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Sample records for critical point symmetry

  1. Partial dynamical symmetry at critical points of quantum phase transitions.

    PubMed

    Leviatan, A

    2007-06-15

    We show that partial dynamical symmetries can occur at critical points of quantum phase transitions, in which case underlying competing symmetries are conserved exactly by a subset of states, and mix strongly in other states. Several types of partial dynamical symmetries are demonstrated with the example of critical-point Hamiltonians for first- and second-order transitions in the framework of the interacting boson model, whose dynamical symmetries correspond to different shape phases in nuclei.

  2. Critical-point symmetry in a finite system.

    PubMed

    Leviatan, A; Ginocchio, J N

    2003-05-30

    At a critical point of a second-order phase transition the intrinsic energy surface is flat and there is no stable minimum value of the deformation. However, for a finite system, we show that there is an effective deformation which can describe the dynamics at the critical point. This effective deformation is determined by minimizing the energy surface after projection onto the appropriate symmetries. We derive analytic expressions for energies and quadrupole rates which provide good estimates for these observables at the critical point.

  3. Symmetry relations for multifractal spectra at random critical points

    NASA Astrophysics Data System (ADS)

    Monthus, Cécile; Berche, Bertrand; Chatelain, Christophe

    2009-12-01

    Random critical points are generically characterized by multifractal properties. In the field of Anderson localization, Mirlin et al (2006 Phys. Rev. Lett. 97 046803) have proposed that the singularity spectrum f(α) of eigenfunctions satisfies the exact symmetry f(2d-α) = f(α)+d-α. In the present paper, we analyze the physical origin of this symmetry in relation to the Gallavotti-Cohen fluctuation relations of large deviation functions that are well known in the field of non-equilibrium dynamics: the multifractal spectrum of the disordered model corresponds to the large deviation function of the rescaling exponent γ = (α-d) along a renormalization trajectory in the effective time t = lnL. We conclude that the symmetry discovered for the specific example of Anderson transitions should actually be satisfied at many other random critical points after an appropriate translation. For many-body random phase transitions, where the critical properties are usually analyzed in terms of the multifractal spectrum H(a) and of the moment exponents X(N) of the two-point correlation function (Ludwig 1990 Nucl. Phys. B 330 639), the symmetry becomes H(2X(1)-a) = H(a)+a-X(1), or equivalently Δ(N) = Δ(1-N) for the anomalous parts \\Delta (N) \\equiv X(N)-NX(1) . We present numerical tests favoring this symmetry for the 2D random Q-state Potts model with varying Q.

  4. 124Te and the E(5) Critical Point Symmetry

    NASA Astrophysics Data System (ADS)

    Ghiţă, D. G.; Căta-Danil, G.; Bucurescu, D.; Căta-Danil, I.; Ivascu, M.; Mihai, C.; Suliman, G.; Stroe, L.; Sava, T.; Zamfir, N. V.

    We present a new study of the low-lying states in 124Te nucleus by γ-ray spectroscopy following 124I β+/ɛ decay. The β radioactive sources were produced in the 124Te(p, n)124I reaction induced by 11 MeV protons, delivered by the Bucharest FN Tandem Accelerator. The γ-rays were measured in a low background area with three large volume HPGe detectors. A total number of 276 milion double coincidence events were recorded in a six-day run. Most of the gamma line intensities previously measured were confirmed with improved accuracy and several gamma lines were obtained for the first time. Our results, combined with those from a recent (n, γ) study are compared with the predictions of the E(5) critical point symmetry model and numerical IBA-1 model calculations at the critical point of the U(5)-O(6) phase transition.

  5. Nontrivial Critical Fixed Point for Replica-Symmetry-Breaking Transitions

    NASA Astrophysics Data System (ADS)

    Charbonneau, Patrick; Yaida, Sho

    2017-05-01

    The transformation of the free-energy landscape from smooth to hierarchical is one of the richest features 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. The existence of these replica-symmetry-breaking phase transitions has, however, long been questioned below their upper critical dimension, du=6 . Here, we obtain evidence for the existence of these transitions in d critical fixed point is found in the strong-coupling regime, we corroborate the result by resumming the perturbative series with inputs from a three-loop calculation and an analysis of its large-order behavior. Our study offers a resolution of the long-lasting controversy surrounding phase transitions in finite-dimensional disordered systems.

  6. Critical point symmetry for the spherical to triaxially deformed shape phase transition

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Pan, Feng; Luo, Yan-An; Draayer, J. P.

    2015-12-01

    The critical point T(5) symmetry for the spherical to triaxially deformed shape phase transition is introduced from the Bohr Hamiltonian by approximately separating variables at a given γ deformation with 0 ° ≤ γ ≤ 30 °. The resulting spectral and E2 properties have been investigated in detail. The results indicate that the original X(5) and Z(5) critical point symmetries can be naturally realized within the T(5) model in the γ = 0 ° and γ = 30 ° limit, respectively, which thus provides a dynamical connection between the two symmetries. Comparison of the theoretical calculations for 148Ce, 160Yb, 192Pt and 194Pt with the corresponding experimental data is also made, which indicates that, to some extent, possible asymmetric deformation may be involved in these transitional nuclei.

  7. Lifetimes in Te124 : Examining critical-point symmetry in the Te nuclei

    DOE PAGES

    Hicks, S. F.; Vanhoy, J. R.; Burkett, P. G.; ...

