in QED3 for different fermion flavors. It is found that the chiral phase transitions in QED3 for different fermion flavors are all typical second-order phase transitions; the critical temperature and order of the chiral phase transition obtained from the chiral condensate and susceptibility are the same with that obtained by the thermodynamic quantities, which means that they are equivalent in describing the chiral phase transition; the critical temperature decreases as the number of fermion flavors increases and there is a boundary that separates the Tc-Nf plane into chiral symmetry breaking and restoration regions.
A unified approach of catastrophic events
Directory of Open Access Journals (Sweden)
S. Nikolopoulos
2004-01-01
Full Text Available Although there is an accumulated charge of theoretical, computational, and numerical work, like catastrophe theory, bifurcation theory, stochastic and deterministic chaos theory, there is an important feeling that these matters do not completely cover the physics of real catastrophic events. Recent studies have suggested that a large variety of complex processes, including earthquakes, heartbeats, and neuronal dynamics, exhibits statistical similarities. Here we are studying in terms of complexity and non linear techniques whether isomorphic signatures emerged indicating the transition from the normal state to the both geological and biological shocks. In the last 15 years, the study of Complex Systems has emerged as a recognized field in its own right, although a good definition of what a complex system is, actually is eluded. A basic reason for our interest in complexity is the striking similarity in behaviour close to irreversible phase transitions among systems that are otherwise quite different in nature. It is by now recognized that the pre-seismic electromagnetic time-series contain valuable information about the earthquake preparation process, which cannot be extracted without the use of important computational power, probably in connection with computer Algebra techniques. This paper presents an analysis, the aim of which is to indicate the approach of the global instability in the pre-focal area. Non-linear characteristics are studied by applying two techniques, namely the Correlation Dimension Estimation and the Approximate Entropy. These two non-linear techniques present coherent conclusions, and could cooperate with an independent fractal spectral analysis to provide a detection concerning the emergence of the nucleation phase of the impending catastrophic event. In the context of similar mathematical background, it would be interesting to augment this description of pre-seismic electromagnetic anomalies in order to cover biological
Diamagnetic phase transitions in two-dimensional conductors
Energy Technology Data Exchange (ETDEWEB)
Bakaleinikov, L.A., E-mail: bakal.ammp@mail.ioffe.ru [A.F. Ioffe Physico-Technical Institute, Russian Academy of Sciences, St. Petersburg 194021 (Russian Federation); Department of Mathematics and Physics, Faculty of Natural Sciences, University of Haifa, Campus Oranim, Tivon 36006 (Israel); Gordon, A. [Department of Mathematics and Physics, Faculty of Natural Sciences, University of Haifa, Campus Oranim, Tivon 36006 (Israel)
2014-11-15
A theory describing the susceptibility amplitude and the magnetic induction bifurcation near the dHvA driven diamagnetic phase transitions in quasi two-dimensional (2D) organic conductors of the (ET){sub 2}X with X=Cu(NCS){sub 2},KHg(SCN){sub 4},I{sub 3},AuBr{sub 2},IBr{sub 2}, etc. is presented. We show that there is a drastic increase in the temperature and magnetic field dependence of the susceptibility amplitude on approaching the diamagnetic phase transition point. Near the phase transition point the temperature and magnetic field dependences are fitted by the ones typical of the mean-field phase transition theory. These dependences confirm the long-range character of the magnetic interactions among the conduction electrons leading to diamagnetic phase transitions. We demonstrate that the magnetic induction splitting of nuclear magnetic resonance (NMR) and muon spin-rotation spectroscopy (μSR) lines due to two Condon domains decreases tending to zero on approaching the diamagnetic phase transition. This decrease is fitted by the temperature and magnetic field dependence of the susceptibility characteristic of the mean-field theory of phase transitions. Performing new susceptibility, NMR and μSR experiments will enable to detect diamagnetic phase transitions and Condon domains in quasi 2D metals. - Highlights: • A theory of diamagnetic phase transitions (DPTs) is presented in 2D organic conductors. • The behaviour of the susceptibility amplitude and the induction splitting is shown near the DPT. • The calculated quantities are described by the mean-field theory of phase transitions.
Phase transition and PTCR effect in erbium doped BT ceramics
Energy Technology Data Exchange (ETDEWEB)
Leyet, Y. [Departamento de Fisica, Facultad de Ciencias Naturales, Universidad de Oriente, C.P. 90500 Santiago de Cuba (Cuba); Instituto Federal de Educacao Ciencia e Tecnologia (IFAM), Av. 7 de Setembro 1975, Centro, Manaus 69020-120, AM (Brazil); Pena, R.; Zulueta, Y. [Departamento de Fisica, Facultad de Ciencias Naturales, Universidad de Oriente, C.P. 90500 Santiago de Cuba (Cuba); Guerrero, F. [Departamento de Fisica, Facultad de Ciencias Naturales, Universidad de Oriente, C.P. 90500 Santiago de Cuba (Cuba); CESI, Universidade do Estado do Amazonas, Ave Mario Andreaza, Amazonas (Brazil); Anglada-Rivera, J. [CESI, Universidade do Estado do Amazonas, Ave Mario Andreaza, Amazonas (Brazil); Romaguera, Y. [INESC TEC, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Perez de la Cruz, J., E-mail: jcruz@inescporto.pt [INESC TEC, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal)
2012-06-25
Highlights: Black-Right-Pointing-Pointer Erbium influence the dielectric response BaTiO{sub 3} ceramics. Black-Right-Pointing-Pointer Features of the phase transition are not explained by phenomenological models. Black-Right-Pointing-Pointer Relaxation parameters do not show influence on ferroelectric-paraelectric phase transition. Black-Right-Pointing-Pointer Dielectric anomaly on BET phase transition is associated with the PTCR effect. - Abstract: In this work the dielectric behaviour and main features of the phase transition of BaTiO{sub 3} and Ba{sub 0.99}Er{sub 0.01}TiO{sub 3} ceramics were carefully investigated. The temperature and frequency dependences of the dielectric properties of erbium doped BaTiO{sub 3} ceramics were measured in the 25-225 Degree-Sign C and 100 Hz to 10 MHz ranges, respectively. From this study, a dielectric anomaly in the ferroelectric-paraelectric phase transition of the Ba{sub 0.99}Er{sub 0.01}TiO{sub 3} ceramic was observed. The features of the samples phase transition were analysed by using Curie-Weiss, Santos-Eiras' and order parameter local phenomenological models. In the BaTiO{sub 3} system, all models showed a normal phase transition, while was not possible to establish the character of the phase transition in the Ba{sub 0.99}Er{sub 0.01}TiO{sub 3} system. The relaxation parameters of conductive processes for the study ferroelectric materials, analysed in the time domain, did not show any influence on the ferroelectric-paraelectric phase transition. Finally, it was demonstrated that the anomaly observed on the phase transition of the erbium doped BaTiO{sub 3} ceramics is associated with the processes that results in the PTCR effect.
Reentrant Phase Transitions in Rotating AdS Black Holes
Altamirano, Natacha; Mann, Robert B
2013-01-01
We study the thermodynamics of higher-dimensional singly spinning asymptotically AdS black holes in the canonical (fixed J) ensemble of extended phase space, where the cosmological constant is treated as pressure and the corresponding conjugate quantity is interpreted as thermodynamic volume. Along with the usual small/large black hole phase transition, we find a new phenomenon of reentrant phase transitions for all d>5 dimensions, in which a monotonic variation of the temperature yields two phase transitions from large to small and back to large black holes. This situation is similar to that seen in multicomponent liquids.
Thermodynamics of Phase Transitions of a Kerr Nonlinear Blackbody
Institute of Scientific and Technical Information of China (English)
CHENG Ze
2008-01-01
We study the thermodynamics of phase transitions of a blackbody whose interior is filled by a Kerr nonlinear crystal. There is a transition temperature To, above which the Kerr nonlinear blackbody is in the normal thermal radiation state, and below which it is in the squeezed thermal radiation state. At To, the Gibbs free energy of the two phases is continuous but the entropy density of the two phases is discontinuous. Hence, there is a jump in the entropy density and this leads to a latent heat density. The photon system undergoes a first-order phase transition from the normal to the squeezed thermal radiation state.
Large N Phase Transitions, Finite Volume, and Entanglement Entropy
Johnson, Clifford V
2014-01-01
Holographic studies of the entanglement entropy of field theories dual to charged and neutral black holes in asymptotically global AdS4 spacetimes are presented. The goal is to elucidate various properties of the quantity that are peculiar to working in finite volume, and to gain access to the behaviour of the entanglement entropy in the rich thermodynamic phase structure that is present at finite volume and large N. The entropy is followed through various first order phase transitions, and also a novel second order phase transition. Behaviour is found that contrasts interestingly with an earlier holographic study of a second order phase transition dual to an holographic superconductor.
CO2 Capture from Flue Gas by Phase Transitional Absorption
Energy Technology Data Exchange (ETDEWEB)
Liang Hu
2009-06-30
A novel absorption process called Phase Transitional Absorption was invented. What is the Phase Transitional Absorption? Phase Transitional Absorption is a two or multi phase absorption system, CO{sub 2} rich phase and CO{sub 2} lean phase. During Absorption, CO{sub 2} is accumulated in CO{sub 2} rich phase. After separating the two phases, CO{sub 2} rich phase is forward to regeneration. After regeneration, the regenerated CO{sub 2} rich phase combines CO{sub 2} lean phase to form absorbent again to complete the cycle. The advantage for Phase Transitional Absorption is obvious, significantly saving on regeneration energy. Because CO{sub 2} lean phase was separated before regeneration, only CO{sub 2} rich phase was forward to regeneration. The absorption system we developed has the features of high absorption rate, high loading and working capacity, low corrosion, low regeneration heat, no toxic to environment, etc. The process evaluation shows that our process is able to save 80% energy cost by comparing with MEA process.
Phase Transition Induced by Small Molecules in Confined Copolymer Films
Institute of Scientific and Technical Information of China (English)
ZHOU Ling
2007-01-01
We investigate the phase transition induced by small molecules in confined copolymer films by using density functional theory.It is found that the addition of small molecules can effectively promote the phase separation of copolymers.In a symmetric diblock copolymer film,the affinity and concentration of small molecules play an important role in the structure transjtions.The disordered-lamellar transitions lamellar-lamellar transitions and the re-entrant transitions of the same structures are observed.Our results have potential applications in the fabrication of new functional materials.
Phase-separation transitions in asymmetric lipid bilayers
Shimobayashi, Shunsuke F; Taniguchi, Takashi
2015-01-01
Morphological transitions of phase separation associated with the asymmetry of lipid composition were investigated using micrometer-sized vesicles of lipid bilayers made from a lipid mixture. The complete macro-phase-separated morphology undergoes a transition to a micro-phase-separation-like morphology via a lorate morphology as a metastable state. The transition leads to the emergence of monodisperse nanosized domains through repeated domain scission events. Moreover, we have numerically confirmed the transitions using the time-dependent Ginzburg-Landau model describing phase separation and the bending elastic membrane, which is quantitatively consistent with experimental results by fixing one free parameter. Our findings suggest that the local spontaneous curvature due to the asymmetric composition plays an essential role in the thermodynamic stabilization of micro-phase separation in lipid bilayers.
Superradiant phase transitions with three-level systems
Baksic, Alexandre; Nataf, Pierre; Ciuti, Cristiano
2013-02-01
We determine the phase diagram of N identical three-level systems interacting with a single photonic mode in the thermodynamical limit (N→∞) by accounting for the so-called diamagnetic term and the inequalities imposed by the Thomas-Reich-Kuhn (TRK) oscillator strength sum rule. The key role of transitions between excited levels and the occurrence of first-order phase transitions is discussed. We show that, in contrast to two-level systems, in the three-level case the TRK inequalities do not always prevent a superradiant phase transition in the presence of a diamagnetic term.
Phase transitions in pure and dilute thin ferromagnetic films
Korneta, W.; Pytel, Z.
1983-10-01
The mean-field model of a thin ferromagnetic film where the nearest-neighbor exchange coupling in surface layers can be different from that inside the film is considered. The phase diagram, equations for the second-order phase-transition lines, and the spontaneous magnetization profiles near the phase transitions are given. It is shown that there is no extra-ordinary transition in a thin film. If the thickness of the film tends to infinity the well-known results for the mean-field model of a semi-infinite ferromagnet are obtained. The generalization for disordered dilute thin ferromagnetic films and semi-infinite ferromagnets is also given.
Superradiant phase transitions with three-level systems
Baksic, Alexandre; Ciuti, Cristiano
2013-01-01
We determine the phase diagram of $N$ identical three-level systems interacting with a single photonic mode in the thermodynamical limit ($N \\to \\infty$) by accounting for the so-called diamagnetic term and the inequalities imposed by the Thomas-Reich-Kuhn (TRK) oscillator strength sum rule. The key role of transitions between excited levels and the occurrence of first-order phase transitions is discussed. We show that, in contrast to two-level systems, in the three-level case the TRK inequalities do not always prevent a superradiant phase transition in presence of a diamagnetic term.
On the Chiral Phase Transition in the Linear Sigma Model
Phat, T H; Hoa, L V; Phat, Tran Huu; Anh, Nguyen Tuan; Hoa, Le Viet
2004-01-01
The Cornwall-Jackiw-Tomboulis (CJT) effective action for composite operators at finite temperature is used to investigate the chiral phase transition within the framework of the linear sigma model as the low-energy effective model of quantum chromodynamics (QCD). A new renormalization prescription for the CJT effective action in the Hartree-Fock (HF) approximation is proposed. A numerical study, which incorporates both thermal and quantum effect, shows that in this approximation the phase transition is of first order. However, taking into account the higher-loop diagrams contribution the order of phase transition is unchanged.
Phase sensitive quantum interference on forbidden transition in ladder scheme
Koganov, Gennady A
2014-01-01
A three level ladder system is analyzed and the coherence of initially electric-dipole forbidden transition is calculated. Due to the presence of two laser fields the initially dipole forbidden transition becomes dynamically permitted due to ac Stark effect. It is shown that such transitions exhibit quantum-interference-related phenomena, such as electromagnetically induced transparency, gain without inversion and enhanced refractive index. Gain and dispersion characteristics of such transitions strongly depend upon the relative phase between the driving and the probe fields. Unlike allowed transitions, gain/absorption behavior of ac-Stark allowed transitions exhibit antisymmetric feature on the Rabi sidebands. It is found that absorption/gain spectra possess extremely narrow sub-natural resonances on these ac Stark allowed forbidden transitions. An interesting finding is simultaneous existence of gain and negative dispersion at Autler-Townes transition which may lead to both reduction of the group velocity a...
Safety performance of traffic phases and phase transitions in three phase traffic theory.
Xu, Chengcheng; Liu, Pan; Wang, Wei; Li, Zhibin
2015-12-01
Crash risk prediction models were developed to link safety to various phases and phase transitions defined by the three phase traffic theory. Results of the Bayesian conditional logit analysis showed that different traffic states differed distinctly with respect to safety performance. The random-parameter logit approach was utilized to account for the heterogeneity caused by unobserved factors. The Bayesian inference approach based on the Markov Chain Monte Carlo (MCMC) method was used for the estimation of the random-parameter logit model. The proposed approach increased the prediction performance of the crash risk models as compared with the conventional logit model. The three phase traffic theory can help us better understand the mechanism of crash occurrences in various traffic states. The contributing factors to crash likelihood can be well explained by the mechanism of phase transitions. We further discovered that the free flow state can be divided into two sub-phases on the basis of safety performance, including a true free flow state in which the interactions between vehicles are minor, and a platooned traffic state in which bunched vehicles travel in successions. The results of this study suggest that a safety perspective can be added to the three phase traffic theory. The results also suggest that the heterogeneity between different traffic states should be considered when estimating the risks of crash occurrences on freeways.
Phase transitions in ferroelectric silicon doped hafnium oxide
Böscke, T. S.; Teichert, St.; Bräuhaus, D.; Müller, J.; Schröder, U.; Böttger, U.; Mikolajick, T.
2011-09-01
We investigated phase transitions in ferroelectric silicon doped hafnium oxide (FE-Si:HfO2) by temperature dependent polarization and x-ray diffraction measurements. If heated under mechanical confinement, the orthorhombic ferroelectric phase reversibly transforms into a phase with antiferroelectric behavior. Without confinement, a transformation into a monoclinic/tetragonal phase mixture is observed during cooling. These results suggest the existence of a common higher symmetry parent phase to the orthorhombic and monoclinic phases, while transformation between these phases appears to be inhibited by an energy barrier.
Phase transitions in simplified models with long-range interactions
Rocha Filho, T. M.; Amato, M. A.; Mello, B. A.; Figueiredo, A.
2011-10-01
We study the origin of phase transitions in several simplified models with long-range interactions. For the self-gravitating ring model, we are unable to observe a possible phase transition predicted by Nardini and Casetti [Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.80.060103 80, 060103R (2009).] from an energy landscape analysis. Instead we observe a sharp, although without any nonanalyticity, change from a core-halo to a core-only configuration in the spatial distribution functions for low energies. By introducing a different class of solvable simplified models without any critical points in the potential energy we show that a behavior similar to the thermodynamics of the ring model is obtained, with a first-order phase transition from an almost homogeneous high-energy phase to a clustered phase and the same core-halo to core configuration transition at lower energies. We discuss the origin of these features for the simplified models and show that the first-order phase transition comes from the maximization of the entropy of the system as a function of energy and an order parameter, as previously discussed by Hahn and Kastner [Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.72.056134 72, 056134 (2005); Eur. Phys. J. BEPJBFY1434-602810.1140/epjb/e2006-00100-7 50, 311 (2006)], which seems to be the main mechanism causing phase transitions in long-range interacting systems.
Integrability and Quantum Phase Transitions in Interacting Boson Models
Dukelsky, J; García-Ramos, J E; Pittel, S
2003-01-01
The exact solution of the boson pairing hamiltonian given by Richardson in the sixties is used to study the phenomena of level crossings and quantum phase transitions in the integrable regions of the sd and sdg interacting boson models.
Instabilities of uniform filtration flows with phase transition
Il'Ichev, A. T.; Tsypkin, G. G.
2008-10-01
New mechanisms of instability are described for vertical flows with phase transition through horizontally extended two-dimensional regions of a porous medium. A plane surface of phase transition becomes unstable at an infinitely large wavenumber and at zero wavenumber. In the latter case, the unstable flow undergoes reversible subcritical bifurcations leading to the development of secondary flows (which may not be horizontally uniform). The evolution of subcritical modes near the instability threshold is governed by the Kolmogorov-Petrovskii-Piskunov equation. Two examples of flow through a porous medium are considered. One is the unstable flow across a water-bearing layer above a layer that carries a vapor-air mixture under isothermal conditions in the presence of capillary forces at the phase transition interface. The other is the vertical flow with phase transition in a high-temperature geothermal reservoir consisting of two high-permeability regions separated by a low-permeability stratum.
Phase transitions in the coal-water-methane system
Energy Technology Data Exchange (ETDEWEB)
Alexeev, A.D.; Ulyanova, E.V.; Kalugina, N.A.; Degtyar, S.E. [Institute of Physical & Mining Processes, Donetsk (Ukraine)
2006-07-01
Low temperature phase transitions in water and methane occurring in fossil coals were studied experimentally using Nuclear Magnetic Resonance (NMR) techniques. Contributions of constituent fluids into narrow line of {sup 1}H NMR wide line spectrum were analyzed.
Lifshitz Transitions in Magnetic Phases of the Periodic Anderson Model
Kubo, Katsunori
2015-09-01
We investigate the reconstruction of a Fermi surface, which is called a Lifshitz transition, in magnetically ordered phases of the periodic Anderson model on a square lattice with a finite Coulomb interaction between f electrons. We apply the variational Monte Carlo method to the model by using the Gutzwiller wavefunctions for the paramagnetic, antiferromagnetic, ferromagnetic, and charge-density-wave states. We find that an antiferromagnetic phase is realized around half-filling and a ferromagnetic phase is realized when the system is far away from half-filling. In both magnetic phases, Lifshitz transitions take place. By analyzing the electronic states, we conclude that the Lifshitz transitions to large ordered-moment states can be regarded as itinerant-localized transitions of the f electrons.
Behavior of the Lyapunov Exponent and Phase Transition in Nuclei
Institute of Scientific and Technical Information of China (English)
WANG Nan; WU Xi-Zhen; LI Zhu-Xia; WANG Ning; ZHUO Yi-Zhong; SUN Xiu-Quan
2000-01-01
Based on the quantum molecular dynamics model, we investigate the dynamical behaviors of the excited nuclear system to simulate the latter stage of heavy ion reactions, which associate with a liquid-gas phase transition. We try to search a microscopic way to describe the phase transition in realnuclei. The Lyapunov exponent is employed and examined for our purpose. We find out that the Lyapunov exponent is one of good microscopic quantities to describe the phase transition in hot nuclei. Coulomb potential and the finite size effect may give a strong influence on the critical temperature. However, the collision term plays a minor role in the process of the liquid-gas phase transition in finite systems.
Dynamical symmetries and causality in non-equilibrium phase transitions
Henkel, Malte
2015-01-01
Dynamical symmetries are of considerable importance in elucidating the complex behaviour of strongly interacting systems with many degrees of freedom. Paradigmatic examples are cooperative phenomena as they arise in phase transitions, where conformal invariance has led to enormous progress in equilibrium phase transitions, especially in two dimensions. Non-equilibrium phase transitions can arise in much larger portions of the parameter space than equilibrium phase transitions. The state of the art of recent attempts to generalise conformal invariance to a new generic symmetry, taking into account the different scaling behaviour of space and time, will be reviewed. Particular attention will be given to the causality properties as they follow for co-variant $n$-point functions. These are important for the physical identification of n-point functions as responses or correlators.
Dynamical Symmetries and Causality in Non-Equilibrium Phase Transitions
Directory of Open Access Journals (Sweden)
Malte Henkel
2015-11-01
Full Text Available Dynamical symmetries are of considerable importance in elucidating the complex behaviour of strongly interacting systems with many degrees of freedom. Paradigmatic examples are cooperative phenomena as they arise in phase transitions, where conformal invariance has led to enormous progress in equilibrium phase transitions, especially in two dimensions. Non-equilibrium phase transitions can arise in much larger portions of the parameter space than equilibrium phase transitions. The state of the art of recent attempts to generalise conformal invariance to a new generic symmetry, taking into account the different scaling behaviour of space and time, will be reviewed. Particular attention will be given to the causality properties as they follow for co-variant n-point functions. These are important for the physical identification of n-point functions as responses or correlators.
Entropy, Macroscopic Information, and Phase Transitions
Parrondo, Juan M. R.
1999-01-01
The relationship between entropy and information is reviewed, taking into account that information is stored in macroscopic degrees of freedom, such as the order parameter in a system exhibiting spontaneous symmetry breaking. It is shown that most problems of the relationship between entropy and information, embodied in a variety of Maxwell demons, are also present in any symmetry breaking transition.
Phase transition in L-alaninium oxalate by photoacoustics
Indian Academy of Sciences (India)
M Sivabarathy; S Natarajan; S K Ramakrishnan; K Ramachandran
2004-10-01
Phase transition in L-alaninium oxalate is studied by using TG, DTA and photoacoustic spectroscopy. A sharp transition at 378 K by photoacoustics is observed whereas at the same temperature the endothermic energy change observed by TG and DTA is not very sharp. This is discussed in detail with reference to the other known data for the organic crystals.
Quantum Shape-Phase Transitions in Finite Nuclei
Leviatan, A
2007-01-01
Quantum shape-phase transitions in finite nuclei are considered in the framework of the interacting boson model. Critical-point Hamiltonians for first- and second-order transitions are identified by resolving them into intrinsic and collective parts. Suitable wave functions and finite-N estimates for observables at the critical-points are derived.
Quantum Shape-Phase Transitions in Finite Nuclei
Energy Technology Data Exchange (ETDEWEB)
Leviatan, A. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel)
2007-05-15
Quantum shape-phase transitions in finite nuclei are considered in the framework of the interacting boson model. Critical-point Hamiltonians for first- and second-order transitions are identified by resolving them into intrinsic and collective parts. Suitable wave functions and finite-N estimates for observables at the critical-points are derived.
Phase transition of bismuth telluride thin films grown by MBE
DEFF Research Database (Denmark)
Fülöp, Attila; Song, Yuxin; Charpentier, Sophie
2014-01-01
A previously unreported phase transition between Bi2Te3 and Bi4Te3 in bismuth telluride grown by molecular beam epitaxy is recorded via XRD, AFM, and SIMS observations. This transition is found to be related to the Te/Bi beam equivalent pressure (BEP) ratio. BEP ratios below 17 favor the formation...
The QCD phase transitions: From mechanism to observables
Energy Technology Data Exchange (ETDEWEB)
Shuryak, E.V.
1997-09-22
This paper contains viewgraphs on quantum chromodynamic phase transformations during heavy ion collisions. Some topics briefly described are: finite T transitions of I molecule pairs; finite density transitions of diquarks polymers; and the softtest point of the equation of state as a source of discontinuous behavior as a function of collision energy or centrality.
Baryogenesis via leptonic CP-violating phase transition
Pascoli, Silvia; Zhou, Ye-Ling
2016-01-01
We propose a new mechanism to generate a lepton asymmetry based on the vacuum CP-violating phase transition (CPPT). This approach differs from classical thermal leptogenesis as a specific seesaw model, and its UV completion, need not be specified. The lepton asymmetry is generated via the dynamically realised coupling of the Weinberg operator during the phase transition. This mechanism provides strong connections with low-energy neutrino experiments.
Quark-gluon plasma phase transition using cluster expansion method
Syam Kumar, A. M.; Prasanth, J. P.; Bannur, Vishnu M.
2015-08-01
This study investigates the phase transitions in QCD using Mayer's cluster expansion method. The inter quark potential is modified Cornell potential. The equation of state (EoS) is evaluated for a homogeneous system. The behaviour is studied by varying the temperature as well as the number of Charm Quarks. The results clearly show signs of phase transition from Hadrons to Quark-Gluon Plasma (QGP).
Partial dynamical symmetry at critical points of quantum phase transitions.
Leviatan, A
2007-06-15
We show that partial dynamical symmetries can occur at critical points of quantum phase transitions, in which case underlying competing symmetries are conserved exactly by a subset of states, and mix strongly in other states. Several types of partial dynamical symmetries are demonstrated with the example of critical-point Hamiltonians for first- and second-order transitions in the framework of the interacting boson model, whose dynamical symmetries correspond to different shape phases in nuclei.
Effect of point defects and disorder on structural phase transitions
Energy Technology Data Exchange (ETDEWEB)
Toulouse, J.
1997-06-01
Since the beginning in 1986, the object of this project has been Structural Phase Transitions (SPT) in real as opposed to ideal materials. The first stage of the study has been centered around the role of Point Defects in SPT`s. Our intent was to use the previous knowledge we had acquired in the study of point defects in non-transforming insulators and apply it to the study of point defects in insulators undergoing phase transitions. In non-transforming insulators, point defects, in low concentrations, marginally affect the bulk properties of the host. It is nevertheless possible by resonance or relaxation methods to study the point defects themselves via their local motion. In transforming solids, however, close to a phase transition, atomic motions become correlated over very large distances; there, even point defects far removed from one another can undergo correlated motions which may strongly affect the transition behavior of the host. Near a structural transition, the elastic properties win be most strongly affected so as to either raise or decrease the transition temperature, prevent the transition from taking place altogether, or simply modify its nature and the microstructure or domain structure of the resulting phase. One of the well known practical examples is calcium-stabilized zirconia in which the high temperature cubic phase is stabilized at room temperature with greatly improved mechanical properties.
Quark-Hadron Phase Transitions in Viscous Early Universe
Tawfik, A
2011-01-01
Based on hot big bang theory, the cosmological matter is conjectured to undergo QCD phase transition(s) to hadrons, when the universe was about $1-10 \\mu$s old. In the present work, we study the quark-hadron phase transition, by taking into account the effect of the bulk viscosity. We analyze the evolution of the quantities relevant for the physical description of the early universe, namely, the energy density $\\rho$, temperature $T$, Hubble parameter $H$ and scale factor $a$ before, during and after the phase transition. To study the cosmological dynamics and the time evolution we use both analytical and numerical methods. By assuming that the phase transition may be described by an effective nucleation theory (prompt {\\it first-order} phase transition), we also consider the case where the universe evolved through a mixed phase with a small initial supercooling and monotonically growing hadronic bubbles. The numerical estimation of the cosmological parameters, $a$ and $H$ for instance, makes it clear that th...
Quantum Phase Transitions and Dimerized Phases in Frustrated Spin Ladder
Institute of Scientific and Technical Information of China (English)
WEN Rui; LIU Guang-Hua; TIAN Guang-Shan
2011-01-01
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-nearestneighbor (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.
Phase transition in extended thermodynamic phase space and charged Horava-Lifshitz black holes
Poshteh, Mohammad Bagher Jahani
2016-01-01
For charged black holes in Horava-Lifshitz gravity, it is shown that a second order phase transition takes place in extended phase space. We study the behavior of specific heat and free energy at the point of transition in canonical and grand canonical ensembles and show that the black hole falls into a state which is locally and globally stable. We relate the second order nature of phase transition to the fact that the phase transition occurs at a sharp temperature and not over a temperature interval. By taking cosmological constant as thermodynamic pressure for charged black holes, we extend Ehrenfest's equations. We obtain nine equations and show that, all of them are satisfied at the point in which the specific heat diverges. We also apply geometrothermodynamics to extended phase space and show that the scalar curvature of Quevedo metric diverges at the point at which the second order phase transition takes place.
Problem-solving phase transitions during team collaboration
DEFF Research Database (Denmark)
Wiltshire, Travis; Butner, Jonathan E.; Fiore, Stephen M.
2017-01-01
) with dynamical systems theory suggesting that when a system is undergoing a phase transition it should exhibit a peak in entropy and that entropy levels should also relate to team performance. Communications from 40 teams that collaborated on a complex problem were coded for occurrence of problem......-solving processes. We applied a sliding window entropy technique to each team's communications and specified criteria for (a) identifying data points that qualify as peaks and (b) determining which peaks were robust. We used multilevel modeling, and provide a qualitative example, to evaluate whether phases exhibit...... phases. Peaks in entropy thus corresponded to qualitative shifts in teams’ CPS communications, providing empirical evidence that teams exhibit phase transitions during CPS. Also, lower average levels of entropy at the phase transition points predicted better CPS performance. We specify future directions...
A Quantum Phase Transition in the Cosmic Ray Energy Distribution
Widom, A; Srivastava, Y
2015-01-01
We here argue that the "knee" of the cosmic ray energy distribution at $E_c \\sim 1$ PeV represents a second order phase transition of cosmic proportions. The discontinuity of the heat capacity per cosmic ray particle is given by $\\Delta c=0.450196\\ k_B$. However the idea of a deeper critical point singularity cannot be ruled out by present accuracy in neither theory nor experiment. The quantum phase transition consists of cosmic rays dominated by bosons for the low temperature phase E E_c$. The low temperature phase arises from those nuclei described by the usual and conventional collective boson models of nuclear physics. The high temperature phase is dominated by protons. The transition energy $E_c$ may be estimated in terms of the photo-disintegration of nuclei.
Signals of the QCD Phase Transition in the Heavens
Schaffner-Bielich, J
2007-01-01
The modern phase diagram of strongly interacting matter reveals a rich structure at high-densities due to phase transitions related to the chiral symmetry of quantum chromodynamics (QCD) and the phenomenon of color superconductivity. These exotic phases have significant impacts on high-density astrophysics as the properties of neutron stars and the evolution of astrophysical systems as proto-neutron stars, core-collapse supernovae and neutron star mergers. Most recent pulsar mass measurements and constraints on neutron star radii are critically discussed. Astrophysical signals for exotic matter and phase transitions in high-density matter proposed recently in the literature are outlined. A strong first order phase transition leads to the emergence of a third family of compact stars besides white dwarfs and neutron stars. The different microphysics of quark matter results in an enhanced r-mode stability window for rotating compact stars compared to normal neutron stars. Future telescope and satellite data will...
