Zhang, Zhao
2010-01-01
The combined effect of the repulsive vector interaction and the positive electric chemical potential on the chiral phase transition is investigated by considering neutral color superconductivity. Under the charge-neutrality constraint, the chiral condensate, diquark condensate and quark number densities are obtained in two-plus-one-flavor Nambu-Jona-Lasinio model with the so called Kobayashi-Maskawa-'t Hooft term. We demonstrate that multiple chiral critical-point structures always exist in the Nambu-Jona-Lasinio model within the self-consistent mean-field approximation, and that the number of chiral critical points can vary from zero to four, which is dependent on the magnitudes of vector interaction and the diquark coupling.
The chiral critical point of $N_f$=3 QCD at finite density to the order $(\\mu/T)^4$
De Forcrand, Philippe
2008-01-01
QCD with three degenerate quark flavours at zero baryon density exhibits a first order thermal phase transition for small quark masses, which changes to a smooth crossover for some critical quark mass m^c_0, i.e. the chiral critical point. It is generally believed that as an (even) function of quark chemical potential, m_c(mu), the critical point moves to larger quark masses, constituting the critical endpoint of a first order phase transition in theories with m\\geq m^c_0. To test this, we consider a Taylor expansion of m_c(mu) around mu=0 and determine the first two coefficients from lattice simulations with staggered fermions on N_t=4 lattices. We employ two different techniques: a) calculating the coefficients directly from a mu=0 ensemble using a novel finite difference method, and b) fitting them to simulation data obtained for imaginary chemical potentials. The mu^2 and mu^4 coefficients are found to be negative by both methods, with consistent absolute values. Combining both methods gives evidence that...
The measurement of the position of the chiral critical end point (CEP) in the QCD phase diagram is under debate. While it is possible to predict its position by using effective models specifically built to reproduce some of the features of the underlying theory (QCD), the quality of the predictions (e.g., the CEP position) obtained by such effective models, depends on whether solving the model equations constitute a well- or ill-posed inverse problem. Considering these predictions as being inverse problems provides tools to evaluate if the problem is ill-conditioned, meaning that infinitesimal variations of the inputs of the model can cause comparatively large variations of the predictions. If it is ill-conditioned, it has major consequences because of finite variations that could come from experimental and/or theoretical errors. In the following, we shall apply such a reasoning on the predictions of a particular Nambu-Jona-Lasinio model within the mean field + ring approximations, with special attention to the prediction of the chiral CEP position in the (T-μ) plane. We find that the problem is ill-conditioned (i.e. very sensitive to input variations) for the T-coordinate of the CEP, whereas, it is well-posed for the μ-coordinate of the CEP. As a consequence, when the chiral condensate varies in a 10MeV range, μ CEP varies far less. As an illustration to understand how problematic this could be, we show that the main consequence when taking into account finite variation of the inputs, is that the existence of the CEP itself cannot be predicted anymore: for a deviation as low as 0.6% with respect to vacuum phenomenology (well within the estimation of the first correction to the ring approximation) the CEP may or may not exist. (orig.)
Biguet, Alexandre; Hansen, Hubert; Brugiere, Timothee [Universite Claude Bernard de Lyon, Institut de Physique Nucleaire de Lyon, CNRS/IN2P3, Villeurbanne Cedex (France); Costa, Pedro [Universidade de Coimbra, Centro de Fisica Computacional, Departamento de Fisica, Coimbra (Portugal); Borgnat, Pierre [CNRS, l' Ecole normale superieure de Lyon, Laboratoire de Physique, Lyon Cedex 07 (France)
2015-09-15
The measurement of the position of the chiral critical end point (CEP) in the QCD phase diagram is under debate. While it is possible to predict its position by using effective models specifically built to reproduce some of the features of the underlying theory (QCD), the quality of the predictions (e.g., the CEP position) obtained by such effective models, depends on whether solving the model equations constitute a well- or ill-posed inverse problem. Considering these predictions as being inverse problems provides tools to evaluate if the problem is ill-conditioned, meaning that infinitesimal variations of the inputs of the model can cause comparatively large variations of the predictions. If it is ill-conditioned, it has major consequences because of finite variations that could come from experimental and/or theoretical errors. In the following, we shall apply such a reasoning on the predictions of a particular Nambu-Jona-Lasinio model within the mean field + ring approximations, with special attention to the prediction of the chiral CEP position in the (T-μ) plane. We find that the problem is ill-conditioned (i.e. very sensitive to input variations) for the T-coordinate of the CEP, whereas, it is well-posed for the μ-coordinate of the CEP. As a consequence, when the chiral condensate varies in a 10MeV range, μ {sub CEP} varies far less. As an illustration to understand how problematic this could be, we show that the main consequence when taking into account finite variation of the inputs, is that the existence of the CEP itself cannot be predicted anymore: for a deviation as low as 0.6% with respect to vacuum phenomenology (well within the estimation of the first correction to the ring approximation) the CEP may or may not exist. (orig.)
Costa, Pedro
2016-06-01
The location of the critical end point (CEP) and the isentropic trajectories in the QCD phase diagram are investigated. We use the (2 +1 ) Nambu-Jona-Lasinio model with the Polyakov loop coupling for different scenarios, namely by imposing zero strange quark density, which is the case in the ultrarelativistic heavy ion collisions, and β equilibrium. The influence of strong magnetic fields and of the vector interaction on the isentropic trajectories around the CEP is discussed. It is shown that the vector interaction and the magnetic field, having opposite effects on the first-order transition, affect the isentropic trajectories differently: as the vector interaction increases, the first-order transition becomes weaker and the isentropes become smoother; when a strong magnetic field is considered, the first-order transition is strengthened and the isentropes are pushed to higher temperatures. No focusing of isentropes in region towards the CEP is seen.
Hyperbolic Weyl point in reciprocal chiral metamaterial
Xiao, Meng; Fan, Shanhui
2016-01-01
We report the existence of Weyl points in a class of non-central symmetric metamaterials, which has time reversal symmetry, but does not have inversion symmetry due to chiral coupling between electric and magnetic fields. This class of metamaterial exhibits either type-I or type-II Weyl points depending on its non-local response. We also provide a physical realization of such metamaterial consisting of an array of metal wires in the shape of elliptical helixes which exhibits type-II Weyl points.
Chiral measurements with the Fixed-Point Dirac operator and construction of chiral currents
In this preliminary study, we examine the chiral properties of the parametrized Fixed-Point Dirac operator DFP, see how to improve its chirality via the Overlap construction, measure the renormalized quark condensate Σ-circumflex and the topological susceptibility χt, and investigate local chirality of near zero modes of the Dirac operator. We also give a general construction of chiral currents and densities for chiral lattice actions
Novel Lifshitz point for chiral transition in the magnetic field
Toshitaka Tatsumi
2015-04-01
Full Text Available Based on the generalized Ginzburg–Landau theory, chiral phase transition is discussed in the presence of magnetic field. Considering the chiral density wave we show that chiral anomaly gives rise to an inhomogeneous chiral phase for nonzero quark-number chemical potential. Novel Lifshitz point appears on the vanishing chemical potential line, which may be directly explored by the lattice QCD simulation.
Jensen, Ole B.; Wind, Simon; Lanng, Ditte Bendix
In this brief article, we shall illustrate the application of the analytical and interventionist concept of ‘Critical Points of Contact’ (CPC) through a number of urban design studios. The notion of CPC has been developed over a span of the last three to four years and is reported in more detail...
The critical end point through observables
Kozlov, G. [Joint Institute for Nuclear Research, Joliot-Curie st.6, Dubna, 141980 (Russian Federation)
2016-01-22
We develop the model of the critical phenomena of strongly interacting matter at high temperatures and baryon densities. The dual Yang-Mills theory with scalar degrees of freedom (the dilatons) is used. The dilatons are the consequence of a spontaneous breaking of a scale symmetry. The phase transitions are considered in systems where the field conjugate to the order parameter has the critical end mode. The critical end point (CEP) is a distinct singular feature existence of which is dictated by the chiral dynamics. The physical realization of CEP is via the influence quantum fluctuations of two-body Bose-Einstein correlations for observed particles to which the critical end mode couples.
QCD Critical Points and Their Associated Soft Modes
Kunihiro, T.; Y. Minami; Zhang, Z
2010-01-01
The mean-field level calculation shows that the QCD matter can have multiple critical points incorporating the color superconductivity under charge neutrality constraint due to the repulsive vector interaction; this actually implies that the QCD matter is very soft for a simultaneous formation of diquark and chiral condensates coupled with the baryonic density. Dynamical density fluctuations are analyzed as possible soft modes around the QCD critical point using dissipative relativistic fluid...
Approaching the chiral point in two-flavour lattice simulations
We investigate the behaviour of the pion decay constant and the pion mass in two-flavour lattice QCD, with the physical and chiral points as ultimate goal. Measurements come from the ensembles generated by the CLS initiative using the O(a)-improved Wilson formulation, with lattice spacing down to about 0.05 fermi and pion masses as low as 190 MeV. The applicability of SU(2) chiral perturbation theory is investigated, and various functional forms, and their range of validity, are compared. The physical scale is set through the kaon decay constant, whose measurement is enabled by inserting a third, heavier valence strange quark.
Chiral Primordial Gravitational Waves from a Lifshitz Point
Takahashi, Tomohiro; Soda, Jiro
2009-01-01
We study primordial gravitational waves produced during inflation in quantum gravity at a Lifshitz point proposed by Ho${\\rm\\check{r}}$ava. Assuming power-counting renormalizability, foliation preserving diffeomorphism invariance, and the condition of detailed balance, we show that primordial gravitational waves are circularly polarized due to parity violation. The chirality of primordial gravitational waves is a quite robust prediction of quantum gravity at a Lifshitz point which can be test...
Possibility of QCD critical point sweep during black hole formation
We discuss the possibility to probe the QCD critical point during the dynamical black hole formation from a gravitational collapse of a massive star, where the temperature and the baryon chemical potential become as high as T∼90 MeV and μB∼1300 MeV. Comparison with the phase boundary in chiral effective models suggests that quark matter is likely to be formed before the horizon is formed. Furthermore, the QCD critical point may be probed during the black hole formation. The critical point is found to move in the lower temperature direction in asymmetric nuclear matter, and in some of the chiral models it is found to be in the reachable region during the black hole formation processes.
Chiral Equivariant Cohomology of a Point: A First Look
Linshaw, Andrew R.
2011-09-01
The chiral equivariant cohomology contains and generalizes the classical equivariant cohomology of a manifold M with an action of a compact Lie group G. For any simple G, there exist compact manifolds with the same classical equivariant cohomology, which can be distinguished by this invariant. When M is a point, this cohomology is an interesting conformal vertex algebra whose structure is still mysterious. In this paper, we scratch the surface of this object in the case G = SU(2).
Critical behaviors near the (tri-)critical end point of QCD within the NJL model
Lu, Ya; Cui, Zhu-Fang; Zong, Hong-Shi
2015-01-01
We investigate the dynamical chiral symmetry breaking and its restoration at finite density and temperature within the two-flavor Nambu-Jona-Lasinio model, and mainly focus on the critical behaviors near the critical end point (CEP) and tricritical point (TCP) of QCD. The co-existence region of the Wigner and Nambu phase is determined in the phase diagram for the massive and massless current quark, respectively. We use the various susceptibilities to locate the CEP/TCP and then extract the critical exponents near them. Our calculations reveal that the various susceptibilities share the same critical behaviors for the physical current quark mass, while they show different features in the chiral limit. Furthermore the critical exponent of order parameter at the TCP, $\\beta$=1/4, differs from that on the $O(4)$ line, $\\beta$=1/2, which indicates a change in the universality class.
Critical behaviors near the (tri-)critical end point of QCD within the NJL model
Lu, Ya; Du, Yi-Lun [Nanjing University, Department of Physics, Nanjing (China); Cui, Zhu-Fang [Nanjing University, Department of Physics, Nanjing (China); CAS, State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Beijing (China); Zong, Hong-Shi [Nanjing University, Department of Physics, Nanjing (China); Joint Center for Particle, Nuclear Physics and Cosmology, Nanjing (China); CAS, State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Beijing (China)
2015-10-15
We investigate the dynamical chiral symmetry breaking and its restoration at finite density and temperature within the two-flavor Nambu-Jona-Lasinio model, and mainly focus on the critical behaviors near the critical end point (CEP) and tricritical point (TCP) of quantum chromodynamics. The multi-solution region of the Nambu and Wigner ones is determined in the phase diagram for the massive and massless current quark, respectively. We use the various susceptibilities to locate the CEP/TCP and then extract the critical exponents near them. Our calculations reveal that the various susceptibilities share the same critical behaviors for the physical current quark mass, while they show different features in the chiral limit. (orig.)
Dynamical net-proton fluctuations near a QCD critical point
Herold, Christoph; Yan, Yupeng; Kobdaj, Chinorat
2016-01-01
We investigate the evolution of the net-proton kurtosis and the kurtosis of the chiral order parameter near the critical point in the model of nonequilibrium chiral fluid dynamics. The order parameter is propagated explicitly and coupled to an expanding fluid of quarks and gluons in order to describe the dynamical situation in a heavy-ion collision. We study the critical region near the critical point on the crossover side. There are two sources of fluctuations: non-critical initial event-by-event fluctuations and critical fluctuations. These fluctuations can be distinguished by comparing a mean-field evolution of averaged thermodynamic quantities with the inclusion of fluctuations at the phase transition. We find that while the initial state fluctuations give rise to flat deviations from statistical fluctuations, critical fluctuations reveal a clear structure of the phase transition. The signals of the critical point in the net-proton and sigma field kurtosis are affected by the nonequilibrium dynamics and t...
Chiral symmetry breaking in three-dimensional quantum electrodynamics as fixed point annihilation
Herbut, Igor F
2016-01-01
Spontaneous chiral symmetry breaking in three dimensional ($d=3$) quantum electrodynamics is understood as annihilation of an infrared-stable fixed point that describes the large-N conformal phase by another unstable fixed point at a critical number of fermions $N=N_c$. We discuss the root of universality of $N_c$ in this picture, together with some features of the phase boundary in the $(d,N)$ plane. In particular, it is shown that as $d\\rightarrow 4$, $N_c\\rightarrow 0$ with a constant slope, our best estimate of which suggests that $N_c = 2.89$ in $d=3$.
Chiral symmetry breaking in three-dimensional quantum electrodynamics as fixed point annihilation
Herbut, Igor F.
2016-07-01
Spontaneous chiral symmetry breaking in three-dimensional (d =3 ) quantum electrodynamics is understood as annihilation of an infrared-stable fixed point that describes the large-N conformal phase by another unstable fixed point at a critical number of fermions N =Nc. We discuss the root of universality of Nc in this picture, together with some features of the phase boundary in the (d ,N ) plane. In particular, it is shown that as d →4 , Nc→0 with a constant slope, our best estimate of which suggests that Nc=2.89 in d =3 .
Dynamical net-proton fluctuations near a QCD critical point
Herold, Christoph; Nahrgang, Marlene; Yan, Yupeng; Kobdaj, Chinorat
2016-02-01
We investigate the evolution of the net-proton kurtosis and the kurtosis of the chiral order parameter near the critical point in the model of nonequilibrium chiral fluid dynamics. The order parameter is propagated explicitly and coupled to an expanding fluid of quarks and gluons in order to describe the dynamical situation in a heavy-ion collision. We study the critical region near the critical point on the crossover side. There are two sources of fluctuations: noncritical initial event-by-event fluctuations and critical fluctuations. These fluctuations can be distinguished by comparing a mean-field evolution of averaged thermodynamic quantities with the inclusion of fluctuations at the phase transition. We find that while the initial state fluctuations give rise to flat deviations from statistical fluctuations, critical fluctuations reveal a clear structure of the phase transition. The signals of the critical point in the net-proton and σ -field kurtosis are affected by the nonequilibrium dynamics and the inhomogeneity of the space-time evolution but they develop clearly.
W-algebras and chiral differential operators at the critical Level
Fortuna, Giorgia
2012-01-01
Let $\\mathcal{A}_{crit}$ be the chiral algebra corresponding to the affine Kac-Moody algebra at the critical level $\\hat{\\mathfrak{g}}_{crit}$. Let $\\mathfrak{Z}_{crit}$ be the center of $\\mathcal{A}_{crit}$. The commutative chiral algebra $\\mathfrak{Z}_{crit}$ admits a canonical deformation into a non-commutative chiral algebra $\\mathcl{W}_{h}$. In this paper we will express the resulting first order deformation via the chiral algebra $\\mathcal{D}_{crit}$ of chiral differential operators of $G((t))$ at the critical level.
QCD critical point sweep during black hole formation
We discuss the possibility to probe the QCD critical point during the prompt black hole formation. In black hole formation processes, temperature and baryon chemical potential become as high as T∼ 90MeV and μB∼ 1300MeV. This high baryon chemical potential would allow nuclear matter to experience the QCD phase transition, and the temperature may be higher than the QCD critical point temperature. We compare the phase boundary in chiral effective models and the thermal environment obtained in the ν radiation hydrodynamical calculation of the gravitational collapse of a 40M⊙ star leading to the black hole formation. This comparison suggests that quark matter is likely to be formed, and the QCD critical point may be swept.
Metallic magnets without inversion symmetry and antiferromagnetic quantum critical points
Fischer, I.A.
2006-07-01
This thesis focusses on two classes of systems that exhibit non-Fermi liquid behaviour in experiments: we investigated aspects of chiral ferromagnets and of antiferromagnetic metals close to a quantum critical point. In chiral ferromagnets, the absence of inversion symmetry makes spin-orbit coupling possible, which leads to a helical modulation of the ferromagnetically ordered state. We studied the motion of electrons in the magnetically ordered state of a metal without inversion symmetry by calculating their generic band-structure. We found that spin-orbit coupling, although weak, has a profound effect on the shape of the Fermi surface: On a large portion of the Fermi surface the electron motion parallel to the helix practically stops. Signatures of this effect can be expected to show up in measurements of the anomalous Hall effect. Recent neutron scattering experiments uncovered the existence of a peculiar kind of partial order in a region of the phase diagram adjacent to the ordered state of the chiral ferromagnet MnSi. Starting from the premise that this partially ordered state is a thermodynamically distinct phase, we investigated an extended Ginzburg-Landau theory for chiral ferromagnets. In a certain parameter regime of the Ginzburg-Landau theory we identified crystalline phases that are reminiscent of the so-called blue phases in liquid crystals. Many antiferromagnetic heavy-fermion systems can be tuned into a regime where they exhibit non-Fermi liquid exponents in the temperature dependence of thermodynamic quantities such as the specific heat capacity; this behaviour could be due to a quantum critical point. If the quantum critical behaviour is field-induced, the external field does not only suppress antiferromagnetism but also induces spin precession and thereby influences the dynamics of the order parameter. We investigated the quantum critical behavior of clean antiferromagnetic metals subject to a static, spatially uniform external magnetic field. We
W-algebras and chiral differential operators at the critical Level
Fortuna, Giorgia
2012-01-01
Let $\\mathcal{A}_{crit}$ be the chiral algebra corresponding to the affine Kac-Moody algebra at the critical level $\\hat{\\mathfrak{g}}_{crit}$. Let $\\mathfrak{Z}_{crit}$ be the center of $\\mathcal{A}_{crit}$. The commutative chiral algebra $\\mathfrak{Z}_{crit}$ admits a canonical deformation into a non-commutative chiral algebra $\\mathcl{W}_{h}$. In this paper we will express the resulting first order deformation via the chiral algebra $\\mathcal{D}_{crit}$ of chiral differential operators of ...
Atropselective Syntheses of (−) and (+) Rugulotrosin A Utilizing Point-to-Axial Chirality Transfer
Qin, Tian; Skraba-Joiner, Sarah L.; Khalil, Zeinab G.; Johnson, Richard P.; Capon, Robert J.; Porco, John A.
2015-01-01
Chiral, dimeric natural products containing complex structures and interesting biological properties have inspired chemists and biologists for decades. A seven step total synthesis of the axially chiral, dimeric tetrahydroxanthone natural product rugulotrosin A is described. The synthesis employs a one-pot Suzuki coupling/dimerization to generate the requisite 2,2'-linked biaryl linkage. Highly selective point-to-axial chirality transfer was achieved using palladium catalysis with achiral pho...
Critical phenomena of emergent magnetic monopoles in a chiral magnet
Kanazawa, N.; Nii, Y.; Zhang, X.-X.; Mishchenko, A. S.; de Filippis, G.; Kagawa, F.; Iwasa, Y.; Nagaosa, N.; Tokura, Y.
2016-05-01
Second-order continuous phase transitions are characterized by symmetry breaking with order parameters. Topological orders of electrons, characterized by the topological index defined in momentum space, provide a distinct perspective for phase transitions, which are categorized as quantum phase transitions not being accompanied by symmetry breaking. However, there are still limited observations of counterparts in real space. Here we show a real-space topological phase transition in a chiral magnet MnGe, hosting a periodic array of hedgehog and antihedgehog topological spin singularities. This transition is driven by the pair annihilation of the hedgehogs and antihedgehogs acting as monopoles and antimonopoles of the emergent electromagnetic field. Observed anomalies in the magnetoresistivity and phonon softening are consistent with the theoretical prediction of critical phenomena associated with enhanced fluctuations of emergent field near the transition. This finding reveals a vital role of topology of the spins in strongly correlated systems.
QCD critical points and their associated soft modes
The mean-field level calculation shows that the QCD matter can have multiple critical points incorporating the color superconductivity under charge neutrality constraint due to the repulsive vector interaction; this actually implies that the QCD matter is very soft for a simultaneous formation of diquark and chiral condensates coupled with the baryonic density. Dynamical density fluctuations are analyzed as possible soft modes around the QCD critical point using dissipative relativistic fluid dynamics. It is found that the entropy fluctuation solely gets enhanced while the sound modes due to mechanical density fluctuations are strongly attenuated around the QCD CP, which may suggest a suppression or even total disappearance of Mach cone at the CP. (author)
QCD Critical Points and Their Associated Soft Modes
Kunihiro, T; Zhang, Z
2010-01-01
The mean-field level calculation shows that the QCD matter can have multiple critical points incorporating the color superconductivity under charge neutrality constraint due to the repulsive vector interaction; this actually implies that the QCD matter is very soft for a simultaneous formation of diquark and chiral condensates coupled with the baryonic density. Dynamical density fluctuations are analyzed as possible soft modes around the QCD critical point using dissipative relativistic fluid dynamics. It is found that the entropy fluctuation solely gets enhanced while the sound modes due to mechanical density fluctuations are strongly attenuated around the QCD CP, which may suggest a suppression or even total disappearance of Mach cone at the CP.
Critical endpoint in the presence of a chiral chemical potential
Cui, Zhu-Fang; Lu, Ya; Roberts, Craig D; Schmidt, Sebastian M; Xu, Shu-Sheng; Zong, Hong-Shi
2016-01-01
A class of Polyakov-loop-modified Nambu--Jona-Lasinio (PNJL) models have been used to support a conjecture that numerical simulations of lattice-regularized quantum chromodynamics (QCD) defined with a chiral chemical potential can provide information about the existence and location of a critical endpoint in the QCD phase diagram drawn in the plane spanned by baryon chemical potential and temperature. That conjecture is challenged by conflicts between the model results and analyses of the same problem using simulations of lattice-regularized QCD (lQCD) and well-constrained Dyson-Schwinger equation (DSE) studies. We find the conflict is resolved in favor of the lQCD and DSE predictions when both a physically-motivated regularization is employed to suppress the contribution of high-momentum quark modes in the definition of the effective potential connected with the PNJL models and the four-fermion coupling in those models does not react strongly to changes in the mean-field that is assumed to mock-up Polyakov l...
Critical point analysis of phase envelope diagram
Soetikno, Darmadi; Kusdiantara, Rudy; Puspita, Dila; Sidarto, Kuntjoro A.; Siagian, Ucok W. R.; Soewono, Edy; Gunawan, Agus Y.