    2017-03-27

    The Doppler-shift attenuation method following inelastic neutron scattering was used to determine the lifetimes of nuclear levels to 3.3-MeV excitation in 124Te. Level energies and spins, γ -ray energies and branching ratios, and multipole-mixing ratios were deduced from measured γ-ray angular distributions at incident neutron energies of 2.40 and 3.30 MeV, γ-ray excitation functions, and γγ coincidence measurements. The newly obtained reduced transition probabilities and level energies for 124Te were compared to critical-point symmetry model predictions. The E(5) and β4 potential critical-point symmetries were also investigated in 122Te and 126Te.

  8. Empirical signatures of quantum phase transitions and universal properties of critical point descriptions and dynamical symmetries

    SciTech Connect

    Casten, R. F.; Bonatsos, Dennis; McCutchan, E. A.

    2009-01-28

    Recently, a new signature for quantum phase transitional regions has been discussed. This signature, based on degeneracies of yrast and intrinsic excitations, can distinguish first and second order phase transitions, and is valid not only at or near the analytic critical points described by X(5) and E(5), but along the phase transitional line connecting them as well. In addition, a study of a number of recent analytic solutions to the Bohr Hamiltonian and of the dynamical symmetries of the IBA Hamiltonian has revealed a set of extremely simple and general analytic formulas that describe the energies of 0{sup +} states. For the case of flat-bottomed geometrical potentials, the formula depends solely on the number of relevant dimensions. For the IBA (large boson number limit) a single formula describes all three dynamical symmetries.

  9. Critical points and symmetries of a free energy function for biaxial nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Chillingworth, D. R. J.

    2015-05-01

    We describe a general mean field model for the free energy function for a homogeneous medium of mutually interacting molecules, based on the formalism for a biaxial nematic liquid crystal set out by Katriel et al (1986) in an influential paper in Liquid Crystals 1 and subsequently called the KKLS formalism. The free energy is expressed as the sum of an entropy term and an interaction (Hamiltonian) term. Using the language of group representation theory we identify the order parameters as averaged components of a linear transformation, and characterize the full symmetry group of the entropy term in the liquid crystal context as a wreath product SO(3) ≀ Z2. The symmetry-breaking role of the Hamiltonian, pointed out by Katriel et al, is here made explicit in terms of centre manifold reduction at bifurcation from isotropy. We use tools and methods of equivariant singularity theory to reduce the bifurcation study to that of a D3-invariant function on R2, ubiquitous in liquid crystal theory, and to describe the ‘universal’ bifurcation geometry in terms of the superposition of a familiar swallowtail surface controlling uniaxial equilibria and another less familiar surface controlling biaxial equilibria. In principle this provides a template for all nematic liquid crystal phase transitions close to isotropy, although further work is needed to identify the absolute minima that are the critical points representing stable phases.

  10. Evolution of the X(5) critical-point symmetry in rotating {\\mathbf {^{176}Os}}

    NASA Astrophysics Data System (ADS)

    Hao, X.; Zhu, L. H.; Wu, X. G.; He, C. Y.; Pan, B.; Zheng, Y.; Wang, L. L.; Wang, L.; Li, X. Q.; Liu, Y.; Ding, H. B.; Li, Z. Y.; Zhang, J. F.; Sun, H. B.; Li, G. S.

    2011-02-01

    Lifetimes of excited states above 10+ in the yrast band in 176Os have been measured using the Doppler shift attenuation method, via the fusion evaporation reaction {^{152}Sm(^{28}Si, 4{{\\it n}})^{176}Os}. Lifetimes of states over 12+ were measured for the first time. The deduced transitional quadruple moments (Qt), together with the previous data using a recoil distance method, are compared with theoretical calculations based on the X(5) model and the interaction boson model. For the states below spin 10+, the data of previous work support an X(5)-like structure, but for the states above 10+, the value of Qt remains almost constant, being the characteristic of a symmetric rotor. The present result suggests that the shape of the nucleus 176Os changes from X(5) critical-point symmetry to an axially deformed rotor with increasing spin.

  11. Quantum critical point of Dirac fermion mass generation without spontaneous symmetry breaking

    NASA Astrophysics Data System (ADS)

    He, Yuan-Yao; Wu, Han-Qing; You, Yi-Zhuang; Xu, Cenke; Meng, Zi Yang; Lu, Zhong-Yi

    2016-12-01

    We study a lattice model of interacting Dirac fermions in (2 +1 ) dimensions space-time with an SU(4) symmetry. While increasing the interaction strength, this model undergoes a continuous quantum phase transition from a weakly interacting Dirac semimetal to a fully gapped and nondegenerate phase without condensing any Dirac fermion bilinear mass operator. This unusual mechanism for mass generation is consistent with recent studies of interacting topological insulators/superconductors, and also consistent with recent progress in the lattice QCD community.

  12. Shape evolution and test of the critical-point symmetry X(5) in 176Os

    NASA Astrophysics Data System (ADS)

    Hao, Xin; Zhu, Li-Hua; Wu, Xiao-Guang; Li, Guang-Sheng; Pan, Bo; Wang, Lie-Lin; Zheng, Yun; Wang, Lei; Li, Xue-Qin; Liu, Ying; Ding, Huai-Bo; Li, Zhong-Yu

    2009-03-01

    The lifetimes of excited states in the yrast band of 176Os have been measured up to I = 20ħ level using the Doppler shift attenuation method. The high-spin states of 176Os were populated via fusion evaporation reaction 152Sm(28Si,4n)176Os at a beam energy of 140 MeV. The results support an X(5) structure for 176Os at low spin. This structure disappears at high spin and shows a symmetry rotor character. The shape change of 176Os is similar to that of 178Os.