Density Functional Theory for Phase-Ordering Transitions
Energy Technology Data Exchange (ETDEWEB)
Wu, Jianzhong [Univ. of California, Riverside, CA (United States)
2016-03-30
Colloids display astonishing structural and dynamic properties that can be dramatically altered by modest changes in the solution condition or an external field. This complex behavior stems from a subtle balance of colloidal forces and intriguing mesoscopic and macroscopic phase transitions that are sensitive to the processing conditions and the dispersing environment. Whereas the knowledge on the microscopic structure and phase behavior of colloidal systems at equilibrium is now well-advanced, quantitative predictions of the dynamic properties and the kinetics of phase-ordering transitions in colloids are not always realized. Many important mesoscopic and off-equilibrium colloidal states remain poorly understood. The proposed research aims to develop a new, unifying approach to describe colloidal dynamics and the kinetics of phase-ordering transitions based on accomplishments from previous work for the equilibrium properties of both uniform and inhomogeneous systems and on novel concepts from the state-of-the-art dynamic density functional theory. In addition to theoretical developments, computational research is designed to address a number of fundamental questions on phase-ordering transitions in colloids, in particular those pertinent to a competition of the dynamic pathways leading to various mesoscopic structures, off-equilibrium states, and crystalline phases. By providing a generic theoretical framework to describe equilibrium, metastable as well as non-ergodic phase transitions concurrent with the colloidal self-assembly processes, accomplishments from this work will have major impacts on both fundamental research and technological applications.
Antiferromagnetic phase transition and spin correlations in NiO
DEFF Research Database (Denmark)
Chatterji, Tapan; McIntyre, G.J.; Lindgård, Per-Anker
2009-01-01
We have investigated the antiferromagnetic (AF) phase transition and spin correlations in NiO by high-temperature neutron diffraction below and above TN. We show that AF phase transition is a continuous second-order transition within our experimental resolution. The spin correlations manifested...... by this process. We determined the critical exponents =0.328±0.002 and =0.64±0.03 and the Néel temperature TN=530±1 K. These critical exponents suggest that NiO should be regarded as a 3dXY system...
Collectivity, Phase Transitions and Exceptional Points in Open Quantum Systems
Heiss, W D; Rotter, I
1998-01-01
Phase transitions in open quantum systems, which are associated with the formation of collective states of a large width and of trapped states with rather small widths, are related to exceptional points of the Hamiltonian. Exceptional points are the singularities of the spectrum and eigenfunctions, when they are considered as functions of a coupling parameter. In the present paper this parameter is the coupling strength to the continuum. It is shown that the positions of the exceptional points (their accumulation point in the thermodynamical limit) depend on the particular type and energy dependence of the coupling to the continuum in the same way as the transition point of the corresponding phase transition.
Gravitational waves from cosmological first order phase transitions
Hindmarsh, Mark; Rummukainen, Kari; Weir, David
2015-01-01
First order phase transitions in the early Universe generate gravitational waves, which may be observable in future space-based gravitational wave observatiories, e.g. the European eLISA satellite constellation. The gravitational waves provide an unprecedented direct view of the Universe at the time of their creation. We study the generation of the gravitational waves during a first order phase transition using large-scale simulations of a model consisting of relativistic fluid and an order parameter field. We observe that the dominant source of gravitational waves is the sound generated by the transition, resulting in considerably stronger radiation than earlier calculations have indicated.
Spin-current probe for phase transition in an insulator
Qiu, Zhiyong; Li, Jia; Hou, Dazhi; Arenholz, Elke; N'diaye, Alpha T.; Tan, Ali; Uchida, Ken-Ichi; Sato, Koji; Okamoto, Satoshi; Tserkovnyak, Yaroslav; Qiu, Z. Q.; Saitoh, Eiji
2016-08-01
Spin fluctuation and transition have always been one of the central topics of magnetism and condensed matter science. Experimentally, the spin fluctuation is found transcribed onto scattering intensity in the neutron-scattering process, which is represented by dynamical magnetic susceptibility and maximized at phase transitions. Importantly, a neutron carries spin without electric charge, and therefore it can bring spin into a sample without being disturbed by electric energy. However, large facilities such as a nuclear reactor are necessary. Here we show that spin pumping, frequently used in nanoscale spintronic devices, provides a desktop microprobe for spin transition; spin current is a flux of spin without an electric charge and its transport reflects spin excitation. We demonstrate detection of antiferromagnetic transition in ultra-thin CoO films via frequency-dependent spin-current transmission measurements, which provides a versatile probe for phase transition in an electric manner in minute devices.
Solid-solid phase transitions via melting in metals
Pogatscher, S.; Leutenegger, D.; Schawe, J. E. K.; Uggowitzer, P. J.; Löffler, J. F.
2016-04-01
Observing solid-solid phase transitions in-situ with sufficient temporal and spatial resolution is a great challenge, and is often only possible via computer simulations or in model systems. Recently, a study of polymeric colloidal particles, where the particles mimic atoms, revealed an intermediate liquid state in the transition from one solid to another. While not yet observed there, this finding suggests that such phenomena may also occur in metals and alloys. Here we present experimental evidence for a solid-solid transition via the formation of a metastable liquid in a `real' atomic system. We observe this transition in a bulk glass-forming metallic system in-situ using fast differential scanning calorimetry. We investigate the corresponding transformation kinetics and discuss the underlying thermodynamics. The mechanism is likely to be a feature of many metallic glasses and metals in general, and may provide further insight into phase transition theory.
Structural phase transitions and topological defects in ion Coulomb crystals
Energy Technology Data Exchange (ETDEWEB)
Partner, Heather L. [Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany); Nigmatullin, Ramil [Institute of Quantum Physics, Albert-Einstein Allee-11, Ulm University, 89069 Ulm (Germany); Burgermeister, Tobias; Keller, Jonas; Pyka, Karsten [Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany); Plenio, Martin B. [Center for Integrated Quantum Science and Technology, Albert-Einstein-Allee 11, Ulm University, 89069 Ulm (Germany); Institute for Theoretical Physics, Albert-Einstein-Allee 11, Ulm University, 89069 Ulm (Germany); Retzker, Alex [Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Givat Ram (Israel); Zurek, Wojciech H. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); Campo, Adolfo del [Department of Physics, University of Massachusetts Boston, Boston, MA 02125 (United States); Mehlstäubler, Tanja E., E-mail: tanja.mehlstaeubler@ptb.de [Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany)
2015-03-01
We use laser-cooled ion Coulomb crystals in the well-controlled environment of a harmonic radiofrequency ion trap to investigate phase transitions and defect formation. Topological defects in ion Coulomb crystals (kinks) have been recently proposed for studies of nonlinear physics with solitons and as carriers of quantum information. Defects form when a symmetry breaking phase transition is crossed nonadiabatically. For a second order phase transition, the Kibble–Zurek mechanism predicts that the formation of these defects follows a power law scaling in the rate of the transition. We demonstrate a scaling of defect density and describe kink dynamics and stability. We further discuss the implementation of mass defects and electric fields as first steps toward controlled kink preparation and manipulation.
Structural phase transitions and topological defects in ion Coulomb crystals
Energy Technology Data Exchange (ETDEWEB)
Partner, Heather L. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Nigmatullin, Ramil [Institute of Quantum Physics, Ulm Univ., Ulm (Germany); Burgermeister, Tobias [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Keller, Jonas [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Pyka, Karsten [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Plenio, Martin B. [Center for Integrated Quantum Science and Technology, Ulm Univ., Ulm, (Germany):Institute for Theoretical Physics, Ulm Univ.,Ulm, (Germany); Retzker, Alex [Racah Institute of Physics, The Hebrew University of Jerusalem, Givat Ram (Israel); Zurek, Wojciech Hubert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); del Campo, Adolfo [Univ. of Massachusetts, Amherst, MA (United States). Dept. of Physics; Mehlstaubler, Tanja E. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany)
2014-11-19
We use laser-cooled ion Coulomb crystals in the well-controlled environment of a harmonic radiofrequency ion trap to investigate phase transitions and defect formation. Topological defects in ion Coulomb crystals (kinks) have been recently proposed for studies of nonlinear physics with solitons and as carriers of quantum information. Defects form when a symmetry breaking phase transition is crossed non-adiabatically. For a second order phase transition, the Kibble-Zurek mechanism predicts that the formation of these defects follows a power law scaling in the rate of the transition. We demonstrate a scaling of defect density and describe kink dynamics and stability. We further discuss the implementation of mass defects and electric fields as first steps toward controlled kink preparation and manipulation.
Folding of a single polymer chain and phase transition
Institute of Scientific and Technical Information of China (English)
DING YanWei; ZHANG GuangZhao
2009-01-01
Using an ultra-sensitive differential scanning calorimetry (US-DSC), we have investigated the folding and aggregation behaviors of poly(N-isopropylacrylamide) (PNIPAM) chains in dilute and semidilute solutions. In the heating process, the intrachain folding and interchain aggregation simultaneously occur in the dilute solutions, and the ratio of intrachain folding increases with decreasing concentra-tion. In the semidilute solutions, PNIPAM chains show limited interchain aggregation with elevated temperature, because most of the PNIPAM chains have been collapsed at lower temperature. In an ex-tremely dilute solution, PNIPAM chains undergo a single folding transition in the heating process. By extrapolating heating rate and concentration to zero, we have obtained the phase transition tempera-ture (Ts) and enthalpy change (AHs) of the single chain folding. AHs is higher than that for a phase transition involving intrachain collapse and interchain aggregation, indicating that a single chain fold-ing can not be taken to be a macroscopic phase transition.
Horava-Lifshitz early universe phase transition beyond detailed balance
Energy Technology Data Exchange (ETDEWEB)
Kheyri, F.; Khodadi, M.; Sepangi, H.R. [Shahid Beheshti University, Department of Physics, Tehran (Iran, Islamic Republic of)
2013-01-15
The early universe is believed to have undergone a QCD phase transition to hadrons at about 10 {mu}s after the big bang. We study such a transition in the context of the non-detailed balance Horava-Lifshitz theory by investigating the effects of the dynamical coupling constant {lambda} in a flat universe. The evolution of the relevant physical quantities, namely the energy density {rho}, temperature T, scale factor a and the Hubble parameter H is investigated before, during and after the phase transition, assumed to be of first order. Also, in view of the recent lattice QCD simulations data, we study a cross-over phase transition of the early universe whose results are based on two different sets of lattice data. (orig.)
Cascading dynamics on random networks: Crossover in phase transition
Liu, Run-Ran; Wang, Wen-Xu; Lai, Ying-Cheng; Wang, Bing-Hong
2012-02-01
In a complex network, random initial attacks or failures can trigger subsequent failures in a cascading manner, which is effectively a phase transition. Recent works have demonstrated that in networks with interdependent links so that the failure of one node causes the immediate failures of all nodes connected to it by such links, both first- and second-order phase transitions can arise. Moreover, there is a crossover between the two types of transitions at a critical system-parameter value. We demonstrate that these phenomena can occur in the more general setting where no interdependent links are present. A heuristic theory is derived to estimate the crossover and phase-transition points, and a remarkable agreement with numerics is obtained.
The Physics of Phase Transitions Concepts and Applications
Papon, Pierre; Meijer, Paul H.E
2006-01-01
The physics of phase transitions is an important area at the crossroads of several fields that play central roles in materials sciences. In this second edition, new developments had been included which came up in the states of matter physics, in particular in the domain of nanomaterials and atomic Bose-Einstein condensates where progress is accelerating. The presentation of several chapters had been improved by bringing better information on some phase transition mechanisms and by illustrating them with new application examples. This work deals with all classes of phase transitions in fluids and solids. It contains chapters on evaporation, melting, solidification, magnetic transitions, critical phenomena, superconductivity, etc., and is intended for graduate students in physics and engineering; for scientists it will serve both as an introduction and an overview. End-of-chapter problems and complete answers are included.
Phase Transitions and Backbones of the Asymmetric Traveling Salesman Problem
Zhang, W
2011-01-01
In recent years, there has been much interest in phase transitions of combinatorial problems. Phase transitions have been successfully used to analyze combinatorial optimization problems, characterize their typical-case features and locate the hardest problem instances. In this paper, we study phase transitions of the asymmetric Traveling Salesman Problem (ATSP), an NP-hard combinatorial optimization problem that has many real-world applications. Using random instances of up to 1,500 cities in which intercity distances are uniformly distributed, we empirically show that many properties of the problem, including the optimal tour cost and backbone size, experience sharp transitions as the precision of intercity distances increases across a critical value. Our experimental results on the costs of the ATSP tours and assignment problem agree with the theoretical result that the asymptotic cost of assignment problem is pi ^2 /6 the number of cities goes to infinity. In addition, we show that the average computation...
Dissipation-driven quantum phase transitions in collective spin systems
Energy Technology Data Exchange (ETDEWEB)
Morrison, S [Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck (Austria); Parkins, A S [Department of Physics, University of Auckland, Private Bag 92019, Auckland (New Zealand)], E-mail: smor161@aucklanduni.ac.nz
2008-10-14
We consider two different collective spin systems subjected to strong dissipation-on the same scale as interaction strengths and external fields-and show that either continuous or discontinuous dissipative quantum phase transitions can occur as the dissipation strength is varied. First, we consider a well-known model of cooperative resonance fluorescence that can exhibit a second-order quantum phase transition, and analyse the entanglement properties near the critical point. Next, we examine a dissipative version of the Lipkin-Meshkov-Glick interacting collective spin model, where we find that either first- or second-order quantum phase transitions can occur, depending only on the ratio of the interaction and external field parameters. We give detailed results and interpretation for the steady-state entanglement in the vicinity of the critical point, where it reaches a maximum. For the first-order transition we find that the semiclassical steady states exhibit a region of bistability. (fast track communication)
Pairing Phase Transitions of Matter under Rotation
Jiang, Yin
2016-01-01
The phases and properties of matter under global rotation have attracted much interest recently. In this paper we investigate the pairing phenomena in a system of fermions under the presence of rotation. We find that there is a generic suppression effect on pairing states with zero angular momentum. We demonstrate this effect with the chiral condensation and the color superconductivity in hot dense QCD matter as explicit examples. In the case of chiral condensation, a new phase diagram in the temperature-rotation parameter space is found, with a nontrivial critical point.
Instabilities near the QCD phase transition in the holographic models
Gürsoy, U.; Lin, S.; Shuryak, E.
2013-01-01
This paper discusses phenomena close to the critical QCD temperature, using the holographic model. One issue studied is the overcooled high-T phase, in which we calculate quasinormal sound modes. We do not find instabilities associated with other first-order phase transitions, but nevertheless obser
Dynamics and phase transitions in A 1C 60 compounds
Schober, H.; Renker, B.; Heid, R.; Tölle, A.
1997-02-01
We present an overview of extensive inelastic neutron scattering experiments carried out on powders of A 1C 60. The various phases leave strong fingerprints in the microscopic dynamics confirming the solid-state chemical reactions. The strong kinetic phase transitions can be followed in real time and turn out to be highly complex.
Kinetics of silica-phase transitions
Energy Technology Data Exchange (ETDEWEB)
Duffy, C.J.
1993-07-01
In addition to the stable silica polymorph quartz, several metastable silica phases are present in Yucca Mountain. The conversion of these phases to quartz is accompanied by volume reduction and a decrease in the aqueous silica activity, which may destabilize clinoptilolite and mordenite. The primary reaction sequence for the silica phases is from opal or glass to disordered opal-CT, followed by ordering of the opal-CT and finally by the crystallization of quartz. The ordering of opal-CT takes place in the solid state, whereas the conversion of opal-CT takes place through dissolution-reprecipitation involving the aqueous phase. It is proposed that the rate of conversion of opal-CT to quartz is controlled by diffusion of defects out of a disordered surface layer formed on the crystallizing quartz. The reaction rates are observed to be dependent on temperature, pressure, degree of supersaturation, and pH. Rate equations selected from the literature appear to be consistent with observations at Yucca Mountain.
The deconfining phase transition in and out of equilibrium
Bazavov, Oleksiy
Recent experiments carried out at the Relativistic Heavy Ion Collider at the Brookhaven National Laboratory provide strong evidence that a matter can be driven from a confined, low-temperature phase, observed in our every day world into a deconfined high-temperature phase of liberated quarks and gluons. The equilibrium and dynamical properties of the deconfining phase transition are thus of great theoretical interest, since they also provide an information about the first femtoseconds of the evolution of our Universe, when the hot primordial soup while cooling has undergone a chain of phase transitions. The aspects of the deconfining phase transition studied in this work include: the dynamics of the SU(3) gauge theory after the heating quench (which models rapid heating in the heavy-ion collisions), equilibrium properties of the phase transition in the SU(3) gauge theory with boundaries at low temperature (small volumes at RHIC suggest that boundary effects cannot be neglected and periodic boundary conditions normally used in lattice simulations do not correspond to the experimental situation), and a study of the order of the transition in U(1) gauge theory.
Non-equilibrium quantum phase transition via entanglement decoherence dynamics
Lin, Yu-Chen; Yang, Pei-Yun; Zhang, Wei-Min
2016-01-01
We investigate the decoherence dynamics of continuous variable entanglement as the system-environment coupling strength varies from the weak-coupling to the strong-coupling regimes. Due to the existence of localized modes in the strong-coupling regime, the system cannot approach equilibrium with its environment, which induces a nonequilibrium quantum phase transition. We analytically solve the entanglement decoherence dynamics for an arbitrary spectral density. The nonequilibrium quantum phase transition is demonstrated as the system-environment coupling strength varies for all the Ohmic-type spectral densities. The 3-D entanglement quantum phase diagram is obtained. PMID:27713556
Ferrofluid nucleus phase transitions in an external uniform magnetic field
Institute of Scientific and Technical Information of China (English)
B. M. Tanygin; S. I. Shulyma; V. F. Kovalenko; M. V. Petrychuk
2015-01-01
The phase transition between a massive dense phase and a diluted superparamagnetic phase has been studied by means of a direct molecular dynamics simulation. The equilibrium structures of the ferrofluid aggregate nucleus are obtained for different values of a temperature and an external magnetic field magnitude. An approximate match of experiment and simulation has been shown for the ferrofluid phase diagram coordinates “field–temperature”. The provided phase coexistence curve has an opposite trend comparing to some of known theoretical results. This contradiction has been discussed. For given experimental parameters, it has been concluded that the present results describe more precisely the transition from linear chains to a dense globes phase. The theoretical concepts which provide the opposite binodal curve dependency trend match other experimental conditions:a diluted ferrofluid, a high particle coating rate, a high temperature, and/or a less particles coupling constant value.
A third-order phase transition in random tilings
Colomo, F
2013-01-01
We consider the domino tilings of an Aztec diamond with a cut-off corner of macroscopic square shape and given size, and address the bulk properties of tilings as the size is varied. We observe that the free energy exhibits a third-order phase transition when the cut-off square, increasing in size, reaches the arctic ellipse---the phase separation curve of the original (unmodified) Aztec diamond. We obtain this result by studying the thermodynamic limit of certain nonlocal correlation function of the underlying six-vertex model with domain wall boundary conditions, the so-called emptiness formation probability (EFP). We consider EFP in two different representations: as a tau-function for Toda chains and as a random matrix model integral. The latter has a discrete measure and a linear potential with hard walls; the observed phase transition shares properties with both Gross-Witten-Wadia and Douglas-Kazakov phase transitions.
Shear induced phase transitions induced in edible fats
Mazzanti, Gianfranco; Welch, Sarah E.; Marangoni, Alejandro G.; Sirota, Eric B.; Idziak, Stefan H. J.
2003-03-01
The food industry crystallizes fats under different conditions of temperature and shear to obtain products with desired crystalline phases. Milk fat, palm oil, cocoa butter and chocolate were crystallized from the melt in a temperature controlled Couette cell. Synchrotron x-ray diffraction studies were conducted to examine the role of shear on the phase transitions seen in edible fats. The shear forces on the crystals induced acceleration of the alpha to beta-prime phase transition with increasing shear rate in milk fat and palm oil. The increase was slow at low shear rates and became very strong above 360 s-1. In cocoa butter the acceleration between beta-prime-III and beta-V phase transition increased until a maximum of at 360 s-1, and then decreased, showing competition between enhanced heat transfer and viscous heat generation.
Quantum phase transitions in the noncommutative Dirac Oscillator
Panella, O
2014-01-01
We study the (2+1) dimensional Dirac oscillator in a homogeneous magnetic field in the non-commutative plane. It is shown that the effect of non-commutativity is twofold: $i$) momentum non commuting coordinates simply shift the critical value ($B_{\\text{cr}}$) of the magnetic field at which the well known left-right chiral quantum phase transition takes place (in the commuting phase); $ii$) non-commutativity in the space coordinates induces a new critical value of the magnetic field, $B_{\\text{cr}}^*$, where there is a second quantum phase transition (right-left), --this critical point disappears in the commutative limit--. The change in chirality associated with the magnitude of the magnetic field is examined in detail for both critical points. The phase transitions are described in terms of the magnetisation of the system. Possible applications to the physics of silicene and graphene are briefly discussed.
Where does the hot electroweak phase transition end?
Csikor, Ferenc; Heitger, J
1999-01-01
We give the nonperturbative phase diagram of the four-dimensional hot electroweak phase transition. A systematic extrapolation $a \\to 0$ is done. Our results show that the finite temperature SU(2)-Higgs phase transition is of first order for Higgs-boson masses $m_H<66.5 \\pm 1.4$ GeV. The full four-dimensional result agrees completely with that of the dimensional reduction approximation. This fact is of particular importance, because it indicates that the fermionic sector of the Standard Model (SM) can be included perturbatively. We obtain that the Higgs-boson endpoint mass in the SM is $72.4 any electroweak phase transition in the SM.
Phase transition properties of a cylindrical ferroelectric nanowire
Indian Academy of Sciences (India)
Wang Ying; Yang Xiong
2013-11-01
Based on the transverse Ising model (TIM) and using the mean-field theory, we investigate the phase transition properties of a cylindrical ferroelectric nanowire. Two different kinds of phase diagrams are constructed. We discuss systematically the effects of exchange interactions and the transverse field parameters on the phase diagrams. Moreover, the cross-over features of the parameters from the ferroelectric dominant phase diagram to the paraelectric dominant phase diagram are determined for the ferroelectric nanowire. In addition, the polarizations of the surface shell and the core are illustrated in detail by modifying the TIM parameters.
Quark-hadron phase transition and strangeness conservation constraints
Saeed-Uddin
1999-01-01
The implications of the strangeness conservation in a hadronic resonance gas (HRG) on the expected phase transition to the quark gluon plasma (QGP) are investigated. It is assumed that under favourable conditions a first order hadron-quark matter phase transition may occur in the hot hadronic matter such as those produced in the ultra-relativistic heavy-ion collisions at CERN and BNL. It is however shown that the criteria of strict strangeness conservation in the HRG may not permit the occurrence of a strict first order equilibrium quark-hadron phase transition unlike a previous study. This emerges as a consequence of the application of a realistic equation of state (EOS) for the HRG and QGP phases, which account for the finite-size effect arising from the short range hard-core hadronic repulsion in the HRG phase and the perturbative QCD interactions in the QGP phase. For a first order hadron-quark matter phase transition to occur one will therefore require large fluctuations in the critical thermal parameters, which might arise due to superheating, supercooling or other nonequlibrium effects. We also discuss a scenario proposed earlier, leading to a possible strangeness separation process during hadronization.
Ab initio theory of helix <-> coil phase transition
DEFF Research Database (Denmark)
Yakubovich, Alexander V.; Solov'yov, Ilia; Solov'yov, Andrey V.
2008-01-01
In this paper, we suggest a theoretical method based on the statistical mechanics for treating the alpha-helix <-> random coil transition in alanine polypeptides. We consider this process as a first-order phase transition and develop a theory which is free of model parameters and is based solely ...... twisting. The suggested theory is general and with some modification can be applied for the description of phase transitions in other complex molecular systems (e.g. proteins, DNA, nanotubes, atomic clusters, fullerenes).......In this paper, we suggest a theoretical method based on the statistical mechanics for treating the alpha-helix random coil transition in alanine polypeptides. We consider this process as a first-order phase transition and develop a theory which is free of model parameters and is based solely...... on fundamental physical principles. It describes essential thermodynamical properties of the system such as heat capacity, the phase transition temperature and others from the analysis of the polypeptide potential energy surface calculated as a function of two dihedral angles, responsible for the polypeptide...
Pressure-induced phase transitions of indium selenide
Rasmussen, Anya Marie
In2Se3 has potential as a phase-change material for memory applications. Understanding its phase diagram is important to achieve controlled switching between phases. Pressure-dependent phase transitions of In2Se3 bulk powders and nanowire samples were studied at room temperature and at elevated temperatures using synchrotron x-ray diffraction and diamond-anvil cells (DACs). alpha-In2Se3 transforms into the beta phase at 0.7 GPa, an order of magnitude lower than phase-transition critical pressures in typical semiconductors. The bulk moduli are reported and the c/a ratio for the beta phase is shown to have a highly nonlinear dependence on pressure. gamma-In2Se3, metastable under ambient conditions, transforms into to the high-pressure beta phase between 2.8 GPa and 3.2 GPa in bulk powder samples and at slightly higher pressures, between 3.2 GPa and 3.7 GPa in nanowire samples. While the gamma phase bulk modulus is similar to that of the beta phase, the decrease due to pressure in the unit cell parameter ratio, c/a, is less than half the decrease seen in the beta phase. Using high-temperature DACs, we investigated how elevated temperatures and pressures affect the crystal structure of In 2Se3. From these measurements, the high-pressure beta phase was found to be metastable. The high-pressure beta phase transitions into the high-temperature beta phase at temperatures above 380 °C.
Extended ensemble theory, spontaneous symmetry breaking, and phase transitions
Xiao, Ming-wen
2006-09-01
In this paper, as a personal review, we suppose a possible extension of Gibbs ensemble theory so that it can provide a reasonable description of phase transitions and spontaneous symmetry breaking. The extension is founded on three hypotheses, and can be regarded as a microscopic edition of the Landau phenomenological theory of phase transitions. Within its framework, the stable state of a system is determined by the evolution of order parameter with temperature according to such a principle that the entropy of the system will reach its minimum in this state. The evolution of order parameter can cause a change in representation of the system Hamiltonian; different phases will realize different representations, respectively; a phase transition amounts to a representation transformation. Physically, it turns out that phase transitions originate from the automatic interference among matter waves as the temperature is cooled down. Typical quantum many-body systems are studied with this extended ensemble theory. We regain the Bardeen Cooper Schrieffer solution for the weak-coupling superconductivity, and prove that it is stable. We find that negative-temperature and laser phases arise from the same mechanism as phase transitions, and that they are unstable. For the ideal Bose gas, we demonstrate that it will produce Bose Einstein condensation (BEC) in the thermodynamic limit, which confirms exactly Einstein's deep physical insight. In contrast, there is no BEC either within the phonon gas in a black body or within the ideal photon gas in a solid body. We prove that it is not admissible to quantize the Dirac field by using Bose Einstein statistics. We show that a structural phase transition belongs physically to the BEC happening in configuration space, and that a double-well anharmonic system will undergo a structural phase transition at a finite temperature. For the O(N)-symmetric vector model, we demonstrate that it will yield spontaneous symmetry breaking and produce
Inhomogeneous field configurations and the electroweak phase transition
Jungnickel, D U; Jungnickel, Dirk-Uwe; Walliser, Dirk
1994-01-01
We investigate the effects of inhomogeneous scalar field configurations on the electroweak phase transition. For this purpose we calculate the leading perturbative correction to the wave function correction term $Z(\\vph,T)$, i.e., the kinetic term in the effective action, for the electroweak Standard Model at finite temperature and the top quark self--mass. Our finding for the fermionic contribution to $Z(\\vph,T)$ is infra--red finite and disagrees with other recent results. In general, neither the order of the phase transition nor the temperature at which it occurs change, once $Z(\\vph,T)$ is included. But a non--vanishing, positive (negative) $Z(\\vph,T)$ enhances (decreases) the critical droplet surface tension and the strength of the phase transition. We find that in the range of parameter space, which allows for a first--order phase transition, the wave function correction term is negative --- indicating a weaker phase transition --- and especially for small field values so large that perturbation theory ...
New insight into the Berezinskii-Kosterlitz-Thouless phase transition
Gerber, Urs; Rejón-Barrera, Fernando G
2014-01-01
We investigate the 2d XY model by using the constraint angle action, which belongs to the class of topological lattice actions. These actions violate important features usually demanded for a lattice action, such as the correct classical continuum limit and the applicability of perturbation theory. Nevertheless, they still lead to the same universal quantum continuum limit and show excellent scaling behavior. By using the constraint angle action we gain new insight into the Berezinskii-Kosterlitz-Thouless phase transition of the 2d XY model. This phase transition is of special interest since it is one of the few examples of a phase transition beyond second order. It is of infinite order and therefore an essential phase transition. In particular, we observe an excellent scaling behavior of the helicity modulus, which characterizes this phase transition. We also observe that the mechanism of (un)binding vortex--anti-vortex pairs follows the usual pattern, although free vortices do not require any energy in the ...
A comparison of observables for solid-solid phase transitions
Energy Technology Data Exchange (ETDEWEB)
Smilowitz, Laura B [Los Alamos National Laboratory; Henson, Bryan F [Los Alamos National Laboratory; Romero, Jerry J [Los Alamos National Laboratory
2009-01-01
The study of solid-solid phase transformations is hindered by the difficulty of finding a volumetric probe to use as a progress variable. Solids are typically optically opaque and heterogeneous. Over the past several years, second harmonic generation (SHG) has been used as a kinetic probe for a solid-solid phase transition in which the initial and final phases have different symmetries. Bulk generation of SHG is allowed by symmetry only in noncentrosymmetric crystallographic space groups. For the organic energetic nitramine octahydro-1,3 ,5,7 -tetranitro-1,3 ,5,7 -tatrazocine (HMX), the beta phase is centro symmetric (space group P2{sub 1}/c) and the delta phase iS noncentrosymmetric (space group P6{sub 1}22) making SHG an extremely sensitive, essentially zero background probe of the phase change progress. We have used SHG as a tool to follow the progress of the transformation from beta to delta phase during the solid-solid transformation. However, kinetic models of the transformation derived using different observables from several other groups have differed, showing later onset for the phase change and faster progression to completion. In this work, we have intercompared several techniques to understand these differences. The three techniques discussed are second harmonic generation, Raman spectroscopy, and differential scanning calorimetry (DSC). The progress of the beta to delta phase transition in HMX observed with each of these different probes will be discussed and advantages and disadvantages of each technique described. This paper compares several different observables for use in measuring the kinetics of solid-solid phase transitions. Relative advantages and disadvantages for each technique are described and a direct comparison of results is made for the beta to delta polymorphic phase transition of the energetic nitramine, octahydro-1,3,5,7-tetranitro-1,3,5,7-tatrazocine.
Beam Combining by Phase Transition Nonlinear Media
1990-02-01
use the Redlich Kwong equation of state for the media we consider. This equation of state can be written RT a p - -b -FT(p.-’ + b)p ; 2-I M (2-1) where...as ac 3 dg-A7 C VA/\\CIIJT (6) The Redlich - Kwong equation of state; i.e., _ RT T-1/2 v-P v(v+P) (7) can be used to compute aP/lT, where the relevant...practical the application of nonlinear phase conjugate techniques to the beam combining of multiple lasers with a coherence characteristic of a
THE NEXT GENERATION TRANSIT SURVEY PROTOTYPING PHASE
Directory of Open Access Journals (Sweden)
J. McCormac
2014-01-01
Full Text Available El Next Generation Transit Survey (NGTS es un nuevo sondeo d e exoplanetas transitantes de campo amplio que tiene como objetivo descubrir exoplanetas del tama ̃no d e Neptuno y super-Tierras entorno a estrellas brillantes ( V < 13 cercanas. NGTS consiste de un arreglo de 12 telescopios o perados rob ́oticamente observando en la banda de 600 − 900 nm. NGTS sondear ́a m ́as de cinco veces el n ́umero de estre llas, con V < 13, que Kepler y por lo tanto proveer ́a los objetivos m ́as brillantes para s er caracterizados con instrumentaci ́on existente y futura (VLT, E-ELT y JWST. En 2009/10 un prototipo del NGTS f ue probado en La Palma, comprobando que un sistema as ́ı puede alcanzar nuestros objetivos de fot ometr ́ıa estelar esencialmente limitada s ́olo por el ruido blanco. Los resultados son resumidos aqu ́ı. NGTS se al imenta de la experiencia del proyecto SuperWASP, que, por muchos a ̃nos, ha liderado la detecci ́on terrestre d e exoplanetas transitantes.
Non-equilibrium phase transitions in a liquid crystal
Dan, K.; Roy, M.; Datta, A.