2014-03-01
Phase diagram or phase envelope is a relation between temperature and pressure that shows the condition of equilibria between the different phases of chemical compounds, mixture of compounds, and solutions. Phase diagram is an important issue in chemical thermodynamics and hydrocarbon reservoir. It is very useful for process simulation, hydrocarbon reactor design, and petroleum engineering studies. It is constructed from the bubble line, dew line, and critical point. Bubble line and dew line are composed of bubble points and dew points, respectively. Bubble point is the first point at which the gas is formed when a liquid is heated. Meanwhile, dew point is the first point where the liquid is formed when the gas is cooled. Critical point is the point where all of the properties of gases and liquids are equal, such as temperature, pressure, amount of substance, and others. Critical point is very useful in fuel processing and dissolution of certain chemicals. Here in this paper, we will show the critical point analytically. Then, it will be compared with numerical calculations of Peng-Robinson equation by using Newton-Raphson method. As case studies, several hydrocarbon mixtures are simulated using by Matlab.
The QCD Critical Point and Related Observables
Nahrgang, Marlene
2016-01-01
The search for the critical point of QCD in heavy-ion collision experiments has sparked enormous interest with the completion of phase I of the RHIC beam energy scan. Here, I review the basics of the thermodynamics of the QCD phase transition and its implications for experimental multiplicity fluctuations in heavy-ion collisions. Several sources of noncritical fluctuations impact the observables and need to be understood in addition to the critical phenomena. Recent progress has been made in dynamical modeling of critical fluctuations, which ultimately is indispensable to understand potential signals of the QCD critical point in heavy-ion collision.
The effective QCD phase diagram and the critical end point
Ayala, Alejandro; Cobos-Martinez, J J; Hernandez-Ortiz, Saul; Raya, Alfredo
2014-01-01
We study the QCD phase diagram on the plane of temperature T and quark chemical potential mu, modelling the strong interactions with the linear sigma model coupled to quarks. The phase transition line is found from the effective potential at finite T and mu taking into accounts the plasma screening effects. We find the location of the critical end point (CEP) to be (mu^CEP/T_c,T^CEP/T_c) sim (1.2,0.8), where T_c is the (pseudo)critical temperature for the crossover phase transition at vanishing mu. This location lies within the region found by lattice inspired calculations. The results show that in the linear sigma model, the CEP's location in the phase diagram is expectedly determined solely through chiral symmetry breaking. The same is likely to be true for all other models which do not exhibit confinement, provided the proper treatment of the plasma infrared properties for the description of chiral symmetry restoration is implemented. Similarly, we also expect these corrections to be substantially relevant...
Correlation Probes of a QCD Critical Point
Csörgö, T
2009-01-01
Critical opalescence is a characteristic experimental signature of a second order phase transition in solid state physics. A new, experimentally accessible measure of opacity and of attenuation length in heavy ion reactions is suggested, as a combination of HBT radii and nuclear modification factors. This opacity is maximal when $\\sqrt{s_{NN}}$, the system size and centrality correspond to the critical point of QCD. To characterize the phase transition at this critical point, the critical exponent of the correlation function can be determined by measuring the L\\'evy index of stability of the Bose-Einstein or HBT correlations. The exponent of the correlation length can be determined from fits to the multiplicity distribution in various pseudorapidity intervals, also as a function of colliding energy, system size, centrality and (chemical) freeze-out temperature. These two critical exponents determine the remaining four critical exponents and the universality class of this second order phase transition. As a co...
Critical Points in Distance Learning System
Airina Savickaitė
2013-08-01
Full Text Available Purpose – This article presents the results of distance learning system analysis, i.e. the critical elements of the distance learning system. The critical points of distance learning are a part of distance education online environment interactivity/community process model. The most important is the fact that the critical point is associated with distance learning participants. Design/methodology/approach – Comparative review of articles and analysis of distance learning module. Findings – A modern man is a lifelong learner and distance learning is a way to be a modern person. The focus on a learner and feedback is the most important thing of learning distance system. Also, attention should be paid to the lecture-appropriate knowledge and ability to convey information. Distance system adaptation is the way to improve the learner’s learning outcomes. Research limitations/implications – Different learning disciplines and learning methods may have different critical points. Practical implications – The information of analysis could be important for both lecturers and students, who studies distance education systems. There are familiar critical points which may deteriorate the quality of learning. Originality/value – The study sought to develop remote systems for applications in order to improve the quality of knowledge. Keywords: distance learning, process model, critical points. Research type: review of literature and general overview.
Anomalies, instantons and chiral symmetry breaking at a Lifshitz point
Bakas, Ioannis
2012-01-01
We give a new twist to an old-fashioned topic in quantum field theory describing violations of the chiral charge conservation of massless fermions through Adler-Bell-Jackiw anomalies in the background of instanton fields in the context of non-relativistic Lifshitz theories. The results we report here summarize in a nut-shell our earlier work on the subject found in arXiv:1103.5693 and arXiv:1110.1332. We present simple examples where index computations can be carried out explicitly focusing, in particular, to gravitational models of Lifshitz type and highlight their differences from ordinary gravity in four space-time dimensions.
Quench dynamics across quantum critical points
We study the quantum dynamics of a number of model systems as their coupling constants are changed rapidly across a quantum critical point. The primary motivation is provided by the recent experiments of Greiner et al. [Nature (London) 415, 39 (2002)] who studied the response of a Mott insulator of ultracold atoms in an optical lattice to a strong potential gradient. In a previous work, it had been argued that the resonant response observed at a critical potential gradient could be understood by proximity to an Ising quantum critical point describing the onset of density wave order. Here we obtain numerical results on the evolution of the density wave order as the potential gradient is scanned across the quantum critical point. This is supplemented by studies of the integrable quantum Ising spin chain in a transverse field, where we obtain exact results for the evolution of the Ising order correlations under a time-dependent transverse field. We also study the evolution of transverse superfluid order in the three-dimensional case. In all cases, the order parameter is best enhanced in the vicinity of the quantum critical point
Nature of the NJL critical end point
The behavior of the scalar channel spectral function is investigated near the critical end point on the temperature-quark chemical potential plane of two-flavor Nambu-Jona-Lasinio (NJL) model within the leading 1/Nc approximation with Nc being the number of colors. It is found that the relevant soft mode at the critical end point is the scalar density fluctuation with space-like dispersion, which is mixed with those of the quark-number and entropy densities, while on the other hand the sigma meson mode stays massive. (Slightly condensed version of the paper, hep-ph/0302167). (author)
QCD critical point: The race is on
Rajiv V Gavai
2015-05-01
A critical point in the phase diagram of quantum chromodynamics (QCD), if established either theoretically or experimentally, would be as profound a discovery as the good-old gas–liquid critical point. Unlike the latter, however, first-principles-based approaches are being employed to locate it theoretically. Due to the short-lived nature of the concerned phases, novel experimental techniques are needed to search for it. The Relativistic Heavy Ion Collider (RHIC) in USA has an experimental programme to do so. This short review is an attempt to provide a glimpse of the race between the theorists and the experimentalists as well as the synergy between them.
Critical points and number of master integrals
Lee, Roman N
2013-01-01
We consider the question about the number of master integrals for a multiloop Feynman diagram. We show that, for a given set of denominators, this number is totally determined by the critical points of the polynomials entering either of the two representations: the parametric representation and the Baikov representation. In particular, for the parametric representation the corresponding polynomial is just the sum of Symanzik polynomials. The relevant topological invariant is the sum of the Milnor numbers of the proper critical points. We present a Mathematica package Mint to automatize the counting of the master integrals.
QCD critical point: the race is on
A critical point in the phase diagram of quantum chromodynamics (QCD), if established either theoretically or experimentally, would be as profound a discovery as the good-old gas-liquid critical point. Unlike the latter, however, first-principles-based approaches are being employed to locate it theoretically. Due to the short-lived nature of the concerned phases, novel experimental techniques are needed to search for it. The Relativistic Heavy Ion Collider (RHIC) in USA has an experimental programme to do so. This short review is an attempt to provide a glimpse of the race between the theorists and the experimentalists as well as the synergy between them. (author)
Dynamical simulation of a linear sigma model near the critical point
The intention of this study is the search for signatures of the chiral phase transition. To investigate the impact of fluctuations, e.g. of the baryon number, on the transition or a critical point, the linear sigma model is treated in a dynamical 3+1D numerical simulation. Chiral fields are approximated as classical fields, quarks are described by quasi particles in a Vlasov equation. Additional dynamic is implemented by quark-quark and quark-sigma-field interaction. For a consistent description of field-particle interactions, a new Monte-Carlo-Langevin-like formalism has been developed and is discussed.
SU (2 )1 chiral edge modes of a critical spin liquid
Poilblanc, Didier; Schuch, Norbert; Affleck, Ian
2016-05-01
Protected chiral edge modes are a well-known signature of topologically ordered phases like the fractional quantum Hall states. Recently, using the framework of projected entangled pair states (PEPS) on the square lattice, we constructed a family of chiral resonating valence bond states with Z2 gauge symmetry. Here we revisit and analyze in full details the properties of the edge modes as given by their entanglement spectra on a cylinder. Surprisingly, we show that the latter can be well described by a chiral SU (2 )1 conformal field theory, as for the ν =1 /2 (bosonic) gapped Laughlin state, although our numerical data suggest a critical bulk compatible with an emergent U(1 ) gauge symmetry. We propose that our family of PEPS may physically describe a boundary between a chiral topological phase and a trivial phase.
Ruggieri, M; Peng, G X
2016-01-01
We study the influence of external electric, $E$, and magnetic, $B$, fields parallel to each other, and of a chiral chemical potential, $\\mu_5$, on the chiral phase transition of Quantum Chromodynamics. Our theoretical framework is a Nambu-Jona-Lasinio model with a contact interaction. Within this model we compute the critical temperature of chiral symmetry restoration, $T_c$, as a function of the chiral chemical potential and field strengths. We find that the fields inhibit and $\\mu_5$ enhances chiral symmetry breaking, in agreement with previous studies.
RHIC Critical Point Search: Assessing STAR's Capabilities
Sorensen, Paul
2007-01-01
In this report we discuss the capabilities and limitations of the STAR detector to search for signatures of the QCD critical point in a low energy scan at RHIC. We find that a RHIC low energy scan will cover a broad region of interest in the nuclear matter phase diagram and that the STAR detector -- a detector designed to measure the quantities that will be of interest in this search -- will provide new observables and improve on previous measurements in this energy range.
Atropselective Syntheses of (−) and (+) Rugulotrosin A Utilizing Point-to-Axial Chirality Transfer
Qin, Tian; Skraba-Joiner, Sarah L.; Khalil, Zeinab G.; Johnson, Richard P.; Capon, Robert J.; Porco, John A.
2014-01-01
Chiral, dimeric natural products containing complex structures and interesting biological properties have inspired chemists and biologists for decades. A seven step total synthesis of the axially chiral, dimeric tetrahydroxanthone natural product rugulotrosin A is described. The synthesis employs a one-pot Suzuki coupling/dimerization to generate the requisite 2,2'-linked biaryl linkage. Highly selective point-to-axial chirality transfer was achieved using palladium catalysis with achiral phosphine ligands. Single X-ray crystal diffraction data was obtained to confirm both the atropisomeric configuration and absolute stereochemistry of rugulotrosin A. Computational studies are described to rationalize the atropselectivity observed in the key dimerization step. Comparison of the crude fungal extract with synthetic rugulotros in A and its atropisomer verified that nature generates a single atropisomer of the natural product. PMID:25698333
Mandal, Ipsita; Tewari, Sumanta
2016-05-01
We show that certain singularities of the Hamiltonian in the complex wave vector space can be used to identify topological quantum phase transitions for 1D chiral topological superconductors/superfluids in the BDI class. These singularities fall into the category of the so-called exceptional points (EP's) studied in the context of non-Hermitian Hamiltonians describing open quantum systems. We also propose a generic formula in terms of the properties of the EP's to quantify the exact number of Majorana zero modes in a particular chiral topological superconducting phase, given the values of the parameters appearing in the Hamiltonian. This formula serves as an alternative to the familiar integer (Z) winding number invariant characterizing topological superconductor/superfluid phases in the chiral BDI class.
Critical point anomalies include expansion shock waves
Nannan, N. R., E-mail: ryan.nannan@uvs.edu [Mechanical Engineering Discipline, Anton de Kom University of Suriname, Leysweg 86, PO Box 9212, Paramaribo, Suriname and Process and Energy Department, Delft University of Technology, Leeghwaterstraat 44, 2628 CA Delft (Netherlands); Guardone, A., E-mail: alberto.guardone@polimi.it [Department of Aerospace Science and Technology, Politecnico di Milano, Via La Masa 34, 20156 Milano (Italy); Colonna, P., E-mail: p.colonna@tudelft.nl [Propulsion and Power, Delft University of Technology, Kluyverweg 1, 2629 HS Delft (Netherlands)
2014-02-15
From first-principle fluid dynamics, complemented by a rigorous state equation accounting for critical anomalies, we discovered that expansion shock waves may occur in the vicinity of the liquid-vapor critical point in the two-phase region. Due to universality of near-critical thermodynamics, the result is valid for any common pure fluid in which molecular interactions are only short-range, namely, for so-called 3-dimensional Ising-like systems, and under the assumption of thermodynamic equilibrium. In addition to rarefaction shock waves, diverse non-classical effects are admissible, including composite compressive shock-fan-shock waves, due to the change of sign of the fundamental derivative of gasdynamics.
Critical point anomalies include expansion shock waves
From first-principle fluid dynamics, complemented by a rigorous state equation accounting for critical anomalies, we discovered that expansion shock waves may occur in the vicinity of the liquid-vapor critical point in the two-phase region. Due to universality of near-critical thermodynamics, the result is valid for any common pure fluid in which molecular interactions are only short-range, namely, for so-called 3-dimensional Ising-like systems, and under the assumption of thermodynamic equilibrium. In addition to rarefaction shock waves, diverse non-classical effects are admissible, including composite compressive shock-fan-shock waves, due to the change of sign of the fundamental derivative of gasdynamics
Critical Opalescence: An Optical Signature for a QCD Critical Point
Csorgo, T
2009-01-01
Four possible scenarios are considered for a transition from a quark-gluon matter to hadronic matter, and their corresponding correlation signatures are discussed. Four criteria are highlighted for a definitive experimental search for a QCD critical point. An old-new experimental measure, the optical opacity (or its inverse the nuclear attenuation length) is determined, in terms of a combination of nuclear suppression factors and a measurement of the relevant fireball length scales. Length scale estimates using either the Hanbury Brown -- Twiss radii or that of the initial nuclear geometry for measurements of optical opacity with respect to the reaction plane yield, somewhat surprizingly, nearly the same nuclear attenuation lenght in 0-5 % most central 200 GeV Au+Au collisions, corresponding to 2.9 $\\pm$ 0.3 fm. The necessity and the possibility of measuring critical exponents is also discussed in the context of determination of the universality class of the QCD critical point. Critical opalescence is propose...
Critical theory of overscreened Kondo fixed points
The low-temperature fixed point of the Kondo model, for k bands and a spin-s impurity, is well understood by Nozieres' Fermi liquid theory for k≤2s. However when k>2s, a new type of non-trivial fixed point is known to occur. We study this fixed point using higher-level Kac-Moody conformal field theory and Cardy's approach to boundary critical phenomena. The specific heat and magnetization are shown to be determined by the leading irrelevant operator and the corresponding critical exponents are obtained exactly. The Wilson ratio is argued to be universal and its exact value is also calculated. The asymptotic finite-size spectrum is determined. Thermodynamic exponents agree precisely with the Bethe ansatz; for k=2, s=1/2, the Wilson ratio also agrees well with the approximate value obtained from the Bethe ansatz; the slope of the β-function agrees with the perturbative result in the large-k limit and the finite-size spectrum agrees excellently with approximate results obtained previously by Wilson's numerical renormalization group method in the case k=2, s=1/2. (orig.)
Dynamical response near quantum critical points
Lucas, Andrew; Podolsky, Daniel; Witczak-Krempa, William
2016-01-01
We study high frequency response functions, notably the optical conductivity, in the vicinity of quantum critical points (QCPs) by allowing for both detuning from the critical coupling and finite temperature. We consider general dimensions and dynamical exponents. This leads to a unified understanding of sum rules. In systems with emergent Lorentz invariance, powerful methods from conformal field theory allow us to fix the high frequency response in terms of universal coefficients. We test our predictions analytically in the large-N O(N) model and using the gauge-gravity duality, and numerically via Quantum Monte Carlo simulations on a lattice model hosting the interacting superfluid-insulator QCP. In superfluid phases, interacting Goldstone bosons qualitatively change the high frequency optical conductivity, and the corresponding sum rule.
Chiral condensates from tau decay: a critical reappraisal
Bordes, J; Penarrocha, J; Schilcher, K; Bordes, Jose; Dominguez, Cesareo A.; Penarrocha, Jose; Schilcher, Karl
2006-01-01
The saturation of QCD chiral sum rules is reanalyzed in view of the new and complete analysis of the ALEPH experimental data on the difference between vector and axial-vector correlators (V-A). Ordinary finite energy sum rules (FESR) exhibit poor saturation up to energies below the tau-lepton mass. A remarkable improvement is achieved by introducing pinched, as well as minimizing polynomial integral kernels. Both methods are used to determine the dimension d=6 and d=8 vacuum condensates in the Operator Product Expansion, with the results: {O}_{6}=-(0.00226 \\pm 0.00055) GeV^6, and O_8=-(0.0053 \\pm 0.0033) GeV^8 from pinched FESR, and compatible values from the minimizing polynomial FESR. Some higher dimensional condensates are also determined, although we argue against extending the analysis beyond dimension $d = 8$. The value of the finite remainder of the (V-A) correlator at zero momentum is also redetermined: \\Pi (0)= -4 \\bar{L}_{10}=0.02579 \\pm 0.00023. The stability and precision of the predictions are si...
Exotic Quantum Critical Points with Staggered Fermions
Ayyar, Venkitesh
2015-01-01
We study two flavors of massless staggered fermions interacting via an on-site four-fermion inter- action and argue that the model contains an exotic quantum critical point separating the perturba- tive massless phase from a massive fermion phase at strong couplings where the fermion bilinear condensate remains zero. We believe that no spontaneous symmetry breaking occurs at the tran- sition. We have extensive calculations in three Euclidian dimensions that are consistent with the existence of a single second order phase transition separating the two phases. Although mean field theory suggests that this transition will turn first order at sufficiently large number of dimensions, preliminary results suggest that the transition remains second order in four-dimensions.
We calculate the temperature T and angular (θ, ϕ) dependencies of the upper critical induction Bc2(θ, ϕ, T) for parallel-spin superconductors with an axially symmetric p-wave pairing interaction pinned to the lattice and a dominant ellipsoidal Fermi surface (FS). For all FS anisotropies, the chiral Scharnberg–Klemm (SK) state Bc2(θ, ϕ, T) exceeds that of the chiral Anderson–Brinkman–Morel (ABM) state and exhibits a kink at θ = θ*(T, ϕ), indicative of a first-order transition from its chiral, nodal-direction behavior to its non-chiral, antinodal-direction behavior. Applicabilities to Sr2RuO4, UCoGe and the candidate topological superconductor CuxBi2Se3 are discussed. (fast track communication)
Applications of chiral symmetry
The author discusses several topics in the applications of chiral symmetry at nonzero temperature. First, where does the rho go? The answer: up. The restoration of chiral symmetry at a temperature Tχ implies that the ρ and a1 vector mesons are degenerate in mass. In a gauged linear sigma model the ρ mass increases with temperature, mρ(Tχ) > mρ(0). The author conjectures that at Tχ the thermal ρ - a1, peak is relatively high, at about ∼1 GeV, with a width approximately that at zero temperature (up to standard kinematic factors). The ω meson also increases in mass, nearly degenerate with the ρ, but its width grows dramatically with temperature, increasing to at least ∼100 MeV by Tχ. The author also stresses how utterly remarkable the principle of vector meson dominance is, when viewed from the modern perspective of the renormalization group. Secondly, he discusses the possible appearance of disoriented chiral condensates from open-quotes quenchedclose quotes heavy ion collisions. It appears difficult to obtain large domains of disoriented chiral condensates in the standard two flavor model. This leads to the last topic, which is the phase diagram for QCD with three flavors, and its proximity to the chiral critical point. QCD may be very near this chiral critical point, and one might thereby generated large domains of disoriented chiral condensates
Zhang, Jingchuan; Lörscher, Christopher; Gu, Qiang; Klemm, Richard A.
2014-01-01
We calculate the temperature $T$ and angular $(\\theta,\\phi)$ dependence of the upper critical induction $B_{c2}(\\theta,\\phi,T)$ for parallel-spin superconductors with an axially symmetric $p$-wave pairing interaction pinned to the lattice and a dominant ellipsoidal Fermi surface (FS). For all FS anisotropies, the chiral Scharnberg-Klemm state $B_{c2}(\\theta,\\phi,T)$ exceeds that of the chiral Anderson-Brinkman-Morel state, and exhibits a kink at $\\theta=\\theta^{*}(T,\\phi)$, indicative of a fi...
Adiabatic waves along interfacial layers near the critical point
Gouin, Henri
2008-01-01
Near the critical point, isothermal interfacial zones are investigated starting from a non-local density of energy. From the equations of motion of thermocapillary fluids, we point out a new kind of adiabatic waves propagating along the interfacial layers. The waves are associated with the second derivatives of densities and propagate with a celerity depending on the proximity of the critical point.
Percolation systems away from the critical point
Deepak Dhar
2002-02-01
This article reviews some effects of disorder in percolation systems away from the critical density c. For densities below c, the statistics of large clusters deﬁnes the animals problem. Its relation to the directed animals problem and the Lee–Yang edge singularity problem is described. Rare compact clusters give rise to Grifﬁths singularities in the free energy of diluted ferromagnets, and lead to a very slow relaxation of magnetization. In biased diffusion on percolation clusters, trapping in dead-end branches leads to asymptotic drift velocity becoming zero for strong bias, and very slow relaxation of velocity near the critical bias ﬁeld.
Critical Point Dryer: Tousimis 916B Series C
Federal Laboratory Consortium — Description: CORAL Name: Critical Point Dryer This system utilizes CO 2to dry fragile suspended and floating structures Specifications / Capabilities: Wafer size up...
Poles Distribution of PVI Transcendents close to a Critical Point
Guzzetti, Davide
2011-01-01
The distribution of the poles of branches of the Painleve' VI transcendents associated to semi-simple Frobenius manifolds is determined close to a critical point. It is shown that the poles accumulate at the critical point, asymptotically along two rays. The example of the Frobenius manifold given by the quantum cohomology of the two-dimensional complex projective space is also considered.
Pole distribution of PVI transcendents close to a critical point
Guzzetti, Davide
2012-12-01
The distribution of the poles of Painlevé VI transcendents associated to semi-simple Frobenius manifolds is determined close to a critical point. It is shown that the poles accumulate at the critical point, asymptotically along two rays. As an example, the Frobenius manifold given by the quantum cohomology of CP2 is considered. The general PVI is also considered.
Has the QCD critical point been observed at RHIC?
Antoniou, N G; Diakonos, F K
2016-01-01
The experimental search for the location of the QCD critical point in the phase diagram is of primary importance. In a recent publication it is claimed that measurements at RHIC lead not only to the location of the critical point ($\\mu_{cep}=95$ MeV, $T_{cep}=165$ MeV) but also to the verification of its universality class ($3d$ Ising system) by extracting the values of the critical exponents ($\\gamma=1.2$, $\
A possibility of 5D gauge unification of SU(2)LxU(1)Y in SU(3)W is examined. The orbifold compactification allows fixed points where SU(2)LxU(1)Y representations can be assigned. We present a few possibilities which give long proton lifetime, top-bottom mass hierarchy from geometry, and reasonable neutrino masses. In general, these chiral models can lead to fixed point anomalies. We can show easily, due to the simplicity of the model, that these anomalies are cancelled by the relevant Chern-Simons terms for all the models we consider. It is also shown that the fixed point U(1)-graviton-graviton anomaly cancels without the help from the Chern-Simons term. Hence, we conjecture that the fixed point anomalies can be cancelled if the effective 4D theory is made anomaly free by locating chiral fermions at the fixed points. (author)
On Critical Point for Two Dimensional Holomorphics Systems
Valenzuela, Francisco
2011-01-01
Let $f:M\\rightarrow M$ be a biholomorphisms on two--dimensional a complex manifold, and let $X\\subseteq M$ be a compact $f$--invariant set such that $f|X$ is asymptotically dissipative and without sinks periodic points. We introduce a solely dynamical obstruction to dominated splitting, namely critical point. Critical point is a dynamical object and capture many of the dynamical properties of their one--dimensional counterpart.