  13. Relative Critical Points

    NASA Astrophysics Data System (ADS)

    Lewis, Debra

    2013-05-01

    Relative equilibria of Lagrangian and Hamiltonian systems with symmetry are critical points of appropriate scalar functions parametrized by the Lie algebra (or its dual) of the symmetry group. Setting aside the structures - symplectic, Poisson, or variational - generating dynamical systems from such functions highlights the common features of their construction and analysis, and supports the construction of analogous functions in non-Hamiltonian settings. If the symmetry group is nonabelian, the functions are invariant only with respect to the isotropy subgroup of the given parameter value. Replacing the parametrized family of functions with a single function on the product manifold and extending the action using the (co)adjoint action on the algebra or its dual yields a fully invariant function. An invariant map can be used to reverse the usual perspective: rather than selecting a parametrized family of functions and finding their critical points, conditions under which functions will be critical on specific orbits, typically distinguished by isotropy class, can be derived. This strategy is illustrated using several well-known mechanical systems - the Lagrange top, the double spherical pendulum, the free rigid body, and the Riemann ellipsoids - and generalizations of these systems.

  14. Comparison of the E(5) Critical Point Symmetry to the {gamma}-Rigid Solution of The Bohr Hamiltonian for {gamma} =30 deg

    SciTech Connect

    Bonatsos, D.; Lenis, D.; Petrellis, D.; Terziev, P. A.; Yigitoglu, I.

    2007-04-23

    A {gamma}-rigid solution of the Bohr Hamiltonian for {gamma}=30 deg. is derived. Bohr Hamiltonians {beta}-part being related to the second order Casimir operator of the Euclidean algebra E(4). The solution is called Z(4) since it is corresponds to the Z(5) model with the {gamma} variable ''frozen''. Parameter-free (up to overall scale factors) predictions for spectra and B(E2) transition rates are in close agreement to the E(5) critical point symmetry as well as to the experimental data in the Xe region around A=130.

  15. Topological phases protected by point group symmetry

    DOE PAGES

    Song, Hao; Huang, Sheng -Jie; Fu, Liang; ...

    2017-02-21

    We consider symmetry-protected topological (SPT) phases with crystalline point group symmetry, dubbed point group SPT (pgSPT) phases. We show that such phases can be understood in terms of lower-dimensional topological phases with on-site symmetry and that they can be constructed as stacks and arrays of these lower-dimensional states. This provides the basis for a general framework to classify and characterize bosonic and fermionic pgSPT phases, which can be applied for arbitrary crystalline point group symmetry and in arbitrary spatial dimensions. We develop and illustrate this framework by means of a few examples, focusing on three-dimensional states. We classify bosonic pgSPTmore » phases and fermionic topological crystalline superconductors with ZP2 (reflection) symmetry, electronic topological crystalline insulators (TCIs) with U(1)×ZP2 symmetry, and bosonic pgSPT phases with C2v symmetry, which is generated by two perpendicular mirror reflections. We also study surface properties, with a focus on gapped, topologically ordered surface states. For electronic TCIs, we find a Z8 × Z2 classification, where the Z8 corresponds to known states obtained from noninteracting electrons, and the Z2 corresponds to a “strongly correlated” TCI that requires strong interactions in the bulk. Lastly, our approach may also point the way toward a general theory of symmetry-enriched topological phases with crystalline point group symmetry.« less

  16. Continuous point symmetries in group field theories

    NASA Astrophysics Data System (ADS)

    Kegeles, Alexander; Oriti, Daniele

    2017-03-01

    We discuss the notion of symmetries in non-local field theories characterized by integro-differential equations of motion, from a geometric perspective. We then focus on group field theory (GFT) models of quantum gravity and provide a general analysis of their continuous point symmetry transformations, including the generalized conservation laws following from them.

  17. The phase transitions between Zn × Zn bosonic topological phases in 1 + 1D, and a constraint on the central charge for the critical points between bosonic symmetry protected topological phases

    NASA Astrophysics Data System (ADS)

    Tsui, Lokman; Huang, Yen-Ta; Jiang, Hong-Chen; Lee, Dung-Hai

    2017-06-01

    The study of continuous phase transitions triggered by spontaneous symmetry breaking has brought revolutionary ideas to physics. Recently, through the discovery of symmetry protected topological phases, it is realized that continuous quantum phase transition can also occur between states with the same symmetry but different topology. Here we study a specific class of such phase transitions in 1 + 1 dimensions - the phase transition between bosonic topological phases protected by Zn ×Zn. We find in all cases the critical point possesses two gap opening relevant operators: one leads to a Landau-forbidden symmetry breaking phase transition and the other to the topological phase transition. We also obtained a constraint on the central charge for general phase transitions between symmetry protected bosonic topological phases in 1 + 1D.

  18. The phase transitions between Zn × Zn bosonic topological phases in 1 + 1D, and a constraint on the central charge for the critical points between bosonic symmetry protected topological phases

    DOE PAGES

    Tsui, Lokman; Huang, Yen-Ta; Jiang, Hong-Chen; ...

    2017-03-27

    The study of continuous phase transitions triggered by spontaneous symmetry breaking has brought revolutionary ideas to physics. Recently, through the discovery of symmetry protected topological phases, it is realized that continuous quantum phase transition can also occur between states with the same symmetry but different topology. Here in this paper we study a specific class of such phase transitions in 1+1 dimensions – the phase transition between bosonic topological phases protected by Zn × Zn. We find in all cases the critical point possesses two gap opening relevant operators: one leads to a Landau-forbidden symmetry breaking phase transition and themore » other to the topological phase transition. We also obtained a constraint on the central charge for general phase transitions between symmetry protected bosonic topological phases in 1+1D.« less

  19. Robust Critical Point Detection

    SciTech Connect

    Bhatia, Harsh

    2016-07-28

    Robust Critical Point Detection is a software to compute critical points in a 2D or 3D vector field robustly. The software was developed as a part of the author's work at the lab as a Phd student under Livermore Scholar Program (now called Livermore Graduate Scholar Program).