2015-09-01
The present manuscript describes kinetic behaviour of the glass transition and non-equilibrium features of the "Nematic-Isotropic" (N-I) phase transition of a well known liquid crystalline material N-(4-methoxybenzylidene)-4-butylaniline from the effects of heating rate and initial temperature on the transitions, through differential scanning calorimetry (DSC), Fourier transform infrared and fluorescence spectroscopy. Around the vicinity of the glass transition temperature (Tg), while only a change in the baseline of the ΔCp vs T curve is observed for heating rate (β) > 5 K min-1, consistent with a glass transition, a clear peak for β ≤ 5 K min-1 and the rapid reduction in the ΔCp value from the former to the latter rate correspond to an order-disorder transition and a transition from ergodic to non-ergodic behaviour. The ln β vs 1000/T curve for the glass transition shows convex Arrhenius behaviour that can be explained very well by a purely entropic activation barrier [Dan et al., Eur. Phys. Lett. 108, 36007 (2014)]. Fourier transform infrared spectroscopy indicates sudden freezing of the out-of-plane distortion vibrations of the benzene rings around the glass transition temperature and a considerable red shift indicating enhanced coplanarity of the benzene rings and, consequently, enhancement in the molecular ordering compared to room temperature. We further provide a direct experimental evidence of the non-equilibrium nature of the N-I transition through the dependence of this transition temperature (TNI) and associated enthalpy change (ΔH) on the initial temperature (at fixed β-values) for the DSC scans. A plausible qualitative explanation based on Mesquita's extension of Landau-deGennes theory [O. N. de Mesquita, Braz. J. Phys. 28, 257 (1998)] has been put forward. The change in the molecular ordering from nematic to isotropic phase has been investigated through fluorescence anisotropy measurements where the order parameter, quantified by the
Second- and First-Order Phase Transitions in CDT
Ambjorn, J; Jurkiewicz, J; Loll, R
2012-01-01
Causal Dynamical Triangulations (CDT) is a proposal for a theory of quantum gravity, which implements a path-integral quantization of gravity as the continuum limit of a sum over piecewise flat spacetime geometries. We use Monte Carlo simulations to analyse the phase transition lines bordering the physically interesting de Sitter phase of the four-dimensional CDT model. Using a range of numerical criteria, we present strong evidence that the so-called A-C transition is first order, while the B-C transition is second order. The presence of a second-order transition may be related to an ultraviolet fixed point of quantum gravity and thus provide the key to probing physics at and possibly beyond the Planck scale.
Characteristics of the chiral phase transition in nonlocal quark models
Dumm, D G
2004-01-01
The characteristics of the chiral phase transition are analyzed within the framework of chiral quark models with nonlocal interactions in the mean field approximation (MFA). In the chiral limit, we show that there is a region of low values of the chemical potential in which the transition is a second order one. In that region, it is possible to perform a Landau expansion and determine the critical exponents which, as expected, turn out to be the MFA ones. Our analysis also allows to obtain semi-analytical expressions for the transition curve and the location of the tricritical point. For the case of finite current quark masses, we study the behavior of various thermodynamical and chiral response functions across the phase transition.
Disorienting the Chiral Condensate at the QCD Phase Transition
Rajagopal, K
1997-01-01
I sketch how long wavelength modes of the pion field can be amplified during the QCD phase transition. If nature had been kinder, and had made the pion mass significantly less than the critical temperature for the transition, then this phenomenon would have characterized the transition in thermal equilibrium. Instead, these long wavelength oscillations of the orientation of the chiral condensate can only arise out of equilibrium. There is a simple non-equilibrium mechanism, plausibly operational during heavy ion collisions, which naturally amplifies these oscillations. The characteristic signature of this phenomenon is large fluctuations in the ratio of the number of neutral pions to the total number of pions in regions of momentum space, that is in phase space in a detector. Detection in a heavy ion collision would imply an out of equilbrium chiral transition.
Phase transitions in the distribution of inelastically colliding inertial particles
Belan, Sergey; Falkovich, Gregory
2015-01-01
It was recently suggested that the sign of particle drift in inhomogeneous temperature or turbulence depends on the particle inertia: weakly inertial particles localize near minima of temperature or turbulence intensity (effects known as thermophoresis and turbophoresis), while strongly inertial particles fly away from minima in an unbounded space. The problem of a particle near minima of turbulence intensity is related to that of two particles in a random flow, so that the localization-delocalization transition in the former corresponds to the path-coalescence transition in the latter. The transition is signaled by the sign change of the Lyapunov exponent that characterizes the mean rate of particle approach to the minimum (which could be wall or another particle). Here we solve analytically this problem for inelastic collisions and derive the phase diagram for the transition in the inertia-inelasticity plane. An important feature of the phase diagram is the region of inelastic collapse: if the restitution c...
How tetraquarks can generate a second chiral phase transition
Pisarski, Robert D
2016-01-01
We consider how tetraquarks can affect the chiral phase transition in theories like QCD, with light quarks coupled to three colors. For two flavors the tetraquark field is an isosinglet, and its effect is minimal. For three flavors, however, the tetraquark field transforms in the same representation of the chiral symmetry group as the usual chiral order parameter, and so for very light quarks there may be two chiral phase transitions, which are both of first order. In QCD, results from the lattice indicate that any transition from the tetraquark condensate is a smooth crossover. In the plane of temperature and quark chemical potential, though, a crossover line for the tetraquark condensate is naturally related to the transition line for color superconductivity. For four flavors we suggest that a triquark field, antisymmetric in both flavor and color, combine to form hexaquarks.
Crystallite size and phase transition demeanor of ceramic steel
Energy Technology Data Exchange (ETDEWEB)
Gusain, Deepak; Srivastava, Varsha [Department of Chemistry, Indian Institute of Technology (Banaras Hindu University) Varanasi, Varanasi 221 005 (India); Singh, Vinay K. [Department of Ceramic Engineering, Indian Institute of Technology (Banaras Hindu University) Varanasi, Varanasi 221 005 (India); Chandra Sharma, Yogesh, E-mail: ysharma.apc@itbhu.ac.in [Department of Chemistry, Indian Institute of Technology (Banaras Hindu University) Varanasi, Varanasi 221 005 (India)
2014-06-01
Zirconia is an important oxide of zirconium used in variety of field ranging from dentistry, fuel cells, and thermal barrier coatings. Phase transition of zirconia is an important phenomenon controlling its fracture strength, low temperature degradability and ion conductivity. In the present study, effect of molar concentration of precursor and calcination temperature on phase transition and crystallite size of zirconia was investigated. All the samples were characterized by X-ray diffractometry (XRD), Differential Thermal Analysis/Thermogravimetric Analysis (DTA/TGA), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). In sample having lowest precursor concentration crystallite size of monoclinic zirconia was found to be lower than that of tetragonal zirconia, simultaneously with the higher proportion of tetragonal zirconia (67.62%) as compared to all other samples (42.75%–58.04%). In all cases, monoclinic to tetragonal phase transition occurs with raise of temperature but in the sample with lowest precursor concentration, tetragonal to monoclinic phase transition occurred on raising the temperature. - Graphical abstract: Display Omitted - Highlights: • Highest proportion of tetragonal phase at lowest precursor concentration. • Tetragonal phase's crystallite size decreased with rise of temperature. • Average particle size of all samples lies in the range of 13 nm–20 nm.
Phase transitions in traffic flow on multilane roads.
Kerner, Boris S; Klenov, Sergey L
2009-11-01
Based on empirical and numerical analyses of vehicular traffic, the physics of spatiotemporal phase transitions in traffic flow on multilane roads is revealed. The complex dynamics of moving jams observed in single vehicle data measured by video cameras on American highways is explained by the nucleation-interruption effect in synchronized flow, i.e., the spontaneous nucleation of a narrow moving jam with the subsequent jam dissolution. We find that (i) lane changing, vehicle merging from on-ramps, and vehicle leaving to off-ramps result in different traffic phases-free flow, synchronized flow, and wide moving jams-occurring and coexisting in different road lanes as well as in diverse phase transitions between the traffic phases; (ii) in synchronized flow, the phase transitions are responsible for a non-regular moving jam dynamics that explains measured single vehicle data: moving jams emerge and dissolve randomly at various road locations in different lanes; (iii) the phase transitions result also in diverse expanded general congested patterns occurring at closely located bottlenecks.
Universality of Holographic Phase Transitions and Holographic Quantum Liquids
Benincasa, Paolo
2009-01-01
We explore the phase structure for defect theories in full generality using the gauge/gravity correspondence. On the gravity side, the systems are constructed by introducing M (probe) D(p+4-2k)-branes in a background generated by N Dp-branes to obtain a codimension-k intersection. The dual gauge theory is a U(N) Supersymmetric Yang-Mills theory on a (1+p-k)-dimensional defect with both adjoint and fundamental degrees of freedom. We focus on the phase structure in the chemical potential versus temperature plane. We observe the existence of two universality classes for holographic gauge theories, which are identified by the order of the phase transition in the interior of the chemical potential/temperature plane. Specifically, all the sensible systems with no defect show a third order phase transition. Gauge theories on a defect with (p-1)-spatial directions are instead characterised by a second order phase transition. One can therefore state that the order of this phase transition is intimately related to the ...
Error-correcting codes and phase transitions
Manin, Yuri I
2009-01-01
The theory of error-correcting codes is concerned with constructing codes that optimize simultaneously transmission rate and relative minimum distance. These conflicting requirements determine an asymptotic bound, which is a continuous curve in the space of parameters. The main goal of this paper is to relate the asymptotic bound to phase diagrams of quantum statistical mechanical systems. We first identify the code parameters with Hausdorff and von Neumann dimensions, by considering fractals consisting of infinite sequences of code words. We then construct operator algebras associated to individual codes. These are Toeplitz algebras with a time evolution for which the KMS state at critical temperature gives the Hausdorff measure on the corresponding fractal. We extend this construction to algebras associated to limit points of codes, with non-uniform multi-fractal measures, and to tensor products over varying parameters.
Quantum decoherence of subcritical bubble in electroweak phase transition
Shiromizu, T
1995-01-01
In a weakly first order phase transition the typical scale of a subcritical bubble calculated in our previous papers turned out to be too small. At this scale quantum fluctuations may dominate and our previous classical result may be altered. So we examine the critical size of a subcritical bubble where quantum-to-classical transition occurs through quantum decoherence. We show that this critical size is almost equal to the typical scale which we previously obtained.
Thermodynamics and Phase Transition in Rotational Kiselev Black Hole
Xu, Zhaoyi
2016-01-01
We calculate the thermodynamical features of rotational Kiselev black holes, specifically we use one order approximate of horizon to calculate thermodynamical features for all $\\omega$. The thermodynamics features include areas, entropies, horizon radii, surface gravities, surface temperatures, Komar energies and irreducible masses at the Cauchy horizon and Event horizon. At the same time the products of these features have been discussed. We find that the products are independent with mass of black hole and determined by $\\omega$ and $\\alpha$. The features in the situations of $\\omega=-2/3,1/3$ and $0$ (quintessence matter, radiation and dust) have been discussed in detail. We also generalize the Smarr mass formula and Christodoulou-Ruffini mass formula to these black holes. Finally we study the phase transition for black holes with different $\\omega$ and obtain the state equation. We analyze the phase transition for $\\omega=1/3$, and find that $\\alpha$ shifts the critical point of phase transition.
Phase transition with an isospin dependent lattice gas model
Energy Technology Data Exchange (ETDEWEB)
Gulminelli, F. [Caen Univ., 14 (France). Lab. de Physique Corpusculaire; Chomaz, Ph. [Grand Accelerateur National d`Ions Lourds (GANIL), 14 - Caen (France)
1998-10-01
The nuclear liquid-gas phase transition is studied within an isospin dependent Lattice Gas Model in the canonical ensemble. Finite size effects on thermodynamical variables are analyzed by a direct calculation of the partition function, and it is shown that phase coexistence and phase transition are relevant concepts even for systems of a few tens of particles. Critical exponents are extracted from the behaviour of the fragment production yield as a function of temperature by means of a finite size scaling. The result is that in a finite system well defined critical signals can be found at supercritical (Kertesz line) as well as subcritical densities. For isospin asymmetric systems it is shown that, besides the modification of the critical temperature, isotopic distributions can provide an extra observable to identify and characterize the transition. (author) 21 refs.
Phase transitions of black holes in massive gravity
Fernando, Sharmanthie
2016-01-01
In this paper we have studied thermodynamics of a black hole in massive gravity in the canonical ensemble. The massive gravity theory in consideration here has a massive graviton due to Lorentz symmetry breaking. The black hole studied here has a scalar charge due to the massive graviton and is asymptotically anti-de Sitter. We have computed various thermodynamical quantities such as temperature, specific heat and free energy. Both the local and global stability of the black hole are studied by observing the behavior of the specific heat and the free energy. We have observed that there is a first order phase transition between small and large black hole for a certain range of the scalar charge. This phase transition is similar to the liquid/gas phase transition at constant temperature for a Van der Waals fluid. The coexistence curves for the small and large black hole branches are also discussed in detail.
Gravitational radiation from first-order phase transitions
Energy Technology Data Exchange (ETDEWEB)
Child, Hillary L.; Giblin, John T. Jr., E-mail: childh@kenyon.edu, E-mail: giblinj@kenyon.edu [Department of Physics, Kenyon College, 201 North College Road, Gambier, OH 43022 (United States)
2012-10-01
It is believed that first-order phase transitions at or around the GUT scale will produce high-frequency gravitational radiation. This radiation is a consequence of the collisions and coalescence of multiple bubbles during the transition. We employ high-resolution lattice simulations to numerically evolve a system of bubbles using only scalar fields, track the anisotropic stress during the process and evolve the metric perturbations associated with gravitational radiation. Although the radiation produced during the bubble collisions has previously been estimated, we find that the coalescence phase enhances this radiation even in the absence of a coupled fluid or turbulence. We comment on how these simulations scale and propose that the same enhancement should be found at the Electroweak scale; this modification should make direct detection of a first-order electroweak phase transition easier.
Lifshitz scaling effects on holographic paramagnetism/ferromagneism phase transition
Zhang, Cheng-Yuan; Jin, Yong-Yi; Chai, Yun-Tian; Hu, Mu-Hong; Zhang, Zhuo
2016-01-01
In the probe limit, we investigate holographic paramagnetism-ferromagnetism phase transition in the four-dimensional (4D) and five-dimensional(5D) Lifshitz black holes by means of numerical and semi-analytical methods, which is realized by introducing a massive 2-form field coupled to the Maxwell field. We find that the Lifshitz dynamical exponent $z$ contributes evidently to magnetic moment and hysteresis loop of single magnetic domain quantitatively not qualitatively. Concretely, in the case without external magnetic field, the spontaneous magnetization and ferromagnetic phase transition happen when the temperature gets low enough, and the critical exponent for the magnetic moment is always $1/2$, which is in agreement with the result from mean field theory. And the increasing $z$ enhances the phase transition and increases the DC resistivity which behaves as the colossal magnetic resistance effect in some materials. Furthermore, in the presence of the external magnetic field, the magnetic susceptibility sa...
Optical Sensor for Characterizing the Phase Transition in Salted Solutions
Claverie, Rémy; Fontana, Marc D.; Duričković, Ivana; Bourson, Patrice; Marchetti, Mario; Chassot, Jean-Marie
2010-01-01
We propose a new optical sensor to characterize the solid-liquid phase transition in salted solutions. The probe mainly consists of a Raman spectrometer that extracts the vibrational properties from the light scattered by the salty medium. The spectrum of the O – H stretching band was shown to be strongly affected by the introduction of NaCl and the temperature change as well. A parameter SD defined as the ratio of the integrated intensities of two parts of this band allows to study the temperature and concentration dependences of the phase transition. Then, an easy and efficient signal processing and the exploitation of a modified Boltzmann equation give information on the phase transition. Validations were done on solutions with varying concentration of NaCl. PMID:22319327
Canonical Entropy and Phase Transition of Rotating Black Hole
Institute of Scientific and Technical Information of China (English)
ZHAO Ren; WU Yue-Qin; ZHANG Li-Chun
2008-01-01
Recently, the Hawking radiation of a black hole has been studied using the tunnel effect method. The radiation spectrum of a black hole is derived. By discussing the correction to spectrum of the rotating black hole, we obtain the canonical entropy. The derived canonical entropy is equal to the sum of Bekenstein-Hawking entropy and correction term. The correction term near the critical point is different from the one near others. This difference plays an important role in studying the phase transition of the black hole. The black hole thermal capacity diverges at the critical point. However, the canonical entropy is not a complex number at this point. Thus we think that the phase transition created by this critical point is the second order phase transition. The discussed black hole is a five-dimensional Kerr-AdS black hole. We provide a basis for discussing thermodynamic properties of a higher-dimensional rotating black hole.
Gravitational Radiation from First-Order Phase Transitions
Child, Hillary L
2012-01-01
It is believed that first order phase transitions at or around the GUT scale will produce high-frequency gravitational radiation. This radiation is a consequence of the collisions and coalescence of multiple bubbles during the transition. We employ high-resolution lattice simulations to numerically evolve a system of bubbles, track the anisotropic stress during the process and evolve the metric perturbations associated with gravitational radiation. Although the radiation produced during the bubble collisions has previously been estimated, we find that the coalescence phase that greatly enhances this radiation even in the absence of turbulence. We comment on how these simulations scale and propose that the same enhancement should be found at the Electroweak scale; this modification should make direct detection of a first-order electroweak phase transition easier.
Phase transition in aluminous silica in the lowermost mantle
Tronnes, R. G.; Andrault, D.; Konopkova, Z.; Morgenroth, W.; Liermann, H.
2012-12-01
Lower mantle basaltic lithologies contain 35-40% Mg-perovskite, 20-30% Ca-perovskite, 15-25% Al-rich phases (NAL and Ca-ferrite phases) and 15-20% silica-dominated phases. The Fe-rich Mg-perovskite makes basaltic material denser than peridotite throughout the lower mantle below 720 km depth, with important implications for mantle dynamics. Partial separation of subducted basaltic crust from depleted lithosphere might occur within the strongly heterogeneous D" zone. Further details on phase transitions and equation of states for the various minerals, however, are needed for more complete insights. The silica-dominated phases have considerable solubility of alumina [1]. We investigated silica with 4 and 6 wt% alumina to 120 GPa, using LH-DAC at the Extreme Conditions Beamline (P02.2) at PETRA-III, DESY. Powdered glass mixed with 10-15 wt% Pt-powder was compressed and heated in NaCl pressure media in Re-gaskets. The transition from the CaCl2-structured phase to seifertite (alpha-PbO2-structure) occurs at about 116 GPa at 2500 K. This is intermediate between the transition pressures of about 122 GPa and 100-113 GPa reported for similar temperatures for pure SiO2 [2] and a basalt composition [1], respectively. The CaCl2-structured silica phase crystallized along with seifertite, consistent with a binary phase loop trending towards lower pressure with increasing Al-content. The presence of an Al-rich Ca-ferrite phase (near the MgAl2O4-NaAlSiO4-join) in basaltic material indicates that the Al-solubility limits for the silica-dominated phases in basaltic compositions may be similar to those in the binary system SiO2-AlO1.5. Based on the X-ray pattern refinement, our samples show no significant volume change across the transition. Even so, the transition could be associated with a significant density change if the Al substitution mechanisms are different in CaCl2-structured phase and seifertite. The most likely situation is that Al-substitution occurs via O-vacancies in the
Guan, Shu-Hui; Liu, Zhi-Pan
2016-02-14
Structural inhomogeneity is ubiquitous in solid crystals and plays critical roles in phase nucleation and propagation. Here, we develop a heterogeneous solid-solid phase transition theory for predicting the prevailing heterophase junctions, the metastable states governing microstructure evolution in solids. Using this theory and first-principles pathway sampling simulation, we determine two types of heterophase junctions pertaining to metal α-ω phase transition at different pressures and predict the reversibility of transformation only at low pressures, i.e. below 7 GPa. The low-pressure transformation is dominated by displacive Martensitic mechanism, while the high-pressure one is controlled by the reconstructive mechanism. The mechanism of α-ω phase transition is thus highly pressure-sensitive, for which the traditional homogeneous model fails to explain the experimental observations. The results provide the first atomic-level evidence on the coexistence of two different solid phase transition mechanisms in one system.
The quark-hadron phase transition and primordial nucleosynthesis
Hogan, Craig J.
After presenting the current view of the processes taking place during the cosmological transition from 'quark soup' to normal hadron matter, attention is given to what happens to cosmological nucleosynthesis in the presence of small-scale baryon inhomogeneities. The QCD phase transition is among the plausible sources of this inhomogeneity. It is concluded that the formation of primordial 'quark nuggets' and other cold exotica requires very low entropy regions at the outset, and that even the more modest nonlinearities perturbing nucleosynthesis probably require some ingredient in addition to a quiescent, mildly supercooled transition.
The quark-hadron phase transition and primordial nucleosynthesis
Hogan, Craig J.
1987-01-01
After presenting the current view of the processes taking place during the cosmological transition from 'quark soup' to normal hadron matter, attention is given to what happens to cosmological nucleosynthesis in the presence of small-scale baryon inhomogeneities. The QCD phase transition is among the plausible sources of this inhomogeneity. It is concluded that the formation of primordial 'quark nuggets' and other cold exotica requires very low entropy regions at the outset, and that even the more modest nonlinearities perturbing nucleosynthesis probably require some ingredient in addition to a quiescent, mildly supercooled transition.
Chern-Simons diffusion rate across different phase transitions
Rougemont, Romulo
2016-01-01
We investigate how the dimensionless ratio given by the Chern-Simons diffusion rate $\\Gamma_{\\textrm{CS}}$ divided by the product of the entropy density $s$ and temperature $T$ behaves across different kinds of phase transitions in the class of bottom-up non-conformal Einstein-dilaton holographic models originally proposed by Gubser and Nellore. By tuning the dilaton potential, one is able to holographically mimic a first order, a second order, or a crossover transition. In a first order phase transition, $\\Gamma_{\\textrm{CS}}/sT$ jumps at the critical temperature (as previously found in the holographic literature), while in a second order phase transition it develops an infinite slope. On the other hand, in a crossover, $\\Gamma_{\\textrm{CS}}/sT$ behaves smoothly, although displaying a fast variation around the pseudo-critical temperature. Furthermore, we also find that $\\Gamma_{\\textrm{CS}}/sT$ increases by orders of magnitude below the critical temperature in a second order phase transition and in a crossov...
Cosmological phase transitions and their properties in the NMSSM
Kozaczuk, Jonathan; Profumo, Stefano; Haskins, Laurel Stephenson; Wainwright, Carroll L.
2015-01-01
We study cosmological phase transitions in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) in light of the Higgs discovery. We use an effective field theory approach to calculate the finite temperature effective potential, focusing on regions with significant tree-level contributions to the Higgs mass, a viable neutralino dark matter candidate, 1-2 TeV stops, and with the remaining particle spectrum compatible with current LHC searches and results. The phase transition structure in viable regions of parameter space exhibits a rich phenomenology, potentially giving rise to one- or two-step first-order phase transitions in the singlet and/or SU(2) directions. We compute several parameters pertaining to the bubble wall profile, including the bubble wall width and Δ β (the variation of the ratio in Higgs vacuum expectation values across the wall). These quantities can vary significantly across small regions of parameter space and can be promising for successful electroweak baryogenesis. We estimate the wall velocity microphysically, taking into account the various sources of friction acting on the expanding bubble wall. Ultra-relativistic solutions to the bubble wall equations of motion typically exist when the electroweak phase transition features substantial supercooling. For somewhat weaker transitions, the bubble wall instead tends to be sub-luminal and, in fact, likely sub-sonic, suggesting that successful electroweak baryogenesis may indeed occur in regions of the NMSSM compatible with the Higgs discovery.
Studies of phase transitions in the aripiprazole solid dosage form.
Łaszcz, Marta; Witkowska, Anna
2016-01-05
Studies of the phase transitions in an active substance contained in a solid dosage form are very complicated but essential, especially if an active substance is classified as a BCS Class IV drug. The purpose of this work was the development of sensitive methods for the detection of the phase transitions in the aripiprazole tablets containing initially its form III. Aripiprazole exhibits polymorphism and pseudopolymorphism. Powder diffraction, Raman spectroscopy and differential scanning calorimetry methods were developed for the detection of the polymorphic transition between forms III and I as well as the phase transition of form III into aripiprazole monohydrate in tablets. The study involved the initial 10 mg and 30 mg tablets, as well as those stored in Al/Al blisters, a triplex blister pack and HDPE bottles (with and without desiccant) under accelerated and long term conditions. The polymorphic transition was not observed in the initial and stored tablets but it was visible on the DSC curve of the Abilify(®) 10 mg reference tablets. The formation of the monohydrate was observed in the diffractograms and Raman spectra in the tablets stored under accelerated conditions. The monohydrate phase was not detected in the tablets stored in the Al/Al blisters under long term conditions. The results showed that the Al/Al blisters can be recommended as the packaging of the aripiprazole tablets containing form III.
Phase transition of lipid-like monolayer characterized by second harmonic generation
Institute of Scientific and Technical Information of China (English)
于安池; 常青; 赵新生; 周晴中; 李东; 黄岩谊; 程天蓉; 黄春辉
1999-01-01
Phase transition of a lipid-like hemicyanine compound characterized by second harmonic generation is studied carefully. The phase transition is assigned as the first order transition between solid state and liquid state. The transition temperature increases with an increase in the surface molecular concentration. A monolayer structure parameter a which is very sensitive to the phase transition is introduced.
Crystal-liquid-gas phase transitions and thermodynamic similarity
Skripov, Vladimir P; Schmelzer, Jurn W P
2006-01-01
Professor Skripov obtained worldwide recognition with his monograph ""Metastable liquids"", published in English by Wiley & Sons. Based upon this work and another monograph published only in Russia, this book investigates the behavior of melting line and the properties of the coexisting crystal and liquid phase of simple substances across a wide range of pressures, including metastable states of the coexisting phases. The authors derive new relations for the thermodynamic similarity for liquid-vapour phase transition, as well as describing solid-liquid, liquid-vapor and liquid-liquid phase tra
Beyond nuclear "pasta" : Phase transitions and neutrino opacity of new "pasta" phases
Alcain, P. N.; Giménez Molinelli, P. A.; Dorso, C. O.
2014-12-01
In this work, we focus on different length scales within the dynamics of nucleons in conditions according to the neutron star crust, with a semiclassical molecular dynamics model, studying isospin symmetric matter at subsaturation densities. While varying the temperature, we find that a solid-liquid phase transition exists, which can be also characterized with a morphology transition. For higher temperatures, above this phase transition, we study the neutrino opacity, and find that in the liquid phase, the scattering of low momenta neutrinos remain high, even though the morphology of the structures differ significatively from those of the traditional nuclear pasta.
Hadron-quark phase transition in dense stars
Energy Technology Data Exchange (ETDEWEB)
Grassi, F.
1987-10-01
An equation of state is computed for a plasma of one flavor quarks interacting through some phenomenological potential, at zero temperature. Assuming that the confining potential is scalar and color-independent, it is shown that the quarks undergo a first-order mass phase transition. In addition, due to the way screening is introduced, all the thermodynamic quantities computed are independent of the actual shape of the interquark potential. This equation of state is then generalized to a several quark flavor plasma and applied to the study of the hadron-quark phase transition inside a neutron star. 45 refs., 4 figs.
Detection of phase transition via convolutional neural network
Tanaka, Akinori
2016-01-01
We design a Convolutional Neural Network (CNN) which studies correlation between discretized inverse temperature and spin configuration of 2D Ising model and show that it can find a feature of the phase transition without teaching any a priori information for it. We also define a new order parameter via the CNN and show that it provides well approximated critical inverse temperature. In addition, we compare the activation functions for convolution layer and find that the Rectified Linear Unit (ReLU) is important to detect the phase transition of 2D Ising model.
Gravitational waves from first-order cosmological phase transitions
Kosowsky, Arthur; Turner, Michael S.; Watkins, Richard
1992-01-01
A first-order cosmological phase transition that proceeds through the nucleation and collision of true-vacuum bubbles is a potent source of gravitational radiation. Possibilities for such include first-order inflation, grand-unified-theory-symmetry breaking, and electroweak-symmetry breaking. We have calculated gravity-wave production from the collision of two scalar-field vacuum bubbles, and, using an approximation based upon these results, from the collision of 20 to 30 vacuum bubbles. We present estimates of the relic background of gravitational waves produced by a first-order phase transition.
Topological conditions for discrete symmetry breaking and phase transitions
Energy Technology Data Exchange (ETDEWEB)
Baroni, Fabrizio; Casetti, Lapo [Dipartimento di Fisica, Universita di Firenze, via G. Sansone 1, I-50019 Sesto Fiorentino (Finland) (Italy)
2006-01-20
In the framework of a recently proposed topological approach to phase transitions, some sufficient conditions ensuring the presence of the spontaneous breaking of a Z{sub 2} symmetry and of a symmetry-breaking phase transition are introduced and discussed. A very simple model, which we refer to as the hypercubic model, is introduced and solved. The main purpose of this model is that of illustrating the content of the sufficient conditions, but it is interesting also in itself due to its simplicity. Then some mean-field models already known in the literature are discussed in the light of the sufficient conditions introduced here.
Quantum phase transition between cluster and antiferromagnetic states
Son, Wonmin; Fazio, Rosario; Hamma, Alioscia; Pascazio, Saverio; Vedral, Vlatko
2011-01-01
We study a Hamiltonian system describing a three spin-1/2 cluster-like interaction competing with an Ising-like exchange. We show that the ground state in the cluster phase possesses symmetry protected topological order. A continuous quantum phase transition occurs as result of the competition between the cluster and Ising terms. At the critical point the Hamiltonian is self-dual. The geometric entanglement is also studied. Our findings in one dimension corroborate the analysis of the two dimensional generalization of the system, indicating, at a mean field level, the presence of a direct transition between an antiferromagnetic and a valence bond solid ground state.
The liquid to vapor phase transition in excited nuclei
Elliott, J B; Phair, L; Wozniak, G J; Lefort, T; Beaulieu, L; Kwiatkowski, K K; Hsi, W C; Pienkowski, L; Breuer, H; Korteling, R G; Laforest, R; Martin, E; Ramakrishnan, E; Rowland, D; Ruangma, A; Viola, V E; Winchester, E M; Yennello, S J
2002-01-01
For many years it has been speculated that excited nuclei would undergo a liquid to vapor phase transition. For even longer, it has been known that clusterization in a vapor carries direct information on the liquid- vapor equilibrium according to Fisher's droplet model. Now the thermal component of the 8 GeV/c pion + 197Au multifragmentation data of the ISiS Collaboration is shown to follow the scaling predicted by Fisher's model, thus providing the strongest evidence yet of the liquid to vapor phase transition.
The liquid to vapor phase transition in excited nuclei
Energy Technology Data Exchange (ETDEWEB)
Elliott, J.B.; Moretto, L.G.; Phair, L.; Wozniak, G.J.; Beaulieu, L.; Breuer, H.; Korteling, R.G.; Kwiatkowski, K.; Lefort, T.; Pienkowski, L.; Ruangma, A.; Viola, V.E.; Yennello, S.J.
2001-05-08
For many years it has been speculated that excited nuclei would undergo a liquid to vapor phase transition. For even longer, it has been known that clusterization in a vapor carries direct information on the liquid-vapor equilibrium according to Fisher's droplet model. Now the thermal component of the 8 GeV/c pion + 197 Au multifragmentation data of the ISiS Collaboration is shown to follow the scaling predicted by Fisher's model, thus providing the strongest evidence yet of the liquid to vapor phase transition.
Hadronic multiplicity distribution and dynamical fluctuations under QGP phase transitions
Institute of Scientific and Technical Information of China (English)
杨纯斌; 鄢文标; 蔡勖
1999-01-01
Hadronic multiplicity distributions in small bins are studied within the Ginzburg-Landau description for quark-hadron phase transitions. Direct comparison of the distributions with Poisson ones （with the same averages） is made in the light of dynamical factors dq for the distributions and ratios Dq≡dq/d1. Scaling behavior between Dq’ s is found, which can be used to detect the formation of quark-gluon plasma. The same method can be used in the analysis of other processes without phase transition.
Plasticity and beyond microstructures, crystal-plasticity and phase transitions
Hackl, Klaus
2014-01-01
The book presents the latest findings in experimental plasticity, crystal plasticity, phase transitions, advanced mathematical modeling of finite plasticity and multi-scale modeling. The associated algorithmic treatment is mainly based on finite element formulations for standard (local approach) as well as for non-standard (non-local approach) continua and for pure macroscopic as well as for directly coupled two-scale boundary value problems. Applications in the area of material design/processing are covered, ranging from grain boundary effects in polycrystals and phase transitions to deep-drawing of multiphase steels by directly taking into account random microstructures.
Antiferrodistortive phase transition in EuTiO3
Goian, V.; Kamba, S.; Pacherova, O.; Drahokoupil, J.; Palatinus, L; Dusek, M.; Rohlicek, J.; Savinov, M.; Laufek, F.; Schranz, W.; Fuith, A; Kachlik, M.; Maca, K.; Shkabko, A.; Sagarna, L.