A critical-point theory of the earthquakes
The scaling hypothesis underlying the theory of the critical point is briefly presented, and its application to earthquakes is outlined. The relevance of the 'self-organized criticality' is emphasized for the critical behavior of the probabilistic seismic events. As it is known, the phase transitions are understood by means of the so-called theory of the critical point. This theory has two ingredients: the renormalization group and the scaling hypothesis. The former gives critical exponents (at least in principle), as based on the general statistical principles of the phase transitions; this part has limited applicability to earthquakes, as long as the adequacy of such general principles to earthquakes is not yet fully known. The latter part however, the scaling hypothesis that underlines the phase transitions, is sufficiently general as to make it a reasonable hypothesis for the critical behavior of a very large class of complex systems, earthquakes included. The 'self-organized criticality' of the new phase occurring at the critical point suggests a general scaling theory. The present critical-point theory for the seismic events suggests the existence of the high intensity precursor seismic activity before the strong main earthquake. The quantitative evaluations obtained using this theory are affected by appreciable errors, caused by the divergent behavior in the critical-point vicinity of the relevant parameters. However, such theory indicated the need for the careful seismic monitoring of the precursor behavior, which may deliver interesting qualitative information. (authors)
Chiral spiral induced by a strong magnetic field
Abuki, H
2016-01-01
We study the modification of the chiral phase structure of QCD due to an external magnetic field. We first demonstrate how the effect of magnetic field can systematically be incorporated into a generalized Ginzburg-Landau framework. We then analyze the phase structure in the vicinity of the chiral critical point. In the chiral limit, the effect is found to be so drastic that it totally washes the tricritical point out of the phase diagram, bringing the continent for the chiral spiral. This is the case no matter how small is the intensity of the magnetic field. On the other hand, the current quark mass protects the chiral critical point from a weak magnetic field. However the critical point will eventually be covered by the chiral spiral phase as the magnetic field grows.
Multi-critical points in weakly anisotropic magnetic systems
This report starts with a rather extensive presentation of the concepts and ideas which constitute the basis of the modern theory of static critical phenomena. It is shown how at a critical point the semi-phenomenological concepts of universality and scaling are directly related to the divergence of the correlation length and how they are extended to a calculational method for critical behaviour in Wilson's Renormalization-Group (RG) approach. Subsequently the predictions of the molecular-field and RG-theories on the phase transitions and critical behaviour in weakly anisotropic antiferromagnets are treated. In a magnetic field applied along the easy axis, these materials can display an (H,T) phase diagram which contains either a bicritical point or a tetracritical point. Especially the behaviour close to these multi-critical points, as predicted by the extended-scaling theory, is discussed. (Auth.)
Shear viscosity at the Ising-nematic quantum critical point in two dimensional metals
Patel, Aavishkar A; Sachdev, Subir
2016-01-01
In a strongly interacting quantum liquid without quasiparticles, general scaling arguments imply that the dimensionless ratio $(k_B /\\hbar)\\, \\eta/s$, where $\\eta$ is the shear viscosity and $s$ is the entropy density, is a universal number. We compute the shear viscosity of the Ising-nematic critical point of metals in spatial dimension $d=2$ by an expansion below $d=5/2$. The anisotropy associated with directions parallel and normal to the Fermi surface leads to a violation of the scaling expectations: $\\eta$ scales in the same manner as a chiral conductivity, and the ratio $\\eta/s$ diverges as $T^{-2/z}$, where $z$ is the dynamic critical exponent for fermionic excitations dispersing normal to the Fermi surface.
Critical point symmetries in nuclei and their empirical realization
Zamfir, N
2002-01-01
There are theoretical and experimental evidences for new symmetries at the critical point of the spherical deformed phase transitions. The critical point in the phase/shape transition from spherical vibrator to a deformed gamma-unstable nucleus, is described by the E(5) symmetry and examples are provided by sup 1 sup 3 sup 4 Ba and sup 1 sup 0 sup 2 Pd. The X(5) analytic solutions for the critical point in the spherical to axially deformed phase/shape transition is closely manifested empirically in sup 1 sup 5 sup 2 Sm and in other N=90 isotones
Information-entropic signature of the critical point
Marcelo Gleiser
2015-07-01
Full Text Available We investigate the critical behavior of continuous (second-order phase transitions in the context of (2+1-dimensional Ginzburg–Landau models with a double-well effective potential. In particular, we show that the recently-proposed configurational entropy (CE—a measure of the spatial complexity of the order parameter in momentum space based on its Fourier-mode decomposition—can be used to identify the critical point. We compute the CE for different temperatures and show that large spatial fluctuations near the critical point (Tc—characterized by a divergent correlation length—lead to a sharp decrease in the associated configurational entropy. We further show that the CE density goes from a scale-free to an approximate scaling behavior |k|−5/3 as the critical point is approached. We reproduce the behavior of the CE at criticality with a percolating many-bubble model.
Spotlighting quantum critical points via quantum correlations at finite temperatures
Werlang, T; Rigolin, Gustavo
2011-01-01
We extend the program initiated in [T. Werlang et al., Phys. Rev. Lett. 105, 095702 (2010)] in several directions. Firstly, we investigate how useful quantum correlations, such as entanglement and quantum discord, are in the detection of critical points of quantum phase transitions when the system is at finite temperatures. For that purpose we study several thermalized spin models in the thermodynamic limit, namely, the XXZ model, the XY model, and the Ising model, all of which with an external magnetic field. We compare the ability of quantum discord, entanglement, and some thermodynamic quantities to spotlight the quantum critical points for several different temperatures. Secondly, for some models we go beyond nearest-neighbors and also study the behavior of entanglement and quantum discord for second nearest-neighbors around the critical point at finite temperature. Finally, we furnish a more quantitative description of how good all these quantities are in spotlighting critical points of quantum phase tra...
Inherently unstable networks collapse to a critical point
Sheinman, M.; Sharma, A.; Alvarado, J.; Koenderink, G. H.; MacKintosh, F. C.
2015-07-01
Nonequilibrium systems that are driven or drive themselves towards a critical point have been studied for almost three decades. Here we present a minimalist example of such a system, motivated by experiments on collapsing active elastic networks. Our model of an unstable elastic network exhibits a collapse towards a critical point from any macroscopically connected initial configuration. Taking into account steric interactions within the network, the model qualitatively and quantitatively reproduces results of the experiments on collapsing active gels.
The critical point of quantum chromodynamics through lattice and experiment
Sourendu Gupta
2011-05-01
This talk discusses methods of extending lattice computations at ﬁnite temperature into regions of ﬁnite chemical potential, and the conditions under which such results from the lattice may be compared to experiments. Such comparisons away from a critical point are absolutely essential for quantitative use of lattice QCD in heavy-ion physics. An outline of various arguments which can then be used to locate the critical point is also presented.
Critical Points and Gr\\"obner Bases: the Unmixed Case
Faugère, Jean-Charles; Spaenlehauer, Pierre-Jean
2012-01-01
We consider the problem of computing critical points of the restriction of a polynomial map to an algebraic variety. This is of first importance since the global minimum of such a map is reached at a critical point. Thus, these points appear naturally in non-convex polynomial optimization which occurs in a wide range of scientific applications (control theory, chemistry, economics,...). Critical points also play a central role in recent algorithms of effective real algebraic geometry. Experimentally, it has been observed that Gr\\"obner basis algorithms are efficient to compute such points. Therefore, recent software based on the so-called Critical Point Method are built on Gr\\"obner bases engines. Let $f_1,..., f_p$ be polynomials in $ \\Q[x_1,..., x_n]$ of degree $D$, $V\\subset\\C^n$ be their complex variety and $\\pi_1$ be the projection map $(x_1,.., x_n)\\mapsto x_1$. The critical points of the restriction of $\\pi_1$ to $V$ are defined by the vanishing of $f_1,..., f_p$ and some maximal minors of the Jacobian...
Identification of critical points of thermal environment in broiler production
AG Menezes
2010-03-01
Full Text Available This paper describes an exploratory study carried out to determine critical control points and possible risks in hatcheries and broiler farms. The study was based in the identification of the potential hazards existing in broiler production, from the hatchery to the broiler farm, identifying critical control points and defining critical limits. The following rooms were analyzed in the hatchery: egg cold storage, pre-heating, incubator, and hatcher rooms. Two broiler houses were studied in two different farms. The following data were collected in the hatchery and broiler houses: temperature (ºC and relative humidity (%, air velocity (m s-1, ammonia levels, and light intensity (lx. In the broiler house study, a questionnaire using information of the Broiler Production Good Practices (BPGP manual was applied, and workers were interviewed. Risk analysis matrices were build to determine Critical Control Points (CCP. After data collection, Statistical Process Control (SPC was applied through the analysis of the Process Capacity Index, using the software program Minitab15®. Environmental temperature and relative humidity were the critical points identified in the hatchery and in both farms. The classes determined as critical control points in the broiler houses were poultry litter, feeding, drinking water, workers' hygiene and health, management and biosecurity, norms and legislation, facilities, and activity planning. It was concluded that CCP analysis, associated with SPC control tools and guidelines of good production practices, may contribute to improve quality control in poultry production.
Thamapipol, Sirinporn
2011-01-01
Half-sandwich chiral electron poor one-point binding ruthenium catalyst that I focused on was one of the research interests in the Kündig group. A more general aim was to apply these catalysts to new transformations, expanding the range of applications that these complexes can satisfactorily catalyze. Only one successful example of asymmetric type 2 IMDA cycloaddition was reported. The challenges arise from the facts that several inconsistencies remain in the reported structure assignment of ...
Critical points of Green's function and geometric function theory
Gustafsson, Björn
2009-01-01
We study questions related to critical points of the Green's function of a bounded multiply connected domain in the complex plane. The motion of critical points, their limiting positions as the pole approaches the boundary and the differential geometry of the level lines of the Green's function are main themes in the paper. A unifying role is played by various affine and projective connections and corresponding M\\"obius invariant differential operators. In the doubly connected case the three Eisenstein series $E_2$, $E_4$, $E_6$ are used. A specific result is that a doubly connected domain is the disjoint union of the set of critical points of the Green's function, the set of zeros of the Bergman kernel and the separating boundary limit positions for these. At the end we consider the projective properties of the prepotential associated to a second order differential operator depending canonically on the domain.
Hints from Lattice for QCD Critical Point Search
Gavai, Rajiv V., E-mail: gavai@tifr.res.in [Department of Theoretical Physics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India)
2011-07-15
The freeze-out curve in the QCD phase diagram embodies a substantial amount of precise experimental data in heavy ion collisions. We present our lattice QCD results along the freeze-out curve. The variance, skew and kurtosis of the event distribution of baryon number are studied at several energies of interest through Pade resummations. A smooth behaviour is predicted for three ratios of these quantities at current RHIC and future LHC energies. Any deviations from these at the RHIC energy scan would signal the presence of a nearby critical point. Our lattice results on the critical point do show such a behaviour.
Critical points for finite Fibonacci chains of point delta-interactions and orthogonal polynomials
De Prunele, E, E-mail: eprunele@univ-fcomte.fr [Institut UTINAM, UMR CNRS 6213, Universite de Franche-Comte, 16 route de Gray, 25030 Besancon Cedex (France)
2011-10-21
For a one-dimensional Schroedinger operator with a finite number n of point delta-interactions with a common intensity, the parameters are the intensity, the n - 1 intercenter distances and the mass. Critical points are points in the parameters space of the Hamiltonian where one bound state appears or disappears. The study of critical points for Hamiltonians with point delta-interactions arranged along a Fibonacci chain is shown to be closely related to the study of the so-called Fibonacci operator, a discrete one-dimensional Schroedinger-type operator, which occurs in the context of tight binding Hamiltonians. These critical points are the zeros of orthogonal polynomials previously studied in the context of special diatomic linear chains with elastic nearest-neighbor interaction. Properties of the zeros (location, asymptotic behavior, gaps, ...) are investigated. The perturbation series from the solvable periodic case is determined. The measure which yields orthogonality is investigated numerically from the zeros. It is shown that the transmission coefficient at zero energy can be expressed in terms of the orthogonal polynomials and their associated polynomials. In particular, it is shown that when the number of point delta-interactions is equal to a Fibonacci number minus 1, i.e. when the intervals between point delta-interactions form a palindrome, all the Fibonacci chains at critical points are completely transparent at zero energy. (paper)
Thermal conductivity at a disordered quantum critical point
Hartnoll, Sean A.; Ramirez, David M.; Santos, Jorge E.
2016-04-01
Strongly disordered and strongly interacting quantum critical points are difficult to access with conventional field theoretic methods. They are, however, both experimentally important and theoretically interesting. In particular, they are expected to realize universal incoherent transport. Such disordered quantum critical theories have recently been constructed holographically by deforming a CFT by marginally relevant disorder. In this paper we find additional disordered fixed points via relevant disordered deformations of a holographic CFT. Using recently developed methods in holographic transport, we characterize the thermal conductivity in both sets of theories in 1+1 dimensions. The thermal conductivity is found to tend to a constant at low temperatures in one class of fixed points, and to scale as T 0.3 in the other. Furthermore, in all cases the thermal conductivity exhibits discrete scale invariance, with logarithmic in temperature oscillations superimposed on the low temperature scaling behavior. At no point do we use the replica trick.
Electron self-trapping at quantum and classical critical points
Auslender, M.I.; Katsnelson, M.I.
2006-01-01
Using Feynman path integral technique estimations of the ground state energy have been found for a conduction electron interacting with order parameter fluctuations near quantum critical points. In some cases only singular perturbation theory in the coupling constant emerges for the electron ground
Oscillatory integrals for phase functions having certain degenerate critical points
Jinmyong; KIM
2008-01-01
The paper is concerned with oscillatory integrals for phase functions having certain de- generate critical points. Under a finite type condition of phase functions we show the estimate of oscillatory integrals of the first kind. The decay of the oscillatory integral depends on indices of the finite type, the spatial dimension and the symbol.
Thermal conductivity at a disordered quantum critical point
Hartnoll, Sean A; Santos, Jorge E
2015-01-01
Strongly disordered and strongly interacting quantum critical points are difficult to access with conventional field theoretic methods. They are, however, both experimentally important and theoretically interesting. In particular, they are expected to realize universal incoherent transport. Such disordered quantum critical theories have recently been constructed holographically by deforming a CFT by marginally relevant disorder. In this paper we find additional disordered fixed points via relevant disordered deformations of a holographic CFT. Using recently developed methods in holographic transport, we characterize the thermal conductivity in both sets of theories in 1+1 dimensions. The thermal conductivity is found to tend to a constant at low temperatures in one class of fixed points, and to scale as $T^{0.3}$ in the other. Furthermore, in all cases the thermal conductivity exhibits discrete scale invariance, with logarithmic in temperature oscillations superimposed on the low temperature scaling behavior....
Diagnosis as the First Critical Point in the Treatment Trajectory
Missel, Malene; Pedersen, Jesper H; Hendriksen, Carsten;
2015-01-01
patients with operable lung cancer in order to identify their needs for care interventions from the point of diagnosis to hospitalization. METHODS: We investigated patients' lived experiences from a longitudinal perspective at 4 critical time points during the treatment trajectory; we present here the...... patient to face a new life situation, and demands one-on-one supportive care. CONCLUSIONS: Diagnosis is the first critical point for patients with operable lung cancer and disrupts their daily life. Patients need psychosocial support during the period from diagnosis to surgical intervention and patient......-tailored one-on-one information. IMPLICATIONS FOR PRACTICE: This article contributes to the knowledge base of support needs of lung cancer patients. Interventions aimed at supportive care during the period between diagnosis and surgical intervention should be researched....
Acceptance dependence of fluctuation measures near the QCD critical point
Ling, Bo; Stephanov, Mikhail A.
2016-03-01
We argue that a crucial determinant of the acceptance dependence of fluctuation measures in heavy-ion collisions is the range of correlations in the momentum space, e.g., in rapidity, Δ ycorr . The value of Δ ycorr˜1 for critical thermal fluctuations is determined by the thermal rapidity spread of the particles at freeze-out, and has little to do with position space correlations, even near the critical point where the spatial correlation length ξ becomes as large as 2-3 fm (this is in contrast to the magnitudes of the cumulants, which are sensitive to ξ ). When the acceptance window is large, Δ y ≫Δ ycorr , the cumulants of a given particle multiplicity, κk, scale linearly with Δ y , or mean multiplicity in acceptance, , and cumulant ratios are acceptance independent. In the opposite regime, Δ y ≪Δ ycorr , the factorial cumulants, κ̂k, scale as (Δy ) k, or k. We demonstrate this general behavior quantitatively in a model for critical point fluctuations, which also shows that the dependence on transverse momentum acceptance is very significant. We conclude that the extension of rapidity coverage as proposed by the STAR Collaboration should significantly increase the magnitude of the critical point fluctuation signatures.
Critical point in the QCD phase diagram for extremely strong background magnetic fields
Endrödi, Gergely
2015-07-01
Lattice simulations have demonstrated that a background (electro)magnetic field reduces the chiral/deconfinement transition temperature of quantum chromodynamics for eB Polyakov loop and in a suppression of the light quark condensates (inverse magnetic catalysis) in the transition region. In this paper, we report on lattice simulations of 1 + 1 + 1-flavor QCD at an unprecedentedly high value of the magnetic field eB = 3 .25 GeV2. Based on the behavior of various observables, it is shown that even at this extremely strong field, inverse magnetic catalysis prevails and the transition, albeit becoming sharper, remains an analytic crossover. In addition, we develop an algorithm to directly simulate the asymptotically strong magnetic field limit of QCD. We find strong evidence for a first-order deconfinement phase transition in this limiting theory, implying the presence of a critical point in the QCD phase diagram. Based on the available lattice data, we estimate the location of the critical point.
Primary caustics and critical points behind a Kerr black hole
Sereno, M
2007-01-01
The primary optical caustic surface behind a Kerr black hole is a four-cusped tube displaced from the line of sight. We compute that in the near asymptotic region through a Taylor expansion of the lightlike geodesics up to and including fourth-order terms in m/b and a/b, where m is the black hole mass, a the spin and b the impact parameter. The corresponding critical locus is elliptical and a point-like source inside the caustics will be imaged as an Einstein cross. With regard to lensing near critical points, a Kerr lens is analogous to a circular lens perturbed by a dipole and a quadrupole potential. The caustic structure of the supermassive black hole in the Galactic center could be probed by lensing of low mass X-ray binaries in the Galactic inner regions or by hot spots in the accretion disk.
Critical points of Wang-Yau quasi-local energy
Miao, Pengzi; Xie, Naqing
2010-01-01
Let Sigma be a spacelike two-surface with spacelike mean curvature vector in a time-oriented space-time N satisfying the dominant energy conditions. In this work, by studying the second variation of the Wang-Yau quasi-local energy Ewy(Sigma, \\cdot) and by a careful study of isometric embeddings of surfaces into R^3, we obtain some partial results on the following questions: (1) Suppose Sigma bounds a compact time-symmetric hypersurface Omega, is the Brown-York mass mby(Sigma,Omega) of Sigma in Omega a local minimum for the Wang-Yau quasi-local energy Ewy(Sigma, \\cdot)? (2) Suppose 0 is a critical point of Ewy(Sigma, \\cdot) and suppose tilde{Sigma} is another closed, embedded, spacelike two-surface which is a small perturbation of Sigma, does there exist a critical point of Ewy(tilde{Sigma},\\cdot)?
Analytic descriptions for transitional nuclei near the critical point
Exact solutions of the Bohr Hamiltonian with a five-dimensional square well potential, in isolation or coupled to a fermion by the five-dimensional spin-orbit interaction, are considered as examples of a new class of dynamical symmetry or Bose-Fermi dynamical symmetry. The solutions provide baselines for experimental studies of even-even [E(5)] and odd-mass [E(5|4)] nuclei near the critical point of the spherical to deformed γ-unstable phase transition
Search for critical points in the SU(2) Higgs model
We study the order of the Higgs phase transition in the SU(2) Higgs model at several values of the gauge coupling β for bare quartic coupling λ=0.5 using Monte Carlo simulations. We determine the internal energy of metastable states on various lattice sizes and estimate that the transition terminates at the critical point located at 1.95c4 and the transition is either weakly first order or of higher order
Critical points in the normative frame of librarianship
Lenart Šetinc
1998-01-01
With the presentation of basic critical points in the normative frame of librarianship,the author intends to contribute an answer to the following questions: Does the existing normative frame support or hinder the development of librarianship in the Republic of Slovenia? Is the normative frame of Slovenian librarianship consistent with European trends in setting of norms for librarianship? Which direction should legislative changes in the field of librarianship take?
$\\pi$N and strangeness sigma terms at the physical point with chiral fermions
Yang, Yi-Bo; Draper, Terrence; Liang, Jian; Liu, Keh-Fei
2015-01-01
Lattice QCD calculation with chiral fermions for the $\\pi$N sigma term $\\sigma_{\\pi N}$ and strangeness sigma term $\\sigma_{sN}$ including chiral interpolation with continuum and volume corrections are provided in this work. We calculate the scalar matrix element for the light/strange quark directly and find $\\sigma_{\\pi N}=44.4(3.2)(4.5)$ MeV with the disconnected insertion part contributing 30(6)(4)%, and $\\sigma_{sN}=32.3(4.7)(4.9)$ MeV, which is somewhat smaller than $\\sigma_{\\pi N}$. The ratio of the strange/light scalar matrix elements $y$ = 0.058(6)(8).
Critical points of the anyon-Hubbard model
Arcila-Forero, J.; Franco, R.; Silva-Valencia, J.
2016-07-01
Anyons are particles with fractional statistics that exhibit a nontrivial change in the wave function under an exchange of particles. Anyons can be considered to be a general category of particles that interpolate between fermions and bosons. We determined the position of the critical points of the one-dimensional anyon-Hubbard model, which was mapped to a modified Bose-Hubbard model where the tunneling depends on the local density and the interchange angle. We studied the latter model by using the density-matrix renormalization-group method and observed that gapped (Mott insulator) and gapless (superfluid) phases characterized the phase diagram, regardless of the value of the statistical angle. The phase diagram for higher densities was calculated and showed that the Mott lobes increase (decrease) as a function of the statistical angle (global density). The position of the critical point separating the gapped and gapless phases was found using quantum information tools, namely the block von Neumann entropy. We also studied the evolution of the critical point with the global density and the statistical angle and showed that the anyon-Hubbard model with a statistical angle θ =π /4 is in the same universality class as the Bose-Hubbard model with two-body interactions.
Turbulence close to the critical point of a fluid
Verhille, Gautier; Lachize, Cecile; Le Gal, Patrice
2012-11-01
Most of experiments in turbulence deal with liquid or gas. With classical fluids it is quite difficult to have both a high Reynolds number and a Mach number high enough to have compressible effects (Ma >~ 0 . 3). In water the sound speed is too large to permit compressible effects (c ~ 1500 m/s at room temperature and atmospheric pressure) and in air the viscosity is not so small (ν ~10-5 m2/s) so it is difficult to have high Reynolds number in a laboratory experiments. On the contrary, a fluid close to its critical point has a small kinematic viscosity, typically 20 times smaller than the water viscosity for SF6, and a small sound speed as the compressibility diverges, c ~ 70 m/s for SF6. Other properties of the fluid are diverging close to the critical point, as the correlation length of the density fluctuation and other goes to zero, as the thermal conductivity. We present here the first study of the modification of a turbulent flow close to the critical point. This flow is created in a rotor stator cavity, a one disk version of the ``french washing machine,'' in a pressurized and thermalized vessel filled up with SF6. Pressure and velocity measurements show an increase of the large scale dynamic whereas the inertial range does not seem to be affected.