  20. Symmetry in critical random Boolean network dynamics.

    PubMed

    Hossein, Shabnam; Reichl, Matthew D; Bassler, Kevin E

    2014-04-01

    Using Boolean networks as prototypical examples, the role of symmetry in the dynamics of heterogeneous complex systems is explored. We show that symmetry of the dynamics, especially in critical states, is a controlling feature that can be used both to greatly simplify analysis and to characterize different types of dynamics. Symmetry in Boolean networks is found by determining the frequency at which the various Boolean output functions occur. There are classes of functions that consist of Boolean functions that behave similarly. These classes are orbits of the controlling symmetry group. We find that the symmetry that controls the critical random Boolean networks is expressed through the frequency by which output functions are utilized by nodes that remain active on dynamical attractors. This symmetry preserves canalization, a form of network robustness. We compare it to a different symmetry known to control the dynamics of an evolutionary process that allows Boolean networks to organize into a critical state. Our results demonstrate the usefulness and power of using the symmetry of the behavior of the nodes to characterize complex network dynamics, and introduce an alternative approach to the analysis of heterogeneous complex systems.

  1. Symmetry in Critical Random Boolean Networks Dynamics

    NASA Astrophysics Data System (ADS)

    Bassler, Kevin E.; Hossein, Shabnam

    2014-03-01

    Using Boolean networks as prototypical examples, the role of symmetry in the dynamics of heterogeneous complex systems is explored. We show that symmetry of the dynamics, especially in critical states, is a controlling feature that can be used to both greatly simplify analysis and to characterize different types of dynamics. Symmetry in Boolean networks is found by determining the frequency at which the various Boolean output functions occur. Classes of functions occur at the same frequency. These classes are orbits of the controlling symmetry group. We find the nature of the symmetry that controls the dynamics of critical random Boolean networks by determining the frequency of output functions utilized by nodes that remain active on dynamical attractors. This symmetry preserves canalization, a form of network robustness. We compare it to a different symmetry known to control the dynamics of an evolutionary process that allows Boolean networks to organize into a critical state. Our results demonstrate the usefulness and power of using symmetry to characterize complex network dynamics, and introduce a novel approach to the analysis of heterogeneous complex systems. This work was supported by the NSF through grants DMR-0908286 and DMR-1206839, and by the AFSOR and DARPA through grant FA9550-12-1-0405.

  2. Symmetry in critical random Boolean network dynamics

    NASA Astrophysics Data System (ADS)

    Hossein, Shabnam; Reichl, Matthew D.; Bassler, Kevin E.

    2014-04-01

    Using Boolean networks as prototypical examples, the role of symmetry in the dynamics of heterogeneous complex systems is explored. We show that symmetry of the dynamics, especially in critical states, is a controlling feature that can be used both to greatly simplify analysis and to characterize different types of dynamics. Symmetry in Boolean networks is found by determining the frequency at which the various Boolean output functions occur. There are classes of functions that consist of Boolean functions that behave similarly. These classes are orbits of the controlling symmetry group. We find that the symmetry that controls the critical random Boolean networks is expressed through the frequency by which output functions are utilized by nodes that remain active on dynamical attractors. This symmetry preserves canalization, a form of network robustness. We compare it to a different symmetry known to control the dynamics of an evolutionary process that allows Boolean networks to organize into a critical state. Our results demonstrate the usefulness and power of using the symmetry of the behavior of the nodes to characterize complex network dynamics, and introduce an alternative approach to the analysis of heterogeneous complex systems.

  3. Teaching Point-Group Symmetry with Three-Dimensional Models

    ERIC Educational Resources Information Center

    Flint, Edward B.

    2011-01-01

    Three tools for teaching symmetry in the context of an upper-level undergraduate or introductory graduate course on the chemical applications of group theory are presented. The first is a collection of objects that have the symmetries of all the low-symmetry and high-symmetry point groups and the point groups with rotational symmetries from 2-fold…

  4. Teaching Point-Group Symmetry with Three-Dimensional Models

    ERIC Educational Resources Information Center

    Flint, Edward B.

    2011-01-01

    Three tools for teaching symmetry in the context of an upper-level undergraduate or introductory graduate course on the chemical applications of group theory are presented. The first is a collection of objects that have the symmetries of all the low-symmetry and high-symmetry point groups and the point groups with rotational symmetries from 2-fold…

  5. A holographic critical point

    SciTech Connect

    DeWolfe, Oliver; Rosen, Christopher; Gubser, Steven S.

    2011-04-15

    We numerically construct a family of five-dimensional black holes exhibiting a line of first-order phase transitions terminating at a critical point at finite chemical potential and temperature. These black holes are constructed so that the equation of state and baryon susceptibilities approximately match QCD lattice data at vanishing chemical potential. The critical end point in the particular model we consider has temperature 143 MeV and chemical potential 783 MeV. Critical exponents are calculated, with results that are consistent with mean-field scaling relations.

  6. Shape phase transitions and critical points

    SciTech Connect

    Alonso, C. E.; Arias, J. M.; Fortunato, L.; Vitturi, A.