2012-01-01
X-ray diffraction, dynamical mechanical analysis and infrared reflectivity studies revealed an antiferrodistortive phase transition in EuTiO3 ceramics. Near 300K the perovskite structure changes from cubic Pm-3m to tetragonal I4/mcm due to antiphase tilting of oxygen octahedra along the c axis (a0a0c- in Glazer notation). The phase transition is analogous to SrTiO3. However, some ceramics as well as single crystals of EuTiO3 show different infrared reflectivity spectra bringing evidence of a ...
Phase transitions in antiferromagnets with a NaCl structure
Energy Technology Data Exchange (ETDEWEB)
Kassan-Ogly, F.A. [Institute of Metal Physics, Ural Division, Russian Academy of Sciences, ul. S.Kovalevskoi 18, Ekaterinburg 620219 (Russian Federation)]. E-mail: felix.kassan-ogly@imp.uran.ru; Filippov, B.N. [Institute of Metal Physics, Ural Division, Russian Academy of Sciences, ul. S.Kovalevskoi 18, Ekaterinburg 620219 (Russian Federation)
2006-05-15
A revised derivation scheme of possible magnetic structures in an FCC lattice with the nearest- and next-nearest-neighbor interactions taken into account is proposed. A model of simultaneous magnetic and structural phase transitions of the first order is developed for antiferromagnets with a NaCl structure and with a strong cubic magnetic anisotropy on the base of synthesis of magnetic modified 6-state Potts model and theoretical models of structural phase transitions in cubic crystals. It is shown that the high-temperature diffuse magnetic scattering of neutrons transforms into magnetic Bragg reflections below Neel point.
Phase transitions in antiferromagnets with a NaCl structure
Kassan-Ogly, F. A.; Filippov, B. N.
2006-05-01
A revised derivation scheme of possible magnetic structures in an FCC lattice with the nearest- and next-nearest-neighbor interactions taken into account is proposed. A model of simultaneous magnetic and structural phase transitions of the first order is developed for antiferromagnets with a NaCl structure and with a strong cubic magnetic anisotropy on the base of synthesis of magnetic modified 6-state Potts model and theoretical models of structural phase transitions in cubic crystals. It is shown that the high-temperature diffuse magnetic scattering of neutrons transforms into magnetic Bragg reflections below Néel point.
Chiral phase transition in QED$_3$ at finite temperature
Wei, Wei; Zong, Hong-Shi
2016-01-01
Chiral phase transition in (2+1)-dimensional quantum electrodynamics (QED$_3$) at finite temperature is investigated in the framework of truncated Dyson-Schwinger equations (DSEs). We go beyond the widely used instantaneous approximation and adopt a method that retains the full frequency dependence of the fermion self-energy. We also take further step to include the effects of wave-function renormalizations and introduce a minimal dressing of the bare vertex. Finally, with the more complete solutions of the truncated DSEs, we revisit the study of chiral phase transition in finite-temperature QED$_3$.
Computational diagnostics for detecting phase transitions during nanoindentation
Energy Technology Data Exchange (ETDEWEB)
Lee, S.M.; Hoover, C.G.; Kallman, J.S.; De Groot, A.J. (Lawrence Livermore National Lab., CA (United States)); Hoover, W.G. (Lawrence Livermore National Lab., CA (United States) California Univ., Livermore, CA (United States). Div. of Applied Science); Wooten, F. (California Univ., Livermore, CA (United States). Div. of Applied Science)
1992-12-01
We study nanoindenmtion of silicon using nonequilibrium molecular dynamics simulations. with up to a million particles. Both crystalline and amorphous silicon samples are considered. We use compumtional diffraction pattems as a diagnostic tool for detecting phase transitions resulting from structural changes. Simulations of crystalline samples show a transition to the amorphous phase in a region a few atomic layers thick surrounding the lateral faces of the indenter, as has been suggested by experimental results. Our simulation results provide estimates for the yield strength (nanohardness) of silicon for a range of temperatures.
Pressure Induced Phase Transition in TiB
Institute of Scientific and Technical Information of China (English)
李凤英; 陈良辰; 王莉君; 顾惠成; 王汝菊; 车荣钲; 沈中毅
2001-01-01
In situ high pressure x-ray diffraction and electrical resistance experiments on TiB have been carried out by using a diamond anvil cell device. The results revealed that the sample undergoes a first-order phase transition at pressures of 3.5 - 5.0 Gpa and 4.0 - 5.5 Gpa for the x-ray diffraction and electrical resistance experiments, respectively. The parameters of the state equation are calculated before and after the phase transition and compared with the values calculated by Mohn et al. [J. Phys. C: Solid State Phys. 21(1988)2829] using the augmented spherical wave method.
Self-aggregation of vapor-liquid phase transition
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
The concept of the molecular free path is introduced to derive a criterion distinguishing active molecules from inactive molecules in liquid phase. Based on molecular self-aggregation theory a concept of the critical aggregation concentration (CAC) of active molecules is proposed to describe the physical configuration before the formation of the nuclei in the process of vapor-liquid phase transition. All active molecules exist in the form of the monomer when the concentration of active molecules is lower than CAC, while the active molecules will generate aggregation once the concentration of the active molecules reaches CAC. However, these aggregates with the aggregation number N smaller than 5 can steadily exist in bulk phase. The other excess active molecules can only produce infinite aggregation and form a critical nucleus of vapor-liquid phase transition. Without outer perturbation the state point of CAC corresponds to the critical superheated or supercooled state in the process of vapor-liquid phase transition. With the aggregate property, the interfacial tension between the bulk phase and the tiny new phase is predicted and a correction is made for the classical nucleation rate in a quite good agreement with experimental results.
Domain structure and phase transition in Sc-doped zirconia
Brunauer, G.; Boysen, H.; Frey, F.; Ehrenberg, H.
2002-01-01
The temperature dependence of the domain structure associated with the ferroelastic phase transition (Fm↔R bar 3 m) in ZrO2 doped with 11% Sc2O3 has been determined from a peak shape analysis of high-resolution synchrotron x-ray powder diffraction data. In the temperature region of coexisting phases the observed characteristic anisotropic broadening and asymmetry of the lines is modelled by three different phases: a main rhombohedral phase, a distorted rhombohedral phase with a smaller c/a ratio, and a cubic phase. The latter two are assigned to the internal structure of the domain walls between two adjacent twin domains. The size and amount of the cubic phase show an initially slow increase with temperature followed by a very steep increase and a slow one after that. The size of the (main) rhombohedral domains remains nearly constant, while (micro-) strain in the distorted regions gradually decreases.
The electroweak phase transition in models with gauge singlets
Energy Technology Data Exchange (ETDEWEB)
Ahriche, A.
2007-04-18
A strong first order phase transition is needed for generating the baryon asymmetry; and also to save it during the electroweak phase transition (EWPT). However this condition is not fulfilled within the Standard Model (SM), but in its extensions. It is widely believed that the existence of singlet scalars in some Standard Model extensions can easily make the EWPT strongly first order. In this work, we will examine the strength of the EWPT in the simplest extension of the SM with a real gauge singlet using the sphaleron energy at the critical temperature. We find that the phase transition is stronger by adding a singlet; and also that the criterion for a strong phase transition {omega}(T{sub c})/T{sub c} >or similar 1, where {omega} = (v{sup 2} + (x - x{sub 0}){sup 2}){sup (}1)/(2) and x(x{sub 0}) is the singlet vacuum expectation value in the broken (symmetric) phase, is not valid for models containing singlets, even though often used in the literature. The usual condition v{sub c}/T{sub c} >or similar 1 is more meaningful, and it is satisfied for the major part of the parameter space for physically allowed Higgs masses. Then it is convenient to study the EWPT in models with singlets that couple only to the Higgs doublets, by replacing the singlets by their vevs. (orig.)
Effect of extrinsic curvature on quark--hadron phase transition
Heydari-Fard, Malihe
2009-01-01
The last phase transition predicted by the standard model of particle physics took place at the QCD scale $T\\sim200$ MeV when the universe was about $t\\sim10^{-5}$ seconds old and the Hubble radius was around 10 Km. In this paper, we consider the quark--hadron phase transition in the context of brane-world cosmology where our universe is a 3-brane embedded in a $m$-dimensional bulk and localization of matter on the brane is achieved by means of a confining potential. We study the behavior of the physical quantities relevant to the description of the early universe like the energy density, temperature and scale factor, before, during, and after the phase transition and investigate the effects of extrinsic curvature on the cosmological phase transition. We show that the brane-world effects reduce the effective temperature of the quark--gluon plasma and of the hadronic fluid. Finally, we discuss the case where the universe evolved through a mixed phase with a small initial supercooling and monotonically growing ...
Phase transition and surface sublimation of a mobile Potts model.
Bailly-Reyre, A; Diep, H T; Kaufman, M
2015-10-01
We study in this paper the phase transition in a mobile Potts model by the use of Monte Carlo simulation. The mobile Potts model is related to a diluted Potts model, which is also studied here by a mean-field approximation. We consider a lattice where each site is either vacant or occupied by a q-state Potts spin. The Potts spin can move from one site to a nearby vacant site. In order to study the surface sublimation, we consider a system of Potts spins contained in a recipient with a concentration c defined as the ratio of the number of Potts spins N(s) to the total number of lattice sites N(L)=N(x)×N(y)×N(z). Taking into account the attractive interaction between the nearest-neighboring Potts spins, we study the phase transitions as functions of various physical parameters such as the temperature, the shape of the recipient, and the spin concentration. We show that as the temperature increases, surface spins are detached from the solid phase to form a gas in the empty space. Surface order parameters indicate different behaviors depending on the distance to the surface. At high temperatures, if the concentration is high enough, the interior spins undergo a first-order phase transition to an orientationally disordered phase. The mean-field results are shown as functions of temperature, pressure, and chemical potential, which confirm in particular the first-order character of the transition.
Phase transitions in traffic flow on multilane roads
Kerner, Boris S.; Klenov, Sergey L.
2009-11-01
Based on empirical and numerical analyses of vehicular traffic, the physics of spatiotemporal phase transitions in traffic flow on multilane roads is revealed. The complex dynamics of moving jams observed in single vehicle data measured by video cameras on American highways is explained by the nucleation-interruption effect in synchronized flow, i.e., the spontaneous nucleation of a narrow moving jam with the subsequent jam dissolution. We find that (i) lane changing, vehicle merging from on-ramps, and vehicle leaving to off-ramps result in different traffic phases—free flow, synchronized flow, and wide moving jams—occurring and coexisting in different road lanes as well as in diverse phase transitions between the traffic phases; (ii) in synchronized flow, the phase transitions are responsible for a non-regular moving jam dynamics that explains measured single vehicle data: moving jams emerge and dissolve randomly at various road locations in different lanes; (iii) the phase transitions result also in diverse expanded general congested patterns occurring at closely located bottlenecks.
Zipf's law emerges asymptotically during phase transitions in communicative systems
Khomtchouk, Bohdan B
2016-01-01
Zipf's law predicts a power-law relationship between word rank and frequency in language communication systems, and is widely reported in texts yet remains enigmatic as to its origins. Computer simulations have shown that language communication systems emerge at an abrupt phase transition in the fidelity of mappings between symbols and objects. Since the phase transition approximates the Heaviside or step function, we show that Zipfian scaling emerges asymptotically at high rank based on the Laplace transform which yields $(1/r)(1-e^{-r})$, where $r$ denotes rank. We thereby demonstrate that Zipf's law gradually emerges from the moment of phase transition in communicative systems. We show that this power-law scaling behavior explains the emergence of natural languages at phase transitions. We find that the emergence of Zipf's law during language communication suggests that the use of rare words in a lexicon (i.e., high $r$) is critical for the construction of an effective communicative system at the phase tra...
Electric field driven mesoscale phase transition in polarized colloids
Khusid, Boris; Elele, Ezinwa; Lei, Qian
2016-11-01
A mesoscale phase transition in a polarized suspension was reported by Kumar, Khusid, Acrivos, PRL95, 2005 and Agarwal, Yethiraj, PRL102, 2009. Following the application of a strong AC field, particles aggregated head-to-tail into chains that bridged the interelectrode gap and then formed a cellular pattern, in which large particle-free domains were enclosed by particle-rich thin walls. Cellular structures were not observed in numerous simulations of field induced phase transitions in a polarized suspension. A requirement for matching the particle and fluid densities to avoid particle settling limits terrestrial experiments to negatively polarized particles. We present data on the phase diagram and kinetics of the phase transition in a neutrally buoyant, negatively polarized suspension subjected to a combination of AC and DC. Surprisingly, a weak DC component drastically speeds up the formation of a cellular pattern but does not affect its key characteristic. However, the application of a strong DC field destroys the cellular pattern, but it restores as the DC field strength is reduced. We also discuss the design of experiments to study phase transitions in a suspension of positively polarized, non-buoyancy-matched particles in the International Space Station. Supported by NASA's Physical Science Research Program, NNX13AQ53G.
Two Phase Flow Mapping and Transition Under Microgravity Conditions
Parang, Masood; Chao, David F.
1998-01-01
In this paper, recent microgravity two-phase flow data for air-water, air-water-glycerin, and air- water-Zonyl FSP mixtures are analyzed for transition from bubbly to slug and from slug to annular flow. It is found that Weber number-based maps are inadequate to predict flow-pattern transition, especially over a wide range of liquid flow rates. It is further shown that slug to annular flow transition is dependent on liquid phase Reynolds number at high liquid flow rate. This effect may be attributed to growing importance of liquid phase inertia in the dynamics of the phase flow and distribution. As a result a new form of scaling is introduced to present data using liquid Weber number based on vapor and liquid superficial velocities and Reynolds number based on liquid superficial velocity. This new combination of the dimensionless parameters seem to be more appropriate for the presentation of the microgravity data and provides a better flow pattern prediction and should be considered for evaluation with data obtained in the future. Similarly, the analysis of bubble to slug flow transition indicates a strong dependence on both liquid inertia and turbulence fluctuations which seem to play a significant role on this transition at high values of liquid velocity. A revised mapping of data using a new group of dimensionless parameters show a better and more consistent description of flow transition over a wide range of liquid flow rates. Further evaluation of the proposed flow transition mapping will have to be made after a wider range of microgravity data become available.
The Noise-Sensitivity Phase Transition in Compressed Sensing
Donoho, David L; Montanari, Andrea
2010-01-01
Consider the noisy underdetermined system of linear equations: y=Ax0 + z0, with n x N measurement matrix A, n \\rhoMSE(\\delta). The phase boundary \\rho = \\rhoMSE(\\delta) is identical to the previously-known phase transition curve for equivalence of l1 - l0 minimization in the k-sparse noiseless case. Hence a single phase boundary describes the fundamental phase transitions both for the noiseless and noisy cases. Extensive computational experiments validate the predictions of this formalism, including the exis tence of game theoretical structures underlying it. Underlying our formalism is the AMP algorithm introduced earlier by the authors. Other papers by the authors detail expressions for the formal MSE of AMP and its close connection to l1-penalized reconstruction. Here we derive the minimax formal MSE of AMP and then read out results for l1-penalized reconstruction.
Efimov-driven phase transitions of the unitary Bose gas.
Piatecki, Swann; Krauth, Werner
2014-03-20
Initially predicted in nuclear physics, Efimov trimers are bound configurations of three quantum particles that fall apart when any one of them is removed. They open a window into a rich quantum world that has become the focus of intense experimental and theoretical research, as the region of 'unitary' interactions, where Efimov trimers form, is now accessible in cold-atom experiments. Here we use a path-integral Monte Carlo algorithm backed up by theoretical arguments to show that unitary bosons undergo a first-order phase transition from a normal gas to a superfluid Efimov liquid, bound by the same effects as Efimov trimers. A triple point separates these two phases and another superfluid phase, the conventional Bose-Einstein condensate, whose coexistence line with the Efimov liquid ends in a critical point. We discuss the prospects of observing the proposed phase transitions in cold-atom systems.
Striped phases in the holographic insulator/superconductor transition
Erdmenger, Johanna; Pang, Da-Wei
2013-01-01
We study striped phases in holographic insulator/superconductor transition by considering a spatially modulated chemical potential in AdS soliton background. Generally striped phases can develop above a critical chemical potential. When the constant leading term in the chemical potential is set to zero, a discontinuity in the plot of charge density versus chemical potential is observed in the limit of large wave vector. We explain this discontinuity using an analytical approach. When the constant leading term in the chemical potential is present, the critical chemical potential is larger than in the case of a homogeneous chemical potential, which indicates that the spatially modulated chemical potential disfavors the phase transition. This behavior is also confirmed qualitatively by analytical calculations. We also calculate the grand canonical potential and find that the striped phase is favored.
Theory of photoinduced phase transitions in itinerant electron systems
Energy Technology Data Exchange (ETDEWEB)
Yonemitsu, Kenji [Institute for Molecular Science, Graduate University for Advanced Studies, Okazaki, Aichi 444-8585 (Japan)], E-mail: kxy@ims.ac.jp; Nasu, Keiichiro [Solid State Theory Division, Institute of Materials Structure Science, KEK, Graduate University for Advanced Studies, CREST JST, Oho 1-1, Tsukuba, Ibaraki 305-0801 (Japan)], E-mail: knasu@post.kek.jp
2008-08-15
Theoretical progress in the research of photoinduced phase transitions is reviewed with closely related experiments. After a brief introduction of stochastic evolution in statistical systems and domino effects in localized electron systems, we treat photoinduced dynamics in itinerant-electron systems. Relevant interactions are required in the models to describe the fast and ultrafast charge-lattice-coupled dynamics after photoexcitations. First, we discuss neutral-ionic transitions in the mixed-stack charge-transfer complex, TTF-CA. When induced by intrachain charge-transfer photoexcitations, the dynamics of the ionic-to-neutral transition are characterized by a threshold behavior, while those of the neutral-to-ionic transition by an almost linear behavior. The difference originates from the different electron correlations in the neutral and ionic phases. Second, we deal with halogen-bridged metal complexes, which show metal, Mott insulator, charge-density-wave, and charge-polarization phases. The latter two phases have different broken symmetries. The charge-density-wave to charge-polarization transition is much more easily achieved than the reverse transition. This is clarified by considering microscopic charge-transfer processes. The transition from the charge-density-wave to Mott insulator phases and that from the Mott insulator to metal phases proceed much faster than those between the low-symmetry phases. Next, we discuss ultrafast, inverse spin-Peierls transitions in an organic radical crystal and alkali-TCNQ from the viewpoint of intradimer and interdimer charge-transfer excitations. Then, we study photogenerated electrons in the quantum paraelectric perovskite, SrTiO{sub 3}, which are assumed to couple differently with soft-anharmonic phonons and breathing-type high-energy phonons. The different electron-phonon couplings result in two types of polarons, a 'super-paraelectric large polaron' with a quasi-global parity violation, and an &apos
Theory of photoinduced phase transitions in itinerant electron systems
Yonemitsu, Kenji; Nasu, Keiichiro
2008-08-01
Theoretical progress in the research of photoinduced phase transitions is reviewed with closely related experiments. After a brief introduction of stochastic evolution in statistical systems and domino effects in localized electron systems, we treat photoinduced dynamics in itinerant-electron systems. Relevant interactions are required in the models to describe the fast and ultrafast charge-lattice-coupled dynamics after photoexcitations. First, we discuss neutral-ionic transitions in the mixed-stack charge-transfer complex, TTF-CA. When induced by intrachain charge-transfer photoexcitations, the dynamics of the ionic-to-neutral transition are characterized by a threshold behavior, while those of the neutral-to-ionic transition by an almost linear behavior. The difference originates from the different electron correlations in the neutral and ionic phases. Second, we deal with halogen-bridged metal complexes, which show metal, Mott insulator, charge-density-wave, and charge-polarization phases. The latter two phases have different broken symmetries. The charge-density-wave to charge-polarization transition is much more easily achieved than the reverse transition. This is clarified by considering microscopic charge-transfer processes. The transition from the charge-density-wave to Mott insulator phases and that from the Mott insulator to metal phases proceed much faster than those between the low-symmetry phases. Next, we discuss ultrafast, inverse spin-Peierls transitions in an organic radical crystal and alkali-TCNQ from the viewpoint of intradimer and interdimer charge-transfer excitations. Then, we study photogenerated electrons in the quantum paraelectric perovskite, SrTiO 3, which are assumed to couple differently with soft-anharmonic phonons and breathing-type high-energy phonons. The different electron-phonon couplings result in two types of polarons, a “super-paraelectric large polaron” with a quasi-global parity violation, and an “off-center-type self
Chiral Phase Transition at Finite Isospin Density in Linear Sigma Model
Institute of Scientific and Technical Information of China (English)
SHU Song; LI Jia-Rong
2005-01-01
Using the linear sigma model, we have introduced the pion isospin chemical potential. The chiral phase transition is studied at finite temperatures and finite isospin densities. We have studied the μ - T phase diagram for the chiral phase transition and found the transition cannot happen below a certain low temperature because of the BoseEinstein condensation in this system. Above that temperature, the chiral phase transition is studied by the isotherms of pressure versus density. We indicate that the transition, in the chiral limit, is a first-order transition from a low-density phase to a high-density phase like a gas-liquid phase transition.
Optically induced phase transition of excitons in coupled quantum dots
Institute of Scientific and Technical Information of China (English)
Chen Zi-Dong
2008-01-01
The weak classical light excitations in many semiconductor quantum dots have been chosen as important solidstate quantum systems for processing quantum information and implementing quantum computing. For strong classical light we predict theoretically a novel phase transition as a function of magnitude of this classical light from the deformed to the normal phases in resonance case, and the essential features of criticality such as the scaling behaviour, critical exponent and universality are also present in this paper.
Recent progress of nuclear liquid gas phase transition
Institute of Scientific and Technical Information of China (English)
MA Yu-Gang; SHEN Wen-Qing
2004-01-01
Recent progress on nuclear liquid gas phase transition (LGPT) has been reviewed, especially for the signals of LGPT in heavy ion collisions. These signals include the power-law charge distribution, cluster emission rate, nuclear Zipf law, bimodality, the largest fluctuation of the fragments, △ -scaling, caloric curve, phase coexistence diagram, critical temperature, critical exponent analysis, negative specific heat capacity and spinodal instability etc. The systematic works of the authors on experimental and theoretical LGPT are also introduced.
Multiple phase transitions in Pauli limited iron-based superconductors
Ptok, Andrzej
2015-01-01
Specific heat measurements have been successfully used to probe unconventional superconducting phases in one-band heavy-fermion and organic superconductors. We extend the method to study successive phase transitions in multi-band materials such as iron based superconductors. The signatures are multiple peaks in the specific heat, at low temperatures and high magnetic field, which can lead the experimental verification of unconventional superconducting states with non-zero total momentum.
P-Wave Holographic Insulator/Superconductor Phase Transition
Akhavan, Amin
2010-01-01
Using a five dimensional AdS soliton in an Einstein-Yang-Mills theory with SU(2) gauge group we study p-wave holographic insulator/superconductor phase transition. To explore the phase structure of the model we consider the system in the probe limit as well as fully back reacted solutions. We will also study zero temperature limit of the p-wave holographic superconductor in four dimensions.
Quantum Fisher information as signature of superradiant quantum phase transition
Wang, T L; Yang, W; Jin, G R; Lambert, N; Nori, F
2013-01-01
The single-mode Dicke model is well-known to undergo a quantum phase transition from the so-called normal phase to the supperradiant phase (hereinafter called the "superradiant quantum phase transition"). Normally, quantum phase transitions are closely related to the critical behavior of quantities such as entanglement, quantum fluctuations, and fidelity. In this paper, we study quantum Fisher information (QFI) of the field mode and that of the atoms in the ground state of the Dicke Hamiltonian. For finite and large enough number of atoms N, our numerical results show that near the critical atom-field coupling, the QFIs of the atomic and the field subsystems can surpass the classical limits, due to the appearance of nonclassical squeezed states. As the coupling increases far beyond the critical point, the two subsystems are in highly mixed states, which degrade the QFI and hence the ultimate phase sensitivity. In the thermodynamic limit, we present analytical results of the QFIs and their relationships with t...
Mapping the QCD Phase Transition with Accreting Compact Stars
Blaschke, David; Grigorian, Hovik
2008-01-01
We discuss an idea for how accreting millisecond pulsars could contribute to the understanding of the QCD phase transition in the high-density nuclear matter equation of state (EoS). It is based on two ingredients, the first one being a ``phase diagram'' of rapidly rotating compact star configurations in the plane of spin frequency and mass, determined with state-of-the-art hybrid equations of state, allowing for a transition to color superconducting quark matter. The second is the study of spin-up and accretion evolution in this phase diagram. We show that the quark matter phase transition leads to a characteristic line in the Omega-M plane, the phase border between neutron stars and hybrid stars with a quark matter core. Along this line a change in the pulsar's moment of inertia entails a waiting point phenomenon in the accreting millisecond X-ray pulsar (AMXP) evolution: most of these objects should therefore be found along the phase border in the Omega-M plane, which may be viewed as the AMXP analog of th...
DEFF Research Database (Denmark)
Kublitz, Anja
for the girl talk is centred on catastrophes or Nakbas, as they are referred to in Arabic. Not only al-Nakba of 1948 when the Palestinians were displaced from their homeland, but also the many recurring wars and the individual catastrophes that involve dead family members, rapes, loss of children and abusive...
On the thermodynamics of phase transitions in metal hydrides
Vita, Andrea
2012-02-01
Metal hydrides are solutions of hydrogen in a metal, where phase transitions may occur depending on temperature, pressure etc. We apply Le Chatelier's principle of thermodynamics to a particular phase transition in TiHx, which can approximately be described as a second-order phase transition. We show that the fluctuations of the order parameter correspond to fluctuations both of the density of H+ ions and of the distance between adjacent H+ ions. Moreover, as the system approaches the transition and the correlation radius increases, we show -with the help of statistical mechanics-that the statistical weight of modes involving a large number of H+ ions (`collective modes') increases sharply, in spite of the fact that the Boltzmann factor of each collective mode is exponentially small. As a result, the interaction of the H+ ions with collective modes makes a tiny suprathermal fraction of the H+ population appear. Our results hold for similar transitions in metal deuterides, too. A violation of an -insofar undisputed-upper bound on hydrogen loading follows.
Liquid-Liquid Phase Transition and Glass Transition in a Monoatomic Model System
Directory of Open Access Journals (Sweden)
Nicolas Giovambattista
2010-12-01
Full Text Available We review our recent study on the polyamorphism of the liquid and glass states in a monatomic system, a two-scale spherical-symmetric Jagla model with both attractive and repulsive interactions. This potential with a parametrization for which crystallization can be avoided and both the glass transition and the liquid-liquid phase transition are clearly separated, displays water-like anomalies as well as polyamorphism in both liquid and glassy states, providing a unique opportunity to study the interplay between the liquid-liquid phase transition and the glass transition. Our study on a simple model may be useful in understanding recent studies of polyamorphism in metallic glasses.
Gravitational phase transitions with an exclusion constraint in position space
Chavanis, Pierre-Henri
2014-01-01
We discuss the statistical mechanics of a system of self-gravitating particles with an exclusion constraint in position space in a space of dimension d. The exclusion constraint puts an upper bound on the density of the system and can stabilize it against gravitational collapse. We plot the caloric curves giving the temperature as a function of the energy and investigate the nature of phase transitions as a function of the size of the system and of the dimension of space in both microcanonical and canonical ensembles. We consider stable and metastable states and emphasize the importance of the latter for systems with long-range interactions. For d ≤ 2, there is no phase transition. For d > 2, phase transitions can take place between a "gaseous" phase unaffected by the exclusion constraint and a "condensed" phase dominated by this constraint. The condensed configurations have a core-halo structure made of a "rocky core" surrounded by an "atmosphere", similar to a giant gaseous planet. For large systems there exist microcanonical and canonical first order phase transitions. For intermediate systems, only canonical first order phase transitions are present. For small systems there is no phase transition at all. As a result, the phase diagram exhibits two critical points, one in each ensemble. There also exist a region of negative specific heats and a situation of ensemble inequivalence for sufficiently large systems. We show that a statistical equilibrium state exists for any values of energy and temperature in any dimension of space. This differs from the case of the self-gravitating Fermi gas for which there is no statistical equilibrium state at low energies and low temperatures when d ≥ 4. By a proper interpretation of the parameters, our results have application for the chemotaxis of bacterial populations in biology described by a generalized Keller-Segel model including an exclusion constraint in position space. They also describe colloids at a fluid
Flow of hypermagnetic helicity in the embryo of a new phase in the electroweak phase transition
Akhmet'ev, P M; Sokoloff, D D
2010-01-01
The dynamics of the magnetic helicity during the electroweak phase transition in the early Universe is studied. It is shown that the boundary surface between symmetric (hypermagnetic) phase and Maxwellian phase with a broken symmetry is a membrana for the separation of the magnetic helicity. Assuming the total linking number of knots of hypermagnetic field is negative, it is proved that the helicity rising in the Maxwellian phase is left-handed.
Electronic properties and phase transitions in low-dimensional semiconductors
Energy Technology Data Exchange (ETDEWEB)
Panich, A M [Department of Physics, Ben-Gurion University of the Negev, PO Box 653, Beer Sheva 84105 (Israel)], E-mail: pan@bgu.ac.il
2008-07-23
We present the first review of the current state of the literature on electronic properties and phase transitions in TlX and TlMX{sub 2} (M = Ga, In; X = Se, S, Te) compounds. These chalcogenides belong to a family of the low-dimensional semiconductors possessing chain or layered structure. They are of significant interest because of their highly anisotropic properties, semi- and photoconductivity, nonlinear effects in their I-V characteristics (including a region of negative differential resistance), switching and memory effects, second harmonic optical generation, relaxor behavior and potential applications for optoelectronic devices. We review the crystal structure of TlX and TlMX{sub 2} compounds, their transport properties under ambient conditions, experimental and theoretical studies of the electronic structure, transport properties and semiconductor-metal phase transitions under high pressure, and sequences of temperature-induced structural phase transitions with intermediate incommensurate states. The electronic nature of the ferroelectric phase transitions in the above-mentioned compounds, as well as relaxor behavior, nanodomains and possible occurrence of quantum dots in doped and irradiated crystals is discussed. (topical review)
Dynamics of Electrically Driven Martensitic Phase Transitions in Fe Nanoislands
Gerhard, L.; Wesselink, R.J.H.; Ostanin, S.; Ernst, A.; Wulfhekel, W.
2013-01-01
Magnetoelectric coupling has attracted interest due to its potential to write magnetic information with electric fields. In the model system of Fe islands on Cu(111), electric fields can induce martensitic phase transitions between ferromagnetic body-centered cubic and antiferromagnetic face-centere
Cooling compact stars and phase transitions in dense QCD
Energy Technology Data Exchange (ETDEWEB)
Sedrakian, Armen [J.W. Goethe University, Institute for Theoretical Physics, Frankfurt am Main (Germany)
2016-03-15
We report new simulations of cooling of compact stars containing quark cores and updated fits to the Cas A fast cooling data. Our model is built on the assumption that the transient behaviour of the star in Cas A is due to a phase transition within the dense QCD matter in the core of the star. Specifically, the fast cooling is attributed to an enhancement in the neutrino emission triggered by a transition from a fully gapped, two-flavor, red-green color-superconducting quark condensate to a superconducting crystalline or an alternative gapless, color-superconducting phase. The blue-colored condensate is modeled as a Bardeen-Cooper-Schrieffer (BCS)-type color superconductor with spin-one pairing order parameter. We study the sensitivity of the fits to the phase transition temperature, the pairing gap of blue quarks and the timescale characterizing the phase transition (the latter modelled in terms of a width parameter). Relative variations in these parameter around their best-fit values larger than 10{sup -3} spoil the fit to the data. We confirm the previous finding that the cooling curves show significant variations as a function of compact star mass, which allows one to account for dispersion in the data on the surface temperatures of thermally emitting neutron stars. (orig.)
Quantum phase transitions with parity-symmetry breaking and hysteresis
Trenkwalder, A.; Spagnolli, G.; Semeghini, G.; Coop, S.; Landini, M.; Castilho, P.; Pezzè, L.; Modugno, G.; Inguscio, M.; Smerzi, A.; Fattori, M.
2016-09-01
Symmetry-breaking quantum phase transitions play a key role in several condensed matter, cosmology and nuclear physics theoretical models. Its observation in real systems is often hampered by finite temperatures and limited control of the system parameters. In this work we report, for the first time, the experimental observation of the full quantum phase diagram across a transition where the spatial parity symmetry is broken. Our system consists of an ultracold gas with tunable attractive interactions trapped in a spatially symmetric double-well potential. At a critical value of the interaction strength, we observe a continuous quantum phase transition where the gas spontaneously localizes in one well or the other, thus breaking the underlying symmetry of the system. Furthermore, we show the robustness of the asymmetric state against controlled energy mismatch between the two wells. This is the result of hysteresis associated with an additional discontinuous quantum phase transition that we fully characterize. Our results pave the way to the study of quantum critical phenomena at finite temperature, the investigation of macroscopic quantum tunnelling of the order parameter in the hysteretic regime and the production of strongly quantum entangled states at critical points.