Ion exchange at the critical point of solution.
Savoy, J D; Baird, J K; Lang, J R
2016-03-11
A mixture of isobutyric acid (IBA)+water has an upper critical point of solution at 26.7°C and an IBA concentration of 4.40M. We have determined the Langmuir isotherms for the hydroxide form of Amberlite IRN-78 resin in contact with mixtures of IBA+water at temperatures, 27.0, 29.0, 31.0 and 38.0°C, respectively. The Langmuir plot at 38.0°C forms a straight line. At the three lower temperatures, however, a peak in the Langmuir plot is observed for IBA concentrations in the vicinity of 4.40M. We regard this peak to be a critical effect not only because it is located close to 4.40M, but also because its height becomes more pronounced as the temperature of the isotherm approaches the critical temperature. For concentrations in the vicinity of the peak, the data indicate that the larger isobutyrate ion is rejected by the resin in favor of the smaller hydroxide ion. This reversal of the expected ion exchange reaction might be used to separate ions according to size. Using the Donnan theory of ion exchange equilibrium, we link the swelling pressure to the osmotic pressure. We show that the peak in the Langmuir plot is associated with a maximum in the "osmotic" energy. This maximum has its origin in the concentration derivative of the osmotic pressure, which goes to zero as the critical point is approached. PMID:26884137
Self-organizing criticality and the method of automatic search of critical points
We discuss the method of automatic search of critical point (MASCP) in the context of self-organizing criticality (SOC). The system analyzed is a contact process that presents a non-equilibrium phase transition between two states: active state and inactive state (the so-called absorbing state). The lattice sites represent infected and healthy individuals. We apply the technique MASCP to the propagation of epidemy in an unidimensional lattice at the criticality (space-domain). We take the technique MASCP to study SOC behavior. The time-series of density of infected individuals is analyzed using two complementary tools: Fourier analysis and detrended fluctuation analysis. We find numeric evidence that the time evolution that drives the system to the critical point in MASCP is not a SOC problem, but Gaussian noise. A SOC problem is characterized by an interaction-dominated system that goes spontaneously to the critical point. In fact MASCP goes by itself to a stationary point but it is not an interaction-dominated process, but a mean-field interaction process
Bulk and boundary critical behavior at Lifshitz points
H W Diehl
2005-05-01
Lifshitz points are multicritical points at which a disordered phase, a homogeneous ordered phase, and a modulated ordered phase meet. Their bulk universality classes are described by natural generalizations of the standard 4 model. Analyzing these models systematically via modern field-theoretic renormalization group methods has been a long-standing challenge ever since their introduction in the middle of 1970s. We survey the recent progress made in this direction, discussing results obtained via dimensionality expansions, how they compare with Monte Carlo results, and open problems. These advances opened the way towards systematic studies of boundary critical behavior at -axial Lifshitz points. The possible boundary critical behavior depends on whether the surface plane is perpendicular to one of the modulation axes or parallel to all of them. We show that the semi-infinite field theories representing the corresponding surface universality classes in these two cases of perpendicular and parallel surface orientation differ crucially in their Hamiltonian's boundary terms and the implied boundary conditions, and explain recent results along with our current understanding of this matter.
The Critical Point Entanglement and Chaos in the Dicke Model
Lina Bao
2015-07-01
Full Text Available Ground state properties and level statistics of the Dicke model for a finite number of atoms are investigated based on a progressive diagonalization scheme (PDS. Particle number statistics, the entanglement measure and the Shannon information entropy at the resonance point in cases with a finite number of atoms as functions of the coupling parameter are calculated. It is shown that the entanglement measure defined in terms of the normalized von Neumann entropy of the reduced density matrix of the atoms reaches its maximum value at the critical point of the quantum phase transition where the system is most chaotic. Noticeable change in the Shannon information entropy near or at the critical point of the quantum phase transition is also observed. In addition, the quantum phase transition may be observed not only in the ground state mean photon number and the ground state atomic inversion as shown previously, but also in fluctuations of these two quantities in the ground state, especially in the atomic inversion fluctuation.
Critical Points of the Electric Field from a Collection of Point Charges
Max, N; Weinkauf, T
2007-02-16
The electric field around a molecule is generated by the charge distribution of its constituents: positively charged atomic nuclei, which are well approximated by point charges, and negatively charged electrons, whose probability density distribution can be computed from quantum mechanics. For the purposes of molecular mechanics or dynamics, the charge distribution is often approximated by a collection of point charges, with either a single partial charge at each atomic nucleus position, representing both the nucleus and the electrons near it, or as several different point charges per atom. The critical points in the electric field are useful in visualizing its geometrical and topological structure, and can help in understanding the forces and motion it induces on a charged ion or neutral dipole. Most visualization tools for vector fields use only samples of the field on the vertices of a regular grid, and some sort of interpolation, for example, trilinear, on the grid cells. There is less risk of missing or misinterpreting topological features if they can be derived directly from the analytic formula for the field, rather than from its samples. This work presents a method which is guaranteed to find all the critical points of the electric field from a finite set of point charges. To visualize the field topology, we have modified the saddle connector method to use the analytic formula for the field.
Critical, elasticity of polyacrylamide above its gel point
Gauthier-Manuel, B.; Guyon, E.
1980-01-01
We study the reticular polymerization of a gel of mono and bisacrylamide around the gelation threshold. A rheological measurement using the Stokes relative displacement of a sphere within the medium gives access to the viscosity below the gel point and to an elastic modulus E above it. From the first determination we deduce the gel time T = Tc (evaluated from the start of the polymerization). A critical variation E(T) ∝ (T - Tc) t is obtained for 2 x 10-3 < (T - T c)/Tc < 10-1 with an exponen...
Black holes as critical point of quantum phase transition
Dvali, Gia [Arnold Sommerfeld Center for Theoretical Physics, Department fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, Muenchen (Germany); Max-Planck-Institut fuer Physik, Muenchen (Germany); CERN, Theory Department, Geneva 23 (Switzerland); New York University, Department of Physics, Center for Cosmology and Particle Physics, New York, NY (United States); Gomez, Cesar [Arnold Sommerfeld Center for Theoretical Physics, Department fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, Muenchen (Germany); Universidad Autonoma de Madrid, Instituto de Fisica Teorica UAM-CSIC, C-XVI, Madrid (Spain)
2014-02-15
We reformulate the quantum black hole portrait in the language of modern condensed matter physics. We show that black holes can be understood as a graviton Bose-Einstein condensate at the critical point of a quantum phase transition, identical to what has been observed in systems of cold atoms. The Bogoliubov modes that become degenerate and nearly gapless at this point are the holographic quantum degrees of freedom responsible for the black hole entropy and the information storage. They have no (semi)classical counterparts and become inaccessible in this limit. These findings indicate a deep connection between the seemingly remote systems and suggest a new quantum foundation of holography. They also open an intriguing possibility of simulating black hole information processing in table-top labs. (orig.)
Generalized simplicial chiral models
Alimohammadi, M
2000-01-01
Using the auxiliary field representation of the simplicial chiral models on a (d-1)-dimensional simplex, we generalize the simplicial chiral models by replacing the term Tr$(AA^{\\d})$ in the Lagrangian of these models, by an arbitrary class function of $AA^{\\d}; V(AA^{\\d})$. This is the same method that has been used in defining the generalized two-dimensional Yang-Mills theories (gYM_2) from ordinary YM_2. We call these models, the " generalized simplicial chiral models ". With the help of the results of one-link integral over a U(N) matrix, we compute the large-N saddle-point equations for eigenvalue density function $\\ro (z)$ in the weak ($\\b >\\b_c$) and strong ($\\b <\\b_c$) regions. In d=2, where the model somehow relates to gYM_2 theory, we solve the saddle-point equations and find $\\ro (z)$ in two region, and calculate the explicit value of critical point $\\b_c$ for $V(B)=TrB^n (B=AA^{\\d})$. For $V(B)=Tr B^2,Tr B^3$ and Tr$B^4$, we study the critical behaviour of the model at d=2, and by calculating t...
Generalized simplicial chiral models
Using the auxiliary field representation of the simplicial chiral models on a (d-1)-dimensional simplex, the simplicial chiral models are generalized through replacing the term Tr(AA†) in the Lagrangian of these models by an arbitrary class function of AA†; V(AA†). This is the same method used in defining the generalized two-dimensional Yang-Mills theories (gYM2) from ordinary YM2. We call these models the 'generalized simplicial chiral models'. Using the results of the one-link integral over a U(N) matrix, the large-N saddle-point equations for eigenvalue density function ρ(z) in the weak (β>βc) and strong (βc) regions are computed. In d=2, where the model is in some sense related to the gYM2 theory, the saddle-point equations are solved for ρ(z) in the two regions, and the explicit value of critical point βc is calculated for V(B)=Tr Bn (B=AA†). For V(B)=Tr B2,Tr B3, and TrB4, the critical behaviour of the model at d=2 is studied, and by calculating the internal energy, it is shown that these models have a third order phase transition
Has the QCD critical point been observed at RHIC? - A Rebuttal
Lacey, Roy A
2016-01-01
This note rebuts an old, but recurring claim by Antoniou, Davis and Diakonos [1] that the critical point and associated critical exponents reported in Ref. [2], is based on an erroneous treatment of scaling relations near the critical point.
Claims that spontaneous chiral symmetry breaking in Q.C.D. is mediated by the U(1) axial anomaly are examined from the viewpoint of effective chiral lagrangians. The proofs are seen to arise from a use of effective chiral lagrangians in which the U(1) axial symmetry is explicitly broken by effects of the anomaly. A U(1) axial invariant chiral lagrangian (to be presented) offers no such proof. (author)
On Locating the Critical End Point in QCD Phase Diagram
Srivastava, P K; Singh, C P
2011-01-01
We use the available two different self-consistent formulations of quasiparticle models and extend their applications for the description of quark gluon plasma (QGP) at non-vanishing baryon chemical potentials. The thermodynamical quantities calculated from these models are compared with the values obtained from lattice simulations and a good agreement between theoretical calculations and lattice QCD data suggests that the values of the parameters used in the paper are consistent. A new equation of state (EOS) for a gas of extended baryons and pointlike mesons is presented here which incorporates the repulsive hard-core interactions arising due to geometrical size of baryons. A first order deconfining phase transition is constructed using Gibb's equilibrium criteria between the hadron gas EOS and quasiparticle model EOS for the weakly interacting quark matter. This leads to an interesting finding that the phase transition line ends at a critical end point beyond which a crossover region exists in the phase di...
Hydrodynamical evolution near the QCD critical end point
Nonaka, C; Nonaka, Chiho; Asakawa, Masayuki
2004-01-01
Hydrodynamical calculations have been successful in describing global observables in ultrarelativistic heavy ion collisions, which aim to observe the production of the quark-gluon plasma. On the other hand, recently, a lot of evidence that there exists a critical end point (CEP) in the QCD phase diagram has been accumulating. Nevertheless, so far, no equation of state with the CEP has been employed in hydrodynamical calculations. In this paper, we construct the equation of state with the CEP on the basis of the universality hypothesis and show that the CEP acts as an attractor of isentropic trajectories. We also consider the time evolution in the case with the CEP and discuss how the CEP affects the final state observables, such as the correlation length, fluctuation, chemical freezeout, kinetic freezeout, and so on. Finally, we argue that the anomalously low kinetic freezeout temperature at the BNL Relativistic Heavy Ion Collider suggests the possibility of the existence of the CEP.
CARS spectroscopy of carbon dioxide in the critical point vicinity
The transformation of the Q-band of the low-frequency 1285-cm-1 component of the 2v2/v1 Fermi doublet of a CO2 molecule is studied in the critical point vicinity (Tc=31.03 0C, Pc=72.8 atm) by the CARS method. CARS spectra were recorded by changing pressure isothermically from 48 to 120 atm at several temperatures in the range between 25 and 360C. At the temperature above 290C, the pressure dependences of the Q-band width pass through the maximum, which exceeds by 40% -50% the typical Q-band width in the liquid phase. The position of the maximum shifts to higher pressures with increasing temperature. The inhomogeneous broadening of the Q-band is interpreted based on the cluster microstructure of a supercritical fluid. (laser applications and other topics in quantum electronics)
Influence of intermolecular forces at critical-point wedge filling
Malijevský, Alexandr; Parry, Andrew O.
2016-04-01
We use microscopic density functional theory to study filling transitions in systems with long-ranged wall-fluid and short-ranged fluid-fluid forces occurring in a right-angle wedge. By changing the strength of the wall-fluid interaction we can induce both wetting and filling transitions over a wide range of temperatures and study the order of these transitions. At low temperatures we find that both wetting and filling transitions are first order in keeping with predictions of simple local effective Hamiltonian models. However close to the bulk critical point the filling transition is observed to be continuous even though the wetting transition remains first order and the wetting binding potential still exhibits a small activation barrier. The critical singularities for adsorption for the continuous filling transitions depend on whether retarded or nonretarded wall-fluid forces are present and are in excellent agreement with predictions of effective Hamiltonian theory even though the change in the order of the transition was not anticipated.
Acceptance dependence of fluctuation measures near the QCD critical point
Ling, Bo
2015-01-01
We argue that a crucial determinant of the acceptance dependence of fluctuation measures in heavy-ion collisions is the range of correlations in the momentum space, e.g., in rapidity, $\\Delta y_{\\rm corr}$. The value of $\\Delta y_{\\rm corr}\\sim1$ for critical thermal fluctuations is determined by the thermal rapidity spread of the particles at freezeout, and has little to do with position space correlations, even near the critical point where the spatial correlation length $\\xi$ becomes as large as $2-3$ fm (this is in contrast to the magnitudes of the cumulants, which are sensitive to $\\xi$). When the acceptance window is large, $\\Delta y\\gg\\Delta y_{\\rm corr}$, the cumulants of a given particle multiplicity, $\\kappa_k$, scale linearly with $\\Delta y$, or mean multiplicity in acceptance, $\\langle N\\rangle$, and cumulant ratios are acceptance independent. While in the opposite regime, $\\Delta y\\ll\\Delta y_{\\rm corr}$, the factorial cumulants, $\\hat\\kappa_k$, scale as $(\\Delta y)^k$, or $\\langle N\\rangle^k$. W...
Energy scales and magnetoresistance at a quantum critical point
The magnetoresistance (MR) of CeCoIn5 is notably different from that in many conventional metals. We show that a pronounced crossover from negative to positive MR at elevated temperatures and fixed magnetic fields is determined by the scaling behavior of quasiparticle effective mass. At a quantum critical point (QCP) this dependence generates kinks (crossover points from fast to slow growth) in thermodynamic characteristics (like specific heat, magnetization, etc.) at some temperatures when a strongly correlated electron system transits from the magnetic field induced Landau-Fermi liquid (LFL) regime to the non-Fermi liquid (NFL) one taking place at rising temperatures. We show that the above kink-like peculiarity separates two distinct energy scales in QCP vicinity - low temperature LFL scale and high temperature one related to NFL regime. Our comprehensive theoretical analysis of experimental data permits to reveal for the first time new MR and kinks scaling behavior as well as to identify the physical reasons for above energy scales
On Prop erties of p-critical Points of Convex Bo dies
Huang Xing; Guo Qi
2015-01-01
Properties of the p-measures of asymmetry and the corresponding aﬃne equivariant p-critical points, defined recently by the second author, for convex bodies are discussed in this article. In particular, the continuity of p-critical points with respect to p on (1,+∞) is confirmed, and the connections between general p-critical points and the Minkowski-critical points (∞-critical points) are investigated. The behavior of p-critical points of convex bodies approximating a convex bodies is studied as well.
Shuxiang YU
2006-01-01
Using the concept of an isolated invariant set, some existence criteria of orbits connecting two critical points bifurcating from a single critical point for ordinary differential equations depending on a parameter are given.
Locating the QCD critical end point using the pressure
Ayala, Alejandro; Cobos-Martinez, J J; Hernandez-Ortiz, Saul; Mizher, Ana Julia; Raya, Alfredo
2015-01-01
We use the linear sigma model coupled to quarks to search for the location of the QCD critical end point (CEP). We compute the effective potential at finite temperature and density up to the contribution of the ring diagrams both in the low and high temperature limits and use it to compute the pressure and the position of the CEP. In the low temperature regime, by comparing to results from lattice inspired calculations, we determine the model coupling constants and compute the pressure. Then, by demanding that the CEP remains in the same location when described by the high temperature behavior of the effective potential, we determine the values of the couplings and compute the pressure again. We show that this procedure gives a good average description of the lattice QCD results for the pressure and that the change from the low to the high temperature domains in this quantity can be attributed to the change in the coupling constants which in turn we link to the change of the effective number of degrees of fre...
Interplay between chiral and deconfinement phase transitions
Mukherjee T.K.
2011-04-01
Full Text Available By using the dressed Polyakov loop or dual chiral condensate as an equivalent order parameter of the deconfinement phase transition, we investigate the relation between the chiral and deconfinement phase transitions at finite temperature and density in the framework of three-flavor Nambu-Jona-Lasinio (NJL model. It is found that in the chiral limit, the critical temperature for chiral phase transition coincides with that of the dressed Polyakov loop in the whole (T,µ plane. In the case of explicit chiral symmetry breaking, it is found that the phase transitions are flavor dependent. For each flavor, the transition temperature for chiral restoration $T^{mathcal{X}}_c$ is smaller than that of the dressed Polyakov loop $T^{mathcal{D}}_c$ in the low baryon density region where the transition is a crossover, and, the two critical temperatures coincide in the high baryon density region where the phase transition is of first order. Therefore, there are two critical end points, i.e, $T^{u,d}_{CEP}$ and $T^{s}_{CEP}$ at finite density. We also explain the feature of $T^{mathcal{X}}_c$ = $T^{mathcal{D}}_c$ in the case of 1st and 2nd order phase transitions, and $T^{mathcal{X}}_c$ < $T^{mathcal{D}}_c$ in the case of crossover, and expect this feature is general and can be extended to full QCD theory.
Interplay between chiral and deconfinement phase transitions
Xu, Fukun; Chen, Huan; Huang, Mei
2011-01-01
By using the dressed Polyakov loop or dual chiral condensate as an equivalent order parameter of the deconfinement phase transition, we investigate the relation between the chiral and deconfinement phase transitions at finite temperature and density in the framework of three-flavor Nambu--Jona-Lasinio (NJL) model. It is found that in the chiral limit, the critical temperature for chiral phase transition coincides with that of the dressed Polyakov loop in the whole $(T,\\mu)$ plane. In the case of explicit chiral symmetry breaking, it is found that the phase transitions are flavor dependent. For each flavor, the transition temperature for chiral restoration $T_c^{\\chi}$ is smaller than that of the dressed Polyakov loop $T_c^{{\\cal D}}$ in the low baryon density region where the transition is a crossover, and, the two critical temperatures coincide in the high baryon density region where the phase transition is of first order. Therefore, there are two critical end points, i.e, $T_{CEP}^{u,d}$ and $T_{CEP}^{s}$ a...
Pion electroproduction, PCAC, chiral Ward identities, and the axial form factor revisited
Fuchs, T.(Department of Physics, TU Dortmund University, 44221, Dortmund, Germany); Scherer, S.
2003-01-01
We re-investigate Adler's PCAC relation in the presence of an external electromagnetic field within the framework of QCD coupled to external fields. We discuss pion electroproduction within a tree-level approximation to chiral perturbation theory and explicitly verify a chiral Ward identity referred to as the Adler-Gilman relation. We critically examine soft-momentum techniques and point out how inadmissable approximations may lead to results incompatible with chiral symmetry. As a result we ...
Magnetic properties in the inhomogeneous chiral phase
Yoshiike, Ryo; Tatsumi, Toshitaka
2016-01-01
We investigate the magnetic properties of quark matter in the inhomogeneous chiral phase, where both scalar and pseudoscalar condensates spatially modulate. The energy spectrum of the lowest Landau level becomes asymmetric about zero in the external magnetic field, and gives rise to the remarkably magnetic properties: quark matter has a spontaneous magnetization, while the magnetic susceptibility does not diverge on the critical point.
Chiral anomalies and differential geometry
Zumino, B.
1983-10-01
Some properties of chiral anomalies are described from a geometric point of view. Topics include chiral anomalies and differential forms, transformation properties of the anomalies, identification and use of the anomalies, and normalization of the anomalies. 22 references. (WHK)
Initial nucleon structure results with chiral quarks at the physical point
Syritsyn, S; Engelhardt, M; Green, J; Izubuchi, T; Jung, C; Krieg, S; Lin, M; Meinel, S; Negele, J; Ohta, S; Pochinsky, A; Shintani, E
2014-01-01
We report initial nucleon structure results computed on lattices with 2+1 dynamical M\\"obius domain wall fermions at the physical point generated by the RBC and UKQCD collaborations. At this stage, we evaluate only connected quark contributions. In particular, we discuss the nucleon vector and axial-vector form factors, nucleon axial charge and the isovector quark momentum fraction. From currently available statistics, we estimate the stochastic accuracy of the determination of $g_A$ and $_{u-d}$ to be around 10%, and we expect to reduce that to 5% within the next year. To reduce the computational cost of our calculations, we extensively use acceleration techniques such as low-eigenmode deflation and all-mode-averaging (AMA). We present a method for choosing optimal AMA parameters.
Comparison study of hybrid VS critical systems in point kinetics
An essential motivation for hybrid systems is a potentially high level of intrinsic safety against reactivity accidents. In this respect, it is necessary to assess the behaviour of an Accelerator Driven System during a TOP, LOF or TOC accident. A comparison between a critical and sub-critical reactor shows a larger sensitivity for the critical system. The ADS has an unquestionable advantage in case of TOP but a less favourable behaviour as for LOFWS type of accidents. However in the ADS cases, the beam could be easily shut off during the transient. Therefore, a part of the R and D effort should be focused on the monitoring and control of power. (author)
Liquid-Vapor Argon Isotope Fractionation from the Triple Point to the Critical Point
Phillips, J. T.; Linderstrøm-Lang, C. U.; Bigeleisen, J.
1972-01-01
twice the statistical scatter of the present data, the present results for the lnα are systematically 5% lower than calculations from vapor pressure data. It is shown that T2 lnα is a linear function of (ρc−ρg), the density difference between the liquid and vapor, in the range 84–120°K. The......The statistical thermodynamic treatment of the equilibrium between a nonideal liquid mixture of isotopes and a vapor phase is extended to include isotope effects on the equation of state of the gas. The result is particularly simple when the isotopic partition functions in a given phase are...... compared at the same molar volume. The isotope fractionation factor α for 36Ar∕40Ar between liquid and vapor has been measured from the triple point to the critical temperature. The results are compared with previous vapor pressure data, which cover the range 84–102°K. Although the agreement is within...
Pasteurised milk and implementation of HACCP (Hazard Analysis Critical Control Point)
T.B Murdiati; A. Priadi; S Rachmawati; Yuningsih
2004-01-01
The purpose of pasteurisation is to destroy pathogen bacteria without affecting the taste, flavor, and nutritional value. A study on the implementation of HACCP (Hazard Analysis Critical Control Point) in producing pasteurized milk was carried out in four processing unit of pasteurised milk, one in Jakarta, two in Bandung and one in Bogor. The critical control points in the production line were identified. Milk samples were collected from the critical points and were analysed for the total nu...
Critical-point analysis of the liquid-vapor interfacial surface tension
Salvino, R. E.
1990-01-01
The interfacial surface tension of the liquid-vapor system is analyzed near the critical point in a manner similar to bulk thermodynamic critical-point analyses. This is accomplished by a critical-point analysis of the single-phase hard-wall surface tension. Both a Landau expansion and a scaling theory equation of state are investigated. Some general exponent relations are derived and, in addition, some thermodynamically defined correlation lengths are discussed.
Cismondi, Martin; Michelsen, Michael Locht
2007-01-01
A general strategy for global phase equilibrium calculations (GPEC) in binary mixtures is presented in this work along with specific methods for calculation of the different parts involved. A Newton procedure using composition, temperature and Volume as independent variables is used for calculation...... of critical lines. Each calculated point is analysed for stability by means of the tangent plane distance, and the occurrence of an unstable point is used to determine a critical endpoint (CEP). The critical endpoint, in turn, is used as the starting point for constructing the three-phase line. The...... equations for the critical endpoint, as well as for points on the three-phase line, are also solved using Newton's method with temperature, molar volume and composition as the independent variables. The different calculations are integrated into a general procedure that allows us to automatically trace...