    2009-05-04

    We investigate different aspects connected with shape phase transitions in nuclei and the possible occurrence of dynamical symmetries at the critical points. We discuss in particular the behaviour of the neighbour odd nuclei at the vicinity of the critical points in the even nuclei. We consider both the case of the transition from the vibrational behaviour to the gamma-unstable deformation (characterized within the collective Bohr hamiltonian by the E(5) critical point symmetry) and the case of the transition from the vibrational behaviour to the stable axial deformation (characterized by the X(5) symmetry). The odd particle is assumed to be moving in the three single particle orbitals j = 1/2,3/2,5/2, a set of orbitals that is known to lead to possible supersymmetric cases. The coupling of the odd particle to the Bohr hamiltonian does lead in fact in the former case at the critical point to the E(5/12) boson-fermion dynamical symmetry. An alternative approach to the two shape transitions is based on the Interacting Boson Fermion Model. In this case suitably parametrized boson-fermion hamiltonians can describe the evolution of the odd system along the shape transitions. At the critical points both energy spectra and electromagnetic transitions were found to display characteristic patterns similar to those displayed by the even nuclei at the corresponding critical point. The behaviour of the odd nuclei can therefore be seen as necessary complementary signatures of the occurrence of the phase transitions.

  7. Critical-Point Symmetries in Boson-Fermion Systems: The Case of Shape Transitions in Odd Nuclei in a Multiorbit Model

    SciTech Connect

    Alonso, C. E.; Arias, J. M.; Vitturi, A.

    2007-02-02

    We investigate phase transitions in boson-fermion systems. We propose an analytically solvable model [E(5/12)] to describe odd nuclei at the critical point in the transition from the spherical to {gamma}-unstable behavior. In the model, a boson core described within the Bohr Hamiltonian interacts with an unpaired particle assumed to be moving in the three single-particle orbitals j=1/2, 3/2, 5/2. Energy spectra and electromagnetic transitions at the critical point compare well with the results obtained within the interacting boson-fermion model, with a boson-fermion Hamiltonian that describes the same physical situation.

  8. Critical-point symmetries in boson-fermion systems: the case of shape transitions in odd nuclei in a multiorbit model.

    PubMed

    Alonso, C E; Arias, J M; Vitturi, A

    2007-02-02

    We investigate phase transitions in boson-fermion systems. We propose an analytically solvable model [E(5/12)] to describe odd nuclei at the critical point in the transition from the spherical to gamma-unstable behavior. In the model, a boson core described within the Bohr Hamiltonian interacts with an unpaired particle assumed to be moving in the three single-particle orbitals j=1/2, 3/2, 5/2. Energy spectra and electromagnetic transitions at the critical point compare well with the results obtained within the interacting boson-fermion model, with a boson-fermion Hamiltonian that describes the same physical situation.

  9. Deconfined Quantum Critical Points

    NASA Astrophysics Data System (ADS)

    Senthi, T.; Vishwanath, Ashvin; Balents, Leon; Sachdev, Subir; Fisher, Matthew P. A.

    The theory of second-order phase transitions is one of the foundations of modern statistical mechanics and condensed-matter theory. A central concept is the observable order parameter, whose nonzero average value characterizes one or more phases. At large distances and long times, fluctuations of the order parameter(s) are described by a continuum field theory, and these dominate the physics near such phase transitions. We show that near second-order quantum phase transitions, subtle quantum interference effects can invalidate this paradigm, and we present a theory of quantum critical points in a variety of experimentally relevant two-dimensional antiferromagnets. The critical points separate phases characterized by conventional "confining" order parameters. Nevertheless, the critical theory contains an emergent gauge field and "deconfined" degrees of freedom associated with fractionalization of the order parameters. We propose that this paradigm for quantum criticality may be the key to resolving a number of experimental puzzles in correlated electron systems and offer a new perspective on the properties of complex materials.

  10. Deconfined quantum critical points.

    PubMed

    Senthil, T; Vishwanath, Ashvin; Balents, Leon; Sachdev, Subir; Fisher, Matthew P A

    2004-03-05

    The theory of second-order phase transitions is one of the foundations of modern statistical mechanics and condensed-matter theory. A central concept is the observable order parameter, whose nonzero average value characterizes one or more phases. At large distances and long times, fluctuations of the order parameter(s) are described by a continuum field theory, and these dominate the physics near such phase transitions. We show that near second-order quantum phase transitions, subtle quantum interference effects can invalidate this paradigm, and we present a theory of quantum critical points in a variety of experimentally relevant two-dimensional antiferromagnets. The critical points separate phases characterized by conventional "confining" order parameters. Nevertheless, the critical theory contains an emergent gauge field and "deconfined" degrees of freedom associated with fractionalization of the order parameters. We propose that this paradigm for quantum criticality may be the key to resolving a number of experimental puzzles in correlated electron systems and offer a new perspective on the properties of complex materials.

  11. From Molecular Point Group Symmetry to Space Group Symmetry.

    ERIC Educational Resources Information Center

    Hathaway, Brian

    1979-01-01

    Describes undergraduate chemistry curricula in which the student is asked to either build a model of one asymmetric unit in the unit cell and to indicate the positions of the symmetry-related units by putting in key atoms, or to identify on a prebuild model the asymetric and symmetry-related units. (BB)

  12. Discovering Symmetry in Everyday Environments: A Creative Approach to Teaching Symmetry and Point Groups

    ERIC Educational Resources Information Center

    Fuchigami, Kei; Schrandt, Matthew; Miessler, Gary L.

    2016-01-01

    A hands-on symmetry project is proposed as an innovative way of teaching point groups to undergraduate chemistry students. Traditionally, courses teaching symmetry require students to identify the point group of a given object. This project asks the reverse: students are instructed to identify an object that matches each point group. Doing so…

  13. Discovering Symmetry in Everyday Environments: A Creative Approach to Teaching Symmetry and Point Groups

    ERIC Educational Resources Information Center

    Fuchigami, Kei; Schrandt, Matthew; Miessler, Gary L.