Commensurate-commensurate magnetic phase transitions in CeSb
DEFF Research Database (Denmark)
Lebech, Bente; Broholm, C.; Clausen, K.;
1986-01-01
The q=2/3 to q=4/7 commensurate-commensurate phase transition in CeSb has been studied by neutron diffraction. On cooling the commensurate wave vector q changes abruptly from 2/3 to a higher-order commensurate value (≈14/23) at T1
Quantum phase transition of a magnet in a spin bath
DEFF Research Database (Denmark)
Rønnow, H.M.; Parthasarathy, R.; Jensen, J.;
2005-01-01
The excitation spectrum of a model magnetic system, LiHoF(4), was studied with the use of neutron spectroscopy as the system was tuned to its quantum critical point by an applied magnetic field. The electronic mode softening expected for a quantum phase transition was forestalled by hyperfine...
Quantum phase transitions in low-dimensional optical lattices
Di Liberto, M.F.
2015-01-01
In this thesis, we discuss quantum phase transitions in low-dimensional optical lattices, namely one- and two-dimensional lattices. The dimensional confinement is realized in experiments by suppressing the hopping in the extra dimensions through a deep potential barrier that prevents the atoms to tu
Nonlinear clustering during the BEC dark matter phase transition
Energy Technology Data Exchange (ETDEWEB)
Freitas, Rodolfo C. de, E-mail: rodolfo.camargo@pq.cnpq.br [Universidade Federal do Espírito Santo, Av. Fernando Ferrari, Goiabeiras, Vitória (Brazil); Instituto Federal de Educação, Ciência e Tecnologia do Espírito Santo, Avenida Vitória 1729, Jucutuquara, Vitória (Brazil); Velten, Hermano, E-mail: velten@pq.cnpq.br [Universidade Federal do Espírito Santo, Av. Fernando Ferrari, Goiabeiras, Vitória (Brazil); UMR 7332, CPT, Aix Marseille Université, 13288, Marseille (France)
2015-12-16
Spherical collapse of the Bose–Einstein condensate (BEC) dark matter model is studied in the Thomas–Fermi approximation. The evolution of the overdensity of the collapsed region and its expansion rate are calculated for two scenarios. We consider the case of a sharp phase transition (which happens when the critical temperature is reached) from the normal dark matter state to the condensate one and the case of a smooth first order phase transition where there is a continuous conversion of “normal” dark matter to the BEC phase. We present numerical results for the physics of the collapse for a wide range of the model’s space parameter, i.e. the mass of the scalar particle m{sub χ} and the scattering length l{sub s}. We show the dependence of the transition redshift on m{sub χ} and l{sub s}. Since small scales collapse earlier and eventually before the BEC phase transition, the evolution of collapsing halos in this limit is indeed the same in both the CDM and the BEC models. Differences are expected to appear only on the largest astrophysical scales. However, we argue that the BEC model is almost indistinguishable from the usual dark matter scenario concerning the evolution of nonlinear perturbations above typical clusters scales, i.e., ≳10{sup 14}M{sub ⊙}. This provides an analytical confirmation for recent results from cosmological numerical simulations (Schive et al., Nat Phys 10:496, 2014)
Unified rotational dynamics of molecular crystals with orientational phase transition
Michel, K.H.; Raedt, H. De
1976-01-01
A unified theory for the rotational dynamics of molecular crystals with orientational phase transitions is given. As basic secular variables one takes symmetry adapted functions, which describe the molecular orientations, and the angular momenta of the molecules. Using Mori’s projection operator tec
Analogy between Landau theory of phase transitions and Lagrangian mechanics
Ribeiro Filho, A.; Tilley, D.R.; Žekš, B.
1984-01-01
Texto completo. Acesso restrito. p. 247–249 It is shown that the definition of a stable point in landau theory is different from that used in mechanics. The implications for numerical work on phase transitions for systems that have a Lffshitz invariant are discussed.
New Insights of Electroweak Phase Transition in NMSSM
Huang, Weicong; Shu, Jing; Wu, Peiwen; Yang, Jin Min
2014-01-01
We perform a detailed semi-analytical analysis of the electroweak phase transition (EWPT) property in NMSSM, which serves as a good benchmark model in which the 126 GeV Higgs mixes with a singlet. In this case, a strongly first order electroweak phase transition (SFOEWPT) is achieved by the tree-level effects and the phase transition strength $\\gamma_c$ is determined by the vacua energy gap at $T=0$. We make an anatomy of the energy gap at both tree-level and loop-level and extract out a dimensionless phase transition parameter $R_\\kappa \\equiv 4 \\kappa v_s / A_\\kappa$, which can replace $A_\\kappa$ in the parameterization and affect the light CP odd and even Higgs spectra. We find that SFOEWPT only occurs in $R_\\kappa \\sim -1$ and positive $R_\\kappa \\lesssim \\mathcal{O}(10)$, which in the non-PQ limit case would prefer either a relatively light CP odd or CP even Higgs boson $\\sim (60, 100)$ GeV, therefore serves as a smoking gun signal and requires new search strategies at the LHC.
A phase transition between localist and distributed representation
Molenaar, P.C.M.; Raijmakers, M.E.J.
2000-01-01
Bifurcation analysis of a real-time implementation of an ART network, which is functionally similar to the generalized localist model discussed in Page's manifesto shows that it yields a phase transition from local to distributed representation owing to continuous variation of the range of inhibitor
Insights into phase transitions and entanglement from density functional theory
Wei, Bo-Bo
2016-11-01
Density functional theory (DFT) has met great success in solid state physics, quantum chemistry and in computational material sciences. In this work we show that DFT could shed light on phase transitions and entanglement at finite temperatures. Specifically, we show that the equilibrium state of an interacting quantum many-body system which is in thermal equilibrium with a heat bath at a fixed temperature is a universal functional of the first derivatives of the free energy with respect to temperature and other control parameters respectively. This insight from DFT enables us to express the average value of any physical observable and any entanglement measure as a universal functional of the first derivatives of the free energy with respect to temperature and other control parameters. Since phase transitions are marked by the nonanalytic behavior of free energy with respect to control parameters, the physical quantities and entanglement measures may present nonanalytic behavior at critical point inherited from their dependence on the first derivative of free energy. We use two solvable models to demonstrate these ideas. These results give new insights for phase transitions and provide new profound connections between entanglement and phase transitions in interacting quantum many-body physics.
Defect Formation in First Order Phase Transitions with Damping
Ferrera, A
1998-01-01
Within the context of first order phase transitions in the early universe, we study the influence of a coupling between the (global U(1)) scalar driving the transition and the rest of the matter content of the theory. The effect of the coupling on the scalar is simulated by introducing a damping term in its equations of motion, as suggested by recent results in the electroweak phase transition. After a preceeding paper, in which we studied the influence that this coupling has in the dynamics of bubble collisions and topological defect formation, we proceed in this paper to quantify the impact of this new effects on the probability of defect creation per nucleating bubble.
Effects of phase transition induced density fluctuations on pulsar dynamics
Directory of Open Access Journals (Sweden)
Partha Bagchi
2015-07-01
Full Text Available We show that density fluctuations during phase transitions in pulsar cores may have non-trivial effects on pulsar timings, and may also possibly account for glitches and anti-glitches. These density fluctuations invariably lead to non-zero off-diagonal components of the moment of inertia, leading to transient wobbling of star. Thus, accurate measurements of pulsar timing and intensity modulations (from wobbling may be used to identify the specific pattern of density fluctuations, hence the particular phase transition, occurring inside the pulsar core. Changes in quadrupole moment from rapidly evolving density fluctuations during the transition, with very short time scales, may provide a new source for gravitational waves.
UNIVERSALITY OF PHASE TRANSITION DYNAMICS: TOPOLOGICAL DEFECTS FROM SYMMETRY BREAKING
Energy Technology Data Exchange (ETDEWEB)
Zurek, Wojciech H. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Del Campo, Adolfo [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2014-02-13
In the course of a non-equilibrium continuous phase transition, the dynamics ceases to be adiabatic in the vicinity of the critical point as a result of the critical slowing down (the divergence of the relaxation time in the neighborhood of the critical point). This enforces a local choice of the broken symmetry and can lead to the formation of topological defects. The Kibble-Zurek mechanism (KZM) was developed to describe the associated nonequilibrium dynamics and to estimate the density of defects as a function of the quench rate through the transition. During recent years, several new experiments investigating formation of defects in phase transitions induced by a quench both in classical and quantum mechanical systems were carried out. At the same time, some established results were called into question. We review and analyze the Kibble-Zurek mechanism focusing in particular on this surge of activity, and suggest possible directions for further progress.
Liquid-Liquid Phase Transition in Nanoconfined Silicon Carbide.
Wu, Weikang; Zhang, Leining; Liu, Sida; Ren, Hongru; Zhou, Xuyan; Li, Hui
2016-03-01
We report theoretical evidence of a liquid-liquid phase transition (LLPT) in liquid silicon carbide under nanoslit confinement. The LLPT is characterized by layering transitions induced by confinement and pressure, accompanying the rapid change in density. During the layering transition, the proportional distribution of tetracoordinated and pentacoordinated structures exhibits remarkable change. The tricoordinated structures lead to the microphase separation between silicon (with the dominant tricoordinated, tetracoordinated, and pentacoordinated structures) and carbon (with the dominant tricoordinated structures) in the layer close to the walls. A strong layer separation between silicon atoms and carbon atoms is induced by strong wall-liquid forces. Importantly, the pressure confinement phase diagram with negative slopes for LLPT lines indicates that, under high pressure, the LLPT is mainly confinement-induced, but under low pressure, it becomes dominantly pressure-induced.
P T phase transition in multidimensional quantum systems
Bender, Carl M.; Weir, David J.
2012-10-01
Non-Hermitian P T-symmetric quantum-mechanical Hamiltonians generally exhibit a phase transition that separates two parametric regions, (i) a region of unbroken P T symmetry in which the eigenvalues are all real, and (ii) a region of broken P T symmetry in which some of the eigenvalues are complex. This transition has recently been observed experimentally in a variety of physical systems. Until now, theoretical studies of the P T phase transition have generally been limited to one-dimensional models. Here, four nontrivial coupled P T-symmetric Hamiltonians, H=\\textstyle {\\frac{1}{2}}p^2+\\textstyle {\\frac{1}{2}}x^2+\\textstyle {\\frac{1}{2}}q^2+\\textstyle {\\frac{1}{2}}y^2+igx^2y, H=\\textstyle {\\frac{1}{2}}p^2+\\textstyle {\\frac{1}{2}}x^2+\\textstyle {\\frac{1}{2}}q^2+y^2+igx^2y, H=\\textstyle {\\frac{1}{2}}p^2+\\textstyle {\\frac{1}{2}}x^2+\\textstyle {\\frac{1}{2}}q^2+\\textstyle {\\frac{1}{2}}y^2+\\textstyle {\\frac{1}{2}}r^2+\\textstyle {\\frac{1}{2}}z^2+igxyz, and H=\\textstyle {\\frac{1}{2}}p^2+ \\textstyle {\\frac{1}{2}}x^2+\\textstyle {\\frac{1}{2}}q^2+y^2+\\textstyle {\\frac{1}{2}}r^2+\\textstyle {\\frac{3}{2}}z^2+igxyz are examined. Based on extensive numerical studies, this paper conjectures that all four models exhibit a phase transition. The transitions are found to occur at g ≈ 0.1, g ≈ 0.04, g ≈ 0.1 and g ≈ 0.05. These results suggest that the P T phase transition is a robust phenomenon not limited to systems having one degree of freedom.
Supersymmetric phase transition in Josephson-tunnel-junction arrays
Energy Technology Data Exchange (ETDEWEB)
Foda, O.
1988-08-31
The fully frustrated XY model in two dimensions exhibits a vortex-unbinding as well as an Ising transition. If the Ising transition overlaps with the critical line that ends on the vortex transition: T/sub I/less than or equal toT/sub V/, then the model is equivalent, at the overlap temperature, to a free massless field theory of 1 boson and 1 Majorana fermion, which is a superconformal field theory, of central charge c=3/2. The model is experimentally realized in terms of an array of Josephson-tunnel junctions in a transverse magnetic field. The experiment reveals a phase transition consistent with T/sub I/=T/sub V/. Thus, at the critical temperature, the array provides a physical realization of a supersymmetric quantum field theory.
Phase transitions in Na2TeO4 ceramics
Indian Academy of Sciences (India)
N K Singh; R N P Choudhary
2000-08-01
Polycrystalline samples of NaTeO4 were prepared by conventional solid-state reaction technique at low temperature (600°C). X-ray powder diffraction (XRD) technique was used to check the formation of single phase NaTeO4 compound with cell parameters = 10.602(1) Å; = 70.622(1) Å and = 8.506(1) Å in orthorhombic crystal system. Detailed studies of dielectric constant () (and loss tangent (tan ) as a function of frequency (400 Hz–10 kHz) and temperature (– 120°C–260°C) show that the compound has two phase transitions in the ferroelectric phase.
Phase transitions in the lattice model of intercalation
Directory of Open Access Journals (Sweden)
T.S. Mysakovych
2008-12-01
Full Text Available The lattice model which can be employed for the description of intercalation of ions in crystals is considered in this work. Pseudospin formalism is used in describing the interaction of electrons with ions. The possibility of hopping of intercalated ions between different positions is taken into account. The thermodynamics of the model is investigated in the mean field approximation. Phase diagrams are built. It is shown that at high values of the parameter of ion transfer, the phase transition to a modulated phase disappears.
A Holographic Model for Paramagnetism/antiferromagnetism Phase Transition
Cai, Rong-Gen
2014-01-01
In this paper we build a holographic model of paramagnetism/antiferromagnetism phase transition, which is realized by introducing two real antisymmetric tensor fields coupling to the background gauge field strength and interacting with each other in a dyonic black brane background. In the case without external magnetic field and in low temperatures, the magnetic moments condense spontaneously in antiparallel manner with the same magnitude, which leads to an antiferromagnetic phase. In the case with weak external magnetic field, the magnetic susceptibility density has a peak at the critical temperature and satisfies the Curie-Weiss law in the paramagnetic phase of antiferromagnetism.
Phase Transition Analysis Based Quality Prediction for Multi-phase Batch Processes
Institute of Scientific and Technical Information of China (English)
赵露平; 赵春晖; 高福荣
2012-01-01
Batch processes are usually involved with multiple phases in the time domain and many researches on process monitoring as well as quality prediction have been done using phase information. However, few of them consider phase transitions, though they exit widely in batch processes and have non-ignorable impacts on product qualities. In the present work, a phase-based partial least squares (PLS) method utilizing transition information is proposed to give both online and offline quality predictions. First, batch processes are divided into several phases using regression parameters other than prior process knowledge. Then both steady phases and transitions which have great influences on qualities are identified as critical-to-quality phases using statistical methods. Finally, based on the analysis of different characteristics of transitions and steady phases, an integrated algorithm is developed for quality prediction. The application to an injection molding process shows the effectiveness of the proposed algorithm in comparison with the traditional MPLS method and the phase-based PLS method.
Phase transition, phase transition temperature and crystal structure of a new compound----Ca2PdWO6
Institute of Scientific and Technical Information of China (English)
傅正民; 李文秀
1996-01-01
A new compound Ca2PdWO6 has been synthesized by solid state sintering. The phase transition of this compound was investigated by means of differential thermal analysis (DTA), X-ray phase analysis, precise measurement of lattice parameters and other methods. It is discovered that the compound has a displacive phase transition of the first order at (806+5)C. The low temperature phase, a-Ca2PdWO6, belongs to orthorhombic system, with space group Pmm2. Its lattice parameters at room temperature are: a=0.79946nm, b=0.55404nm and c=0.58008nm. The measured density is Dm=6.26g/cm3, and each unit cell contains two formula weights. The high temperature phase, Ca2PdWO6, belongs to the cubic system, with space group fm3m and the lattice parameter is a = 0.810 3 nm at 860C; Z = 4. The calculated density is Dx=5.821g/cm3. The crystal structure of Ca2PdWO6 and Ca,PdWO6 was also determined by means of the X-ray polycrystal diffraction method. The factors influencing phase transition temperature are discussed in detail.
Electroweak phase transition and baryogenesis in the nMSSM
Energy Technology Data Exchange (ETDEWEB)
Huber, Stephan J. [Theory Division, CERN, CH-1211 Geneva 23 (Switzerland)]. E-mail: stephan.huber@cern.ch; Konstandin, Thomas [Department of Physics, Royal Institute of Technology (KTH), AlbaNova University Center, Roslagstullsbacken 11, 106 91 Stockholm (Sweden)]. E-mail: konstand@theophys.kth.se; Prokopec, Tomislav [Institute for Theoretical Physics (ITF) and Spinoza Institute, Utrecht University, Leuvenlaan 4, Postbus 80.195, 3508 TD Utrecht (Netherlands)]. E-mail: t.prokopec@phys.uu.nl; Schmidt, Michael G. [Institut fuer Theoretische Physik, Heidelberg University, Philosophenweg 16, D-69120 Heidelberg (Germany)]. E-mail: m.g.schmidt@thphys.uni-heidelberg.de
2006-11-20
We analyze the nMSSM with CP violation in the singlet sector. We study the static and dynamical properties of the electroweak phase transition. We conclude that electroweak baryogenesis in this model is generic in the sense that if the present limits on the mass spectrum are applied, no severe additional tuning is required to obtain a strong first-order phase transition and to generate a sufficient baryon asymmetry. For this we determine the shape of the nucleating bubbles, including the profiles of CP-violating phases. The baryon asymmetry is calculated using the advanced transport theory to first and second order in gradient expansion presented recently. Still, first and second generation sfermions must be heavy to avoid large electric dipole moments.
Origin of the phase transition in lithiated molybdenum disulfide
Cheng, Yingchun
2014-11-25
Phase transitions and phase engineering in two-dimensional MoS2 are important for applications in electronics and energy storage. By in situ transmission electron microscopy, we find that H-MoS2 transforms to T-LiMoS2 at the early stages of lithiation followed by the formation of Mo and Li2S phases. The transition from H-MoS2 to T-LiMoS2 is explained in terms of electron doping and electron - phonon coupling at the conduction band minima. Both are essential for the development of two-dimensional semiconductor-metal contacts based on MoS2 and the usage of MoS2 as anode material in Li ion batteries. (Figure Presented).
Supercooling across first-order phase transitions in vortex matter
Indian Academy of Sciences (India)
P Chaddah; S B Roy
2000-06-01
Hysteresis in cycling through ﬁrst-order phase transitions in vortex matter, akin to the well-studied phenomenon of supercooling of water, has been discussed in literature. Hysteresis can be seen while varying either temperature or magnetic ﬁeld (and thus the density of vortices). Our recent work on phase transitions with two control variables shows that the observable region of metastability of the supercooled phase would depend on the path followed in - space, and will be larger when is lowered at constant compared to the case when is lowered at constant . We discuss the effect of isothermal ﬁeld variations on metastable supercooled states produced by ﬁeld-cooling. This path dependence is not a priori applicable to metastability caused by reduced diffusivity or hindered kinetics.
14N NQR and phase transitions in tetracyanoquinodimethanide alkaline salts
Ambrosetti, R.; Angelone, R.; Colligiani, A.; Murgich, J.
1983-12-01
14N NQR lines of RbTCNQ and NaTCNQ polycrystalline samples, measured as a function of temperature, show small but sharp discontinuities at the regular-alternant phase transition (found respectively at 214 K and 346 K), together with the expected change in spectral multiplicity. No ν - lines were detected in NaTCNQ. Co-existence of phases, more marked in NaTCNQ, shows up in NQR data. The use of a pulsed, FT spectrometer yields estimates of T 1 relaxation time: it shows no discontinuity at the phase transition, is around 1 ms at room temperature for ν+ lines, more than 2 order of magnitudes larger for ν - lines, increases smoothly on decreasing temperature.
Phase transition studies of the odd-mass 123-135Xe isotopes based on SU(1,1) algebra in IBFM
Jafarizadeh, M. A.; Fouladi, N.; Ghapanvari, M.; Fathi, H.
2016-07-01
In this paper, we have investigated the positive-parity states in the odd-mass transitional 123-135Xe isotopes within the framework of the interacting boson-fermion model. Two solvable extended transitional Hamiltonians which are based on SU(1,1) algebra are employed to provide an investigation of quantum phase transition (QPT) between the spherical and deformed gamma — unstable shapes along the chain of Xe isotopes. The low-states energy spectra and B(E2) values for these nuclei have been calculated and compared with the experimental data. The predicted excitation energies and B(E2) transition rates of the odd isotopes are found to agree well with the experimental data. We have also analyzed the critical behavior of even-odd Xe isotopes via Catastrophe Theory in combination with a coherent state formalism to generate energy surfaces and special isotopes which are the best candidates for the critical point are identified.
Parisi, Filippo; Sciascia, Luciana; Princivalle, Francesco; Merli, Marcello
2012-02-01
In order to characterize the pressure-induced decomposition of ringwoodite (γ-Mg2SiO4), the topological analysis of the electron density ρ( r), based upon the theory of atoms in molecules (AIM) developed by Bader in the framework of the catastrophe theory, has been performed. Calculations have been carried out by means of the ab initio CRYSTAL09 code at the HF/DFT level, using Hamiltonians based on the Becke- LYP scheme containing hybrid Hartree-Fock/density functional exchange-correlation terms. The equation of state at 0 K has been constructed for the three phases involved in the post-spinel phase transition (ringwoodite → Mg-perovskite + periclase) occurring at the transition zone-lower mantel boundary. The topological results show that the decomposition of the ringwoodite at high pressures is caused by a conflict catastrophe. Furthermore, topological evidences of the central role played by the oxygen atoms to facilitate the pressure-induced ringwoodite decomposition and the subsequent phase transition have been noticed.
Comparing two tetraalkylammonium ionic liquids. II. Phase transitions
Lima, Thamires A.; Paschoal, Vitor H.; Faria, Luiz F. O.; Ribeiro, Mauro C. C.; Ferreira, Fabio F.; Costa, Fanny N.; Giles, Carlos
2016-06-01
Phase transitions of the ionic liquids n-butyl-trimethylammonium bis(trifluoromethanesulfonyl)imide, [N1114][NTf2], and methyl-tributylammonium bis(trifluoromethanesulfonyl)imide, [N1444][NTf2], were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) measurements, and Raman spectroscopy. XRD and Raman spectra were obtained as a function of temperature at atmospheric pressure, and also under high pressure at room temperature using a diamond anvil cell (DAC). [N1444][NTf2] experiences glass transition at low temperature, whereas [N1114][NTf2] crystallizes or not depending on the cooling rate. Both the ionic liquids exhibit glass transition under high pressure. XRD and low-frequency Raman spectra provide a consistent physical picture of structural ordering-disordering accompanying the thermal events of crystallization, glass transition, cold crystallization, pre-melting, and melting. Raman spectra in the high-frequency range of some specific cation and anion normal modes reveal conformational changes of the molecular structures along phase transitions.
Influence of pions on the hadron-quark phase transition
Energy Technology Data Exchange (ETDEWEB)
Lourenco, O.; Dutra, M.; Frederico, T.; Malheiro, M. [Departamento de Fisica, Instituto Tecnologico de Aeronautica-CTA, 12228-900, Sao Jose dos Campos (Brazil); Delfino, A. [Instituto de Fisica, Universidade Federal Fluminense, Av. Litoranea s/n, 24210-150, Boa Viagem, Niteroi RJ (Brazil)
2013-05-06
In this work we present the features of the hadron-quark phase transition diagrams in which the pions are included in the system. To construct such diagrams we use two different models in the description of the hadronic and quark sectors. At the quark level, we consider two distinct parametrizations of the Polyakov-Nambu-Jona-Lasinio (PNJL) models. In the hadronic side, we use a well known relativistic mean-field (RMF) nonlinear Walecka model. We show that the effect of the pions on the hadron-quark phase diagrams is to move the critical end point (CEP) of the transitions lines. Such an effect also depends on the value of the critical temperature (T{sub 0}) in the pure gauge sector used to parametrize the PNJL models. Here we treat the phase transitions using two values for T{sub 0}, namely, T{sub 0}= 270 MeV and T{sub 0}= 190 MeV. The last value is used to reproduce lattice QCD data for the transition temperature at zero chemical potential.
Pressure induced phase transition in FeGa alloys
Devreugd, Christopher; Ahart, Muhtar; Gehring, Peter; Viehland, Dwight; Hemley, Russell
2011-03-01
Giant magnetostriction in Fe-- x Ga alloys (15 -- x - 27) offers potential for future generations of sensors and actuators. A maximum in the magnetostrictive strain is found at Ga content of about 19 percent, which is ten times higher than that of pure alpha-Fe. To investigate the behavior of FeGa alloys under pressure, we chose a slow cooled alloy of FeGa-19 as our sample and performed x-ray diffraction experiments in a diamond anvil cell up to 45 GPa. Diffraction pattern shows powder rings associated with (110), (200), and (211) Bragg reflections from expected bcc structure of iron below 24 GPa. We also observed the intensity increases along the powder rings associated with the crystal structure of Galfenol. Considering the (110) Bragg peak splits into three peaks above 24 GPa, our results indicate that FeGa alloy undergoes a bcc cubic to a hexagonal transition around 24 GPa. When the pressure is decreased, the hcp phase transforms back to the bcc phase. The transition mechanism can be understood by using the analogy to the bcc-hcp phase transition in pure iron under pressure. The transition in iron is a martensitic or displacive one. The hcp structure can be derived from the bcc structure through a relatively minor distortion of the bcc structure.
Characterizing Phase Transitions in a Model of Neutral Evolutionary Dynamics
Scott, Adam; King, Dawn; Bahar, Sonya
2013-03-01
An evolutionary model was recently introduced for sympatric, phenotypic evolution over a variable fitness landscape with assortative mating (Dees & Bahar 2010). Organisms in the model are described by coordinates in a two-dimensional phenotype space, born at random coordinates with limited variation from their parents as determined by a mutation parameter, mutability. The model has been extended to include both neutral evolution and asexual reproduction in Scott et al (submitted). It has been demonstrated that a second order, non-equilibrium phase transition occurs for the temporal dynamics as the mutability is varied, for both the original model and for neutral conditions. This transition likely belongs to the directed percolation universality class. In contrast, the spatial dynamics of the model shows characteristics of an ordinary percolation phase transition. Here, we characterize the phase transitions exhibited by this model by determining critical exponents for the relaxation times, characteristic lengths, and cluster (species) mass distributions. Missouri Research Board; J.S. McDonnell Foundation
Influence of pions on the hadron-quark phase transition
Lourenço, O; Frederico, T; Delfino, A; Malheiro, M
2013-01-01
In this work we present the features of the hadron-quark phase transition diagrams in which the pions are included in the system. To construct such diagrams we use two different models in the description of the hadronic and quark sectors. At the quark level, we consider two distinct parametrizations of the Polyakov-Nambu-Jona-Lasinio (PNJL) models. In the hadronic side, we use a well known relativistic mean-field (RMF) nonlinear Walecka model. We show that the effect of the pions on the hadron-quark phase diagrams is to move the critical end point (CEP) of the transitions lines. Such an effect also depends on the value of the critical temperature (T_0) in the pure gauge sector used to parametrize the PNJL models. Here we treat the phase transitions using two values for T_0, namely, T_0 = 270 MeV and T_0 = 190 MeV. The last value is used to reproduce lattice QCD data for the transition temperature at zero chemical potential.
Phase Transitions and Metastability in Self-Propelled Particle systems
Kulkarni, Ajinkya; Thampi, Sumesh; Panchagnula, Mahesh
2016-11-01
Ordered motion of self-propelling micro-organisms produce interesting patterns. The objective of this study is to investigate the nature of the transition from disorganized thermal-like motion to organized vortical motion, and the resulting metastability in systems of self-propelled particles. A modified version of the Standard Vicsek Model has been used, where the particles are modeled as soft disks with finite mass, confined in a circular domain. We observe multiple phases as the local co-ordination coefficient is varied. We analyze the nature of transitions by calculating Binder Cumulants of the order parameters. An occurrence of metastability is investigated in the hysteretic region. The switching between the steady states of the system in the hysteretic region has been triggered via artificial nucleation of randomly picked particles spanning the entire domain. In addition, the effect of domain size on the nature of the phase transitions has been studied. Finally the motivation for these phase transitions has been explained via thrust generation ability and the geometry of the confinement.
78 FR 30951 - SBIR/STTR Phase I to Phase II Transition Benchmarks
2013-05-23
... ADMINISTRATION SBIR/STTR Phase I to Phase II Transition Benchmarks AGENCY: U.S. Small Business Administration...; Amended. SUMMARY: The Small Business Administration (SBA) is soliciting comments on proposed amendments to... Director, Office of Innovation, Small Business Administration, 409 Third Street SW., Washington, DC...
A Phase Transition for Circle Maps and Cherry Flows
Palmisano, Liviana
2013-07-01
We study C 2 weakly order preserving circle maps with a flat interval. The main result of the paper is about a sharp transition from degenerate geometry to bounded geometry depending on the degree of the singularities at the boundary of the flat interval. We prove that the non-wandering set has zero Hausdorff dimension in the case of degenerate geometry and it has Hausdorff dimension strictly greater than zero in the case of bounded geometry. Our results about circle maps allow to establish a sharp phase transition in the dynamics of Cherry flows.
A Phase Transition for Circle Maps and Cherry Flows
Palmisano, Liviana
2012-01-01
We study $C^{2}$ weakly order preserving circle maps with a flat interval. The main result of the paper is about a sharp transition from degenerate geometry to bounded geometry depending on the degree of the singularities at the boundary of the flat interval. We prove that the non-wandering set has zero Hausdorff dimension in the case of degenerate geometry and it has Hausdorff dimension strictly greater than zero in the case of bounded geometry. Our results about circle maps allow to establish a sharp phase transition in the dynamics of Cherry flows.
Electroweak Phase Transition in the U(1)'-MSSM
Ahriche, Amine
2010-01-01
In this work, we have investigated the nature of the electroweak phase transition (EWPT) in the U(1) extended Minimal Supersymmetric Standard Model (UMSSM) without introducing any exotic filds. The effective potential has been estimated exactly at finite temperature taking into account the whole particle spectrum. For reasonable values of the lightest Higgs and neutralino, we found that the EWPT could be strongly first order due to: 1) the interactions of the singlet with the doublets in the effective potential, and 2) the evolution of the wrong vacuum, that delays the transition.
Dynamical Phase Transition in a Model for Evolution with Migration
Waclaw, Bartłomiej; Allen, Rosalind J.; Evans, Martin R.
2010-12-01
We study a simple quasispecies model for evolution in two different habitats, with different fitness landscapes, coupled through one-way migration. Our key finding is a dynamical phase transition at a critical value of the migration rate, at which the time to reach the steady state diverges. The genetic composition of the population is qualitatively different above and below the transition. Using results from localization theory, we show that the critical migration rate may be very small—demonstrating that evolutionary outcomes can be very sensitive to even a small amount of migration.
Charge fluctuations in chiral models and the QCD phase transition
Skokov, V; Karsch, F; Redlich, K
2011-01-01
We consider the Polyakov loop-extended two flavor chiral quark--meson model and discuss critical phenomena related with the spontaneous breaking of the chiral symmetry. The model is explored beyond the mean-field approximation in the framework of the functional renormalisation group. We discuss properties of the net-quark number density fluctuations as well as their higher cumulants. We show that with the increasing net-quark number density, the higher order cumulants exhibit a strong sensitivity to the chiral crossover transition. We discuss their role as probes of the chiral phase transition in heavy-ion collisions at RHIC and LHC.
Rescuing a Quantum Phase Transition with Quantum Noise
Zhang, Gu; Novais, E.; Baranger, Harold U.
2017-02-01
We show that placing a quantum system in contact with an environment can enhance non-Fermi-liquid correlations, rather than destroy quantum effects, as is typical. The system consists of two quantum dots in series with two leads; the highly resistive leads couple charge flow through the dots to the electromagnetic environment, the source of quantum noise. While the charge transport inhibits a quantum phase transition, the quantum noise reduces charge transport and restores the transition. We find a non-Fermi-liquid intermediate fixed point for all strengths of the noise. For strong noise, it is similar to the intermediate fixed point of the two-impurity Kondo model.
Noise-induced phase transitions in neuronal networks
Lee, K -E; Goltsev, A V
2013-01-01
Using an exactly solvable cortical model of a neuronal network, we show that, by increasing the intensity of shot noise (flow of random spikes bombarding neurons), the network undergoes first- and second-order non-equilibrium phase transitions. We study the nature of the transitions, bursts and avalanches of neuronal activity. Saddle-node and supercritical Hopf bifurcations are the mechanisms of emergence of sustained network oscillations. We show that the network stimulated by shot noise behaves similar to the Morris-Lecar model of a biological neuron stimulated by an applied current.