Universal Entanglement Entropy in 2D Conformal Quantum Critical Points
Hsu, Benjamin; Mulligan, Michael; Fradkin, Eduardo; Kim, Eun-Ah
2008-12-05
We study the scaling behavior of the entanglement entropy of two dimensional conformal quantum critical systems, i.e. systems with scale invariant wave functions. They include two-dimensional generalized quantum dimer models on bipartite lattices and quantum loop models, as well as the quantum Lifshitz model and related gauge theories. We show that, under quite general conditions, the entanglement entropy of a large and simply connected sub-system of an infinite system with a smooth boundary has a universal finite contribution, as well as scale-invariant terms for special geometries. The universal finite contribution to the entanglement entropy is computable in terms of the properties of the conformal structure of the wave function of these quantum critical systems. The calculation of the universal term reduces to a problem in boundary conformal field theory.
Critical Point of Ising Films with Different Growth Directions
WANG Huai-yu; ZHOU Yun-song; D.L.Lin
2000-01-01
The critical temperature Tc of a spin-l/2 Ising film of cubic structures is calculated by the variational cumulant expansion method for three directions of growth. The results from different growth directions are analysed and compared with each other. In the present model, the Tc values depend largely on the number of nearest neighbors in a monolayer for films with the same number of monolayers but grown in different directions. For sc, bcc and fcc structures, the highest Tc is found along the (100), (110), and (111) direction, respectively.
based on the knowledge of the reactivity insertion. 2. Initiation probability for one neutron P(t). 3. Initiation probability with the neutron source PS (t). Japanese specialists told us that the accident happened during the seventh batch pouring. They estimated the keff before and at the end of this operation: After the sixth batch, K=0.981, and at the end of the seventh batch, K=1.030. When the accident happened (neutron burst), 3 $ was inserted in 15 s, so if we suppose a linear insertion, we have a slope equal to 20 c/s. We may write K(t) = 1 + wt with w = 0.2 β = 0.00160/s. During the accident, there was between 14 and 16 kg of uranium with an enrichment of 18.8%. We have calculated PS(t) and we have taken into account six internal source levels: 1. spontaneous fission: 150 to 170 to 200 n/s; 2. (α, n) reactions and others of this type, and amplification of the internal source during the delayed critical phase: 500 to 1000 to 2000 n/s. In Fig. 2, we can see that the initiation occurred almost surely before 7 s and with a probability close to 0.46 before 2 s with a source of 200 n/s. With a source of 2000 n/s, we have higher initiation probabilities; for example, the initiation occurred almost surely before 2 s and with a probability close to 0.77 before 1 s after the critical time. These results are interesting because they show that a supercritical system does not lead immediately to initiation. One may have short supercritical excursion with no neutron production. The point model approach is useful for gaining a good understanding of what can be the stochastic neutronic contribution for the interpretation of criticality accidents. The results described in this paper may be useful for the interpretation of the time delay between the critical state time and the neutron burst. The thought process we have described may be used in the 'real world', that is, with multigroup or continuous-energy simulations
Phenomenological Consequences of Enhanced Bulk Viscosity Near the QCD Critical Point
Monnai, Akihiko; Yin, Yi
2016-01-01
In the proximity of the QCD critical point the bulk viscosity of quark-gluon matter is expected to be proportional to nearly the third power of the critical correlation length, and become significantly enhanced. This work is the first attempt to study the phenomenological consequences of enhanced bulk viscosity near the QCD critical point. For this purpose, we implement the expected critical behavior of the bulk viscosity within a non-boost-invariant, longitudinally expanding $1+1$ dimensional causal relativistic hydrodynamical evolution at non-zero baryon density. We demonstrate that the critically-enhanced bulk viscosity induces a substantial non-equilibrium pressure, effectively softening the equation of state, and leads to sizable effects in the flow velocity and single particle distributions at the freeze-out. The observable effects that may arise due to the enhanced bulk viscosity in the vicinity of the QCD critical point can be used as complimentary information to facilitate searches for the QCD critic...
Magnetic quantum critical point and superconductivity in UPt3 doped with Pd
Visser,, Richard G F; Graf, M. J.; Estrela, P.; Amato, A.; Baines, C.; Andreica, D.; Gygax, F. N.; Schenck, A.
2000-01-01
Transverse-field muon spin relaxation measurements have been carried out on the heavy-fermion superconductor UPt3 doped with small amounts of Pd. We find that the critical Pd concentration for the emergence of the large-moment antiferromagnetic phase is ~0.6 at.%Pd. At the same Pd content, superconductivity is completely suppressed. The existence of a magnetic quantum critical point in the phase diagram, which coincides with the critical point for superconductivity, provides evidence for ferr...
Schwahn, D.; Mortensen, K.; Janssen, S.
1994-01-01
The critical behavior of a polymer blend was measured by small-angle neutron scattering above and below the critical temperature T-c, i.e., outside and inside the unstable region. The critical exponents and the amplitudes of the susceptibility and the correlation length were determined. For T > T...
A large N phase transition in the continuum two dimensional SU(N) X SU(N) principal chiral model
R. Narayanan; Neuberger, H.; Vicari, E.
2008-01-01
It is established by numerical means that the continuum large N principal chiral model in two dimensions has a phase transition in a smoothed two point function at a critical distance of the order of the correlation length.
Critical control points of complementary food preparation and handling in eastern Nigeria.
2001-01-01
OBJECTIVE: To investigate microbial contamination and critical control points (CCPs) in the preparation and handling of complementary foods in 120 households in Imo state, Nigeria. METHODS: The Hazard Analysis Critical Control Point (HACCP) approach was used to investigate processes and procedures that contributed to microbial contamination, growth and survival, and to identify points where controls could be applied to prevent or eliminate these microbiological hazards or reduce them to accep...
Zou, Dandan; Cao, Xin [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Lu, Xinpei, E-mail: luxinpei@hotmail.com [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China); Ostrikov, Kostya [School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland 4000 (Australia); Comonwealth Scientific and Industrial Research Organization, P.O. Box 218, Sydney, New South Wales 2070 (Australia)
2015-10-15
The interaction of time-varying electromagnetic fields and solid, liquid, and gaseous matter may lead to electrical breakdown phenomena through the excitation of ionization waves or streamers that control the dynamics of localized plasma propagation through the media. The streamers usually propagate along straight lines, either between random points in space or along a certain direction in a guided mode. Here, we report on a new type of plasma discharges with the regular helical propagation pattern driven by a pulsed dc voltage in nitrogen at sub-atmospheric-pressure conditions. The helical guided streamers, named chiral streamers or chi-streamers, are excited without any external magnetic fields, which commonly cause helical plasma motions. We also demonstrate a hybrid propagation mode involving the interchangeable chiral streamers and the straight-line propagating plasmas. High-speed, time-resolved optical imaging reveals that the chiral streamers and the hybrid patterns are made of spatially localized discrete plasma bullets, similar to the straight-line guided streamers. These results may enable effective control of propagation of confined plasmas and electromagnetic energy along pre-determined, potentially deterministic paths, which have important implications for the development of next-generation plasma-based radiation sources, communication devices, and medical treatments.
Zou, Dandan; Cao, Xin; Lu, Xinpei; Ostrikov, Kostya Ken
2015-10-01
The interaction of time-varying electromagnetic fields and solid, liquid, and gaseous matter may lead to electrical breakdown phenomena through the excitation of ionization waves or streamers that control the dynamics of localized plasma propagation through the media. The streamers usually propagate along straight lines, either between random points in space or along a certain direction in a guided mode. Here, we report on a new type of plasma discharges with the regular helical propagation pattern driven by a pulsed dc voltage in nitrogen at sub-atmospheric-pressure conditions. The helical guided streamers, named chiral streamers or chi-streamers, are excited without any external magnetic fields, which commonly cause helical plasma motions. We also demonstrate a hybrid propagation mode involving the interchangeable chiral streamers and the straight-line propagating plasmas. High-speed, time-resolved optical imaging reveals that the chiral streamers and the hybrid patterns are made of spatially localized discrete plasma bullets, similar to the straight-line guided streamers. These results may enable effective control of propagation of confined plasmas and electromagnetic energy along pre-determined, potentially deterministic paths, which have important implications for the development of next-generation plasma-based radiation sources, communication devices, and medical treatments.
The critical behavior of the refractive index near liquid-liquid critical points.
Losada-Pérez, Patricia; Glorieux, Christ; Thoen, Jan
2012-04-14
The nature of the critical behavior in the refractive index n is revisited in the framework of the complete scaling formulation. A comparison is made with the critical behavior of n as derived from the Lorentz-Lorenz equation. Analogue anomalies to those predicted for the dielectric constant ε, namely, a leading |t|(2β) singularity in the coexistence-curve diameter in the two-phase region and a |t|(1-α) along the critical isopleth in the one phase region, are expected in both cases. However, significant differences as regards the amplitudes of both singularities are obtained from the two approaches. Analysis of some literature data along coexistence in the two-phase region and along the critical isopleth in the one-phase region provide evidence of an intrinsic effect, independent of the density, in the critical anomalies of n. This effect is governed by the shift of the critical temperature with an electric field, which is supposed to take smaller values at optical frequencies than at low frequencies in the Hz to MHz range. PMID:22502528
Construction of Neural Networks that Do Not Have Critical Points Based on Hierarchical Structure
Tohru Nitta
2013-10-01
Full Text Available a critical point is a point at which the derivatives of an error function are all zero. It has been shown in the literature that critical points caused by the hierarchical structure of a real-valued neural network (NN can be local minima or saddle points, although most critical points caused by the hierarchical structure are saddle points in the case of complex-valued neural networks. Several studies have demonstrated that singularity of those kinds has a negative effect on learning dynamics in neural networks. As described in this paper, the decomposition of high-dimensional neural networks into low-dimensional neural networks equivalent to the original neural networks yields neural networks that have no critical point based on the hierarchical structure. Concretely, the following three cases are shown: (a A 2-2-2 real-valued NN is constructed from a 1-1-1 complex-valued NN. (b A 4-4-4 real-valued NN is constructed from a 1-1-1 quaternionic NN. (c A 2-2-2 complex-valued NN is constructed from a 1-1-1 quaternionic NN. Those NNs described above do not suffer from a negative effect by singular points during learning comparatively because they have no critical point based on a hierarchical structure.
The phase transition and classification of critical points in the multistability chemical reactions
ChunhuaZHANG; FugenWU; ChunyanWU; FaOU
2000-01-01
In this paper, we study the phase transition and classification of critical points in multistability chemical reaction systems. Referring to the spirit of Landau's theory of phase transitions, this paper deals with the varied transitions and critical phenomena in multistable chemical systems. It is demonstrated that the higher the order of the multistability,the wider the variety of phase transitions will be. A classification scheme of critical points according to the stability criterion and the thermodynamic potential continuity is suggested.It is useful for us to study critical phenomena especially in the non-equilibrium systems including the multi-stable chemical ones.
Vapor-like liquid coexistence densities affect the extension of the critical point's influence zone
Rivera, Jose Luis; Guerra-Gonzalez, Roberto
2015-01-01
The critical point affects the coexistence behavior of the vapor-liquid equilibrium densities. The length of the critical influence zone is under debate because for some properties, like shear viscosity, the extension is only a few degrees, while for others, such as the density order parameter, the critical influence zone range covers up to hundreds of degrees below the critical temperature. Here we show that for a simple molecular potential of ethane, the critical influence zone covers a wide zone of tens of degrees (below the critical temperature) down to a transition temperature, at which the apparent critical influence zone vanishes and the transition temperature can be predicted through a pressure analysis of the coexisting bulk liquid phase. The liquid phases within the apparent critical influence zone show low densities, making them behave internally like their corresponding vapor phases. Therefore, the experimentally observed wide extension of the critical influence zone is due to a vapor-like effect ...
Nonequilibrium pion dynamics near the critical point in a constituent quark model
Boyanovsky, D; Wang, S Y
2003-01-01
We study static and dynamical critical phenomena of chiral symmetry breaking in a two-flavor Nambu--Jona-Lasinio constituent quark model. We obtain the low-energy effective action for scalar and pseudoscalar degrees of freedom to lowest order in quark loops and to quadratic order in the meson fluctuations around the mean field. The \\emph{static} limit of critical phenomena is shown to be described by a Ginzburg-Landau effective action including \\emph{spatial} gradients. Hence \\emph{static} critical phenomena is described by the universality class of the O(4) Heisenberg ferromagnet. \\emph{Dynamical} critical phenomena is studied by obtaining the equations of motion for pion fluctuations. We find that for $T
Visualizing Robustness of Critical Points for 2D Time-Varying Vector Fields
Wang, B.
2013-06-01
Analyzing critical points and their temporal evolutions plays a crucial role in understanding the behavior of vector fields. A key challenge is to quantify the stability of critical points: more stable points may represent more important phenomena or vice versa. The topological notion of robustness is a tool which allows us to quantify rigorously the stability of each critical point. Intuitively, the robustness of a critical point is the minimum amount of perturbation necessary to cancel it within a local neighborhood, measured under an appropriate metric. In this paper, we introduce a new analysis and visualization framework which enables interactive exploration of robustness of critical points for both stationary and time-varying 2D vector fields. This framework allows the end-users, for the first time, to investigate how the stability of a critical point evolves over time. We show that this depends heavily on the global properties of the vector field and that structural changes can correspond to interesting behavior. We demonstrate the practicality of our theories and techniques on several datasets involving combustion and oceanic eddy simulations and obtain some key insights regarding their stable and unstable features. © 2013 The Author(s) Computer Graphics Forum © 2013 The Eurographics Association and Blackwell Publishing Ltd.
Chiral Magnetic Effect and Chiral Phase Transition
FU Wei-Jie; LIU Yu-Xin; WU Yue-Liang
2011-01-01
We study the influence of the chiral phase transition on the chiral magnetic effect.The azimuthal chargeparticle correlations as functions of the temperature are calculated.It is found that there is a pronounced cusp in the correlations as the temperature reaches its critical value for the QCD phase transition.It is predicted that there will be a drastic suppression of the charge-particle correlations as the collision energy in RHIC decreases to below a critical value.We show then the azimuthal charge-particle correlations can be the signal to identify the occurrence of the QCD phase transitions in RHIC energy scan experiments.
Critical limit one-point correlations of monodromy fields on Z2
Monodromy fields on Z2 are a family of lattice fields in two dimensions which are a natural generalization of the two dimensional Ising field occurring in the C*-algebra approach to Statistical Mechanics. A criterion for the critical limit one point correlation of the monodromy field σa(M) at aelement ofZ2, lims↑1a(M)>, is deduced for matrices Melement ofGL(p, C) having non-negative eigenvalues. Using this criterion not-identity 2x2 matrices are found with finite critical limit one point correlation. The general set of pxp matrices with finite critical limit one point correlations is also considered and a conjecture for the critical limit n point correlations postulated. (orig.)
The thermodynamics and transport properties of transition metals in critical point
Khomkin, Alexander L
2016-01-01
A new method for calculating the critical point parameters (density, temperature, pressure and electrical conductivity) and binodal of vapor-liquid (dielectric-metal) phase transition is proposed. It is based on the assumption that cohesion, which determines the main properties of solid state, also determines the properties in the vicinity of the critical point. Comparison with experimental and theoretical data available for transition metals is made.
Critical point quantities and integrability conditions for a class of quintic systems
刘一戎; 肖萍
2004-01-01
For a class of quintic systems, the first 16 critical point quantities are obtained by computer algebraic system Mathematica, and the necessary and sufficient conditions that there exists an exact integral in a neighborhood of the origin are also given. The technique employed is essentially different from usual ones. The recursive formula for computation of critical point quantities is linear and then avoids complex integral operations. Some results show an interesting contrast with the related results on quadratic systems.
The general shape of the temperature dependence of the static susceptibility in a biasing field conjugated to the order parameter is analysed with the use of the simplest equation of state compatible with the Widom and Griffiths scaling hypothesis. The corresponding curves are demonstrated to show from two to four inflection points, from which a discontinuous inflection point is found to occur exactly at the critical point whenever the critical exponent of susceptibility differs from one: γ≠. The unique inflection point occurring below the temperature of the maximum of the susceptibility in the case of the classical critical exponents, i.e. in the mean field theory, is also shown to be strictly independent of the biasing field. New scaling invariants related to the inflection points are found and their analytical expressions are given for the considered equation of state. The usefulness of the theoretical results to the analysis of experimental data is discussed
21 CFR 123.6 - Hazard analysis and Hazard Analysis Critical Control Point (HACCP) plan.
2010-04-01
... 21 Food and Drugs 2 2010-04-01 2010-04-01 false Hazard analysis and Hazard Analysis Critical... Provisions § 123.6 Hazard analysis and Hazard Analysis Critical Control Point (HACCP) plan. (a) Hazard analysis. Every processor shall conduct, or have conducted for it, a hazard analysis to determine...
Influence of super-ohmic dissipation on a disordered quantum critical point
We investigate the combined influence of quenched randomness and dissipation on a quantum critical point with O(N) order-parameter symmetry. Utilizing a strong-disorder renormalization group, we determine the critical behavior in one space dimension exactly. For super-ohmic dissipation, we find a Kosterlitz-Thouless type transition with conventional (power-law) dynamical scaling. The dynamical critical exponent depends on the spectral density of the dissipative baths. We also discuss the Griffiths singularities, and we determine observables.
Influence of super-ohmic dissipation on a disordered quantum critical point
Vojta, Thomas [Department of Physics, Missouri University of Science and Technology, Rolla, MO 65409 (United States); Hoyos, Jose A [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, C.P. 369, Sao Carlos, Sao Paulo 13560-970 (Brazil); Mohan, Priyanka; Narayanan, Rajesh, E-mail: vojtat@mst.edu, E-mail: hoyos@ifsc.usp.br, E-mail: priyanka@physics.iitm.ac.in, E-mail: rnarayanan@physics.iitm.ac.in [Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India)
2011-03-09
We investigate the combined influence of quenched randomness and dissipation on a quantum critical point with O(N) order-parameter symmetry. Utilizing a strong-disorder renormalization group, we determine the critical behavior in one space dimension exactly. For super-ohmic dissipation, we find a Kosterlitz-Thouless type transition with conventional (power-law) dynamical scaling. The dynamical critical exponent depends on the spectral density of the dissipative baths. We also discuss the Griffiths singularities, and we determine observables.
Long-term mortality after critical care: what is the starting point?
Ranzani, Otavio T.; Zampieri, Fernando G.; Park, Marcelo; Salluh, Jorge IF
2013-01-01
Mortality is still the most assessed outcome in the critically ill patient and is routinely used as the primary end-point in intervention trials, cohort studies, and benchmarking analysis. Despite this, interest in patient-centered prognosis after ICU discharge is increasing, and several studies report quality of life and long-term outcomes after critical illness. In a recent issue of Critical Care, Cuthbertson and colleagues reported interesting results from a cohort of 439 patients with sep...
Molecular dynamics simulation of a binary mixture near the lower critical point
Pousaneh, Faezeh; Edholm, Olle; Maciołek, Anna
2016-07-01
2,6-lutidine molecules mix with water at high and low temperatures but in a wide intermediate temperature range a 2,6-lutidine/water mixture exhibits a miscibility gap. We constructed and validated an atomistic model for 2,6-lutidine and performed molecular dynamics simulations of 2,6-lutidine/water mixture at different temperatures. We determined the part of demixing curve with the lower critical point. The lower critical point extracted from our data is located close to the experimental one. The estimates for critical exponents obtained from our simulations are in a good agreement with the values corresponding to the 3D Ising universality class.
Hamiltonian and linear-space structure for damped oscillators: II. Critical points
The eigenvector expansion developed in the preceding paper for a system of damped linear oscillators is extended to critical points, where eigenvectors merge and the time-evolution operator H assumes a Jordan-block structure. The representation of the bilinear map is obtained in this basis. Perturbations εΔH around an Mth order critical point generically lead to eigenvalue shifts ∼ε1/M dependent on only one matrix element, with the M eigenvalues splitting in equiangular directions in the complex plane. Small denominators near criticality are shown to cancel
Degenerate optomechanical parametric oscillators: cooling in the vicinity of a critical point
Degenfeld-Schonburg, Peter; Hartmann, Michael J; Navarrete-Benlloch, Carlos
2015-01-01
Degenerate optomechanical parametric oscillators are optical resonators in which a mechanical degree of freedom is coupled to a cavity mode that is nonlinearly amplified via parametric down-conversion of an external pumping laser. Below a critical pumping power the down-converted field is purely quantum-mechanical, making the theoretical description of such systems very challenging. Here we introduce a theoretical approach that is capable of describing this regime, even at the critical point itself. We find that the down-converted field can induce significant mechanical cooling and identify the process responsible of this as a "cooling by heating" mechanism. Moreover, we show that, contrary to naive expectations and semi-classical predictions, cooling is not optimal at the critical point, where the photon number is largest. Our approach opens the possibility for analyzing further hybrid dissipative quantum systems in the vicinity of critical points.
The Lieb-Liniger model at the critical point as toy model for Black Holes
Panchenko, Mischa
2015-01-01
In a previous series of papers it was proposed that black holes can be understood as Bose-Einstein condensates at the critical point of a quantum phase transition. Therefore other bosonic systems with quantum criticalities, such as the Lieb-Liniger model with attractive interactions, could possibly be used as toy models for black holes. Even such simple models are hard to analyse, as mean field theory usually breaks down at the critical point. Very few analytic results are known. In this paper we present a method of studying such systems at quantum critical points analytically. We will be able to find explicit expressions for the low energy spectrum of the Lieb-Liniger model and thereby to confirm the expected black hole like properties of such systems. This opens up an exciting possibility of constructing and studying black hole like systems in the laboratory.
Degenerate optomechanical parametric oscillators: Cooling in the vicinity of a critical point
Degenfeld-Schonburg, Peter; Abdi, Mehdi; Hartmann, Michael J.; Navarrete-Benlloch, Carlos
2016-02-01
Degenerate optomechanical parametric oscillators are optical resonators in which a mechanical degree of freedom is coupled to a cavity mode that is nonlinearly amplified via parametric down-conversion of an external pumping laser. Below a critical pumping power the down-converted field is purely quantum mechanical, making the theoretical description of such systems very challenging. Here we introduce a theoretical approach that is capable of describing this regime, even at the critical point itself. We find that the down-converted field can induce significant mechanical cooling and identify the process responsible of this as a cooling-by-heating mechanism. Moreover, we show that, contrary to naive expectations and semiclassical predictions, cooling is not optimal at the critical point, where the photon number is largest. Our approach opens the possibility of analyzing further hybrid dissipative quantum systems in the vicinity of critical points.
Critical point of a rotating Bose-Einstein condensates in optical lattice
El-Badry, Azza M.; Soliman, Shemi S. M.; Hassan, Ahmed S.
2016-06-01
In this paper, we have considered the critical point (critical atoms' number and the corresponding critical temperature) of rotating condensate bosons trapped in optical lattices. Our system is formed by loading three dimensional harmonically trapped boson atoms into a 1D (axial direction) or 2D (radial direction) optical lattice. The system subjected to rotating with angular velocity Ω around to the axial direction z-axis. We employ the semiclassical approximation to calculate the critical point. Effects of the optical lattice depth, direction (axial or radial) and the rotation rate on the critical point are investigated using the semiclassical approximation. The calculated results showed that the temperature dependence of the critical point is changed in an optical lattice and depends crucially on the rotation rate. The effect of the finite size for one-dimensional optical lattice case, as required by experiment, is discussed. The outcome results furnish useful qualitatively theoretical results for the future Bose-Einstein condensation experiments in such traps.