    2016-01-01

    A hands-on symmetry project is proposed as an innovative way of teaching point groups to undergraduate chemistry students. Traditionally, courses teaching symmetry require students to identify the point group of a given object. This project asks the reverse: students are instructed to identify an object that matches each point group. Doing so…

  14. Description of nuclear octupole and quadrupole deformation close to axial symmetry: Critical-point behavior of {sup 224}Ra and {sup 224}Th

    SciTech Connect

    Bizzeti, P. G.; Bizzeti-Sona, A. M.

    2008-02-15

    The model, introduced in a previous paper, for the description of the octupole and quadrupole degrees of freedom in conditions close to axial symmetry, is applied to situations of shape phase transitions where the quadrupole amplitude can reach zero. The transitional nuclei {sup 224,226}Ra and {sup 224}Th are discussed in the frame of this model. Their level schemes can be reasonably accounted for by assuming a square-well potential in two dimensions. Electromagnetic transition amplitudes are also evaluated and compared with existing experimental data.

  15. Fermion-induced quantum critical points.

    PubMed

    Li, Zi-Xiang; Jiang, Yi-Fan; Jian, Shao-Kai; Yao, Hong

    2017-08-22

    A unified theory of quantum critical points beyond the conventional Landau-Ginzburg-Wilson paradigm remains unknown. According to Landau cubic criterion, phase transitions should be first-order when cubic terms of order parameters are allowed by symmetry in the Landau-Ginzburg free energy. Here, from renormalization group analysis, we show that second-order quantum phase transitions can occur at such putatively first-order transitions in interacting two-dimensional Dirac semimetals. As such type of Landau-forbidden quantum critical points are induced by gapless fermions, we call them fermion-induced quantum critical points. We further introduce a microscopic model of SU(N) fermions on the honeycomb lattice featuring a transition between Dirac semimetals and Kekule valence bond solids. Remarkably, our large-scale sign-problem-free Majorana quantum Monte Carlo simulations show convincing evidences of a fermion-induced quantum critical points for N = 2, 3, 4, 5 and 6, consistent with the renormalization group analysis. We finally discuss possible experimental realizations of the fermion-induced quantum critical points in graphene and graphene-like materials.Quantum phase transitions are governed by Landau-Ginzburg theory and the exceptions are rare. Here, Li et al. propose a type of Landau-forbidden quantum critical points induced by gapless fermions in two-dimensional Dirac semimetals.

  16. Anticoherence of spin states with point-group symmetries

    NASA Astrophysics Data System (ADS)

    Baguette, D.; Damanet, F.; Giraud, O.; Martin, J.

    2015-11-01

    We investigate multiqubit permutation-symmetric states with maximal entropy of entanglement. Such states can be viewed as particular spin states, namely anticoherent spin states. Using the Majorana representation of spin states in terms of points on the unit sphere, we analyze the consequences of a point-group symmetry in their arrangement on the quantum properties of the corresponding state. We focus on the identification of anticoherent states (for which all reduced density matrices in the symmetric subspace are maximally mixed) associated with point-group-symmetric sets of points. We provide three different characterizations of anticoherence and establish a link between point symmetries, anticoherence, and classes of states equivalent through stochastic local operations with classical communication. We then investigate in detail the case of small numbers of qubits and construct infinite families of anticoherent states with point-group symmetry of their Majorana points, showing that anticoherent states do exist to arbitrary order.

  17. The critical end point through observables

    SciTech Connect

    Kozlov, G.

    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.

  18. Davies Critical Point and Tunneling

    NASA Astrophysics Data System (ADS)

    La, Hoseong

    2012-04-01

    From the point of view of tunneling, the physical meaning of the Davies critical point of a second-order phase transition in the black hole thermodynamics is clarified. At the critical point, the nonthermal contribution vanishes so that the black hole radiation is entirely thermal. It separates two phases: one with radiation enhanced by the nonthermal contribution, the other suppressed by the nonthermal contribution. We show this in both charged and rotating black holes. The phase transition is also analyzed in the cases in which emissions of charges and angular momenta are incorporated.

  19. Critical fermion density for restoring spontaneously broken symmetry

    NASA Astrophysics Data System (ADS)

    Kleinert, Hagen; Xue, She-Sheng

    2015-07-01

    We show how the phenomenon of spontaneous symmetry breakdown is affected by the presence of a sea of fermions in the system. When its density exceeds a critical value, the broken symmetry can be restored. We calculate the critical value and discuss the consequences for three different physical systems: First, for the Standard Model (SM) of particle physics, where the spontaneous symmetry breakdown leads to nonzero masses of intermediate gauge bosons and fermions. The symmetry restoration will greatly enhance various processes with dramatic consequences for the early universe. Second, for the Gell-Mann-Lévy σ-model of nuclear physics, where the symmetry breakdown gives rise to the nucleon and meson masses. The symmetry restoration may have important consequences for formation or collapse of stellar cores. Third, for the superconductive phase of condensed-matter, where the BCS condensate at low-temperature may be destroyed by a too large electron density.

  20. Critical points of metal vapors

    SciTech Connect

    Khomkin, A. L. Shumikhin, A. S.

    2015-09-15

    A new method is proposed for calculating the parameters of critical points and binodals for the vapor–liquid (insulator–metal) phase transition in vapors of metals with multielectron valence shells. The method is based on a model developed earlier for the vapors of alkali metals, atomic hydrogen, and exciton gas, proceeding from the assumption that the cohesion determining the basic characteristics of metals under normal conditions is also responsible for their properties in the vicinity of the critical point. It is proposed to calculate the cohesion of multielectron atoms using well-known scaling relations for the binding energy, which are constructed for most metals in the periodic table by processing the results of many numerical calculations. The adopted model allows the parameters of critical points and binodals for the vapor–liquid phase transition in metal vapors to be calculated using published data on the properties of metals under normal conditions. The parameters of critical points have been calculated for a large number of metals and show satisfactory agreement with experimental data for alkali metals and with available estimates for all other metals. Binodals of metals have been calculated for the first time.