Pressure-induced phase transitions in L-alanine, revisited.
Tumanov, N A; Boldyreva, E V; Kolesov, B A; Kurnosov, A V; Quesada Cabrera, R
2010-08-01
The effect of pressure on L-alanine has been studied by X-ray powder diffraction (up to 12.3 GPa), single-crystal X-ray diffraction, Raman spectroscopy and optical microscopy (up to approximately 6 GPa). No structural phase transitions have been observed. At approximately 2 GPa the cell parameters a and b become accidentally equal to each other, but without a change in space-group symmetry. Neither of two transitions reported by others (to a tetragonal phase at approximately 2 GPa and to a monoclinic phase at approximately 9 GPa) was observed. The changes in cell parameters were continuous up to the highest measured pressures and the cells remained orthorhombic. Some important changes in the intermolecular interactions occur, which also manifest themselves in the Raman spectra. Two new orthorhombic phases could be crystallized from a MeOH/EtOH/H(2)O pressure-transmitting mixture in the pressure range 0.8-4.7 GPa, but only if the sample was kept at these pressures for at least 1-2 d. The new phases converted back to L-alanine on decompression. Judging from the Raman spectra and cell parameters, the new phases are most probably not L-alanine but its solvates.
Phase transition, phase transition mechanism and crystal structure of a new compound-Ca2FeWO6
Institute of Scientific and Technical Information of China (English)
傅正民; 李文秀
1995-01-01
A new compound Ca2FeWO6 has been synthesized by solid state sintering. The phase transition of this compound was investigated by means of differential thermal analysis (DTA), X-ray powder diffraction and other methods. It is discovered that the compound has a displacive phase transition of the first order at (706±5)℃. The low temperature phase. α-Ca2FeWO6. belongs to orthorhombic system, with space group Pmm2. Its lattice parameters at room temperature are; a = 0.77051 nm, 6=0.54242nm and r = 0.551 08 nm, the measured density is Dm = 6.04g/cm3, and each unit cell contains two formula weight. The high temperature phase, β-Ca2FeWO6, belongs to the cubic system, with space group Fm3m and the lattice parameter is a = 0.780 8 nm at 750℃, z = 4. The calculated density is Dx = 5.802g/cm3, The crystal structures of α-Ca2FeWO6 and β-Ca2FeWO6 were also determined by means of the X-ray polycrystal diffraction method. The phase transition mechanism is expounded in detail.
Antiferrodistortive phase transition in EuTiO3
Goian, V.; Kamba, S.; Pacherová, O.; Drahokoupil, J.; Palatinus, L.; Dušek, M.; Rohlíček, J.; Savinov, M.; Laufek, F.; Schranz, W.; Fuith, A.; Kachlík, M.; Maca, K.; Shkabko, A.; Sagarna, L.; Weidenkaff, A.; Belik, A. A.
2012-08-01
X-ray diffraction, dynamical mechanical analysis, and infrared reflectivity studies revealed an antiferrodistortive phase transition in EuTiO3 ceramics. Near 300 K, the perovskite structure changes from cubic Pm3¯m to tetragonal I4/mcm due to antiphase tilting of oxygen octahedra along the c axis (a0a0c- in Glazer notation). The phase transition is analogous to SrTiO3. However, some ceramics as well as single crystals of EuTiO3 show different infrared reflectivity spectra bringing evidence of a different crystal structure. In such samples, electron diffraction revealed an incommensurate tetragonal structure with modulation wave vector q ≃ 0.38 a*. Extra phonons in samples with modulated structure are activated in the IR spectra due to folding of the Brillouin zone. We propose that defects such as Eu3+ and oxygen vacancies strongly influence the temperature of the phase transition to antiferrodistortive phase as well as the tendency to incommensurate modulation in EuTiO3.
Standing magnetic wave on Ising ferromagnet: Nonequilibrium phase transition
Halder, Ajay; Acharyya, Muktish
2016-12-01
The dynamical response of an Ising ferromagnet to a plane polarised standing magnetic field wave is modelled and studied here by Monte Carlo simulation in two dimensions. The amplitude of standing magnetic wave is modulated along the direction x. We have detected two main dynamical phases namely, pinned and oscillating spin clusters. Depending on the value of field amplitude the system is found to undergo a phase transition from oscillating spin cluster to pinned as the system is cooled down. The time averaged magnetisation over a full cycle of magnetic field oscillations is defined as the dynamic order parameter. The transition is detected by studying the temperature dependences of the variance of the dynamic order parameter, the derivative of the dynamic order parameter and the dynamic specific heat. The dependence of the transition temperature on the magnetic field amplitude and on the wavelength of the magnetic field wave is studied at a single frequency. A comprehensive phase boundary is drawn in the plane described by the temperature and field amplitude for two different wavelengths of the magnetic wave. The variation of instantaneous line magnetisation during a period of magnetic field oscillation for standing wave mode is compared to those for the propagating wave mode. Also the probability that a spin at any site, flips, is calculated. The above mentioned variations and the probability of spin flip clearly distinguish between the dynamical phases formed by propagating magnetic wave and by standing magnetic wave in an Ising ferromagnet.
Higher-order phase transitions on financial markets
Kasprzak, A.; Kutner, R.; Perelló, J.; Masoliver, J.
2010-08-01
Statistical and thermodynamic properties of the anomalous multifractal structure of random interevent (or intertransaction) times were thoroughly studied by using the extended continuous-time random walk (CTRW) formalism of Montroll, Weiss, Scher, and Lax. Although this formalism is quite general (and can be applied to any interhuman communication with nontrivial priority), we consider it in the context of a financial market where heterogeneous agent activities can occur within a wide spectrum of time scales. As the main general consequence, we found (by additionally using the Saddle-Point Approximation) the scaling or power-dependent form of the partition function, Z(q'). It diverges for any negative scaling powers q' (which justifies the name anomalous) while for positive ones it shows the scaling with the general exponent τ(q'). This exponent is the nonanalytic (singular) or noninteger power of q', which is one of the pilar of higher-order phase transitions. In definition of the partition function we used the pausing-time distribution (PTD) as the central one, which takes the form of convolution (or superstatistics used, e.g. for describing turbulence as well as the financial market). Its integral kernel is given by the stretched exponential distribution (often used in disordered systems). This kernel extends both the exponential distribution assumed in the original version of the CTRW formalism (for description of the transient photocurrent measured in amorphous glassy material) as well as the Gaussian one sometimes used in this context (e.g. for diffusion of hydrogen in amorphous metals or for aging effects in glasses). Our most important finding is the third- and higher-order phase transitions, which can be roughly interpreted as transitions between the phase where high frequency trading is most visible and the phase defined by low frequency trading. The specific order of the phase transition directly depends upon the shape exponent α defining the stretched
A Transition to Metallic Hydrogen: Evidence of the Plasma Phase Transition
Silvera, Isaac; Zaghoo, Mohamed; Salamat, Ashkan
The insulator-metal transition in hydrogen is one of the most outstanding problems in condensed matter physics. The high-pressure metallic phase is now predicted to be liquid atomic from T =0 K to very high temperatures. We have conducted measurements of optical properties of hot dense hydrogen in the region of 1.1-1.7 Mbar and up to 2200 K in a diamond anvil cell using pulsed laser heating of the sample. We present evidence in two forms: a plateau in the heating curves (average laser power vs temperature) characteristic of a first-order phase transition with latent heat, and changes in transmittance and reflectance characteristic of a metal for temperatures above the plateau temperature. For thick films the reflectance saturates at ~0.5. The phase line of this transition has a negative slope in agreement with theories of the so-called plasma phase transition. The NSF, Grant DMR-1308641, the DOE Stockpile Stewardship Academic Alliance Program, Grant DE-FG52-10NA29656, and NASA Earth and Space Science Fellowship Program, Award NNX14AP17H supported this research.
Naumis, Gerardo G
2012-06-01
When a liquid melt is cooled, a glass or phase transition can be obtained depending on the cooling rate. Yet, this behavior has not been clearly captured in energy-landscape models. Here, a model is provided in which two key ingredients are considered in the landscape, metastable states and their multiplicity. Metastable states are considered as in two level system models. However, their multiplicity and topology allows a phase transition in the thermodynamic limit for slow cooling, while a transition to the glass is obtained for fast cooling. By solving the corresponding master equation, the minimal speed of cooling required to produce the glass is obtained as a function of the distribution of metastable states.
Wainwright, Carroll L.
2012-09-01
I present a numerical package (CosmoTransitions) for analyzing finite-temperature cosmological phase transitions driven by single or multiple scalar fields. The package analyzes the different vacua of a theory to determine their critical temperatures (where the vacuum energy levels are degenerate), their supercooling temperatures, and the bubble wall profiles which separate the phases and describe their tunneling dynamics. I introduce a new method of path deformation to find the profiles of both thin- and thick-walled bubbles. CosmoTransitions is freely available for public use.Program summaryProgram Title: CosmoTransitionsCatalogue identifier: AEML_v1_0Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEML_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 8775No. of bytes in distributed program, including test data, etc.: 621096Distribution format: tar.gzProgramming language: Python.Computer: Developed on a 2009 MacBook Pro. No computer-specific optimization was performed.Operating system: Designed and tested on Mac OS X 10.6.8. Compatible with any OS with Python installed.RAM: Approximately 50 MB, mostly for loading plotting packages.Classification: 1.9, 11.1.External routines: SciPy, NumPy, matplotLibNature of problem: I describe a program to analyze early-Universe finite-temperature phase transitions with multiple scalar fields. The goal is to analyze the phase structure of an input theory, determine the amount of supercooling at each phase transition, and find the bubble-wall profiles of the nucleated bubbles that drive the transitions.Solution method: To find the bubble-wall profile, the program assumes that tunneling happens along a fixed path in field space. This reduces the equations of motion to one dimension, which can then be solved using the overshoot
Catastrophic Antiphospholipid Syndrome
Directory of Open Access Journals (Sweden)
Rawhya R. El-Shereef
2016-01-01
Full Text Available This paper reports one case of successfully treated patients suffering from a rare entity, the catastrophic antiphospholipid syndrome (CAPS. Management of this patient is discussed in detail.
Habitability and cosmic catastrophes
Hanslmeier, Arnold; McKay, Christopher P
2008-01-01
Catastrophic cosmic events such as asteroid impacts appear in the range of some 100 million years and have drastically affected evolution. The author discusses whether and how such events could have occurred in recently found extrasolar planetary systems.
Structural phase transitions in boron carbide under stress
Korotaev, P.; Pokatashkin, P.; Yanilkin, A.
2016-01-01
Structural transitions in boron carbide B4C under stress were studied by means of first-principles molecular dynamics in the framework of density functional theory. The behavior depends strongly on degree of non-hydrostatic stress. Under hydrostatic stress continuous bending of the three-atom C-B-C chain was observed up to 70 GPa. The presence of non-hydrostatic stress activates abrupt reversible chain bending, which is displacement of the central boron atom in the chain with the formation of weak bonds between this atom and atoms in the nearby icosahedra. Such structural change can describe a possible reversible phase transition in dynamical loading experiments. High non-hydrostatic stress achieved in uniaxial loading leads to disordering of the initial structure. The formation of carbon chains is observed as one possible transition route.
Dynamic phase transitions in confined lubricant fluids under shear
Energy Technology Data Exchange (ETDEWEB)
Drummond, Carlos; Israelachvili, Jacob
2001-04-01
A surface force apparatus was used to measure the transient and steady-state friction forces between molecularly smooth mica surfaces confining thin films of squalane, C{sub 30}H{sub 62}, a saturated, branched hydrocarbon liquid. The dynamic friction ''phase diagram'' was determined under different shearing conditions, especially the transitions between stick-slip and smooth sliding ''states'' that exhibited a chaotic stick-slip regime. The apparently very different friction traces exhibited by simple spherical, linear, and branched hydrocarbon films under shear are shown to be due to the much longer relaxation times and characteristic length scales associated with transitions from rest to steady-state sliding, and vice versa, in the case of branched liquids. The physical reasons and tribological implications for the different types of transitions observed with spherical, linear, and branched fluids are discussed.
The Next Generation Transit Survey—Prototyping Phase
McCormac, J.; Pollacco, D.; Wheatley, P. J.; West, R. G.; Walker, S.; Bento, J.; Skillen, I.; Faedi, F.; Burleigh, M. R.; Casewell, S. L.; Chazelas, B.; Genolet, L.; Gibson, N. P.; Goad, M. R.; Lawrie, K. A.; Ryans, R.; Todd, I.; Udry, S.; Watson, C. A.
2017-02-01
We present the prototype telescope for the Next Generation Transit Survey, which was built in the UK in 2008/2009 and tested on La Palma in the Canary Islands in 2010. The goals for the prototype system were severalfold: to determine the level of systematic noise in an NGTS-like system; demonstrate that we can perform photometry at the (sub) millimagnitude level on transit timescales across a wide-field; show that it is possible to detect transiting super-Earth and Neptune-sized exoplanets and prove the technical feasibility of the proposed planet survey. We tested the system for around 100 nights and met each of the goals above. Several key areas for improvement were highlighted during the prototyping phase. They have been subsequently addressed in the final NGTS facility, which was recently commissioned at ESO Cerro Paranal, Chile.
Instabilities near the QCD phase transition in the holographic models
Gursoy, Umut; Shuryak, Edward
2013-01-01
The paper discusses phenomena close to the critical QCD temperature, using the holographic model. One issue studied is the overcooled high-T phase, in which we calculate quasi normal sound modes. We do not find instabilities associated with other first order phase transitions, but nevertheless observe drastic changes in sound propagation/dissipation. The rest of the paper considers a cluster of the high-T phase in the UV in coexistence with the low-T phase, in a simplified ansatz in which the wall separating them is positioned only in the holographic coordinate. This allows to find the force on the wall and classical motion of the cluster. When classical motion is forbidden, we evaluate tunneling probability through the remaining barrier.
Piezoelectric properties of rhombohedral ferroelectric materials with phase transition
Zhao, Xiaofang; Soh, A. K.
2015-12-01
The temporal evolution of domain structure and its piezoelectric behavior of ferroelectric material BaTiO3 during the transition process from rhombohedral to tetragonal phase under an applied electric field have been studied by employing Landau-Ginzburg theory and the phase-field method. The results obtained show that, during the transformation process, the intermediate phase was monoclinic MA phase, and several peak values of piezoelectric coefficient appeared at the stage where obvious change of domain pattern occurred. In addition, by comparing the cases of applied electric field with different frequencies, it was found that the maximum piezoelectric coefficient obtained decreased with increasing frequency value. These results are of great significance in tuning the properties of engineering domains in ferroelectrics, and could provide more fundamentals to the design of ferroelectric devices.
Phase transitions in Bergshoeff–Hohm–Townsend massive gravity
Ghodrati, Mahdis; Naseh, Ali
2017-04-01
We present the Hawking–Page phase diagrams in the Bergshoeff–Hohm–Townsend (BHT) massive gravity theory for different solutions, such as the phase transitions between vacuum \\text{Ad}{{\\text{S}}3} and BTZ black hole, warped \\text{Ad}{{\\text{S}}3} and warped BTZ black hole in grand canonical and in non-local/quadratic ensembles, Lifshitz black hole and the new hairy black hole solutions. We observe that except for the black holes in quadratic ensemble, for other cases in the non-chiral theory of BHT the phase diagrams are symmetric with respect to the direction of angular momentum, as we expected. We conclude that for presenting the phase diagrams of warped \\text{Ad}{{\\text{S}}3} black holes, only the grand canonical ensemble should be used.
Can large fermion chemical potentials suppress the electroweak phase transition ?
Quimbay, C; Hurtado, R; Quimbay, Carlos; Morales, John; Hurtado, Rafael
2000-01-01
We calculate the critical temperature $(T_c$) of the electroweak phase transition in the minimal standard model considering simultaneously temperature ($T$) and fermion chemical potential ($\\mu_f$) effects over the effective potential. The calculation is performed in the one-loop approximation to the effective potential at non-zero temperature using the real time formalism of the thermal field theory. We show that it exists a fermion chemical potential critical value ($\\mu_f^c$) for which the Higgs boson condensate vanishes at T=0. If $T$ and $\\mu_f$ effects are considered simultaneously, it is shown that for $\\mu_f \\geq \\mu_f^c$ then $T_c^2 \\leq 0$, implying that the electroweak phase transition might not take place.
Phase transitions in the $sdg$ interacting boson model
Van Isacker, P; Zerguine, S
2009-01-01
A geometric analysis of the $sdg$ interacting boson model is performed. A coherent-state is used in terms of three types of deformation: axial quadrupole ($\\beta_2$), axial hexadecapole ($\\beta_4$) and triaxial ($\\gamma_2$). The phase-transitional structure is established for a schematic $sdg$ hamiltonian which is intermediate between four dynamical symmetries of U(15), namely the spherical ${\\rm U}(5)\\otimes{\\rm U}(9)$, the (prolate and oblate) deformed ${\\rm SU}_\\pm(3)$ and the $\\gamma_2$-soft SO(15) limits. For realistic choices of the hamiltonian parameters the resulting phase diagram has properties close to what is obtained in the $sd$ version of the model and, in particular, no transition towards a stable triaxial shape is found.
Geometry of dynamics, Lyapunov exponents and phase transitions
Caiani, L; Clementi, C; Pettini, M; Caiani, Lando; Casetti, Lapo; Clementi, Cecilia; Pettini, Marco
1997-01-01
The Hamiltonian dynamics of classical planar Heisenberg model is numerically investigated in two and three dimensions. By considering the dynamics as a geodesic flow on a suitable Riemannian manifold, it is possible to analytically estimate the largest Lyapunov exponent in terms of some curvature fluctuations. The agreement between numerical and analytical values for Lyapunov exponents is very good in a wide range of temperatures. Moreover, in the three dimensional case, in correspondence with the second order phase transition, the curvature fluctuations exibit a singular behaviour which is reproduced in an abstract geometric model suggesting that the phase transition might correspond to a change in the topology of the manifold whose geodesics are the motions of the system.
Statistical mechanics of soft-boson phase transitions
Gupta, Arun K.; Hill, Christopher T.; Holman, Richard; Kolb, Edward W.
1991-01-01
The existence of structure on large (100 Mpc) scales, and limits to anisotropies in the cosmic microwave background radiation (CMBR), have imperiled models of structure formation based solely upon the standard cold dark matter scenario. Novel scenarios, which may be compatible with large scale structure and small CMBR anisotropies, invoke nonlinear fluctuations in the density appearing after recombination, accomplished via the use of late time phase transitions involving ultralow mass scalar bosons. Herein, the statistical mechanics are studied of such phase transitions in several models involving naturally ultralow mass pseudo-Nambu-Goldstone bosons (pNGB's). These models can exhibit several interesting effects at high temperature, which is believed to be the most general possibilities for pNGB's.
Gravitational Waves From a Dark (Twin) Phase Transition
Schwaller, Pedro
2015-01-01
In this work, we show that a large class of models with a composite dark sector undergo a strong first order phase transition in the early universe, which could lead to a detectable gravitational wave signal. We summarise the basic conditions for a strong first order phase transition for SU(N) dark sectors with n_f flavours, calculate the gravitational wave spectrum and show that, depending on the dark confinement scale, it can be detected at eLISA or in pulsar timing array experiments. The gravitational wave signal provides a unique test of the gravitational interactions of a dark sector, and we discuss the complementarity with conventional searches for new dark sectors. The discussion includes Twin Higgs and SIMP models as well as symmetric and asymmetric composite dark matter scenarios.
Nanoscale Thermotropic Phase Transitions Enhance Photothermal Microscopy Signals
Parra-Vasquez, A Nicholas G; Cognet, Laurent; Lounis, Brahim; 10.1021/jz300369d
2012-01-01
The photothermal heterodyne imaging technique enabled studies of individual weakly absorbing nano-objects in various environments. It uses a photo-induced change in the refractive index of the environment. Taking advantage of the dramatic index of refraction change occurring around a thermotropic liquid crystalline phase transition, we demonstrate a 40-fold signal-to-noise ratio enhancement for gold nanoparticles imaged in 4-Cyano-4'-pentylbiphenyl (5CB) liquid crystals over those in a water environment. We studied the photothermal signal as a function of probe laser polarization, heating power, and sample temperature quantifying the optimal enhancement. This study established photothermal microscopy as a valuable technique for inducing and/or detecting local phase transitions at the nanometer scales.
Perceptions of healthy eating in transitional phases of life
DEFF Research Database (Denmark)
Bech-Larsen, Tino; Kazbare, Laura
2014-01-01
Purpose - Although adolescents and older adults are often targets for nutritional change interventions, little has been done to explore how people in these transitional life phases perceive the matter themselves. The purpose of the study reported in this article is to explore and compare...... adolescents’ and older adults’ own perceptions of the barriers and facilitators of a change towards healthier eating. Design/methodology/approach - This study design consisted of four focus groups that were conducted with adolescents and older adults to identify their health orientations, and their expected......). Originality/value - The study and findings reported in this article contribute by providing the first steps towards a better understanding of how social cognition and self-efficacy perceptions related to healthy eating develop in the transitional phases of adolescence and older adulthood. In order...
Collapse of Flow: Probing the Order of the Phase Transition
Stöcker, Horst
2007-01-01
We discuss the present collective flow signals for the phase transition to the quark-gluon plasma (QGP) and the collective flow as a barometer for the equation of state (EoS). We emphasize the importance of the flow excitation function from 1 to $50 A$ GeV: here the hydrodynamic model has predicted the collapse of the $v_1$-flow at $\\sim 10 A$ GeV and of the $v_2$-flow at $\\sim 40 A$ GeV. In the latter case, this has recently been observed by the NA49 collaboration. Since hadronic rescattering models predict much larger flow than observed at this energy, we interpret this observation as potential evidence for a first order phase transition at high baryon density $\\rho_B$.
Holographic phase transition in the Gauss-Bonnet gravity
Zeng, Xiao-Xiong; Li, Li-Fang
2016-01-01
The Van der Waals-like phase transition is observed in temperature-thermal entropy plane in spherically symmetric charged Gauss-Bonnet-AdS black hole background. In terms of AdS/CFT, the non-local observables such as holographic entanglement entropy, Wilson loop, and two point correlation function of very heavy operators in the field theory dual to spherically symmetric charged Gauss-Bonnet-AdS black hole have been investigated. All of them exhibit the Van der Waals-like phase transition for a fixed charge parameter or Gauss-Bonnet parameter in such gravity background. Further, with choosing various values of charge or Gauss-Bonnet parameter, the equal area law and the critical exponent of the heat capacity are found to be consistent with that in temperature-thermal entropy plane.
Phase transitions in insertion electrodes for lithium batteries
Energy Technology Data Exchange (ETDEWEB)
Thackeray, M. M.
2000-02-02
Phase transitions that occur during lithium insertion into layered and framework structures are discussed in the context of their application as positive and negative electrodes in lithium-ion batteries. The discussion is focused on the two-dimensional structures of graphite, LiNi{sub 1{minus}x}M{sub x}O{sub 2} (M = Co, Ti and Mg), and Li{sub 1.2}V{sub 3}O{sub 8}; examples of framework structures with a three-dimensional interstitial space for Li{sup +}-ion transport include the spinel oxides and intermetallic compounds with zinc-blende-type structures. The phase transitions are discussed in terms of their tolerance to lithium insertion and extraction and to the chemical stability of the electrodes in the cell environment.
Network Inoculation: Heteroclinics and phase transitions in an epidemic model
Yang, Hui; Gross, Thilo
2016-01-01
In epidemiological modelling, dynamics on networks, and in particular adaptive and heterogeneous networks have recently received much interest. Here we present a detailed analysis of a previously proposed model that combines heterogeneity in the individuals with adaptive rewiring of the network structure in response to a disease. We show that in this model qualitative changes in the dynamics occur in two phase transitions. In a macroscopic description one of these corresponds to a local bifurcation whereas the other one corresponds to a non-local heteroclinic bifurcation. This model thus provides a rare example of a system where a phase transition is caused by a non-local bifurcation, while both micro- and macro-level dynamics are accessible to mathematical analysis. The bifurcation points mark the onset of a behaviour that we call network inoculation. In the respective parameter region exposure of the system to a pathogen will lead to an outbreak that collapses, but leaves the network in a configuration wher...
Holographic insulator/superconductor phase transition with Weyl corrections
Zhao, Zixu; Jing, Jiliang
2012-01-01
We analytically investigate the phase transition between the holographic insulator and superconductor with Weyl corrections by using the variational method for the Sturm-Liouville eigenvalue problem. We find that similar to the curvature corrections, in p-wave model, the higher Weyl couplings make the insulator/superconductor phase transition harder to occur. However, in s-wave case the Weyl corrections do not influence the critical chemical potential, which is in contrast to the effect caused by the curvature corrections. Moreover, we observe that the Weyl corrections will not affect the critical phenomena and the critical exponent of the system always takes the mean-field value in both models. Our analytic results are found to be in good agreement with the numerical findings.
Analytical Studies on Holographic Insulator/Superconductor Phase Transitions
Cai, Rong-Gen; Zhang, Hai-Qing
2011-01-01
We investigate the analytical properties of the s-wave and p-wave holographic insulator/superconductor phase transitions at zero temperature. In the probe limit, we analytically calculate the critical chemical potentials at which the insulator/superconductor phase transition occurs. Those resulting analytical values perfectly match the previous numerical values. We also study the relations between the condensation values and the chemical potentials near the critical point. We find that the critical exponent for condensation operator is 1/2 for both models. The linear relations between the charge density and the chemical potential near the critical point are also deduced in this paper, which are qualitatively consistent with the previous numerical results.
QCD deconfinement phase transitions and collapsing quark stars
Bednarek, I; Manka, R; Bednarek, Ilona; Biesiada, Marek; Manka, Ryszard
1996-01-01
In this paper we discuss the QCD phase-transitions in the nontopological soliton model of quark confinement and explore possible astrophysical consequences. Our key idea is to look at quark stars (which are believed to exist since the quark matter is energetically preferred over the ordinary matter) from the point of view of soliton model. We propose that the phase transition taking place during the core collapse of massive evolved star may provide a new physical effect not taken into account in modeling the supernova explosions. We also point out the possibility that merging quark stars may produce gamma-ray bursts energetic enough to be at cosmological distances. Our idea based on the finite-temperature nontopologiocal soliton model overcomes major difficulties present in neutron star merger scenario --- the baryon loading problem and nonthermal spectra of the bursts.
The electroweak phase transition in minimal supergravity models
Nanopoulos, Dimitri V
1994-01-01
We have explored the electroweak phase transition in minimal supergravity models by extending previous analysis of the one-loop Higgs potential to include finite temperature effects. Minimal supergravity is characterized by two higgs doublets at the electroweak scale, gauge coupling unification, and universal soft-SUSY breaking at the unification scale. We have searched for the allowed parameter space that avoids washout of baryon number via unsuppressed anomalous Electroweak sphaleron processes after the phase transition. This requirement imposes strong constraints on the Higgs sector. With respect to weak scale baryogenesis, we find that the generic MSSM is {\\it not} phenomenologically acceptable, and show that the additional experimental and consistency constraints of minimal supergravity restricts the mass of the lightest CP-even Higgs even further to $m_h\\lsim 32\\GeV$ (at one loop), also in conflict with experiment. Thus, if supergravity is to allow for baryogenesis via any other mechanism above the weak...
The Growth of Bubbles in Cosmological Phase Transitions
Ignatius, J; Kurki-Suonio, H; Laine, Mikko
1994-01-01
We study how bubbles grow after the initial nucleation event in generic first-order cosmological phase transitions characterised by the values of latent heat, interface tension and correlation length, and driven by a scalar order parameter $\\phi$. Equations coupling $\\phi$ and the fluid variables $v$ and $T$ and depending on a dissipative constant $\\Gamma$ are derived and solved numerically in the 1+1 dimensional case starting from a slightly deformed critical bubble configuration. Parameters corresponding to QCD and electroweak phase transitions are chosen and the whole history of the bubble with formation of combustion and shock fronts is computed as a function of $\\Gamma$. Both deflagrations and detonations can appear depending on the values of the parameters. Reheating due to collisions of bubbles is also computed.
Benford's Law: Detection of Quantum Phase Transitions similarly as Earthquakes
De, Aditi Sen
2011-01-01
More than a century earlier, it was predicted that the first significant digit appearing in a data, be it from natural sciences or from some mathematical series, will be nonuniformly distributed, with the number one appearing with the highest frequency. This law goes by the name of Benford's law. It has been observed to hold for data from a huge variety of sources, ranging from earthquakes to infectious disease cases. Quantum phase transitions are cooperative phenomena where qualitative changes occur in physical quantities of a many-body system at zero temperature. We find that Benford's law can be applied to detect quantum phase transitions in a way that is very similar to how it can distinguish earthquakes from background noise. Being certainly of very different physical origins, seismic activity and quantum cooperative phenomena may therefore be detected by similar methods. The result may provide methods to overcome the limitations associated with precise measurements in experiments.
Scaling of the local quantum uncertainty at quantum phase transitions
Energy Technology Data Exchange (ETDEWEB)
Coulamy, I.B.; Warnes, J.H.; Sarandy, M.S., E-mail: msarandy@if.uff.br; Saguia, A.
2016-04-29
We investigate the local quantum uncertainty (LQU) between a block of L qubits and one single qubit in a composite system of n qubits driven through a quantum phase transition (QPT). A first-order QPT is analytically considered through a Hamiltonian implementation of the quantum search. In the case of second-order QPTs, we consider the transverse-field Ising chain via a numerical analysis through density matrix renormalization group. For both cases, we compute the LQU for finite-sizes as a function of L and of the coupling parameter, analyzing its pronounced behavior at the QPT. - Highlights: • LQU is suitable for the analysis of block correlations. • LQU exhibits pronounced behavior at quantum phase transitions. • LQU exponentially saturates in the quantum search. • Concavity of LQU indicates criticality in the Ising chain.
Hawking–Page phase transition in new massive gravity
Directory of Open Access Journals (Sweden)
Shao-Jun Zhang
2015-07-01
Full Text Available We consider Hawking–Page phase transition between the BTZ black hole with M≥0 and the thermal soliton with M=−1 in new massive gravity. By comparing the on-shell free energies, we can see that there exists a critical temperature. The thermal soliton is more probable than the black hole below the critical temperature while the black hole is more probable than the thermal soliton above the critical temperature. By consistently constructing the off-shell free energies taking into account the conical singularity, we show that there exist infinite non-equilibrium states connecting the BTZ black hole and the thermal soliton, so that they provide a picture of continuous evolution of the phase transition.
Topological String in Quantum-Chromodynamical Chiral Phase Transitions
Institute of Scientific and Technical Information of China (English)
LI Yun-De
2005-01-01
@@ It is pointed out that if in heavy ion collision processes, the quark-gluon plasma SU(2) chiral phase transition really takes place and the phase transition is a second order. Then the topological string, i.e., the π string, will be formed. The main effect of this phenomenon is that there will be a number of pions produced by decay of the π string in the final state. The pions from the decay of the π string lead to the same effect of decreasing the Hanbury-Brown-Twiss peak in two-pion spectra which is just as that of the long-lived hadronic resonances.At relativistic heavy-ion collision and large hadron collision energies, it is expected that the factors are about α～ 0.7 - 0.9 and α～ 0.6 - 0.85, respectively.
Volume phase transitions of cholesteric liquid crystalline gels
Energy Technology Data Exchange (ETDEWEB)
Matsuyama, Akihiko, E-mail: matuyama@bio.kyutech.ac.jp [Department of Bioscience and Bioinformatics, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Kawazu 680-4, Iizuka, Fukuoka 820-8502 (Japan)
2015-05-07
We present a mean field theory to describe anisotropic deformations of a cholesteric elastomer without solvent molecules and a cholesteric liquid crystalline gel immersed in isotropic solvents at a thermal equilibrium state. Based on the neoclassical rubber theory of nematic elastomers, we derive an elastic energy and a twist distortion energy, which are important to determine the shape of a cholesteric elastomer (or gel). We demonstrate that when the elastic energy dominates in the free energy, the cholesteric elastomer causes a spontaneous compression in the pitch axis and elongates along the director on the plane perpendicular to the pitch axis. Our theory can qualitatively describe the experimental results of a cholesteric elastomer. We also predict the first-order volume phase transitions and anisotropic deformations of a gel at the cholesteric-isotropic phase transition temperature. Depending on a chirality of a gel, we find a prolate or oblate shape of cholesteric gels.