The principle of corresponding state on the fluctuation structure, which is the spatial distribution of various clusters of molecules caused by density fluctuations, in supercritical states around the critical points has been investigated. In this paper, we performed Molecular Dynamics (MD) simulation to extract the fluctuation structure around the critical points of 2-Center-Lennard-Jones (2CLJ) fluids, whose characteristics change by their molecular elongations. First, we indentified some critical points of 2CLJ fluids with comparatively shorter elongations applying Lotfi's function, which correctly describes the liquid-vapor coexistence line of Lennard-Jones (LJ) fluid, and successfully defined each critical point. Next, two methods were applied in the estimation of the fluctuation structure: one is the evaluation of the dispersion of the number of molecules at a certain domain, and the other is the calculation of static structure factor. As a result, in 2CLJ fluids which have shorter molecular elongations comparatively, the principle of corresponding state is satisfied because of the small differences in the fluctuation structures extracted in the present two methods. On the other hand, some results imply that the fluctuation may decrease in 2CLJ fluids which have the longer molecular elongations although more accurate evaluation of the critical points in those fluids is necessary for the further investigation. (author)
Completely mixed state is a critical point for three-qubit entanglement
Tamaryan, Sayatnova, E-mail: sayat@mail.yerphi.am [Department of Theoretical Physics, A. Alikhanyan National Laboratory, Yerevan (Armenia)
2011-06-06
Pure three-qubit states have five algebraically independent and one algebraically dependent polynomial invariants under local unitary transformations and an arbitrary entanglement measure is a function of these six invariants. It is shown that if the reduced density operator of a some qubit is a multiple of the unit operator, than the geometric entanglement measure of the pure three-qubit state is absolutely independent of the polynomial invariants and is a constant for such tripartite states. Hence a one-particle completely mixed state is a critical point for the geometric measure of entanglement. -- Highlights: → Geometric measure of pure three-qubits is expressed in terms of polynomial invariants. → When one Bloch vector is zero the measure is independent of the remaining invariants. → Hence a one-particle completely mixed state is a critical point for the geometric measure. → The existence of the critical points is an inherent feature of the entanglement.
Chen, Min; Gao, Xin
2014-01-01
to avoid such a performance decrease by the disconnection of these low temperature TEMs, provided that the critical power point can be accurately determined. In this paper, firstly a rigorous and universal formulation is fully detailed to mathematically determine the conceptions and conditions of the...... critical power point in the series and parallel TEM arrays. Secondly, experiments of a series-parallel hybrid interconnected TEG are presented to clearly quantify the theoretical analyses. Finally, the hierarchical simulation, based on the SPICE (simulation program with integrated circuit emphasis......) platform, is applied to estimate the critical power point. By numerically modeling the nonlinear physical processes of the TEG, the simulation can be used as an enabling technique in any model-based controller to dynamically minimize the mismatch power loss within the TEM matrix of any configuration. In...
Hazard analysis and critical control point (HACCP) history and conceptual overview.
Hulebak, Karen L; Schlosser, Wayne
2002-06-01
The concept of Hazard Analysis and Critical Control Point (HACCP) is a system that enables the production of safe meat and poultry products through the thorough analysis of production processes, identification of all hazards that are likely to occur in the production establishment, the identification of critical points in the process at which these hazards may be introduced into product and therefore should be controlled, the establishment of critical limits for control at those points, the verification of these prescribed steps, and the methods by which the processing establishment and the regulatory authority can monitor how well process control through the HACCP plan is working. The history of the development of HACCP is reviewed, and examples of practical applications of HACCP are described. PMID:12088233
Critical Two-Point Function of the 4-Dimensional Weakly Self-Avoiding Walk
Bauerschmidt, Roland; Brydges, David C.; Slade, Gordon
2015-08-01
We prove decay of the critical two-point function for the continuous-time weakly self-avoiding walk on , in the upper critical dimension d = 4. This is a statement that the critical exponent exists and is equal to zero. Results of this nature have been proved previously for dimensions using the lace expansion, but the lace expansion does not apply when d = 4. The proof is based on a rigorous renormalisation group analysis of an exact representation of the continuous-time weakly self-avoiding walk as a supersymmetric field theory. Much of the analysis applies more widely and has been carried out in a previous paper, where an asymptotic formula for the susceptibility is obtained. Here, we show how observables can be incorporated into the analysis to obtain a pointwise asymptotic formula for the critical two-point function. This involves perturbative calculations similar to those familiar in the physics literature, but with error terms controlled rigorously.
Determination of liquid-liquid critical point composition using 90∘ laser light scattering
Williamson, J. Charles; Brown, Allison M.; Helvie, Elise N.; Dean, Kevin M.
2016-04-01
Despite over a century of characterization efforts, liquid-liquid critical point compositions are difficult to identify with good accuracy. Reported values vary up to 10% for even well-studied systems. Here, a technique is presented for high-precision determination of the critical composition of a partially miscible binary liquid system. Ninety-degree laser light-scattering intensities from single-phase samples are analyzed using an equation derived from nonclassical power laws and the pseudospinodal approximation. Results are reported for four liquid-liquid systems (aniline + hexane, isobutyric acid + water, methanol + cyclohexane, and methanol + carbon disulfide). Compared to other methods, the 90∘ light-scattering approach has a strong dependence on composition near the critical point, is less affected by temperature fluctuations, and is insensitive to the presence of trace impurities in the samples. Critical compositions found with 90∘ light scattering are precise to the parts-per-thousand level and show long-term reproducibility.
Critical point dewetting observed in the liquid Se-Tl system on a quartz substrate
We have studied the wetting phenomena of the liquid Se-Tl system on a quartz substrate by photography and ellipsometry, and found that a thin layer of the Se-rich liquid phase intrudes between the Tl-rich liquid phase and the quartz substrate in the temperature region far below the critical temperature. Surprisingly, neither the Se-rich nor the Tl-rich wetting film is formed near the critical temperature, indicating the critical point dewetting. In addition, we found that the temperature difference between the surface and the bulk liquid induces the transition between the wetting and non-wetting states. In order to interpret the observation, we constructed a model grand potential, incorporating the long-range interaction, the temperature difference and gravity. From this analysis, it is suggested that the combination of the long-range force and gravity plays an important role in overcoming the critical point wetting phenomena
Barlow, Nathaniel S., E-mail: nsbsma@rit.edu [School of Mathematical Sciences, Rochester Institute of Technology, Rochester, New York 14623 (United States); Schultz, Andrew J., E-mail: ajs42@buffalo.edu; Kofke, David A., E-mail: kofke@buffalo.edu [Department of Chemical and Biological Engineering, University at Buffalo, State University of New York, Buffalo, New York 14260 (United States); Weinstein, Steven J., E-mail: sjweme@rit.edu [Department of Chemical Engineering, Rochester Institute of Technology, Rochester, New York 14623 (United States)
2015-08-21
The mathematical structure imposed by the thermodynamic critical point motivates an approximant that synthesizes two theoretically sound equations of state: the parametric and the virial. The former is constructed to describe the critical region, incorporating all scaling laws; the latter is an expansion about zero density, developed from molecular considerations. The approximant is shown to yield an equation of state capable of accurately describing properties over a large portion of the thermodynamic parameter space, far greater than that covered by each treatment alone.
The mathematical structure imposed by the thermodynamic critical point motivates an approximant that synthesizes two theoretically sound equations of state: the parametric and the virial. The former is constructed to describe the critical region, incorporating all scaling laws; the latter is an expansion about zero density, developed from molecular considerations. The approximant is shown to yield an equation of state capable of accurately describing properties over a large portion of the thermodynamic parameter space, far greater than that covered by each treatment alone
Time-Averaged Behaviour at the Critical Parameter Point of Transition to Spatiotemporal Chaos
贺凯芬
2001-01-01
A time-averaged behaviour is found to be important for investigating the critical behaviour in parameter space for the transition from temporal chaos to spatiotemporal chaos by using an energy representation. Considering any wave solution as a superposition of the steady wave with its perturbation wave, we find that when approaching the critical parameter point the averaged positive interaction energy for the k = 1 mode becomes competitive with the negative one, with the summation displaying a scaling behaviour of power law.
Welter, D A; Schöler, J; Rosenquist, T H
1978-11-01
Bone marrow nuclei fixed with modified Carnoy's, then stained with gallocyanin chromalum followed by air drying showed no difference in morphology when compared by means of scanning electron microscopy with similar nuclei prepared by critical point drying. Glutaraldehyde at pH 4.0 and 7.1, mercury-containing Zenker's fluid, and chromalum alone, all of which are considered to be nuclear protein cross-linking fixatives, failed to preserve the nuclear morphology as well as gallocyanin-chromalum or critical point prepared bone marro nuclei. PMID:89717
Hazard analysis and critical control point (HACCP) for an ultrasound food processing operation.
Chemat, Farid; Hoarau, Nicolas
2004-05-01
Emerging technologies, such as ultrasound (US), used for food and drink production often cause hazards for product safety. Classical quality control methods are inadequate to control these hazards. Hazard analysis of critical control points (HACCP) is the most secure and cost-effective method for controlling possible product contamination or cross-contamination, due to physical or chemical hazard during production. The following case study on the application of HACCP to an US food-processing operation demonstrates how the hazards at the critical control points of the process are effectively controlled through the implementation of HACCP. PMID:15081991
Probing the QCD Critical Point with Relativistic Heavy-Ion Collisions
Bass, Steffen A; Quammen, Cory; Canary, Hal; Healey, Christopher G; Taylor, Russell M
2012-01-01
We utilize an event-by-event relativistic hydrodynamic calculation performed at a number of different incident beam energies to investigate the creation of hot and dense QCD matter near the critical point. Using state-of-the-art analysis and visualization tools we demonstrate that each collision event probes QCD matter characterized by a wide range of temperatures and baryo-chemical potentials, making a dynamical response of the system to the vicinity of the critical point very difficult to isolate above the background.
Pasteurised milk and implementation of HACCP (Hazard Analysis Critical Control Point
T.B Murdiati
2004-10-01
Full Text Available The purpose of pasteurisation is to destroy pathogen bacteria without affecting the taste, flavor, and nutritional value. A study on the implementation of HACCP (Hazard Analysis Critical Control Point in producing pasteurized milk was carried out in four processing unit of pasteurised milk, one in Jakarta, two in Bandung and one in Bogor. The critical control points in the production line were identified. Milk samples were collected from the critical points and were analysed for the total number of microbes. Antibiotic residues were detected on raw milks. The study indicated that one unit in Bandung dan one unit in Jakarta produced pasteurized milk with lower number of microbes than the other units, due to better management and control applied along the chain of production. Penisilin residues was detected in raw milk used by unit in Bogor. Six critical points and the hazard might arise in those points were identified, as well as how to prevent the hazards. Quality assurance system such as HACCP would be able to produce high quality and safety of pasteurised milk, and should be implemented gradually.
The Quenched Critical Point for Self-Avoiding Walk on Random Conductors
Chino, Yuki; Sakai, Akira
2016-05-01
Following similar analysis to that in Lacoin (Probab Theory Relat Fields 159: 777-808, 2014), we can show that the quenched critical point for self-avoiding walk on random conductors on Z^d is almost surely a constant, which does not depend on the location of the reference point. We provide upper and lower bounds which are valid for all d≥ 1.
Enhancement of superconductivity near the ferromagnetic quantum critical point in UCoGe
Slooten, E.; Naka, T.; Gasparini, A.; Huang, Y. K.; Visser,, Richard G F
2009-01-01
We report a high-pressure single crystal study of the superconducting ferromagnet UCoGe. Ac-susceptibility and resistivity measurements under pressures up to 2.2 GPa show ferromagnetism is smoothly depressed and vanishes at a critical pressure $p_c = 1.4$ GPa. Near the ferromagnetic critical point superconductivity is enhanced. Upper-critical field measurements under pressure show $B_{c2}(0)$ attains remarkably large values, which provides solid evidence for spin-triplet superconductivity ove...
Influence of super-ohmic dissipation on a disordered quantum critical point.
Vojta, Thomas; Hoyos, José A; Mohan, Priyanka; Narayanan, Rajesh
2011-03-01
We investigate the combined influence of quenched randomness and dissipation on a quantum critical point with O(N) order-parameter symmetry. Utilizing a strong-disorder renormalization group, we determine the critical behavior in one space dimension exactly. For super-ohmic dissipation, we find a Kosterlitz-Thouless type transition with conventional (power-law) dynamical scaling. The dynamical critical exponent depends on the spectral density of the dissipative baths. We also discuss the Griffiths singularities, and we determine observables. PMID:21339559
Universal Organization of Resting Brain Activity at the Thermodynamic Critical Point
Yu, Shan; Shriki, Oren; Plenz, Dietmar
2013-01-01
Thermodynamic criticality describes emergent phenomena in a wide variety of complex systems. In the mammalian brain, the complex dynamics that spontaneously emerge from neuronal interactions have been characterized as neuronal avalanches, a form of critical branching dynamics. Here, we show that neuronal avalanches also reflect that the brain dynamics are organized close to a thermodynamic critical point. We recorded spontaneous cortical activity in monkeys and humans at rest using high-density intracranial microelectrode arrays and magnetoencephalography, respectively. By numerically changing a control parameter equivalent to thermodynamic temperature, we observed typical critical behavior in cortical activities near the actual physiological condition, including the phase transition of an order parameter, as well as the divergence of susceptibility and specific heat. Finite-size scaling of these quantities allowed us to derive robust critical exponents highly consistent across monkey and humans that uncover ...
Image-plane Analysis of n-point-mass Lens Critical Curves and Caustics
Danek, Kamil
2015-01-01
The interpretation of gravitational microlensing events caused by planetary systems or multiple stars is based on the n-point mass lens model. The first planets detected by microlensing were well described by the two-point-mass model of a star with one planet. By the end of 2014, four events involving three-point-mass lenses had been announced. Two of the lenses were stars with two planetary companions each; two were binary stars with a planet orbiting one component. While the two-point-mass model is well understood, the same cannot be said for lenses with three or more components. Even the range of possible critical-curve topologies and caustic geometries of the three-point-mass lens remains unknown. In this paper we provide new tools for mapping the critical-curve topology and caustic cusp number in the parameter space of n-point-mass lenses. We perform our analysis in the image plane of the lens. We show that all contours of the Jacobian are critical curves of re-scaled versions of the lens configuration. ...
Coupling of pion condensate, chiral condensate and Polyakov loop in an extended NJL model
Zhang, Zhao; Liu, Yu-Xin
2006-01-01
The Nambu Jona-Lasinio model with a Polyakov loop is extended to finite isospin chemical potential case, which is characterized by simultaneous coupling of pion condensate, chiral condensate and Polyakov loop. The pion condensate, chiral condensate and the Polyakov loop as functions of temperature and isospin chemical potential are investigated by minimizing the thermodynamic potential of the system. The resulting $(T,\\mu_I)$ phase diagram is studied with emphasis on the critical point and Po...
Types of critical points of the Kowalevski gyrostat in double field
Kharlamov, M. P.; Ryabov, P. E.; Savushkin, A. Y.; Smirnov, G. E.
2012-01-01
The problem of motion of the Kowalevski type gyrostat in double force field is considered. According to the classification used in the theory of Liouville integrable Hamiltonian systems, the types of critical points of all ranks of the integral map are calculated.
Improved Criteria for Acceptable Yield Point Elongation in Surface Critical Steels
Dr. David Matlock; Dr. John Speer
2007-05-30
Yield point elongation (YPE) is considered undesirable in surface critical applications where steel is formed since "strain lines" or Luders bands are created during forming. This project will examine in detail the formation of luders bands in industrially relevant strain states including the influence of substrate properties and coatings on Luders appearance. Mechanical testing and surface profilometry were the primary methods of investigation.
Numerical simulation of turbulent heat transfer close to the critical point
Boersma, B.J.; Pecnik, R.; Nemati, H.; Peeters, J.W.R.
2015-01-01
In this paper we discuss the effect of sharp property variations on the turbulent heat transfer in fluids close the critical point. The governing equations for this flow regime are discussed, a short description of the numerical tools that have been developed to study these flows is given. Finally,
Numerical simulation of turbulent heat transfer close to the critical point
Boersma, B.J.; Pecnik, R.; H. Nemati; Peeters, J.W.R.
2015-01-01
In this paper we discuss the effect of sharp property variations on the turbulent heat transfer in fluids close the critical point. The governing equations for this flow regime are discussed, a short description of the numerical tools that have been developed to study these flows is given. Finally, some results for supercritical heat transfer in developing turbulent pipe flow are presented.
Quadratic growth and critical point stability of semi-algebraic functions
Drusvyatskiy, D.; Ioffe, A. D.
2013-01-01
We show that quadratic growth of a semi-algebraic function is equivalent to strong metric subregularity of the subdifferential --- a kind of stability of generalized critical points. In contrast, this equivalence can easily fail outside of the semi-algebraic setting. As a consequence, we derive necessary conditions and sufficient conditions for optimality in subdifferential terms.
Valat, C; Champiat, D; Degorce-Dumas, J R; Thomas, O
2004-01-01
Starting from a new approach for water pollution control and wastewater treatment plant management, the hazard analysis and critical control point (HACCP) quality concept, the interest for the development of new rapid and sensitive methods such as bioluminescence-based methods is evident. After an introduction of the HACCP procedure, a bibliographic study of the bioluminescence potentiality is presented and discussed. PMID:14979548
Kouhia, R.; Tůma, Miroslav; Mäkinen, J.; Fedoroff, A.; Marjamäki, H.
108-109, October (2012), s. 110-117. ISSN 0045-7949 R&D Projects: GA ČR(CZ) GAP108/11/0853 Institutional research plan: CEZ:AV0Z10300504 Keywords : non-linear eigenvalue problem * equilibrium equations * critical points * preconditioned iterations Subject RIV: BA - General Mathematics Impact factor: 1.509, year: 2012
Absence of Critical Points of Solutions to the Helmholtz Equation in 3D
Alberti, Giovanni S.
2015-01-01
The focus of this paper is to show the absence of critical points for the solutions to the Helmholtz equation in a bounded domain $\\Omega\\subset\\mathbb{R}^{3}$, given by \\[ \\left\\{ \\begin{array}{l} -\\rm{div}(a\\,\
Infinite-disorder critical points of models with stretched exponential interactions
We show that an interaction decaying as a stretched exponential function of distance, J(l)∼e−cla, is able to alter the universality class of short-range systems having an infinite-disorder critical point. To do so, we study the low-energy properties of the random transverse-field Ising chain with the above form of interaction by a strong-disorder renormalization group (SDRG) approach. We find that the critical behavior of the model is controlled by infinite-disorder fixed points different from those of the short-range model if 0 1/2, the model belongs to the same universality class as its short-range variant. The entanglement entropy of a block of size L increases logarithmically with L at the critical point but, unlike the short-range model, the prefactor is dependent on disorder in the range 0 < a < 1/2. Numerical results obtained by an improved SDRG scheme are found to be in agreement with the analytical predictions. The same fixed points are expected to describe the critical behavior of, among others, the random contact process with stretched exponentially decaying activation rates. (paper)
Quantum correction to conductivity close to ferromagnetic quantum critical point in two dimensions
We study the temperature dependence of the conductivity due to quantum interference processes for a two-dimensional disordered itinerant electron system close to a ferromagnetic quantum critical point. Near the quantum critical point, the cross-over between diffusive and ballistic regimes of quantum interference effects occurs at a temperature T* 1/τγ(EFτ)2 where γ is the parameter associated with the Landau damping of the spin fluctuations, τ is the impurity scattering time, and EF is the Fermi energy. For a generic choice of parameters, T* is smaller than the nominal crossover scale 1/τ. In the ballistic quantum critical regime, the conductivity behaves as T1/3. (author)
Observation of the critical end point in the phase diagram for hot and dense nuclear matter
Lacey, Roy A
2014-01-01
Excitation functions for the Gaussian emission source radii difference ($R^2_{\\text{out}} - R^2_{\\text{side}}$) obtained from two-pion interferometry measurements in Au+Au ($\\sqrt{s_{NN}}= 7.7 - 200$ GeV) and Pb+Pb ($\\sqrt{s_{NN}}= 2.76$ TeV) collisions, are studied for a broad range of collision centralities. The observed non-monotonic excitation functions validate the finite-size scaling patterns expected for the deconfinement phase transition and the critical end point (CEP), in the temperature vs. baryon chemical potential ($T,\\mu_B$) plane of the nuclear matter phase diagram. A Finite-Size Scaling (FSS) analysis of these data indicate a second order phase transition with the estimates $T^{\\text{cep}} \\sim 165$~MeV and $\\mu_B^{\\text{cep}} \\sim 100$~MeV for the location of the critical end point. The critical exponents ($\
The critical adsorption point of self-avoiding walks: a finite-size scaling approach.
Luo, Meng-Bo
2008-01-28
The critical adsorption of self-avoiding polymer chain in a simple cubic lattice onto a flat surface is studied with Monte Carlo simulations. The dependence of number of surface contacts M on chain length N and polymer-surface interaction epsilon is investigated by a finite-size scaling approach. We estimate the critical adsorption point epsilon(c)=0.291+/-0.002 and the exponent phi=0.54+/-0.01. The asymptotic behaviors M proportional variant N for epsilon>epsilon(c) and M proportional variant N(0) for epsilon
Magnetic-field control of quantum critical points of valence transition.
Watanabe, Shinji; Tsuruta, Atsushi; Miyake, Kazumasa; Flouquet, Jacques
2008-06-13
We study the mechanism of how critical end points of first-order valence transitions are controlled by a magnetic field. We show that the critical temperature is suppressed to be a quantum critical point (QCP) by a magnetic field, and unexpectedly, the QCP exhibits nonmonotonic field dependence in the ground-state phase diagram, giving rise to the emergence of metamagnetism even in the intermediate valence-crossover regime. The driving force of the field-induced QCP is clarified to be cooperative phenomena of the Zeeman and Kondo effects, which create a distinct energy scale from the Kondo temperature. This mechanism explains the peculiar magnetic response in CeIrIn(5) and the metamagnetic transition in YbXCu(4) for X=In as well as the sharp contrast between X=Ag and Cd. PMID:18643524
Second-order magnetic critical points at finite magnetic fields: Revisiting Arrott plots
Bustingorry, S.; Pomiro, F.; Aurelio, G.; Curiale, J.
2016-06-01
The so-called Arrott plot, which consists in plotting H /M against M2, with H the applied magnetic field and M the magnetization, is used to extract valuable information in second-order magnetic phase transitions. Besides, it is widely accepted that a negative slope in the Arrott plot is indicative of a first-order magnetic transition. This is known as the Banerjee criterion. In consequence, the zero-field transition temperature T* is reported as the characteristic first-order transition temperature. By carefully analyzing the mean-field Landau model used for studying first-order magnetic transitions, we show in this work that T* corresponds in fact to a triple point where three first-order lines meet. More importantly, this analysis reveals the existence of two symmetrical second-order critical points at finite magnetic field (Tc,±Hc) . We then show that a modified Arrott plot can be used to obtain information about these second-order critical points. To support this idea we analyze experimental data on La2 /3Ca1 /3MnO3 and discuss an estimate for the location of the triple point and the second-order critical points.
Critical points of the cosmic velocity and the uncertainties in the value of the Hubble constant
Liu, Hao; Naselsky, Pavel
2016-01-01
The existence of critical points for the peculiar velocity field is a natural feature of the correlated vector field. These points appear in contact zones of the velocity domains with different orientation of the averaged velocity vector. At the same time peculiar velocities are the cause of the scatter of the Hubble expansion rate. We propose that a more precise determination of the Hubble constant can be made by restricting analysis to subsample of observational data containing only the zones around the critical points of the peculiar velocity field, associated with voids and saddle points. On large-scales the critical points where the first derivative of the gravitational potential vanishes can be easily identified using the density field and classified by the behavior of the Hessian of the gravitational potential. We use high- resolution N-body simulations to show that these regions are stable in time and hence are excellent tracers of the initial conditions. Furthermore, we show that the variance of the ...