  1. The Critical Point Facility (CPF)

    NASA Technical Reports Server (NTRS)

    1992-01-01

    The Critical Point Facility (CPF) is an ESA multiuser facility designed for microgravity research onboard Spacelab. It has been conceived and built to offer investigators opportunities to conduct research on critical point phenomena in microgravity. This facility provides the high precision and stability temperature standards required in this field of research. It has been primarily designed for the purpose of optical investigations of transparent fluids. During a Spacelab mission, the CPF automatically processes several thermostats sequentially, each thermostat corresponding to an experiment. The CPF is now integrated in Spacelab at Kennedy Space Center, in preparation for the International Microgravity Lab. mission. The CPF was designed to submit transparent fluids to an adequate, user defined thermal scenario, and to monitor their behavior by using thermal and optical means. Because they are strongly affected by gravity, a good understanding of critical phenomena in fluids can only be gained in low gravity conditions. Fluids at the critical point become compressed under their own weight. The role played by gravity in the formation of interfaces between distinct phases is not clearly understood.

  2. Conformal symmetry of the critical 3D Ising model inside a sphere

    NASA Astrophysics Data System (ADS)

    Cosme, Catarina; Lopes, J. M. Viana Parente; Penedones, João

    2015-08-01

    We perform Monte-Carlo simulations of the three-dimensional Ising model at the critical temperature and zero magnetic field. We simulate the system in a ball with free boundary conditions on the two dimensional spherical boundary. Our results for one and two point functions in this geometry are consistent with the predictions from the conjectured conformal symmetry of the critical Ising model.

  3. Random Lie-point symmetries of stochastic differential equations

    NASA Astrophysics Data System (ADS)

    Gaeta, Giuseppe; Spadaro, Francesco

    2017-05-01

    We study the invariance of stochastic differential equations under random diffeomorphisms and establish the determining equations for random Lie-point symmetries of stochastic differential equations, both in Ito and in Stratonovich forms. We also discuss relations with previous results in the literature.

  4. From physics to biology by extending criticality and symmetry breakings.

    PubMed

    Longo, G; Montévil, M

    2011-08-01

    Symmetries play a major role in physics, in particular since the work by E. Noether and H. Weyl in the first half of last century. Herein, we briefly review their role by recalling how symmetry changes allow to conceptually move from classical to relativistic and quantum physics. We then introduce our ongoing theoretical analysis in biology and show that symmetries play a radically different role in this discipline, when compared to those in current physics. By this comparison, we stress that symmetries must be understood in relation to conservation and stability properties, as represented in the theories. We posit that the dynamics of biological organisms, in their various levels of organization, are not "just" processes, but permanent (extended, in our terminology) critical transitions and, thus, symmetry changes. Within the limits of a relative structural stability (or interval of viability), variability is at the core of these transitions. Copyright © 2011 Elsevier Ltd. All rights reserved.

  5. Beauty is Attractive: Moduli Trapping at Enhanced Symmetry Points

    SciTech Connect

    Kofman, L

    2004-02-27

    We study quantum effects on moduli dynamics arising from the production of particles which are light at points of enhanced symmetry in moduli space. The resulting forces trap the moduli at these points. Moduli trapping occurs in time-dependent quantum field theory, as well as in systems of moving D-branes, where it leads the branes to combine into stacks. Trapping also occurs in the presence of gravity, though the range over which the moduli can roll is limited by Hubble friction. We observe that a scalar field trapped on a steep potential can induce a stage of acceleration of the universe, which we call trapped inflation. Moduli trapping ameliorates the cosmological moduli problem and may affect vacuum selection. In particular, rolling moduli are most powerfully attracted to the points of greatest symmetry. Given suitable assumptions about the dynamics of the very early universe, this effect might help to explain why among the plethora of possible vacuum states of string theory, we appear to live in one with a large number of (spontaneously broken) symmetries.

  6. Correlations in avalanche critical points.

    PubMed

    Cerruti, Benedetta; Vives, Eduard

    2009-07-01

    Avalanche dynamics and related power-law statistics are ubiquitous in nature, arising in phenomena such as earthquakes, forest fires, and solar flares. Very interestingly, an analogous behavior is associated with many condensed-matter systems, such as ferromagnets and martensites. Bearing it in mind, we study the prototypical random-field Ising model at T=0. We find a finite correlation between waiting intervals and the previous avalanche size. This correlation is not found in other models for avalanches but it is experimentally found in earthquakes and in forest fires. Our study suggests that this effect occurs in critical points that are at the end of a first-order discontinuity separating two regimes: one with high activity from another with low activity.

  7. Correlations in avalanche critical points

    NASA Astrophysics Data System (ADS)

    Cerruti, Benedetta; Vives, Eduard

    2009-07-01

    Avalanche dynamics and related power-law statistics are ubiquitous in nature, arising in phenomena such as earthquakes, forest fires, and solar flares. Very interestingly, an analogous behavior is associated with many condensed-matter systems, such as ferromagnets and martensites. Bearing it in mind, we study the prototypical random-field Ising model at T=0 . We find a finite correlation between waiting intervals and the previous avalanche size. This correlation is not found in other models for avalanches but it is experimentally found in earthquakes and in forest fires. Our study suggests that this effect occurs in critical points that are at the end of a first-order discontinuity separating two regimes: one with high activity from another with low activity.