Complex Nonlinearity Chaos, Phase Transitions, Topology Change and Path Integrals
Ivancevic, Vladimir G
2008-01-01
Complex Nonlinearity: Chaos, Phase Transitions, Topology Change and Path Integrals is a book about prediction & control of general nonlinear and chaotic dynamics of high-dimensional complex systems of various physical and non-physical nature and their underpinning geometro-topological change. The book starts with a textbook-like expose on nonlinear dynamics, attractors and chaos, both temporal and spatio-temporal, including modern techniques of chaos–control. Chapter 2 turns to the edge of chaos, in the form of phase transitions (equilibrium and non-equilibrium, oscillatory, fractal and noise-induced), as well as the related field of synergetics. While the natural stage for linear dynamics comprises of flat, Euclidean geometry (with the corresponding calculation tools from linear algebra and analysis), the natural stage for nonlinear dynamics is curved, Riemannian geometry (with the corresponding tools from nonlinear, tensor algebra and analysis). The extreme nonlinearity – chaos – corresponds to th...
Quantum Phase Transitions in Anti-ferromagnetic Planar Cubic Lattices
Wellard, C J; Wellard, Cameron; Orus, Roman
2004-01-01
Motivated by its relation to an NP-hard problem we analyze the ground state properties of anti-ferromagnetic Ising-spin networks in planar cubic lattices under the action of homogeneous transverse and longitudinal magnetic fields. We consider different instances of the cubic geometry and find a set of quantum phase transitions for each one of the systems, which we characterize by means of entanglement behavior and majorization theory. Entanglement scaling at the critical region is in agreement with results arising from conformal symmetry, therefore even the simplest planar systems can display very large amounts of quantum correlation. No conclusion can be made as to the scaling behavior of the minimum energy gap, with the data allowing equally good fits to exponential and power law decays. Analysis of entanglement and especially of majorization instead of the energy spectrum proves to be a good way of detecting quantum phase transitions in highly frustrated configurations.
Electron star birth: a continuous phase transition at nonzero density.
Hartnoll, Sean A; Petrov, Pavel
2011-03-25
We show that charged black holes in anti-de Sitter spacetime can undergo a third-order phase transition at a critical temperature in the presence of charged fermions. In the low temperature phase, a fraction of the charge is carried by a fermion fluid located a finite distance from the black hole. In the zero temperature limit, the black hole is no longer present and all charge is sourced by the fermions. The solutions exhibit the low temperature entropy density scaling s~T(2/z) anticipated from the emergent IR criticality of recently discussed electron stars.
Pressure-induced phase transition in GaN nanocrystals
Cui, Q; Zhang, W; Wang, X; Zhang, J; Cui, T; Xie, Y; Liu, J; Zou, G
2002-01-01
High-pressure in situ energy-dispersive x-ray diffraction experiments on GaN nanocrystals with 50 nm diameter have been carried out using a synchrotron x-ray source and a diamond-anvil cell up to about 79 GPa at room temperature. A pressure-induced first-order structural phase transition from the wurtzite-type structure to the rock-salt-type structure starts at about 48.8 GPa. The rock-salt-type phase persists to the highest pressure in our experimental range.
SOLID PHASE TRANSITION OF SYNDIOTACTIC POLYSTYRENE IN SUPERCRITICAL CO2
Institute of Scientific and Technical Information of China (English)
Yu-ying Li; Jia-song He
2002-01-01
Solid phase transition of the a form crystals to the β form crystals in syndiotactic polystyrene (sPS) samples has occurred in supercritical CO2. This transformation is different from those detected under other conditions. The effects of some factors (e.g. time, temperature, and pressure) on the solid phase transformation of sPS in supercritical CO2 were analyzed in detail. Experimental results show that longer time, higher temperature or higher pressure favors the transformation of the α form crystals to the β form crystals.
Quantum phase transition induced by real-space topology
Li, C.; Zhang, G.; Lin, S.; Song, Z.
2016-12-01
A quantum phase transition (QPT), including both topological and symmetry breaking types, is usually induced by the change of global parameters, such as external fields or global coupling constants. In this work, we demonstrate the existence of QPT induced by the real-space topology of the system. We investigate the groundstate properties of the tight-binding model on a honeycomb lattice with the torus geometry based on exact results. It is shown that the ground state experiences a second-order QPT, exhibiting the scaling behavior, when the torus switches to a tube, which reveals the connection between quantum phase and the real-space topology of the system.
Noncongruence of phase transitions in strongly interacting matter
Hempel, Matthias; Schramm, Stefan; Iosilevskiy, Igor
2015-01-01
First-order phase transitions (PTs) with more than one globally conserved charge, so-called noncongruent PTs, have characteristic differences compared to congruent PTs (e.g., dimensionality of phase diagrams and location of critical points and endpoints). Here we discuss the noncongruent features of the QCD PT and compare it with the nuclear liquid-gas (LG) PT, for symmetric and asymmetric matter in heavy-ion collisions and neutron stars. In addition, we have identified a principle difference between the LG and the QCD PT: they have opposite slopes in the pressure-temperature plane.
Thermodynamic geometry, phase transitions, and the Widom line.
Ruppeiner, G; Sahay, A; Sarkar, T; Sengupta, G
2012-11-01
A microscopic characterization, based on the thermodynamic curvature R, is proposed for first-order liquid-gas phase transitions. Near the critical point, where R is proportional to the correlation volume ξ(3), we propose that R takes the same value in the coexisting phases. This proposal allows a determination of the liquid-gas coexistence curve with no use of the problematic Maxwell equal area construction. Furthermore, |R| ~ ξ(3) allows a direct determination of the Widom line in the supercritical regime. We illustrate with input from the van der Waals model and the National Institute of Standards and Technology Chemistry WebBook.
Phase transition of light on complex quantum networks.
Halu, Arda; Garnerone, Silvano; Vezzani, Alessandro; Bianconi, Ginestra
2013-02-01
Recent advances in quantum optics and atomic physics allow for an unprecedented level of control over light-matter interactions, which can be exploited to investigate new physical phenomena. In this work we are interested in the role played by the topology of quantum networks describing coupled optical cavities and local atomic degrees of freedom. In particular, using a mean-field approximation, we study the phase diagram of the Jaynes-Cummings-Hubbard model on complex networks topologies, and we characterize the transition between a Mott-like phase of localized polaritons and a superfluid phase. We found that, for complex topologies, the phase diagram is nontrivial and well defined in the thermodynamic limit only if the hopping coefficient scales like the inverse of the maximal eigenvalue of the adjacency matrix of the network. Furthermore we provide numerical evidences that, for some complex network topologies, this scaling implies an asymptotically vanishing hopping coefficient in the limit of large network sizes. The latter result suggests the interesting possibility of observing quantum phase transitions of light on complex quantum networks even with very small couplings between the optical cavities.
AdS Monopole Black Hole and Phase Transition
Miyashita, Shoichiro
2016-01-01
We study the Einstein-SO(3)Yang-Mills-Higgs system with a negative cosmological constant, and find the monopole black hole solutions as well as the trivial Reissner-Nordstr\\"{o}m black hole. We discuss thermodynamical stability of the monopole black hole in an isolated system. We expect a phase transition between those two black holes when the mass of a black hole increases or decreases. The type of phase transition depends on the cosmological constant $\\Lambda$ as well as the vacuum expectation value $v$ and the coupling constant $\\lambda$ of the Higgs field. Fixing $\\lambda$ small, we find there are two critical values of the cosmological constant $\\Lambda_{\\rm cr (1)}(v)$ and $\\Lambda_{\\rm cr(2)}(v)$, which depend on $v$. If $\\Lambda_{\\rm cr(1)}(v)<\\Lambda (<0)$, we find the first order transition, while if $\\Lambda_{\\rm cr(2)}(v)<\\Lambda<\\Lambda_{\\rm cr(1)}(v)$, the transition becomes second order. For the case of $\\Lambda_{b}(v)<\\Lambda<\\Lambda_{\\rm (2)}(v)$, we again find the first ord...
Phase transitions in community detection: A solvable toy model
Ver Steeg, Greg; Moore, Cristopher; Galstyan, Aram; Allahverdyan, Armen
2014-05-01
Recently, it was shown that there is a phase transition in the community detection problem. This transition was first computed using the cavity method, and has been proved rigorously in the case of q = 2 groups. However, analytic calculations using the cavity method are challenging since they require us to understand probability distributions of messages. We study analogous transitions in the so-called “zero-temperature inference” model, where this distribution is supported only on the most likely messages. Furthermore, whenever several messages are equally likely, we break the tie by choosing among them with equal probability, corresponding to an infinitesimal random external field. While the resulting analysis overestimates the thresholds, it reproduces some of the qualitative features of the system. It predicts a first-order detectability transition whenever q > 2 (as opposed to q > 4 according to the finite-temperature cavity method). It also has a regime analogous to the “hard but detectable” phase, where the community structure can be recovered, but only when the initial messages are sufficiently accurate. Finally, we study a semisupervised setting where we are given the correct labels for a fraction ρ of the nodes. For q > 2, we find a regime where the accuracy jumps discontinuously at a critical value of ρ.
New Cyclic Voltammetry Method for Examining Phase Transitions: Simulated Results
2006-01-01
We propose a new experimental technique for cyclic voltammetry, based on the first-order reversal curve (FORC) method for analysis of systems undergoing hysteresis. The advantages of this electrochemical FORC (EC-FORC) technique are demonstrated by applying it to dynamical models of electrochemical adsorption. The method can not only differentiate between discontinuous and continuous phase transitions, but can also quite accurately recover equilibrium behavior from dynamic analysis of systems...
Diffused phase transition in fine-grained bismuth vanadate ceramics
Shantha, K; Varma, KBR
1999-01-01
Nanocrystalline powders of ferroelectric bismuth vanadate, Bi4V2O11 (n-BiV), with crystallite size less than 50 nm, were obtained by mechanical milling of a stoichiometric mixture of bismuth oxide and vanadium pentoxide. The n-BiV powders on sintering yielded high-density, fine-grained ceramics with improved dielectric and polar characteristics. Dielectric studies on samples obtained from milled powders indicated that the ferroelectric-to-paraelectric phase transition temperature is strongly ...
Electroweak Phase Transitions in left-right symmetric models
Barenboim, G; Barenboim, Gabriela; Rius, Nuria
1998-01-01
We study the finite-temperature effective potential of minimal left-right symmetric models containing a bidoublet and two triplets in the scalar sector. We perform a numerical analysis of the parameter space compatible We perform a numerical analysis of the parameter space compatible with the requirement that baryon asymmetry is not washed out by sphaleron processes after the electroweak phase transition. We find that the spectrum of scalar particles for these acceptable cases is consistent with present experimental bounds.
Sinai Diffusion at Quasi-1D Topological Phase Transitions
Bagrets, Dmitry; Altland, Alexander; Kamenev, Alex
2016-11-01
We consider critical quantum transport in disordered topological quantum wires at the transition between phases with different topological indices. Focusing on the example of thermal transport in class D ("Majorana") quantum wires, we identify a transport universality class distinguished for anomalous retardation in the propagation of excitations—a quantum generalization of Sinai diffusion. We discuss the expected manifestations of this transport mechanism for heat propagation in topological superconductors near criticality and provide a microscopic theory explaining the phenomenon.
Topology and Phase Transitions in the Little-Parks Experiment
Berger, Jorge; Rubinstein, Jacob
1996-01-01
This is an analytic study of the problem of transitions between normal and superconducting phases for a sample which encloses a magnetic flux. A preliminary study of this problem, based on numerical minimization of the free energy for a particular form of the thickness of the sample, was published in Phys. Rev. Lett. {\\bf 75}, 320 (1995). For a sample of uniform thickness the order parameter is uniform, but even infinitesimal deviations from uniform thickness give rise to a singly connected s...
Possible shape phase transition in the heavy Kr isotopes
Energy Technology Data Exchange (ETDEWEB)
Bucurescu, D.; Constantinescu, G.; Cutoiu, D.; Ivascu, M.; Zamfir, N.V. (Institutul de Fizica si Inginerie Nucleara, Bucharest (Romania))
1981-06-01
Potential energy surfaces of Kr isotopes computed in the variables (epsilon,..gamma..) are presented. They account qualitatively for the main features observed experimentally for the lighter isotopes and predict that a shape phase transition, similar to that known for the heavy (A of the order of 100) Sr and Zr nuclei, should be observed in the neutron-rich isotopes between the neutron numbers 58 and 60.
PHASE TRANSITION PROPERTIES OF A TWO COMPONENT FINITE MAGNETIC SUPERLATTICE
Institute of Scientific and Technical Information of China (English)
WANG XIAO-GUANG; LIU NING-NING; PAN SHAO-HUA; YANG GUO-ZHEN
2000-01-01
We study an (l, n) finite superlattice, which consists of two alternative magnetic materials(components) of l and n atomic layers, respectively. Based on the Ising model, we examine the phase transition properties of the magnetic superlattice. By transfer matrix method we derive the equation for Curie temperature of the superlattice. Numerical results are obtained for the dependence of Curie temperature on the thickness and exchange constants of the superlattice.
Nonlinear clustering during the BEC dark matter phase transition
Energy Technology Data Exchange (ETDEWEB)
Freitas, Rodolfo C. de [Universidade Federal do Espirito Santo, Vitoria (Brazil); Ciencia e Tecnologia do Espirito Santo, Instituto Federal de Educacao, Vitoria (Brazil); Velten, Hermano [Universidade Federal do Espirito Santo, Vitoria (Brazil); Aix Marseille Universite, UMR 7332, CPT, Marseille (France)
2015-12-15
Spherical collapse of the Bose-Einstein condensate (BEC) dark matter model is studied in the Thomas-Fermi approximation. The evolution of the overdensity of the collapsed region and its expansion rate are calculated for two scenarios. We consider the case of a sharp phase transition (which happens when the critical temperature is reached) from the normal dark matter state to the condensate one and the case of a smooth first order phase transition where there is a continuous conversion of ''normal'' dark matter to the BEC phase. We present numerical results for the physics of the collapse for a wide range of the model's space parameter, i.e. the mass of the scalar particle m{sub χ} and the scattering length l{sub s}. We show the dependence of the transition redshift on m{sub χ} and l{sub s}. Since small scales collapse earlier and eventually before the BEC phase transition, the evolution of collapsing halos in this limit is indeed the same in both the CDM and the BEC models. Differences are expected to appear only on the largest astrophysical scales. However, we argue that the BEC model is almost indistinguishable from the usual dark matter scenario concerning the evolution of nonlinear perturbations above typical clusters scales, i.e., >or similar 10{sup 14}M{sub s}un. This provides an analytical confirmation for recent results from cosmological numerical simulations (Schive et al., Nat Phys 10:496, 2014). (orig.)
Phase Transition of Spin-Peierls Systems with Impurities
Institute of Scientific and Technical Information of China (English)
XU Bo-Wei; DING Guo-Hui; YE Fei
2000-01-01
The quasi-one-dimensional spin-Peierls(SP) systems with impurities are studied in their bosonized form. The spins of the dimerized state are bounded into singlets with an SP gap, while the impurities of doped systems will induce fluctuations of the coupling strength between the spins at different sites and break some pairs of spin singlets. The doping suppresses the dimerized SP state and induces a Kosterlitz-Thouless phase transition from the dimerized state into the undimerized one.
Phase transition of p-adic Ising λ-model
Energy Technology Data Exchange (ETDEWEB)
Dogan, Mutlay; Akın, Hasan [Department of Mathematics, Faculty of Education, Zirve University, Gaziantep, TR27260 (Turkey); Mukhamedov, Farrukh [Department of Computational & Theoretical Sciences Faculty of Science, International Islamic University Malaysia P.O. Box, 141, 25710, Kuantan Pahang (Malaysia)
2015-09-18
We consider an interaction of the nearest-neighbors and next nearest-neighbors for the mixed type p-adic λ-model with spin values (−1, +1) on a Cayley tree of order two. In the previous work we have proved the existence of the p-adic Gibbs measure for the model. In this work we have proved the existence of the phase transition occurs for the model.
Phase transition in tumor growth: I avascular development
Izquierdo-Kulich, E.; Rebelo, I.; Tejera, E.; Nieto-Villar, J. M.
2013-12-01
We propose a mechanism for avascular tumor growth based on a simple chemical network. This model presents a logistic behavior and shows a “second order” phase transition. We prove the fractal origin of the empirical logistics and Gompertz constant and its relation to mitosis and apoptosis rate. Finally, the thermodynamics framework developed demonstrates the entropy production rate as a Lyapunov function during avascular tumor growth.
The Quantum Space Phase Transitions for Particles and Force Fields
Directory of Open Access Journals (Sweden)
Chung D.-Y.
2006-07-01
Full Text Available We introduce a phenomenological formalism in which the space structure is treated in terms of attachment space and detachment space. Attachment space attaches to an object, while detachment space detaches from the object. The combination of these spaces results in three quantum space phases: binary partition space, miscible space and binary lattice space. Binary lattice space consists of repetitive units of alternative attachment space and detachment space. In miscible space, attachment space is miscible to detachment space, and there is no separation between attachment space and detachment spaces. In binary partition space, detachment space and attachment space are in two separat continuous regions. The transition from wavefunction to the collapse of wavefuction under interference becomes the quantum space phase transition from binary lattice space to miscible space. At extremely conditions, the gauge boson force field undergoes a quantum space phase transition to a "hedge boson force field", consisting of a "vacuum" core surrounded by a hedge boson shell, like a bubble with boundary.
Deformation Behavior across the Zircon-Scheelite Phase Transition.
Yue, Binbin; Hong, Fang; Merkel, Sébastien; Tan, Dayong; Yan, Jinyuan; Chen, Bin; Mao, Ho-Kwang
2016-09-23
The pressure effects on plastic deformation and phase transformation mechanisms of materials are of great importance to both Earth science and technological applications. Zircon-type materials are abundant in both nature and the industrial field; however, there is still no in situ study of their deformation behavior. Here, by employing radial x-ray diffraction in a diamond anvil cell, we investigate the dislocation-induced texture evolution of zircon-type gadolinium vanadate (GdVO_{4}) in situ under pressure and across its phase transitions to its high-pressure polymorphs. Zircon-type GdVO_{4} develops a (001) compression texture associated with dominant slip along ⟨100⟩{001} starting from 5 GPa. This (001) texture transforms into a (110) texture during the zircon-scheelite phase transition. Our observation demonstrates a martensitic mechanism for the zircon-scheelite transformation. This work will help us understand the local deformation history in the upper mantle and transition zone and provides fundamental guidance on material design and processing for zircon-type materials.
Phase transition for gluon field: a qualitative analysis
Dzhunushaliev, Vladimir
2012-01-01
The phase transition for SU(3) gauge field (without quarks) is considered. It is shown that the phase transition is due to the fact that at high temperatures the partition function should be calculated as for a gas of gluons, whereas at low temperatures as the sum over energy levels of correlated quantum states of SU(3) gauge field. A correlated quantum state for strongly interacting fields is defined as a nonperturbative quantum state of strongly interacting fields. The energy spectrum of these quantum states are discrete one. A lower bound of the phase transition temperature by comparing of the average energy for the perturbative and nonperturbative regimes is estimated (for glueball being in thermal equilibrium with the thermostat). It is shown that this quantity is associated with a mass gap. In a scalar model of glueball its energy is calculated. It is shown that this energy is the mass gap. If we set the glueball mass $ \\approx 1.5 \\cdot 10^3$ Mev then it is found that the corresponding value of couplin...
Phase transitions for information diffusion in random clustered networks
Lim, Sungsu; Shin, Joongbo; Kwak, Namju; Jung, Kyomin
2016-09-01
We study the conditions for the phase transitions of information diffusion in complex networks. Using the random clustered network model, a generalisation of the Chung-Lu random network model incorporating clustering, we examine the effect of clustering under the Susceptible-Infected-Recovered (SIR) epidemic diffusion model with heterogeneous contact rates. For this purpose, we exploit the branching process to analyse information diffusion in random unclustered networks with arbitrary contact rates, and provide novel iterative algorithms for estimating the conditions and sizes of global cascades, respectively. Showing that a random clustered network can be mapped into a factor graph, which is a locally tree-like structure, we successfully extend our analysis to random clustered networks with heterogeneous contact rates. We then identify the conditions for phase transitions of information diffusion using our method. Interestingly, for various contact rates, we prove that random clustered networks with higher clustering coefficients have strictly lower phase transition points for any given degree sequence. Finally, we confirm our analytical results with numerical simulations of both synthetically-generated and real-world networks.
Conformal phase transition as a new perspective on conventional superconductors
Energy Technology Data Exchange (ETDEWEB)
Nogueira, Flavio [Theoretische Physik III, Ruhr-Universitaet Bochum (Germany); Sudbo, Asle [Dept. of Physics, Norwegian University of Science and Technology (Norway)
2015-07-01
We argue that the phase transition in strong type I superconductors features charged fluctuations, meaning that it is essentially driven by thermal fluctuations of the magnetic field. This is simply a consequence of the small value of the Ginzburg parameter in the deep type I regime. We substantiate this conclusion by a generalization of the Ginzburg criterion to include charged fluctuations. Finally, we demonstrate by means of a renormalization group analysis that the correlation length actually does not obey a power law as function of T-T{sub c}. Rather it features an essential singularity at T{sub c}, which is characteristic of a so called conformal phase transition, one known example of it being the Berezinski-Kosterliz-Thouless (BKT) phase transition in two-dimensional superfluids. We argue that a similar behavior happens in three-dimensional strongly type I superconductors. One important prediction from our theory that may be tested experimentally by microwave measurement is a universal discontinuous jump in the superfluid density.
A Model Study Of The Deconfining Phase Transition
Velytsky, A
2004-01-01
The study of the deconfining phase transition or crossover is important for the understanding of properties of nuclear matter and the quark gluon plasma. Heavy ion collisions experiments are capable of creating conditions necessary for deconfinement. The dynamics of this process and not only its equilibrium properties are of interest. In this dissertation non-equilibrium aspects of rapid heating and cooling of the QCD vacuum are studied in a model framework. The 3-D Potts model with an external magnetic field is an effective model of QCD (of pure SU(3) gauge theory, when the magnetic field is set to zero), which we study by means of Monte Carlo simulations. Other models are used to understand the influence of the strength of the phase transition. In our investigations these systems are temperature driven through a phase transition or a rapid crossover using updating procedures in the Glauber universality class. We study hysteresis cycles with different updating speeds and simulations of a quench. Qualitativel...
Nuclear Matter Phase Transition in Infinite and Finite Systems
Terranova, S.; Bonasera, A.
2005-04-01
A new "semiclassical" model of the nuclear matter, composed of u, d colored quarks, is proposed. The approach, named Constrained Molecular Dynamics (CoMD) is based on the molecular dynamics simulation of the quarks, which interact through the Richardson's potential, and on a constraint due to Pauli blocking. With a suitable choice of the quark masses, some possible Equation of State (EOS) of the nuclear matter, at temperature equal to zero and finite baryon density, are obtained. These equations of state, not only present some known properties of the nuclear matter, as the Quark-Gluon Plasma (QGP) phase transition, but also shown the existence of a new state, the Exotic Color Clustering (ECC) state, in which cluster of quarks with the same color are formed. Some new quantities, "indicators" of the phase transition, are introduced: three order parameters, Mc2, Mc3, Mc4 defined trough the Gell-Mann matrices λα, and the lifetime of the J/Ψ particle. The behavior of the J/Ψ particle is studied also in the "finite" systems, obtained by expanding the corresponding "infinite" systems. It seems that the dynamics and the finite size effects do not wash completely the phase transition occurred in infinite systems, and the J/Ψ particle is still a good signature.
Infinite N phase transitions in continuum Wilson loop operators
Narayanan, R
2006-01-01
We define smoothed Wilson loop operators on a four dimensional lattice and check numerically that they have a finite and nontrivial continuum limit. The continuum operators maintain their character as unitary matrices and undergo a phase transition at infinite N reflected by the eigenvalue distribution closing a gap in its spectrum when the defining smooth loop is dilated from a small size to a large one. If this large N phase transition belongs to a solvable universality class one might be able to calculate analytically the string tension in terms of the perturbative Lambda-parameter. This would be achieved by matching instanton results for small loops to the relevant large-N-universal function which, in turn, would be matched for large loops to an effective string theory. Similarities between our findings and known analytical results in two dimensional space-time indicate that the phase transitions we found only affect the eigenvalue distribution, but the traces of finite powers of the Wilson loop operators...
Deformation Behavior across the Zircon-Scheelite Phase Transition
Yue, Binbin; Hong, Fang; Merkel, Sébastien; Tan, Dayong; Yan, Jinyuan; Chen, Bin; Mao, Ho-Kwang
2016-09-01
The pressure effects on plastic deformation and phase transformation mechanisms of materials are of great importance to both Earth science and technological applications. Zircon-type materials are abundant in both nature and the industrial field; however, there is still no in situ study of their deformation behavior. Here, by employing radial x-ray diffraction in a diamond anvil cell, we investigate the dislocation-induced texture evolution of zircon-type gadolinium vanadate (GdVO4 ) in situ under pressure and across its phase transitions to its high-pressure polymorphs. Zircon-type GdVO4 develops a (001) compression texture associated with dominant slip along ⟨100 ⟩{001 } starting from 5 GPa. This (001) texture transforms into a (110) texture during the zircon-scheelite phase transition. Our observation demonstrates a martensitic mechanism for the zircon-scheelite transformation. This work will help us understand the local deformation history in the upper mantle and transition zone and provides fundamental guidance on material design and processing for zircon-type materials.
Optical characterization of phase transitions in pure polymers and blends
Energy Technology Data Exchange (ETDEWEB)
Mannella, Gianluca A.; Brucato, Valerio; La Carrubba, Vincenzo, E-mail: vincenzo.lacarrubba@unipa.it [Department of Civil, Environmental, Aerospace and Materials Engineering (DICAM), University of Palermo, Viale delle Scienze, Ed. 8, 90128 Palermo (Italy)
2015-12-17
To study the optical properties of polymeric samples, an experimental apparatus was designed on purpose and set up. The sample is a thin film enclosed between two glass slides and a PTFE frame, with a very thin thermocouple placed on sample for direct temperature measurement. This sample holder was placed between two aluminum slabs, equipped with a narrow slit for optical measurements and with electrical resistances for temperature control. Sample was enlightened by a laser diode, whereas transmitted light was detected with a photodiode. Measurements were carried out on polyethylene-terephtalate (PET) and two different polyamides, tested as pure polymers and blends. The thermal history imposed to the sample consisted in a rapid heating from ambient temperature to a certain temperature below the melting point, a stabilization period, and then a heating at constant rate. After a second stabilization period, the sample was cooled. The data obtained were compared with DSC measurements performed with the same thermal history. In correspondence with transitions detected via DSC (e.g. melting, crystallization and cold crystallization), the optical signal showed a steep variation. In particular, crystallization resulted in a rapid decrease of transmitted light, whereas melting gave up an increase of light transmitted by the sample. Further variations in transmitted light were recorded for blends, after melting: those results may be related to other phase transitions, e.g. liquid-liquid phase separation. All things considered, the apparatus can be used to get reliable data on phase transitions in polymeric systems.
Cosmological Phase Transitions and their Properties in the NMSSM
Kozaczuk, Jonathan; Haskins, Laurel Stephenson; Wainwright, Carroll L
2014-01-01
We study cosmological phase transitions in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) in light of the Higgs discovery. We use an effective field theory approach to calculate the finite temperature effective potential, focusing on regions with significant tree-level contributions to the Higgs mass, a viable neutralino dark matter candidate, 1-2 TeV stops, and with the remaining particle spectrum compatible with current LHC searches and results. The phase transition structure in viable regions of parameter space exhibits a rich phenomenology, potentially giving rise to one- or two-step first-order phase transitions in the singlet and/or $SU(2)$ directions. We compute several parameters pertaining to the bubble wall profile, including the bubble wall width and $\\Delta\\beta$ (the variation of the ratio in Higgs vacuum expectation values across the wall). These quantities can vary significantly across small regions of parameter space and can be promising for successful electroweak baryogenesis. We e...
Digital herders and phase transition in a voting model
Hisakado, Masato
2011-01-01
In this paper, we discuss a voting model with two candidates, $C_1$ and $C_2$. We set two types of voters--herders and independents. The voting of independent voters is based on their fundamental values; on the other hand, the voting of herders is based on the number of votes. Herders always select the majority of the previous $r$ votes, which is visible to them. We call them digital herders. We can accurately calculate the distribution of votes for special cases. When $r\\geq 3$, we find that a phase transition occurs at the upper limit of $t$, where $t$ is the discrete time (or number of votes). As the fraction of herders increases, the model features a phase transition beyond which a state where most voters make the correct choice coexists with one where most of them are wrong. On the other hand, when $r<3$, there is no phase transition. In this case, the herder's performance is the same as that of the independent voters. At last, from the simple experiments, we recognize the behavior of human beings.
On simulated annealing phase transitions in phylogeny reconstruction.
Strobl, Maximilian A R; Barker, Daniel
2016-08-01
Phylogeny reconstruction with global criteria is NP-complete or NP-hard, hence in general requires a heuristic search. We investigate the powerful, physically inspired, general-purpose heuristic simulated annealing, applied to phylogeny reconstruction. Simulated annealing mimics the physical process of annealing, where a liquid is gently cooled to form a crystal. During the search, periods of elevated specific heat occur, analogous to physical phase transitions. These simulated annealing phase transitions play a crucial role in the outcome of the search. Nevertheless, they have received comparably little attention, for phylogeny or other optimisation problems. We analyse simulated annealing phase transitions during searches for the optimal phylogenetic tree for 34 real-world multiple alignments. In the same way in which melting temperatures differ between materials, we observe distinct specific heat profiles for each input file. We propose this reflects differences in the search landscape and can serve as a measure for problem difficulty and for suitability of the algorithm's parameters. We discuss application in algorithmic optimisation and as a diagnostic to assess parameterisation before computationally costly, large phylogeny reconstructions are launched. Whilst the focus here lies on phylogeny reconstruction under maximum parsimony, it is plausible that our results are more widely applicable to optimisation procedures in science and industry.
Hybrid phase transition into an absorbing state: Percolation and avalanches.
Lee, Deokjae; Choi, S; Stippinger, M; Kertész, J; Kahng, B
2016-04-01
Interdependent networks are more fragile under random attacks than simplex networks, because interlayer dependencies lead to cascading failures and finally to a sudden collapse. This is a hybrid phase transition (HPT), meaning that at the transition point the order parameter has a jump but there are also critical phenomena related to it. Here we study these phenomena on the Erdős-Rényi and the two-dimensional interdependent networks and show that the hybrid percolation transition exhibits two kinds of critical behaviors: divergence of the fluctuations of the order parameter and power-law size distribution of finite avalanches at a transition point. At the transition point global or "infinite" avalanches occur, while the finite ones have a power law size distribution; thus the avalanche statistics also has the nature of a HPT. The exponent β_{m} of the order parameter is 1/2 under general conditions, while the value of the exponent γ_{m} characterizing the fluctuations of the order parameter depends on the system. The critical behavior of the finite avalanches can be described by another set of exponents, β_{a} and γ_{a}. These two critical behaviors are coupled by a scaling law: 1-β_{m}=γ_{a}.
Phase transitions in human IgG solutions.
Wang, Ying; Lomakin, Aleksey; Latypov, Ramil F; Laubach, Jacob P; Hideshima, Teru; Richardson, Paul G; Munshi, Nikhil C; Anderson, Kenneth C; Benedek, George B
2013-09-28
Protein condensations, such as crystallization, liquid-liquid phase separation, aggregation, and gelation, have been observed in concentrated antibody solutions under various solution conditions. While most IgG antibodies are quite soluble, a few outliers can undergo condensation under physiological conditions. Condensation of IgGs can cause serious consequences in some human diseases and in biopharmaceutical formulations. The phase transitions underlying protein condensations in concentrated IgG solutions is also of fundamental interest for the understanding of the phase behavior of non-spherical protein molecules. Due to the high solubility of generic IgGs, the phase behavior of IgG solutions has not yet been well studied. In this work, we present an experimental approach to study IgG solutions in which the phase transitions are hidden below the freezing point of the solution. Using this method, we have investigated liquid-liquid phase separation of six human myeloma IgGs and two recombinant pharmaceutical human IgGs. We have also studied the relation between crystallization and liquid-liquid phase separation of two human cryoglobulin IgGs. Our experimental results reveal several important features of the generic phase behavior of IgG solutions: (1) the shape of the coexistence curve is similar for all IgGs but quite different from that of quasi-spherical proteins; (2) all IgGs have critical points located at roughly the same protein concentration at ~100 mg/ml while their critical temperatures vary significantly; and (3) the liquid-liquid phase separation in IgG solutions is metastable with respect to crystallization. These features of phase behavior of IgG solutions reflect the fact that all IgGs have nearly identical molecular geometry but quite diverse net inter-protein interaction energies. This work provides a foundation for further experimental and theoretical studies of the phase behavior of generic IgGs as well as outliers with large propensity to
Phase Transition and Structure of Silver Azide at High Pressure
Energy Technology Data Exchange (ETDEWEB)
D Hou; F Zhang; C Ji; T Hannon; H Zhu; J Wu; V Levitas; Y Ma
2011-12-31
Silver azide (AgN{sub 3}) was compressed up to 51.3 GPa. The results reveal a reversible second-order orthorhombic-to-tetragonal phase transformation starting from ambient pressure and completing at 2.7 GPa. The phase transition is accompanied by a proximity of cell parameters a and b, a 3{sup o} rotation of azide anions, and a change of coordination number from 4-4 (four short, four long) to eight fold. The crystal structure of the high pressure phase is determined to be in I4/mcm space group, with Ag at 4a, N{sub 1} at 4d, and N{sub 2} at 8h Wyckoff positions. Both of the two phases have anisotropic compressibility: the orthorhombic phase exhibits an anomalous expansion under compression along a-axis and is more compressive along b-axis than c-axis; the tetragonal phase is more compressive along the interlayer direction than the intralayer directions. The bulk moduli of the orthorhombic and tetragonal phases are determined to be K{sub OT} = 39{+-}5 GPa with K{sub OT'} = 10{+-}7 and K{sub OT} = 57 {+-}2 GPa with K{sub OT'} = 6.6{+-}0.2, respectively.