This study was designed to determine the critical photon irradiance for growth and daily compensation point of juvenile Sargassum macrocarpum. Sampling and measurement of natural light conditions were carried out in the S. macrocarpum population at a depth of 8 m off Kiwado in Fukawa Bay, Yamaguchi Prefecture, Japan, from April to June 1998. Photosynthesis and respiration of the juvenile thalli, and diurnal changes in solar irradiance were measured for the same period. The critical photon irradiance for growth of the juvenile thalli observed on the population floor was 1.0–1.5% on the sea surface. The photosynthetic rate of leaf of juvenile thalli increased linearly with increasing photon irradiance when light levels were lower than 50 μM/m2 per s. The respiratory rate and light compensation point of the juvenile thalli were 2.49 μL O2/cm2 per h and 4.98 μM/m2 per s, respectively. The daily compensation point was estimated with a mathematical model based on photosynthesis–light equations and diurnal changes in solar irradiance. For a day of average solar irradiance over the period of the present study, the estimated daily compensation point of the juvenile thalli was 1.3% on the sea surface. This value agreed well with the observed critical photon irradiance for growth of juvenile S. macrocarpum on the population floor. The results of the study confirm that the mathematical model is effective for estimating the daily compensation point
Functional renormalization group analysis of the soft mode at the QCD critical point
Yokota, Takeru; Kunihiro, Teiji; Morita, Kenji
2016-07-01
We make an intensive investigation of the soft mode at the quantum chromodynamics (QCD) critical point on the basis of the functional renormalization group (FRG) method in the local potential approximation. We calculate the spectral functions ρ_{σ, π}(ω, p) in the scalar (σ) and pseudoscalar (π) channels beyond the random phase approximation in the quark-meson model. At finite baryon chemical potential μ with a finite quark mass, the baryon-number fluctuation is coupled to the scalar channel and the spectral function in the σ channel has a support not only in the time-like (ω > p) but also in the space-like (ω < p) regions, which correspond to the mesonic and the particle-hole phonon excitations, respectively. We find that the energy of the peak position of the latter becomes vanishingly small with the height being enhanced as the system approaches the QCD critical point, which is a manifestation of the fact that the phonon mode is the soft mode associated with the second-order transition at the QCD critical point, as has been suggested by some authors. Moreover, our extensive calculation of the spectral function in the (ω, p) plane enables us to see that the mesonic and phonon modes have the respective definite dispersion relations ω_{σ.ph}(p), and it turns out that ω_{σ}(p) crosses the light-cone line into the space-like region, and then eventually merges into the phonon mode as the system approaches the critical point more closely. This implies that the sigma-mesonic mode also becomes soft at the critical point. We also provide numerical stability conditions that are necessary for obtaining the accurate effective potential from the flow equation.
System of hazard analysis and critical control points are deployed in a production plant of liquid nitrogen. The fact that the nitrogen has become a complement to food packaging to increase shelf life, or provide a surface that protect it from manipulation, has been the main objective. Analysis of critical control points for the nitrogen production plant has been the adapted methodology. The knowledge of both the standard and the production process, as well as the on site verification process, have been necessary. In addition, all materials and/or processing units that are found in contact with the raw material or the product under study were evaluated. Such a way that the intrinsic risks of each were detected, from the physical, chemical and biological points of view according to the origin or pollution source. For each found risk was evaluated the probability of occurrence according to the frequency and gravity of it, with these variables determined was achieved the definition of the type of risk detected. In the cases that was presented a greater risk or critical, these were subjected decision tree; with which is concluded the non determination of critical control points. However, for each one of them were established the maximum permitted limits. To generate each of the results it has literature or scientific reference of reliable provenance, where is indicated properly the support of the evaluated matter. In a general way, the material matrix and the process matrix are found without critical control points; so that the project is concluded in the analysis, and it has to generate without the monitoring system and verification. To increase this project is suggested in order to cover the packaging system of gaseous nitrogen, due to it was delimited to liquid nitrogen. Furthermore, the liquid nitrogen is a 100% automated and closed process so the introduction of contaminants is very reduced, unlike the gaseous nitrogen process. (author)
Inoue, Yoshihisa
2004-01-01
Direct Asymmetric Photochemistry with Circularly Polarized Light, H. RauCoherent Laser Control of the Handedness of Chiral Molecules, P. Brumer and M. ShapiroMagnetochiral Anisotropy in Asymmetric Photochemistry, G.L.J.A.RikkenEnantiodifferentiating Photosensitized Reactions, Y. InoueDiastereodifferentiating Photoreactions, N. Hoffmann and J.-P. PeteChirality in Photochromism, Y. Yokoyama and M. SaitoChiral Photochemistry with Transition Metal Complexes, S. Sakaki and T. HamadaTemplate-Induced Enantioselective Photochemical Reactions in S
Kharzeev, Dmitri E.; Yee, Ho-Ung
2012-01-01
We consider the properties of electric circuits involving Weyl semimetals. The existence of the anomaly-induced chiral magnetic current in a Weyl semimetal subjected to magnetic field causes an interesting and unusual behavior of such circuits. We consider two explicit examples: i) a circuit involving the "chiral battery" and ii) a circuit that can be used as a "quantum amplifier" of magnetic field. The unique properties of these circuits stem from the chiral anomaly and may be utilized for c...
Hyperscaling violation at the Ising-nematic quantum critical point in two dimensional metals
Eberlein, Andreas; Sachdev, Subir
2016-01-01
Understanding optical conductivity data in the optimally doped cuprates in the framework of quantum criticality requires a strongly-coupled quantum critical metal which violates hyperscaling. In the simplest scaling framework, hyperscaling violation can be characterized by a single non-zero exponent $\\theta$, so that in a spatially isotropic state in $d$ spatial dimensions, the specific heat scales with temperature as $T^{(d-\\theta)/z}$, and the optical conductivity scales with frequency as $\\omega^{(d-\\theta-2)/z}$ for $\\omega \\gg T$, where $z$ is the dynamic critical exponent. We study the Ising-nematic critical point, using the controlled dimensional regularization method proposed by Dalidovich and Lee (Phys. Rev. B {\\bf 88}, 245106 (2013)). We find that hyperscaling is violated, with $\\theta =1$ in $d=2$. We expect that similar results apply to Fermi surfaces coupled to gauge fields in $d=2$.
Ali, M.
2012-01-01
This thesis investigated how to develop an approach for the systematic and science based assessment of those points in food production systems that have a critical effect on quality; such points could be designated as critical quality points (CQPs). One of the fundamental objectives of quality contr
Critical points and phase transitions in 5d compactifications of M-theory
We study critical points of the BPS mass Z, the BPS string tension Zm, the black hole potential V and the gauged central charge potential P for M-theory compactified on Calabi-Yau three-folds. We first show that the stabilization equations for Z (determining the black hole entropy) take an extremely simple form in five dimensions as opposed to four dimensions. The stabilization equations for Zm are also very simple and determine the size of the infinite adS3throat of the string. The black hole potential in general exhibits two classes of critical points: supersymmetric critical points which coincide with those of the central charge and non-supersymmetric critical points. We then generalize the discussion to the entire extended Kaehler cone encompassing topologically different but birationally equivalent Calabi-Yau three-folds that are connected via flop transitions. We examine behavior of the four potentials to probe the nature of these phase transitions. We find that V and P are continuous but not smooth across the flop transition, while Z and its first two derivatives, as well as Zm and its first derivative, are continuous. This in turn implies that supersymmetric stabilization of Z and Zm for a given configuration takes place in at most one point throughout the entire extended Kaehler cone. The corresponding black holes (or string states) interpolate between different Calabi-Yau three-folds. At the boundaries of the extended Kaehler cone we observe that electric states become massless and/or magnetic strings become tensionless. (orig.)
Kim, Y H; Kaur, N; Atkins, B M; Dalal, N S; Takano, Y
2009-12-11
At a quantum critical point (QCP)--a zero-temperature singularity in which a line of continuous phase transition terminates--quantum fluctuations diverge in space and time, leading to exotic phenomena that can be observed at nonzero temperatures. Using a quantum antiferromagnet, we present calorimetric evidence that nuclear spins frozen in a high-temperature nonequilibrium state by temperature quenching are annealed by quantum fluctuations near the QCP. This phenomenon, with readily detectable heat release from the nuclear spins as they are annealed, serves as an excellent marker of a quantum critical region around the QCP and provides a probe of the dynamics of the divergent quantum fluctuations. PMID:20366226
Travelling waves near a critical point of a binary fluid mixture
Gouin, Henri; Ruggeri, Tommaso; 10.1016/j.ijnonlinmec.2011.09.016
2011-01-01
Travelling waves of densities of binary fluid mixtures are investigated near a critical point. The free energy is considered in a non-local form taking account of the density gradients. The equations of motions are applied to a universal form of the free energy near critical conditions and can be integrated by a rescaling process where the binary mixture is similar to a single fluid. Nevertheless, density solution profiles obtained are not necessarily monotonic. As indicated in Appendix, the results might be extended to other topics like finance or biology.
Barlow, Nathaniel S; Schultz, Andrew J; Weinstein, Steven J; Kofke, David A
2015-08-21
The mathematical structure imposed by the thermodynamic critical point motivates an approximant that synthesizes two theoretically sound equations of state: the parametric and the virial. The former is constructed to describe the critical region, incorporating all scaling laws; the latter is an expansion about zero density, developed from molecular considerations. The approximant is shown to yield an equation of state capable of accurately describing properties over a large portion of the thermodynamic parameter space, far greater than that covered by each treatment alone. PMID:26298108
Intrinsic low pass filtering improves signal-to-noise ratio in critical-point flexure biosensors
Jain, Ankit; Alam, Muhammad Ashraful, E-mail: alam@purdue.edu [School of ECE, Purdue University, West Lafayette, Indiana 47906 (United States)
2014-08-25
A flexure biosensor consists of a suspended beam and a fixed bottom electrode. The adsorption of the target biomolecules on the beam changes its stiffness and results in change of beam's deflection. It is now well established that the sensitivity of sensor is maximized close to the pull-in instability point, where effective stiffness of the beam vanishes. The question: “Do the signal-to-noise ratio (SNR) and the limit-of-detection (LOD) also improve close to the instability point?”, however remains unanswered. In this article, we systematically analyze the noise response to evaluate SNR and establish LOD of critical-point flexure sensors. We find that a flexure sensor acts like an effective low pass filter close to the instability point due to its relatively small resonance frequency, and rejects high frequency noise, leading to improved SNR and LOD. We believe that our conclusions should establish the uniqueness and the technological relevance of critical-point biosensors.
Intrinsic low pass filtering improves signal-to-noise ratio in critical-point flexure biosensors
A flexure biosensor consists of a suspended beam and a fixed bottom electrode. The adsorption of the target biomolecules on the beam changes its stiffness and results in change of beam's deflection. It is now well established that the sensitivity of sensor is maximized close to the pull-in instability point, where effective stiffness of the beam vanishes. The question: “Do the signal-to-noise ratio (SNR) and the limit-of-detection (LOD) also improve close to the instability point?”, however remains unanswered. In this article, we systematically analyze the noise response to evaluate SNR and establish LOD of critical-point flexure sensors. We find that a flexure sensor acts like an effective low pass filter close to the instability point due to its relatively small resonance frequency, and rejects high frequency noise, leading to improved SNR and LOD. We believe that our conclusions should establish the uniqueness and the technological relevance of critical-point biosensors.
The Critical Point of a Sigmoidal Curve: the Generalized Logistic Equation Example
Bilge, Ayse Humeyra; Ozdemir, Yunus
2014-01-01
Let $y(t)$ be a smooth sigmoidal curve, $y^{(n)}(t)$ be its $n$th derivative, $\\{t_{m,i}\\}$ and $\\{t_{a,i}\\}$, $i=1,2,\\dots$ be the set of points where respectively the derivatives of odd and even order reach their extreme values. The "critical point of the sigmoidal curve" is defined to be the common limit of the sequences $\\{t_{m,i}\\}$ and $\\{t_{a,i}\\}$, provided that the limit exists. We prove that if $f(t)=\\frac{dy}{dt}$ is an even function such that the magnitude of the analytic represen...
Kallin, Catherine; Berlinsky, John
2016-05-01
Chiral superconductivity is a striking quantum phenomenon in which an unconventional superconductor spontaneously develops an angular momentum and lowers its free energy by eliminating nodes in the gap. It is a topologically non-trivial state and, as such, exhibits distinctive topological modes at surfaces and defects. In this paper we discuss the current theory and experimental results on chiral superconductors, focusing on two of the best-studied systems, Sr2RuO4, which is thought to be a chiral triplet p-wave superconductor, and UPt3, which has two low-temperature superconducting phases (in zero magnetic field), the lower of which is believed to be chiral triplet f-wave. Other systems that may exhibit chiral superconductivity are also discussed. Key signatures of chiral superconductivity are surface currents and chiral Majorana modes, Majorana states in vortex cores, and the possibility of half-flux quantum vortices in the case of triplet pairing. Experimental evidence for chiral superconductivity from μSR, NMR, strain, polar Kerr effect and Josephson tunneling experiments are discussed.
Elliptic Euler–Poisson–Darboux equation, critical points and integrable systems
The structure and properties of families of critical points for classes of functions W(z, z-bar ) obeying the elliptic Euler–Poisson–Darboux equation E(1/2, 1/2) are studied. General variational and differential equations governing the dependence of critical points in variational (deformation) parameters are found. Explicit examples of the corresponding integrable quasi-linear differential systems and hierarchies are presented. There are the extended dispersionless Toda/nonlinear Schrödinger hierarchies, the ‘inverse’ hierarchy and equations associated with the real-analytic Eisenstein series E(β, β-bar ;1/2) among them. The specific bi-Hamiltonian structure of these equations is also discussed. (paper)
Athermal domain-wall creep near a ferroelectric quantum critical point.
Kagawa, Fumitaka; Minami, Nao; Horiuchi, Sachio; Tokura, Yoshinori
2016-01-01
Ferroelectric domain walls are typically stationary because of the presence of a pinning potential. Nevertheless, thermally activated, irreversible creep motion can occur under a moderate electric field, thereby underlying rewritable and non-volatile memory applications. Conversely, as the temperature decreases, the occurrence of creep motion becomes less likely and eventually impossible under realistic electric-field magnitudes. Here we show that such frozen ferroelectric domain walls recover their mobility under the influence of quantum fluctuations. Nonlinear permittivity and polarization-retention measurements of an organic charge-transfer complex reveal that ferroelectric domain-wall creep occurs via an athermal process when the system is tuned close to a pressure-driven ferroelectric quantum critical point. Despite the heavy masses of material building blocks such as molecules, the estimated effective mass of the domain wall is comparable to the proton mass, indicating the realization of a ferroelectric domain wall with a quantum-particle nature near the quantum critical point. PMID:26880041
Critical points of the Bose–Hubbard model with three-body local interaction
Avila, C.A.; Franco, R. [Departamento de Física, Universidad Nacional de Colombia, A.A. 5997, Bogotá (Colombia); Souza, A.M.C. [Departamento de Física, Universidade Federal de Sergipe, 49100-000 São Cristovão, SE (Brazil); Figueira, M.S. [Instituto de Física, Universidade Federal Fluminense, Av. Litorânea s/n, 24210-346 Niterói, Rio de Janeiro (Brazil); Silva-Valencia, J., E-mail: jsilvav@unal.edu.co [Departamento de Física, Universidad Nacional de Colombia, A.A. 5997, Bogotá (Colombia)
2014-09-12
Using the density matrix renormalization group method, we study a one-dimensional system of bosons that interact with a local three-body term. We calculate the phase diagram for higher densities, where the Mott insulator lobes are surrounded by the superfluid phase. We also show that the Mott insulator lobes always grow as a function of the density. The critical points of the Kosterlitz–Thouless transitions were determined through the von Neumann block entropy, and its dependence on the density is given by a power law with a negative exponent. - Highlights: • We studied the Bose–Hubbard model with a local three-body interaction term. • We show that the Mott insulator lobes always grow as a function of the density. • We found a power law dependence of the critical point position with the density.
Critical points of the Bose–Hubbard model with three-body local interaction
Using the density matrix renormalization group method, we study a one-dimensional system of bosons that interact with a local three-body term. We calculate the phase diagram for higher densities, where the Mott insulator lobes are surrounded by the superfluid phase. We also show that the Mott insulator lobes always grow as a function of the density. The critical points of the Kosterlitz–Thouless transitions were determined through the von Neumann block entropy, and its dependence on the density is given by a power law with a negative exponent. - Highlights: • We studied the Bose–Hubbard model with a local three-body interaction term. • We show that the Mott insulator lobes always grow as a function of the density. • We found a power law dependence of the critical point position with the density
A nontrivial critical fixed point for replica-symmetry-breaking transitions
Charbonneau, Patrick
2016-01-01
The transformation of the free-energy landscape from smooth to fractal is the richest feature of mean-field disordered systems. A well-studied example is the de Almeida-Thouless transition for spin glasses in a magnetic field, and a similar phenomenon--the Gardner transition--has recently been predicted for structural glasses. However, the existence of these phase transitions has been called into question below the upper critical dimension d_u=6. Here, we obtain evidence for these transitions in dimensions d
Hazard Analysis and Critical Control Points System for a Bull Semen Production Centre.
Goularte, K L; Madeira, E M; Ferreira, C E R; Duval, E H; Vieira, A D; Mondadori, R G; Lucia, T
2015-12-01
Bull semen production centres (SPC) generally present satisfactory quality control for sperm processing, but non-standardized hygiene procedures. This study describes a Hazard Analysis and Critical Control Points (HACCP) system developed for bull SPC and subsequently implemented in a commercial SPC. After the identification of hazards at each step of semen processing and the determination of their risk and severity, monitoring and corrective procedures were designed to assess the system's efficiency. The HACCP system identified six microbiological hazards, 10 physical hazards, four chemical hazards and three critical control points. After the establishment of Good Processing Practices, Standard Operating Procedures and Standard Sanitizing Operating Procedures, the system was validated through an audit, to identify eventual failures and to define measures to correct them. PMID:26477334
Photon emission rates near the critical point in the linear sigma model
Wunderlich, Falk
2015-01-01
Employing the linear sigma model, the effective masses of quasi-particle excitations are found to exhibit significant variations within the phase diagram, which has a critical point at non-zero chemical potential, where a first-order phase transition sets in. Soft-photon emission rates in lowest order display, for selected channels, a sensible dependence on the effective masses of the involved excitations and let us argue that they could map out the phase diagram.
Mahmoud El-Hofi; El-Sayed El-Tanboly; Azza Ismail
2010-01-01
Background. HACCP, or the Hazard Analysis and Critical Control Point System has been recognised as an effective and rational means of assuring food safety from primary production through to final consumption, using a “farm to table” methodology. The application of this preventive oriented approach would give the food producer better control over operation, better manufacturing practices and greater efficiencies, including reduced wastes. Material and methods. Th...
Correlation length as an indicator of critical point behavior prior to a large earthquake
Tyupkin, Yu. S.; Geophysical Center, RAS, Molodezhnaya 3, 117296 Moscow, Russian Federation; Di Giovambattista, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia
2005-01-01
A large earthquake preparation is often manifested in correlation of seismicity in an area whose characteristic dimension greatly exceeds a dimension of source of main shock. Zfller et al. [G. Zfller, S. Hainzl, J. Kurths, Observation of growing correlation length as an indicator for critical point behavior prior to large earthquakes, J. Geophys. Res. 106 (2001) 2167– 2176] show the growth of correlation length of earthquakes prior to nine large earthquakes in California according to...
Analytical solution of point kinetic equations for sub-critical systems
This article presents an analytical solution for the set of point kinetic equations for sub-critical reactors. This solution stems from the ordinary, non-homogeneous differential equation that rules the neutron density and that presents the incomplete Gamma function in its functional form. The method used proved advantageous and allowed practical applications such as the linear insertion of reactivity, considering an external constant source or with both varying linearly. (author)
Equation of State for Supercooled Water Near the Liquid-Liquid Critical Point
Anisimov, M. A.; Fuentevilla, D. A.
2006-01-01
We have developed a scaled parametric equation of state to describe and predict thermodynamic properties of supercooled water. The equation of state, built on the growing evidence that the critical point of supercooled liquid-liquid water separation exists, is universal in terms of theoretical scaling fields and is shown to belong to the Ising-model class of universality. The theoretical scaling fields are postulated to be analytical combinations of the physical fields, pressure and temperatu...
Muktish Acharyya; Ajanta Bhowal Acharyya
2011-01-01
We solve the equilibrium meanfield equation of state of Ising ferromagnet (obtained from Bragg-Williams theory) by Newton-Raphson method.The number of iterations required to get a convergent solution (within a specified accuracy) of equilibrium magnetisation, at any particular temperature, is observed to diverge in a power law fashion as the temperature approaches the critical value.This is identified as the critical slowing down.The exponent is also estimated.This value of the exponent is compared with that obtained from analytic solution.Besides this, the numerical results are also compared with some experimental results exhibiting satisfactory degree of agreement.It is observed from this study that the information of the invariance of time scale at the critical point is present in the meanfield equilibrium equation of state of Ising ferromagnet.
Kharkov, Yaroslav; Oleg P Sushkov Team
We consider two spin 1 / 2 fermions in a two-dimensional magnetic system that is close to the O (3) magnetic quantum critical point (QCP) which separates magnetically ordered and disordered phases. Focusing on the disordered phase in the vicinity of the QCP, we demonstrate that the criticality results in a strong long range attraction between the fermions, with potential V (r) ~ - 1 /rα , α ~ 0 . 75 , where r is separation between the fermions. The mechanism of the enhanced attraction is similar to Casimir effect and corresponds to multi-magnon exchange processes between the fermions. While we consider a model system, the problem is originally motivated by recent experimental establishment of magnetic QCP in hole doped cuprates under the superconducting dome at doping of about 10%. We suggest the mechanism of magnetic critical enhancement of pairing in cuprates.
A spectroscopic ellipsometric investigation of new critical points of Zn1-xMnxS epilayers
Zn1-xMnxS epilayers were grown on GaAs (1 0 0) substrates by hot-wall epitaxy. X-ray diffraction (XRD) patterns revealed that all the epilayers have a zincblende structure. The optical properties were investigated using spectroscopic ellipsometry at 300 K from 3.0 to 8.5 eV. The obtained data were analyzed for determining the critical points of pseudodielectric function spectra, = 1(E)> + i2(E)>, such as E0, E0 + Δ0, and E1, and three E2 (Σ, Δ, Γ) structures at a lower Mn composition range. These critical points were determined by analytical line-shapes fitted to numerically calculated derivatives of their pseudodielectric functions. The observation of new peaks, as well as the shifting and broadening of the critical points of Zn1-xMnxS epilayers, were investigated as a function of Mn composition by ellipsometric measurements for the first time. The characteristics of the peaks changed with increasing Mn composition. In particular, four new peaks were observed between 4.0 and 8.0 eV for Zn1-xMnxS epilayers, and their characteristics were investigated in this study
Gattenlöhner, S; Hannes, W-R; Ostrovsky, P M; Gornyi, I V; Mirlin, A D; Titov, M
2014-01-17
We explore the longitudinal conductivity of graphene at the Dirac point in a strong magnetic field with two types of short-range scatterers: adatoms that mix the valleys and "scalar" impurities that do not mix them. A scattering theory for the Dirac equation is employed to express the conductance of a graphene sample as a function of impurity coordinates; an averaging over impurity positions is then performed numerically. The conductivity σ is equal to the ballistic value 4e2/πh for each disorder realization, provided the number of flux quanta considerably exceeds the number of impurities. For weaker fields, the conductivity in the presence of scalar impurities scales to the quantum-Hall critical point with σ≃4×0.4e2/h at half filling or to zero away from half filling due to the onset of Anderson localization. For adatoms, the localization behavior is also obtained at half filling due to splitting of the critical energy by intervalley scattering. Our results reveal a complex scaling flow governed by fixed points of different symmetry classes: remarkably, all key manifestations of Anderson localization and criticality in two dimensions are observed numerically in a single setup. PMID:24484036
The numerical renormalization group method is used to investigate zero-temperature phase transitions in quantum impurity systems, in particular in the particle-hole symmetric soft-gap Anderson model. The model displays two stable phases whose fixed points can be built up of non-interacting single-particle states. In contrast, the quantum phase transitions turn out to be described by interacting fixed points, and their excitations cannot be described in terms of free particles. We show that the structure of the many-body spectrum of these critical fixed points can be understood using renormalized perturbation theory close to certain values of the bath exponents which play the role of critical dimensions. Contact is made with perturbative renormalization group calculations for the soft-gap Anderson and Kondo models. A complete description of the quantum critical many-particle spectra is achieved using suitable marginal operators; technically this can be understood as epsilon-expansion for full many-body spectra
Lee, Hyun-Jung [Theoretische Physik III, Elektronische Korrelationen und Magnetismus, Institut fuer Physik, Universitaet Augsburg, D-86135 Augsburg (Germany); Bulla, Ralf [Theoretische Physik III, Elektronische Korrelationen und Magnetismus, Institut fuer Physik, Universitaet Augsburg, D-86135 Augsburg (Germany); Vojta, Matthias [Institut fuer Theorie der Kondensierten Materie, Universitaet Karlsruhe, D-76128 Karlsruhe (Germany)
2005-11-02
The numerical renormalization group method is used to investigate zero-temperature phase transitions in quantum impurity systems, in particular in the particle-hole symmetric soft-gap Anderson model. The model displays two stable phases whose fixed points can be built up of non-interacting single-particle states. In contrast, the quantum phase transitions turn out to be described by interacting fixed points, and their excitations cannot be described in terms of free particles. We show that the structure of the many-body spectrum of these critical fixed points can be understood using renormalized perturbation theory close to certain values of the bath exponents which play the role of critical dimensions. Contact is made with perturbative renormalization group calculations for the soft-gap Anderson and Kondo models. A complete description of the quantum critical many-particle spectra is achieved using suitable marginal operators; technically this can be understood as epsilon-expansion for full many-body spectra.
Overlapping Modularity at the Critical Point of k-Clique Percolation
Tóth, Bálint; Vicsek, Tamás; Palla, Gergely
2013-05-01
One of the most remarkable social phenomena is the formation of communities in social networks corresponding to families, friendship circles, work teams, etc. Since people usually belong to several different communities at the same time, the induced overlaps result in an extremely complicated web of the communities themselves. Thus, uncovering the intricate community structure of social networks is a non-trivial task with great potential for practical applications, gaining a notable interest in the recent years. The Clique Percolation Method (CPM) is one of the earliest overlapping community finding methods, which was already used in the analysis of several different social networks. In this approach the communities correspond to k-clique percolation clusters, and the general heuristic for setting the parameters of the method is to tune the system just below the critical point of k-clique percolation. However, this rule is based on simple physical principles and its validity was never subject to quantitative analysis. Here we examine the quality of the partitioning in the vicinity of the critical point using recently introduced overlapping modularity measures. According to our results on real social and other networks, the overlapping modularities show a maximum close to the critical point, justifying the original criteria for the optimal parameter settings.
Euler strut: a mechanical analogy for dynamics in the vicinity of a critical point
Bobnar, Jaka; Podgornik, Rudolf [Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, SI-1000 Ljubljana (Slovenia); Susman, Katarina; Cepic, Mojca [Faculty of Education, University of Ljubljana, SI-1000 Ljubljana (Slovenia); Parsegian, V Adrian [Department of Physics, University of Massachusetts, Amherst, MA 01003 (United States); Rand, Peter R [1278 Line 2 RR No 6 Niagara-on-the-Lake, Ontario L0S1J0 (Canada)
2011-07-15
An anchored elastic filament (Euler strut) under an external point load applied to its free end is a simple model for a second-order phase transition. In the static case, a load greater than the critical load causes a Euler buckling instability, leading to a change in the filament's shape. The analysis of filament dynamics with an external point load at its end shows that when approaching the critical end-load, the period of such an inverted pendulum diverges in a fashion analogous to a 'soft mode' critical slowing down in, for example, a ferroelectric phase transition of displacive type. We thus show that an advanced concept of solid state physics, i.e. 'soft mode' dynamics and critical slowing down, observable in a variety of second-order phase transitions, can be actualized in this simple mechanical system. The variable loads attached to a vertical spring allow for an experimental implementation and quantitative measurements as an illustration of this analogy.
Oral Mucosal Disorders: Problems and Questions What are the Critical Points?
A. Tülin Mansur
2012-12-01
Full Text Available Oral mucosal disorders comprise more than 200 pathological conditions or diseases, grouped in different categories including genetic, inflammatory, infectious and neoplastic. In this report the key points in diagnosis and treatment of oral mucosal disorders are briefly underlined, and indications, precautions, and contraindications are pointed out. In addition, some clues are given to the dermatologists for management of common symptoms of oral disorders, such as pain, dry mouth and halitosis, which greatly disrupt the quality of life. Moreover, the frequently encountered problems in daily practice including contact stomatitis, effects of dental prostheses, dental materials, and topical agents on oral mucosa, and the critical points in surgical interventions of oral disorders are reviewed.
[Theses on critical gerontology from a social science point of view].
Köster, D
2012-10-01
This contribution formulates several key statements concerning a critical gerontology and is intended as a starting point for further thought and discussion from the perspective of critical social sciences. In terms of scientific theory, it follows a concept of normative universalism, distinguishing itself from a mere "science of order", which would be restricted to social self-observation. The assumptions focus on dealing with the social construct of age(ing) under the conditions of modern capitalist societies and on putting age(ing) into context with neo-liberal economic and social politics. This contribution explains some aspects of restructuring the German welfare state into an "activating state", a process accompanied by the casualisation of many older people's life circumstances. Moreover, some cultural perspectives of self-determined life in old age are demonstrated, which invariably should also be seen as a learning task. In this way, the complex interactions between gerontology and social and political practice in terms of praxeological and critical research are covered in their totality. At the same time, critical gerontology is oriented towards what is humanly possible and attempts to identify restrictions to a fulfilling life in old age and to suggest perspectives of how such restrictions can be overcome. The aim is to reflect on our own professional behaviour, to make it more compatible theoretically with critical scientific discourses on ageing and thus contribute to the emancipation of older people from discourses of dominance. PMID:22911392
Bhattacharjee, Jayanta K.; Kaatze, Udo; Mirzaev, Sirojiddin Z.
2010-06-01
The nature and origin of sound attenuation due to critical fluctuations near the liquid consolute point are discussed. Starting from basic principles, the background of critical phenomena is reviewed and the conceptions of theoretical approaches to describe the critical contributions to the propagation of sound are analysed. Experimental broadband spectra of suitable binary systems are evaluated jointly with results from quasi-elastic light scattering, shear viscosity and heat capacity measurements to verify or disprove theoretical predictions. It is shown that spectra of systems without or with only small-amplitude ultrasonic contribution from noncritical relaxation processes can be represented by theory with the asymptotic high-frequency sonic attenuation coefficient as a simple adjustable parameter. As a result, sonic spectra of more complex systems, exhibiting significant contributions from noncritical ultrasonic relaxations, are discussed assuming the critical part to be known from theory and auxiliary data. This modus operandi allows for a clear extraction of parameters relevant to the noncritical elementary processes in liquid mixtures, such as conformational changes, protolysis and hydrolysis reactions, monomer exchange from micelles and rotational isomerizations of membrane molecules. The influence of the critical dynamics on the noncritical kinetics is disclosed for some topical examples.
Neural avalanches at the critical point between replay and non-replay of spatiotemporal patterns.
Silvia Scarpetta
Full Text Available We model spontaneous cortical activity with a network of coupled spiking units, in which multiple spatio-temporal patterns are stored as dynamical attractors. We introduce an order parameter, which measures the overlap (similarity between the activity of the network and the stored patterns. We find that, depending on the excitability of the network, different working regimes are possible. For high excitability, the dynamical attractors are stable, and a collective activity that replays one of the stored patterns emerges spontaneously, while for low excitability, no replay is induced. Between these two regimes, there is a critical region in which the dynamical attractors are unstable, and intermittent short replays are induced by noise. At the critical spiking threshold, the order parameter goes from zero to one, and its fluctuations are maximized, as expected for a phase transition (and as observed in recent experimental results in the brain. Notably, in this critical region, the avalanche size and duration distributions follow power laws. Critical exponents are consistent with a scaling relationship observed recently in neural avalanches measurements. In conclusion, our simple model suggests that avalanche power laws in cortical spontaneous activity may be the effect of a network at the critical point between the replay and non-replay of spatio-temporal patterns.
Heat capacity singularity of binary liquid mixtures at the liquid-liquid critical point.
Méndez-Castro, Pablo; Troncoso, Jacobo; Peleteiro, José; Romaní, Luis
2013-10-01
The critical anomaly of the isobaric molar heat capacity for the liquid-liquid phase transition in binary nonionic mixtures is explained through a theory based on the general assumption that their partition function can be exactly mapped into that of the Ising three-dimensional model. Under this approximation, it is found that the heat capacity singularity is directly linked to molar excess enthalpy. In order to check this prediction and complete the available data for such systems, isobaric molar heat capacity and molar excess enthalpy near the liquid-liquid critical point were experimentally determined for a large set of binary liquid mixtures. Agreement between theory and experimental results-both from literature and from present work-is good for most cases. This fact opens a way for explaining and predicting the heat capacity divergence at the liquid-liquid critical point through basically the same microscopic arguments as for molar excess enthalpy, widely used in the frame of solution thermodynamics. PMID:24229116
Change of carrier density at the pseudogap critical point of a cuprate superconductor.
Badoux, S; Tabis, W; Laliberté, F; Grissonnanche, G; Vignolle, B; Vignolles, D; Béard, J; Bonn, D A; Hardy, W N; Liang, R; Doiron-Leyraud, N; Taillefer, Louis; Proust, Cyril
2016-03-10
The pseudogap is a partial gap in the electronic density of states that opens in the normal (non-superconducting) state of cuprate superconductors and whose origin is a long-standing puzzle. Its connection to the Mott insulator phase at low doping (hole concentration, p) remains ambiguous and its relation to the charge order that reconstructs the Fermi surface at intermediate doping is still unclear. Here we use measurements of the Hall coefficient in magnetic fields up to 88 tesla to show that Fermi-surface reconstruction by charge order in the cuprate YBa2Cu3Oy ends sharply at a critical doping p = 0.16 that is distinctly lower than the pseudogap critical point p* = 0.19 (ref. 11). This shows that the pseudogap and charge order are separate phenomena. We find that the change in carrier density n from n = 1 + p in the conventional metal at high doping (ref. 12) to n = p at low doping (ref. 13) starts at the pseudogap critical point. This shows that the pseudogap and the antiferromagnetic Mott insulator are linked. PMID:26901870
Search for signatures of phase transition and critical point in heavy ion collisions
The general concepts in the critical phenomena related with the notions of 'scaling' and 'universality' are considered. Behavior of various systems near a phase transition is displayed. Search for clear signatures of the phase transition of the nuclear matter and location of the critical point in heavy ion collisions (HIC) is discussed. The experimental data on inclusive spectra measured in HIC at RHIC and SPS over a wide range of energies sNN1/2 = 9-200 GeV are analyzed in the framework of z-scaling. A microscopic scenario of the constituent interactions is presented. Dependence of the energy loss on the momentum of the produced hadron, energy and centrality of the collision is studied. Self-similarity of the constituent interactions described in terms of momentum fractions is used to characterize the nuclear medium by 'specific heat' and colliding nuclei by fractal dimensions. Preferable kinematical regions to search for signatures of the phase transition of the nuclear matter produced in HIC are discussed. Discontinuity of the 'specific heat' is assumed to be a signature of the phase transition and the critical point
Infinite-randomness critical point in the two-dimensional disordered contact process.
Vojta, Thomas; Farquhar, Adam; Mast, Jason
2009-01-01
We study the nonequilibrium phase transition in the two-dimensional contact process on a randomly diluted lattice by means of large-scale Monte Carlo simulations for times up to 10;{10} and system sizes up to 8000x8000 sites. Our data provide strong evidence for the transition being controlled by an exotic infinite-randomness critical point with activated (exponential) dynamical scaling. We calculate the critical exponents of the transition and find them to be universal, i.e., independent of disorder strength. The Griffiths region between the clean and the dirty critical points exhibits power-law dynamical scaling with continuously varying exponents. We discuss the generality of our findings and relate them to a broader theory of rare region effects at phase transitions with quenched disorder. Our results are of importance beyond absorbing state transitions because, according to a strong-disorder renormalization group analysis, our transition belongs to the universality class of the two-dimensional random transverse-field Ising model. PMID:19257005
Indications for a critical point in the phase diagram for hot and dense nuclear matter
Lacey, Roy A
2016-01-01
Two-pion interferometry measurements are studied for a broad range of collision centralities in Au+Au (Root_s = 7.7 - 200 GeV) and Pb+Pb (Root_s = 2.76 TeV) collisions. They indicate non-monotonic excitation functions for the Gaussian emission source radii difference [(R_out)^2 - (R_side)^2], suggestive of reaction trajectories which spend a fair amount of time near a "soft point" in the equation of state (EOS) that coincides with the critical end point (CEP). A Finite-Size Scaling (FSS) analysis of these excitation functions, provides further validation tests for the CEP. It also indicates a second order phase transition at the CEP, and the values T^{cep} ~ 165 MeV and mu_B^{cep} ~ 95 MeV for its location in the (T, mu_B)-plane of the phase diagram. The static critical exponents (nu ~ 0.66 and gamma ~ 1.2) extracted via the same FSS analysis, place this CEP in the 3D Ising model universality class. A Dynamic Finite-Size Scaling analysis gives the estimate z ~ 0.87 for the dynamic critical exponent.
Chirality Quantum Phase Transition in Noncommutative Dirac Oscillator
The charged Dirac oscillator on a noncommutative plane coupling to a uniform perpendicular magnetic held is studied in this paper. We map the noncommutative plane to a commutative one by means of Bopp shift and study this problem on the commutative plane. We find that this model can be mapped onto a quantum optics model which contains Anti—Jaynes—Cummings (AJC) or Jaynes—Cummings (JC) interactions when a dimensionless parameter ζ (which is the function of the intensity of the magnetic held) takes values in different regimes. Furthermore, this model behaves as experiencing a chirality quantum phase transition when the dimensionless parameter ζ approaches the critical point. Several evidences of the chirality quantum phase transition are presented. We also study the non-relativistic limit of this model and find that a similar chirality quantum phase transition takes place in its non-relativistic limit. (physics of elementary particles and fields)
NMSSM Inflation and Domain Walls from a Tri-critical Point of View
Aval, Hadi Gholian
2016-01-01
In this paper we want to study the conditions in which we could bring a universe filled with different $Z_3$ vacua created during the Next to Minimal Supersymmetric Standard Model (NMSSM) electroweak symmetry breaking at $\\textit{O} (10)^2$ GeV and a three dimensional three states diluted Potts model together in the same universality class. Then we use Cardy-Jacobsen conjecture to prove that there might be a tri-critical point in the NMSSM electroweak epoch of early universe. We prove that due to the existence of this point there would be no cosmological domain wall problem. Moreover, at this point the heat capacity and correlation length diverge which lead to a huge amount of energy release at constant temperature and a new mechanism for cosmological structure formation. Also, the entropy decrease after the tri-critical phase transition could explain the problem of low initial entropy in early universe. Finally, we combine Cardy-Jacobsen and Yaffe-Svetitsky conjectures to show that there might be a tri-criti...
Eralp, Tugce; Levins, Alex; Shavorskiy, Andrey; Jenkins, Stephen J.; Held, Georg
2012-01-01
Both enantiomers of serine adsorb on the intrinsically chiral Cu{531} surface in two different adsorption geometries, depending on the coverage. At saturation, substrate bonds are formed through the two oxygen atoms of the carboxylate group and the amino group (μ3 coordination), whereas at lower coverage, an additional bond is formed through the deprotonated β−OH group (μ4 coordination). The latter adsorption geometry involves substrate bonds through three side groups of the chiral center,...
Mapping the current-current correlation function near a quantum critical point
Prodan, Emil; Bellissard, Jean
2016-05-01
The current-current correlation function is a useful concept in the theory of electron transport in homogeneous solids. The finite-temperature conductivity tensor as well as Anderson's localization length can be computed entirely from this correlation function. Based on the critical behavior of these two physical quantities near the plateau-insulator or plateau-plateau transitions in the integer quantum Hall effect, we derive an asymptotic formula for the current-current correlation function, which enables us to make several theoretical predictions about its generic behavior. For the disordered Hofstadter model, we employ numerical simulations to map the current-current correlation function, obtain its asymptotic form near a critical point and confirm the theoretical predictions.
The Cambrian explosion triggered by critical turning point in genome size evolution.
Li, Dirson Jian; Zhang, Shengli
2010-02-01
The Cambrian explosion is a grand challenge to science today and involves multidisciplinary study. This event is generally believed as a result of genetic innovations, environmental factors and ecological interactions, even though there are many conflicts on nature and timing of metazoan origins. The crux of the matter is that an entire roadmap of the evolution is missing to discern the biological complexity transition and to evaluate the critical role of the Cambrian explosion in the overall evolutionary context. Here, we calculate the time of the Cambrian explosion by a "C-value clock"; our result quite fits the fossil records. We clarify that the intrinsic reason of genome evolution determined the Cambrian explosion. A general formula for evaluating genome size of different species has been found, by which the genome size evolution can be illustrated. The Cambrian explosion, as a major transition of biological complexity, essentially corresponds to a critical turning point in genome size evolution. PMID:20074549
Floss, H.G. [Univ. of Washington, Seattle, WA (United States)
1994-12-01
This paper deals with compounds that are chiral-at least in part, due to isotope substitution-and their use in tracing the steric course of enzyme reaction in vitro and in vivo. There are other applications of isotopically chiral compounds (for example, in analyzing the steric course of nonenzymatic reactions and in probing the conformation of biomolecules) that are important but they will not be discussed in this context.
Castellanos Rey, Liliana C; Villamil Jiménez, Luis C; Romero Prada, Jaime R
2004-01-01
The Hazard Analysis and Critical Control Point system (HACCP), recommended by different international organizations as the Codex Alimentarius Commission, the World Trade Organization (WTO), the International Office of Epizootics (OIE) and the International Convention for Vegetables Protection (ICPV) amongst others, contributes to ensuring the innocuity of food along the agro-alimentary chain and requires of Good Manufacturing Practices (GMP) for its implementation, GMP's which are legislated in most countries. Since 1997, Colombia has set rules and legislation for application of HACCP system in agreement with international standards. This paper discusses the potential and difficulties of the legislation enforcement and suggests some policy implications towards food safety. PMID:15656068
Application of hazard analysis and critical control point system in the dairy industry.
Kassem, M; Salem, E; Ahwal, A M; Saddik, M; Gomaa, N F
2002-01-01
This study aimed to assess the hygiene quality of some packaged milk (pasteurized or sterilized) and dairy products before and after application of a hazard analysis and critical control point (HACCP) system at a milk and dairy products company in Cairo, Egypt. The steps taken to put HACCP in place are described and the process was monitored to assess its impact. Assessment of the hygiene quality of the milk and dairy products before and after HACCP showed an improvement in quality and an overall improvement in the conditions at the company. PMID:15330567
Lattice determination of the critical point of QCD at finite $T$ and $\\mu$
Fodor, Z
2002-01-01
Based on universal arguments it is believed that there is a critical point (E) in QCD on the temperature (T) versus chemical potential (\\mu) plane, which is of extreme importance for heavy-ion experiments. Using finite size scaling and a recently proposed lattice method to study QCD at finite \\mu we determine the location of E in QCD with n_f=2+1 dynamical staggered quarks with semi-realistic masses on L_t=4 lattices. Our result is T_E=160 \\pm 3.5 MeV and
We reinvestigate Adler's partially conserved axial-vector current relation in the presence of an external electromagnetic field within the framework of QCD coupled to external fields. We discuss pion electroproduction within a tree-level approximation to chiral perturbation theory and explicitly verify a chiral Ward identity referred to as the Adler-Gilman relation. We critically examine soft-momentum techniques and point out how inadmissable approximations may lead to results incompatible with chiral symmetry. As a result we confirm that threshold pion electroproduction is indeed a tool to obtain information on the axial form factor of the nucleon
Tunable circular dichroism due to the chiral anomaly in Weyl semimetals
Hosur, Pavan; Qi, Xiao-Liang
2014-01-01
Weyl semimetals are a three dimensional gapless topological phase in which bands intersect at arbitrary points -- the Weyl nodes -- in the Brillouin zone. These points carry a topological quantum number known as the \\emph{chirality} and always appear in pairs of opposite chiralities. The notion of chirality leads to anomalous non-conservation of chiral charge, known as the \\emph{chiral anomaly}, according to which charge can be pumped between Weyl nodes of opposite chiralities by an electroma...
Functional renormalization group analysis of the soft mode at the QCD critical point
Yokota, Takeru; Morita, Kenji
2016-01-01
We make an intensive investigation of the soft mode at the QCD critical point on the basis of the the functional renormalization group (FRG) method in the local potential approximation. We calculate the the spectral functions $\\rho_{\\sigma, \\pi}(\\omega, p)$ in the scalar ($\\sigma$) and pseudoscalar ($\\pi$) channels beyond the random phase approximation in the quark-meson model. At finite baryon chemical potential $\\mu$ with a finite quark mass, the baryon-number fluctuation is coupled to the scalar channel and the spectral function in the $\\sigma$ channel has a support not only in the time-like ($\\omega > p$) and but also in the space-like ($\\omega < p$) regions, which correspond to the mesonic and the particle-hole phonon excitations, respectively. We find that the energy of the peak position of the latter becomes vanishingly small with the height being enhanced as the system approaches the QCD critical point, which is a manifestation of the fact that the phonon mode is the soft mode associated with the s...
Several aspect of shape phase transitions and critical point symmetries are reviewed in this contribution within the frameworks of the Interacting Boson Model (IBM) and the Interacting Boson Fermion Model (IBFM) for even and odd systems respectively and compared with collective geometric models. We discuss in particular the case of an odd j = 3/2 particle coupled to an even-even boson core that undergoes a transition from the spherical limit U(5) to the γ-unstable limit O(6). The spectrum and transition rates at the critical point are similar to those of the even core and they agree qualitatively with the E(5/4) boson-fermion symmetry. We discuss also the UBF (5) to SUBF (3) shape phase transition in which the allowed fermionic orbitals are j = 1/2; 3/2; 5/2. The formalism of the intrinsic or coherent states is used to describe in details the ground state as well as the excited β- and γ- bands. This formalism is also used to calculate the Potential Energy Surface of the cubic quadrupole operator that leads to triaxiality. (author)
万永革; 吴忠良; 周公威
2003-01-01
Whether or not a small stress change can trigger a big earthquake is one of the most important problems related to the critical point hypothesis for earthquakes. We investigate global earthquakes with different focal mechanisms which have different levels of ambient shear stress. This ambient stress level is the stress level required by the earthquakes for their occurrence. Earthquake pairs are studied to see whether the occurrence of the preceding event encourages the occurrence of the succeeding one in terms of the Coulomb stress triggering. It is observed that the stress triggering effect produced by the change of Coulomb failure stress in the same order of magnitudes,about 10-2 MPa, is distinctly different for different focal mechanisms, and thus for different ambient stress levels.For non-strike-slip earthquakes with a relatively low ambient stress level, the triggering effect is more evident,while for strike-slip earthquakes with a relatively high ambient stress level, there is no evident triggering effect.This water level test provides an observational support to the critical point hypothesis for earthquakes.
Gardner, I A
1997-12-01
On-farm HACCP (hazard analysis critical control points) monitoring requires cost-effective, yet accurate and reproducible tests that can determine the status of cows, milk, and the dairy environment. Tests need to be field-validated, and their limitations need to be established so that appropriate screening strategies can be initiated and test results can be rationally interpreted. For infections and residues of low prevalence, tests or testing strategies that are highly specific help to minimize false-positive results and excessive costs to the dairy industry. The determination of the numbers of samples to be tested in HACCP monitoring programs depends on the specific purpose of the test and the likely prevalence of the agent or residue at the critical control point. The absence of positive samples from a herd test should not be interpreted as freedom from a particular agent or residue unless the entire herd has been tested with a test that is 100% sensitive. The current lack of field-validated tests for most of the chemical and infectious agents of concern makes it difficult to ensure that the stated goals of HACCP programs are consistently achieved. PMID:9436129