Phase transition of solid bismuth under high pressure
Chen, Hai-Yan; Xiang, Shi-Kai; Yan, Xiao-Zhen; Zheng, Li-Rong; Zhang, Yi; Liu, Sheng-Gang; Bi, Yan
2016-10-01
As a widely used pressure calibrator, the structural phase transitions of bismuth from phase I, to phase II, to phase III, and then to phase V with increasing pressure at 300 K have been widely confirmed. However, there are different structural versions for phase III, most of which are determined by x-ray diffraction (XRD) technology. Using x-ray absorption fine structure (XAFS) measurements combined with ab initio calculations, we show that the proposed incommensurate composite structure of bismuth of the three configurations is the best option. An abnormal continuous increase of the nearest-neighbor distance of phase III with elevated pressure is also observed. The electronic structure transformation from semimetal to metal is responsible for the complex behavior of structure transformation. Project supported by the National Natural Science Foundation of China (Grant Nos. 10904133, 11304294, 11274281, 11404006, and U1230201), the Development Foundation of China Academy of Engineering Physics (Grant Nos. 2015B0101004, 2013B0401062, and 2012A0101001), the Research Foundation of the Laboratory of Shock Wave and Detonation, China (Grant No. 9140C670201140C67282).
Domain structure and phase transition in Sc-doped zirconia
Energy Technology Data Exchange (ETDEWEB)
Brunauer, G.; Boysen, H.; Frey, F. [Institute for Crystallography und Applied Mineralogy, LMU Muenchen, Munich (Germany); Ehrenberg, H. [Institute for Materials Science, TU Darmstadt, Darmstadt (Germany)
2002-01-21
The temperature dependence of the domain structure associated with the ferroelastic phase transition (Fm{sup 3-bar}m{r_reversible}R{sup 3-bar}m) in ZrO{sub 2} doped with 11% Sc{sub 2}O{sub 3} has been determined from a peak shape analysis of high-resolution synchrotron x-ray powder diffraction data. In the temperature region of coexisting phases the observed characteristic anisotropic broadening and asymmetry of the lines is modelled by three different phases: a main rhombohedral phase, a distorted rhombohedral phase with a smaller c/a ratio, and a cubic phase. The latter two are assigned to the internal structure of the domain walls between two adjacent twin domains. The size and amount of the cubic phase show an initially slow increase with temperature followed by a very steep increase and a slow one after that. The size of the (main) rhombohedral domains remains nearly constant, while (micro-) strain in the distorted regions gradually decreases. (author)
Electrically induced phase transition in GeSbTe alloys
Energy Technology Data Exchange (ETDEWEB)
Bruns, Gunnar; Schlockermann, Carl; Woda, Michael; Wuttig, Matthias [I. Physikalisches Institut Ia, RWTH Aachen, 52056 Aachen (Germany)
2008-07-01
While phase change materials have already successfully been applied in rewriteable optical data storage, they are now also promising to form the basis for novel non-volatile electrical data storage devices. To understand the physical concepts of these so-called Phase Change Random Access Memory (PCRAM) it is mandatory to gain a deeper insight into the switching process between the highly resistive amorphous and the lowly resistive crystalline phase. The fast phase transitions between the amorphous and crystalline state of GeSbTe-based alloys has so far often been studied using pulsed laser irradiation. In this work an alternative approach is employed to investigate this transition. Electrical pulses are used to rapidly and reversibly switch between the two states. For these experiments a setup was built with a specially designed contacting circuit board to meet the requirements of electrical measurements on a nanosecond timescale. The influence of the pulse parameters on the change of device resistance was determined for different initial states. Furthermore the high time resolution of 0.4 ns allows investigation of transient electrical effects like the so-called threshold switching first described by Ovshinsky in the late 1960s.
A superconductor to superfluid phase transition in liquid metallic hydrogen.
Babaev, Egor; Sudbø, Asle; Ashcroft, N W
2004-10-07
Although hydrogen is the simplest of atoms, it does not form the simplest of solids or liquids. Quantum effects in these phases are considerable (a consequence of the light proton mass) and they have a demonstrable and often puzzling influence on many physical properties, including spatial order. To date, the structure of dense hydrogen remains experimentally elusive. Recent studies of the melting curve of hydrogen indicate that at high (but experimentally accessible) pressures, compressed hydrogen will adopt a liquid state, even at low temperatures. In reaching this phase, hydrogen is also projected to pass through an insulator-to-metal transition. This raises the possibility of new state of matter: a near ground-state liquid metal, and its ordered states in the quantum domain. Ordered quantum fluids are traditionally categorized as superconductors or superfluids; these respective systems feature dissipationless electrical currents or mass flow. Here we report a topological analysis of the projected phase of liquid metallic hydrogen, finding that it may represent a new type of ordered quantum fluid. Specifically, we show that liquid metallic hydrogen cannot be categorized exclusively as a superconductor or superfluid. We predict that, in the presence of a magnetic field, liquid metallic hydrogen will exhibit several phase transitions to ordered states, ranging from superconductors to superfluids.
Holographic phase transitions from higgsed, non abelian charged black holes
Giordano, Gastón L.; Lugo, Adrián R.
2015-07-01
We find solutions of a gravity-Yang-Mills-Higgs theory in four dimensions that represent asymptotic anti-de Sitter charged black holes with partial/full gauge symme-try breaking. We then apply the AdS/CFT correspondence to study the strong coupling regime of a 2 + 1 quantum field theory at temperature T and finite chemical potential, which undergoes transitions to phases exhibiting the condensation of a composite charged vector operator below a critical temperature T c , presumably describing p + ip/p-wave su-perconductors. In the case of p + ip-wave superconductors the transitions are always of second order. But for p-wave superconductors we determine the existence of a critical value αc of the gravitational coupling (for fixed Higgs v.e.v. parameter ) beyond which the transitions become of first order. As a by-product, we show that the p-wave phase is energetically favored over the p + ip one, for any values of the parameters. We also find the ground state solutions corresponding to zero temperature. Such states are described by domain wall geometries that interpolate between AdS 4 spaces with different light veloc-ities, and for a given , they exist below a critical value of the coupling. The behavior of the order parameter as function of the gravitational coupling near the critical coupling suggests the presence of second order quantum phase transitions. We finally study the dependence of the solution on the Higgs coupling, and find the existence of a critical value beyond which no condensed solution is present.
Wei, Wei
2011-01-01
As a neutron star spins down, its core density increase, changing the relative equilibrium concentration, and causing deconfinement phase transition as well. hadron matter are converted into quark matter in the interior, which enhances the deviation of chemical equilibrium state. We study such deviations and its chemical energy release.Applying to the simulation of cooling neutron stars, we find the surface effective temperature of neutron stars is promoted obviously. This implies that the deconfinement phase transition is able to raise the chemical heating efficiency.
Dynamical phase transition in a simple model of competing shops
Lambert, Gaultier; Bertin, Eric
2011-01-01
We consider a simple model in which a set of agents randomly visit one of two competing shops selling the same perishable products (typically food). The satisfaction of agents with respect to a given store is related to the freshness of the previously bought products. Agents then choose with a higher probability the store they are most satisfied with. Studying the model both through numerical simulations and mean-field analytical methods, we find a rich behaviour with continuous and discontinuous phase transitions between a symmetric phase where both stores maintain the same level of activity, and a phase with broken symmetry where one of the two shops attracts more customers than the other.
Screening phase transitions in two-dimensional Coulomb gas
Energy Technology Data Exchange (ETDEWEB)
Gallavotti, G.; Nicolo, F.
1984-07-01
Infrared properties of a Coulomb gas in two dimensions and with fixed ultraviolet cutoff are studied. The existence of infinitely many thresholds Tu = 1/Ke 1/8 pi (1-1/zu)sup-1 in the interval of temperatures 1/Ke1/8 pi, 1/4 pi, where K is the Boltzmann constant and e = /e/ is the charge of the positive particle, is proved. Such thresholds are conjectured to reflect a sequence of transitions from a pure multipole phase (the Koesterlitz-Thouless region) to the plasma phase via an infinite number of intermediate phases. Mathematically the free energy becomes more and more differentiable as a function of the activity lambda, near lambda = 0, as the temperature decreases.
Finite density QCD phase transition in the heavy quark region
Saito, H; Kanaya, K; Ohno, H; Ejiri, S; Nakagawa, Y; Hatsuda, T; Umeda, T
2012-01-01
We extend our previous study of the QCD phase structure in the heavy quark region to non-zero chemical potentials. To identify the critical point where the first order deconfining transition terminates, we study an effective potential defined by the probability distribution function of the plaquette and the Polyakov loop. The reweighting technique is shown to be powerful in evaluating the effective potential in a wide range of the plaquette and Polyakov loop expectation values. We adopt the cumulant expansion to overcome the sign problem in the calculation of complex phase of the quark determinant. We find that the method provides us with an intuitive and powerful way to study the phase structure. We estimate the location of the critical point at finite chemical potential in the heavy quark region.
A time-dependent Ginzburg-Landau phase field formalism for shock-induced phase transitions
Haxhimali, Tomorr; Belof, Jonathan L.; Benedict, Lorin X.
2017-01-01
Phase-field models have become popular in the last two decades to describe a host of free-boundary problems. The strength of the method relies on implicitly describing the dynamics of surfaces and interfaces by a continuous scalar field that enters the global grand free energy functional of the system. Here we explore the potential utility of this method in order to describe shock-induced phase transitions. To this end we make use of the Multiphase Field Theory (MFT) to account for the existence of multiple phases during the transition, and we couple MFT to a hydrodynamic model in the context of a new LLNL code for phase transitions, SAMSA. As a demonstration of this approach, we apply our code to the α - ɛ-Fe phase transition under shock wave loading conditions and compare our results with experiments of Jensen et. al. [J. Appl. Phys., 105:103502 (2009)] and Barker and Hollenbach [J. Appl. Phys., 45:4872 (1974)].
Sherkatghanad, Zeinab; Mirzaeyan, Zahra; Mansoori, Seyed Ali Hosseini
2014-01-01
We consider the critical behaviors and phase transitions of Gauss Bonnet-Born Infeld-AdS black holes (GB-BI-AdS) for $d=5,6$ and the extended phase space. We assume the cosmological constant, $\\Lambda$, the coupling coefficient $\\alpha$, and the BI parameter $\\beta$ to be thermodynamic pressures of the system. Having made these assumptions, the critical behaviors are then studied in the two canonical and grand canonical ensembles. We find "reentrant and triple point phase transitions" (RPT-TP) and "multiple reentrant phase transitions" (multiple RPT) with increasing pressure of the system for specific values of the coupling coefficient $\\alpha$ in the canonical ensemble. Also, we observe a reentrant phase transition (RPT) of GB-BI-AdS black holes in the grand canonical ensemble and for $d=6$. These calculations are then expanded to the critical behavior of Born-Infeld-AdS (BI-AdS) black holes in the third order of Lovelock gravity and in the grand canonical ensemble to find a Van der Waals behavior for $d=7$ ...
An Investigation of Magnetically Induced Structural Phase Transitions Near a Magnetic Phase Boundary
Brown, D. E.; Hoffmann, C. A.; Hua, J.; Totapally, S.; Mais, J.; Chmaissem, O.; Dabrowski, B.; Ren, Yang
2004-03-01
The structural properties of the perovskite La_1-xSr_xMnO_3, x = 0.55, have been studied using synchrotron powder x-ray diffraction under high magnetic fields (up to 6 Tesla) for zero field cooled and field cooled conditions. This compound has an interesting phase transition point where both structural and magnetic properties change. As temperature decreases, it undergoes a tetragonal (I4/mcm) to orthorhombic (Fmmm) first-order structural phase transition while simultaneously undergoing a ferromagnetic to an A-type antiferromagnetic magnetic phase transition. Under the application of a strong magnetic field, the structure can be forced from the ferromagnetic tetragonal structure to the antiferromagnetic orthorhombic structure, which is nearly a reversible process. Thus the strong competition between the magnetic phases can be significantly affected by applying an external magnetic field. The magnetic perovskites, such as the colossal magnetoresistive materials, appear to be susceptible to such large and surprising magnetically induced phase transitions. Work at NIU is supported by the State of Illinois under HECA. Work at APS/ANL is supported by the US DOE-BES No. W-31-109-ENG-38.
Serotonin enhances solitariness in phase transition of the migratory locust
Directory of Open Access Journals (Sweden)
Xiaojiao eGuo
2013-10-01
Full Text Available The behavioral plasticity of locusts is a striking trait presented during the reversible phase transition between solitary and gregarious individuals. However, the results of serotonin as a neurotransmitter from the migratory locust Locusta migratoria in phase transition showed an alternative profile compared to the results from the desert locust Schistoserca gregaria. In this study, we investigated the roles of serotonin in the brain during the phase change of the migratory locust. During the isolation of gregarious nymphs, the concentration of serotonin in the brain increased significantly, whereas serotonin receptors (i.e. 5-HT1, 5-HT2 and 5-HT7 we identified here showed invariable expression patterns. Pharmacological intervention showed that serotonin injection in the brain of gregarious nymphs did not induced the behavior change toward solitariness, but injection of this chemical in isolated gregarious nymphs accelerated the behavioral change from gregarious to solitary phase. During the crowding of solitary nymphs, the concentration of serotonin in the brain remained unchanged, whereas 5-HT2 increased after 1 h of crowding and maintained stable expression level thereafter. Activation of serotonin-5-HT2 signaling with a pharmaceutical agonist inhibited the gregariousness of solitary nymphs in crowding treatment. These results indicate that the fluctuations of serotonin content and 5-HT2 expression are results of locust phase change. Overall, this study demonstrates that serotonin enhances the solitariness of the gregarious locusts. Serotonin may regulate the withdrawal-like behavioral pattern displayed during locust phase change and this mechanism is conserved in different locust species.
Phase transition in predator-prey ecosystems and a connection to transitional turbulence
Shih, Hong-Yan; Goldenfeld, Nigel
2015-03-01
We suggest how the transition from laminar fluid flow to turbulence can be connected to the extinction phase transition in spatially-extended predator-prey systems. By measuring the statistics of spontaneous relaminarization, spatiotemporal intermittency and expanding turbulent puffs in hydrodynamics equations and mapping them to the corresponding states in the predator-prey model, the extinction event and the formation and propagation of spatial patterns in ecology can be interpreted as the instabilities in fluid systems. We also summarize the general phenomena of such predator-prey dynamics in a wide class of transitional turbulence systems such as magnetohydrodynamics. This work was partially supported by the National Science Foundation through Grant NSF-DMR-1044901.
Phase transition in compact stars due to a violent shock
Mishustin, Igor; Nandi, Rana; Satarov, Leonid
2014-01-01
In this letter we study the dynamics of a first order phase transition from nucleonic to quark matter in neutron stars. Using standard equations of state for these two phases we find the density range where such a transition is possible. Then we study the transformation of the star assuming that the quark core is formed via a spherical shock wave. The thermodynamical conditions in the quark core are found from the conservation laws across the transition region. Their dependence on the density and velocity of the incoming nuclear matter are studied. It is found that the shock is especially violent in the beginning of the conversion process when the velocity of the infalling matter is especially high. As the shock propagates further from the center the front velocity first increases and reaches a maximum value when the incoming velocity is around $0.2$. Finally, the front velocity quickly goes to zero when incoming matter velocity approaches zero. We have shown that the density and pressure jumps are especially...
Signatures of shape phase transitions in odd-mass nuclei
Nomura, K.; Nikšić, T.; Vretenar, D.
2016-12-01
Quantum phase transitions between competing ground-state shapes of atomic nuclei with an odd number of protons or neutrons are investigated in a microscopic framework based on nuclear energy density functional theory and the particle-plus-boson-core coupling scheme. The boson-core Hamiltonian, as well as the single-particle energies and occupation probabilities of the unpaired nucleon, are completely determined by constrained self-consistent mean-field calculations for a specific choice of the energy density functional and paring interaction, and only the strength parameters of the particle-core coupling are adjusted to reproduce selected spectroscopic properties of the odd-mass system. We apply this method to odd-A Eu and Sm isotopes with neutron number N ≈90 , and explore the influence of the single unpaired fermion on the occurrence of a shape phase transition. Collective wave functions of low-energy states are used to compute quantities that can be related to quantum order parameters: deformations, excitation energies, E 2 transition rates, and separation energies, and their evolution with the control parameter (neutron number) is analyzed.
Holographic phase transitions from higgsed, non abelian charged black holes
Giordano, Gaston L
2015-01-01
We find solutions of a gravity-Yang-Mills-Higgs theory in four dimensions that represent asymptotic anti-de Sitter charged black holes with partial/full gauge symmetry breaking. We then apply the AdS/CFT correspondence to study the strong coupling regime of a $2+1$ quantum field theory at temperature $T$ and finite chemical potential, which undergoes transitions to phases exhibiting the condensation of a composite charged vector operator below a critical temperature $T_c$, presumably describing $p+ip/p$-wave superconductors. In the case of $p+ip$-wave superconductors the transitions are always of second order. But for $p$-wave superconductors we determine the existence of a critical value $\\alpha_c$ of the gravitational coupling (for fixed Higgs v.e.v. parameter $\\hat m_W$) beyond which the transitions become of first order. As a by-product, we show that the $p$-wave phase is energetically favored over the $p+ip$ one, for any values of the parameters. Finally we find the ground state solutions corresponding t...
Magnetism and phase transitions in LaCoO3
Durand, A. M.; Belanger, D. P.; Booth, C. H.; Ye, F.; Chi, S.; Fernandez-Baca, J. A.; Bhat, M.
2013-09-01
Neutron scattering and magnetometry measurements have been used to study phase transitions in LaCoO3 (LCO). For H ≤ 100 Oe, evidence for a ferromagnetic (FM) transition is observed at Tc ≈ 87 K. For 1 kOe ≤ H ≤ 60 kOe, no transition is apparent. For all H, Curie-Weiss analysis shows predominantly antiferromagnetic (AFM) interactions for T > Tc, but the lack of long-range AFM order indicates magnetic frustration. We argue that the weak ferromagnetism in bulk LCO is induced by lattice strain, as is the case with thin films and nanoparticles. The lattice strain is present at the bulk surfaces and at the interfaces between the LCO and a trace cobalt oxide phase. The ferromagnetic ordering in the LCO bulk is strongly affected by the Co-O-Co angle (γ), in agreement with recent band calculations which predict that ferromagnetic long-range order can only take place above a critical value, γC. Consistent with recent thin film estimations, we find γC = 162.8°. For γ > γC, we observe power-law behavior in the structural parameters. γ decreases with T until the critical temperature, To ≈ 37 K below To the rate of change becomes very small. For T < To, FM order appears to be confined to regions close to the surfaces, likely due to the lattice strain keeping the local Co-O-Co angle above γC.
Magnetism and phase transitions in LaCoO3
Energy Technology Data Exchange (ETDEWEB)
Belanger, David P [University of California, Santa Cruz; Durand, Alice M [University of California, Santa Cruz; Booth, C [Lawrence Berkeley National Laboratory (LBNL); Ye, Feng [ORNL; Chi, Songxue [ORNL; Fernandez-Baca, Jaime A [ORNL; Bhat, M [Castilleja School
2013-01-01
Neutron scattering and magnetometry measurements have been used to study phase transitions in LaCoO3 (LCO). For H 100 Oe, evidence for a ferromagnetic (FM) transition is observed at Tc 87 K. For 1 kOe H 60 kOe, no transition is apparent. For all H, Curie Weiss analysis shows predominantly antiferromagnetic (AFM) interactions for T > Tc, but the lack of long-range AFM order indicates magnetic frustration. We argue that the weak ferromagnetism in bulk LCO is induced by lattice strain, as is the case with thin films and nanoparticles. The lattice strain is present at the bulk surfaces and at the interfaces between the LCO and a trace cobalt oxide phase. The ferromagnetic ordering in the LCO bulk is strongly affected by the Co O Co angle ( ), in agreement with recent band calculations which predict that ferromagnetic long-range order can only take place above a critical value, C. Consistent with recent thin film estimations, we find C D 162:8. For > C, we observe power-law behavior in the structural parameters. decreases with T until the critical temperature, To 37 K; below To the rate of change becomes very small. For T < To, FM order appears to be confined to regions close to the surfaces, likely due to the lattice strain keeping the local Co O Co angle above C.
Pressure induced phase transition behaviour in -electron based dialuminides
Indian Academy of Sciences (India)
P Ch Sahu; N V Chandra Shekar
2000-05-01
The rare-earth and actinide based compounds are endowed with several exotic physical and chemical properties due to the presence of -electrons. These properties exhibit interesting changes under the action of various thermodynamic ﬁelds and hence continues to be a subject of extensive research. For instance, under pressure, the nature of -electrons can be changed from localized to itinerant, leading to a variety of changes in their structural, physical and chemical properties. The present review on the high pressure phase transition behaviour of dialuminides of rare earths and actinides is an outcome of research in our laboratory during the last ﬁve years using a unique combination of a Guinier diffractometer and a diamond anvil cell built in-house. To bring out the correlations between the compressibility and structural behaviour with the electronic structure, we have also carried out electronic structure calculation. Further, the usefulness of Villars' three parameter structure maps in predicting pressure induced structural transitions has been explored and this has been illustrated with the available phase transition data.
Is Geothermal Simulation a "Catastrophe"?
Energy Technology Data Exchange (ETDEWEB)
Nguyen, V.V.; Pinder, George F.
1980-12-16
All numerical simulators of geothermal reservoirs depend upon an accurate representation of the thermodynamics of steam-water systems. These relationships are required to render tractable the system of balance equations derived from the physics of flow through porous media. While it is generally recognized that the steam-water system (i.e. two phase) is not in thermodynamic equilibrium, equihbrium thermodynamics are employed in its description. In this paper, we present an alternative view based on non-equilibrium thermodynamics. The underpinnings of this approach are found in a branch of topology generally referred to as "catastrophe theory". [Thom, 1975
Core-collapse supernova matter: light clusters, pasta phase and phase transitions
Pais, Helena; Newton, William G; Stone, Jirina R
2015-01-01
The pasta phase in core-collapse supernova matter (finite temperatures and fixed proton fractions) is studied within relativistic mean field models. Two different calculations are used for comparison, the Thomas-Fermi (TF) and the Coexisting Phases (CP) approximations. The effects of including light clusters in nuclear matter and the densities at which the transitions between pasta configurations and to uniform matter occur are also investigated. Finally, a comparison with a finite temperature Skyrme-Hartree-Fock calculation is drawn.
Deconfinement Phase Transition in an Expanding Quark system in Relaxation Time Approximation
Yang, Z; Yang, Zhenwei; Zhuang, Pengfei
2004-01-01
We investigated the effects of nonequilibrium and collision terms on the deconfinement phase transition of an expanding quark system in Friedberg-Lee model in relaxation time approximation. By calculating the effective quark potential, the critical temperature of the phase transition is dominated by the mean field, while the collisions among quarks and mesons change the time structure of the phase transition significantly.
Phase transitions and hysteresis of cooperative contagion processes
Chen, Li; Brockmann, Dirk
2016-01-01
We investigate the effects of cooperation between two interacting infectious diseases that spread and stabilize in a host population. We propose a model in which individuals that are infected with one disease are more likely to acquire the second disease, both diseases following the susceptible-infected-susceptible reaction scheme. We analyze cooperative coinfection in stochastic network models as well as the idealized, well-mixed mean field system and show that cooperative mechanisms dramatically change the nature of phase transitions compared to single disease dynamics. We show that, generically, cooperative coinfection exhibits discontinuous transitions from the disease free to high prevalence state when a critical transmission rate is crossed. Furthermore, cooperative coinfection exhibits two distinct critical points, one for outbreaks the second one for eradication that can be substantially lower. This implies that cooperative coinfection exhibits hysteresis in its response to changing effective transmis...
Phase transitions in contagion processes mediated by recurrent mobility patterns
Balcan, Duygu; 10.1038/nphys1944
2011-01-01
Human mobility and activity patterns mediate contagion on many levels, including the spatial spread of infectious diseases, diffusion of rumors, and emergence of consensus. These patterns however are often dominated by specific locations and recurrent flows and poorly modeled by the random diffusive dynamics generally used to study them. Here we develop a theoretical framework to analyze contagion within a network of locations where individuals recall their geographic origins. We find a phase transition between a regime in which the contagion affects a large fraction of the system and one in which only a small fraction is affected. This transition cannot be uncovered by continuous deterministic models due to the stochastic features of the contagion process and defines an invasion threshold that depends on mobility parameters, providing guidance for controlling contagion spread by constraining mobility processes. We recover the threshold behavior by analyzing diffusion processes mediated by real human commutin...
Electroweak Phase Transition in the MSSM 4-Dimensional Lattice Simulations
Csikor, Ferenc; Hegedüs, P; Jakovác, A; Katz, S D; Piróth, A
2000-01-01
Recent lattice results have shown that there is no Standard Model (SM) electroweak phase transition (EWPT) for Higgs boson masses above \\approx 72 GeV, which is below the present experimental limit. According to perturbation theory and 3-dimensional (3d) lattice simulations there could be an EWPT in the Minimal Supersymmetric Standard Model (MSSM) that is strong enough for baryogenesis up to m_h \\approx 105 GeV. In this letter we present the results of our large scale 4-dimensional (4d) lattice simulations for the MSSM EWPT. We carried out infinite volume and continuum limit extrapolations, which show a somewhat weaker transition than suggested by 3d simulations. The upper bound of the lightest Higgs boson mass for a MSSM baryogenesis scenario is m_h = 97 +/- 4 GeV. We determined the properties of the bubble wall that are important for a successful baryogenesis.
Windows open for highly tunable magnetostructural phase transitions
Li, Y.
2016-07-18
An attempt was made to tailor the magnetostructural transitions over a wide temperature range under the principle of isostructural alloying. A series of wide Curie-temperature windows (CTWs) with a maximal width of 377 K between 69 and 446 K were established in the Mn1− yCoyNiGe1− xSix system. Throughout the CTWs, the magnetic-field-induced metamagnetic behavior and giant magnetocaloric effects are obtained. The (Mn,Co)Ni(Ge,Si) system shows great potential as multifunctional phase-transition materials that work in a wide range covering liquid-nitrogen and above water-boiling temperatures. Moreover, general understanding of isostructural alloying and CTWs constructed in (Mn,Co)Ni(Ge,Si) as well as (Mn,Fe)Ni(Ge,Si) is provided.
Geometry and Dynamics of Vortex Loops at Superfluid Phase Transitions
Williams, Gary A.
2004-03-01
The geometrical properties of thermally-excited vortex loops near a superfluid phase transition can be deduced from the dynamics of the transition. The frictional force on a loop is proportional to the total length of the vortex core, and hence depends on the fractal Hausdorff dimension DH of the random-walking core. By comparing the results for the loop dynamics with the dynamic-scaling predictions of Halperin and Hohenberg for the relaxation time, we find DH = (D+2)/2 = 2.5 in D = 3 dimensions, if the dynamic exponent is z = D/2. Computing the frequency-dependence of the superfluid density and comparing with the dynamic scaling of Fisher, Fisher, and Huse gives just the same value. Since Shenoy and co-workers have found precisely the same DH from a Flory-scaling analysis of the loop random walk, our results show that Shenoy's theory is exact if dynamic scaling is exact.
Gravitational mechanism for baryogenesis in the cosmological QCD phase transition
Antunes, V; Novello, M
2016-01-01
One of the biggest puzzles in modern cosmology is the observed baryon asymmetry in the universe. In current models of baryogenesis gravity plays a secondary role, although the process is believed to have happened in the early universe, under the influence of an intense gravitational field. In the present work we resume Sakharov's original program for baryogenesis and propose a central role for gravity in the process. This is achieved through a non-minimal coupling (NMC) between the gravitational field and both the strong interaction field and the quark fields. When in action, the present mechanism leads to baryon number non-conservation and CP violation. Moreover, the NMC induces reduced effective quark masses, which favours a first order QCD phase transition. As a consequence, a baryon asymmetry can be attained in the transition from the quark epoch to the hadron epoch.
Absorbing State Phase Transition with Competing Quantum and Classical Fluctuations
Marcuzzi, Matteo; Buchhold, Michael; Diehl, Sebastian; Lesanovsky, Igor
2016-06-01
Stochastic processes with absorbing states feature examples of nonequilibrium universal phenomena. While the classical regime has been thoroughly investigated in the past, relatively little is known about the behavior of these nonequilibrium systems in the presence of quantum fluctuations. Here, we theoretically address such a scenario in an open quantum spin model which, in its classical limit, undergoes a directed percolation phase transition. By mapping the problem to a nonequilibrium field theory, we show that the introduction of quantum fluctuations stemming from coherent, rather than statistical, spin flips alters the nature of the transition such that it becomes first order. In the intermediate regime, where classical and quantum dynamics compete on equal terms, we highlight the presence of a bicritical point with universal features different from the directed percolation class in a low dimension. We finally propose how this physics could be explored within gases of interacting atoms excited to Rydberg states.
Heat storage by phase transition, equation of state
Energy Technology Data Exchange (ETDEWEB)
Stunic, Z.
1984-01-01
Incongruent phase transitions accompanied by phase separation frequently cause a deterioration of heat-of-fusion storing systems. This kind of deterioration progresses, cycle after cycle, and is especially damaging in technical devices in which hydrated salts, e.g. CaCl/sub 2/ x 6H/sub 2/O, Na/sub 2/SO/sub 4/ x 10H/sub 2/O, Na/sub 2/S/sub 2/O/sub 3/ x 5H/sub 2/O, etc., are used as heat storing materials. Processes contributing to deterioration of hydrated-salt systems are analyzed, novel thermodynamic characteristics are proposed to enable unambiguous descriptions, and these are related in an equation of state for triads of characteristics so that any one of them can be calculated if the other two are known. State equations fo the three salts mentioned above are represented graphically in three-dimensional diagrams. Predictions deduced from state equations are tested experimentally with systems undergoing rapid (or purely incongruent) and slow (or pseudocongruent) phase transitions (CaCl/sub 2/ x 6H/sub 2/O and Na/sub 2/SO/sub 4/ 10H/sub 2/O, respectively). Good accordance between prognosis and experiment is shown.
Phase transition in traffic jam experiment on a circuit
Tadaki, Shin-ichi; Kikuchi, Macoto; Fukui, Minoru; Nakayama, Akihiro; Nishinari, Katsuhiro; Shibata, Akihiro; Sugiyama, Yuki; Yosida, Taturu; Yukawa, Satoshi
2013-10-01
The emergence of a traffic jam is considered to be a dynamical phase transition in a physics point of view; traffic flow becomes unstable and changes phase into a traffic jam when the car density exceeds a critical value. In order to verify this view, we have been performing a series of circuit experiments. In our previous work (2008 New J. Phys. 10 033001), we demonstrated that a traffic jam emerges even in the absence of bottlenecks at a certain high density. In this study, we performed a larger indoor circuit experiment in the Nagoya Dome in which the positions of cars were observed using a high-resolution laser scanner. Over a series of sessions at various values of density, we found that jammed flow occurred at high densities, whereas free flow was conserved at low densities. We also found indications of metastability at an intermediate density. The critical density is estimated by analyzing the fluctuations in speed and the density-flow relation. The value of this critical density is consistent with that observed on real expressways. This experiment provides strong support for physical interpretations of the emergence of traffic jams as a dynamical phase transition.