  8. Phase diagram and critical end point for strongly interacting quarks.

    PubMed

    Qin, Si-xue; Chang, Lei; Chen, Huan; Liu, Yu-xin; Roberts, Craig D

    2011-04-29

    We introduce a method based on chiral susceptibility, which enables one to draw a phase diagram in the chemical-potential-temperature plane for strongly interacting quarks whose interactions are described by any reasonable gap equation, even if the diagrammatic content of the quark-gluon vertex is unknown. We locate a critical end point at (μ(E),T(E))∼(1.0,0.9)T(c), where T(c) is the critical temperature for chiral-symmetry restoration at μ=0, and find that a domain of phase coexistence opens at the critical end point whose area increases as a confinement length scale grows.

  9. Unconventional quantum critical points in systems of strongly interacting bosons

    NASA Astrophysics Data System (ADS)

    Zaleski, T. A.; Kopeć, T. K.

    2014-09-01

    Using the combined Bogoliubov method and the quantum rotor approach, we map the Bose-Hubbard Hamiltonian of strongly interacting bosons onto U(1) phase action. By unraveling consequences of the nontrivial topology of the U(1) gauge group and the associated ground state degeneracy we found a close kinship of the zero-temperature divergence of the compressibility and the topological susceptibility at degeneracy points, which marks a novel quantum criticality governed by topological features rather than the Landau principle of the symmetry breaking. We argue that the existence of this new type of the criticality may be instrumental in explaining unconventional quantum critical points observed in superconducting cuprates.

  10. Quantum Critical Spin-2 Chain with Emergent SU(3) Symmetry

    NASA Astrophysics Data System (ADS)

    Chen, Pochung; Xue, Zhi-Long; McCulloch, I. P.; Chung, Ming-Chiang; Huang, Chao-Chun; Yip, S.-K.

    2015-04-01

    We study the quantum critical phase of an SU(2) symmetric spin-2 chain obtained from spin-2 bosons in a one-dimensional lattice. We obtain the scaling of the finite-size energies and entanglement entropy by exact diagonalization and density-matrix renormalization group methods. From the numerical results of the energy spectra, central charge, and scaling dimension we identify the conformal field theory describing the whole critical phase to be the SU (3 )1 Wess-Zumino-Witten model. We find that, while the Hamiltonian is only SU(2) invariant, in this critical phase there is an emergent SU(3) symmetry in the thermodynamic limit.

  11. Symmetry, Point Groups, and Character Tables, Part 3, Character Tables and Their Significance

    ERIC Educational Resources Information Center

    Orchin, Milton; Jaffe, H. H.

    1970-01-01

    Presents the third of a series of articles on symmetry. Describes the symmetry properties of molecules in translatiional and rotational motion. Presents these dynamic symmetry properties in character tables for five point groups. Supplements the article with more rigorous material involving spectroscopic states, degenerate point groups and…

  12. Broken vertex symmetry and finite zero-point entropy in the artificial square ice ground state

    SciTech Connect

    Gliga, Sebastian; Kákay, Attila; Heyderman, Laura J.; Hertel, Riccardo; Heinonen, Olle G.

    2015-08-26

    In this paper, we study degeneracy and entropy in the ground state of artificial square ice. In theoretical models, individual nanomagnets are typically treated as single spins with only two degrees of freedom, leading to a twofold degenerate ground state with intensive entropy and thus no zero-point entropy. Here, we show that the internal degrees of freedom of the nanostructures can result, through edge bending of the magnetization and breaking of local magnetic symmetry at the vertices, in a transition to a highly degenerate ground state with finite zero-point entropy, similar to that of the pyrochlore spin ices. Finally, we find that these additional degrees of freedom have observable consequences in the resonant spectrum of the lattice, and predict the occurrence of edge “melting” above a critical temperature at which the magnetic symmetry is restored.

  13. Broken vertex symmetry and finite zero-point entropy in the artificial square ice ground state

    DOE PAGES

    Gliga, Sebastian; Kákay, Attila; Heyderman, Laura J.; ...

    2015-08-26

    In this paper, we study degeneracy and entropy in the ground state of artificial square ice. In theoretical models, individual nanomagnets are typically treated as single spins with only two degrees of freedom, leading to a twofold degenerate ground state with intensive entropy and thus no zero-point entropy. Here, we show that the internal degrees of freedom of the nanostructures can result, through edge bending of the magnetization and breaking of local magnetic symmetry at the vertices, in a transition to a highly degenerate ground state with finite zero-point entropy, similar to that of the pyrochlore spin ices. Finally, wemore » find that these additional degrees of freedom have observable consequences in the resonant spectrum of the lattice, and predict the occurrence of edge “melting” above a critical temperature at which the magnetic symmetry is restored.« less

  14. Confinement of monopoles and scaling theory near unconventional critical points

    NASA Astrophysics Data System (ADS)

    Powell, Stephen

    2013-02-01

    Conventional ordering transitions, described by the Landau paradigm, are characterized by the symmetries broken at the critical point. Within the constrained manifold occurring at low temperatures in certain frustrated systems, unconventional transitions are possible that defy this type of description. While the critical point exists only in the limit where defects in the constraint are vanishingly rare, unconventional criticality can be observed throughout a broad region of the phase diagram. This work presents a formalism for incorporating the effects of such defects within the framework of scaling theory and the renormalization group, leading to universal results for the critical behavior. The theory is applied to two transitions occurring within a model of spin ice, and the results are confirmed using Monte Carlo simulations. Relevance to experiments, particularly in the spin-ice compounds, is discussed, along with implications for simulations of related transitions, such as the cubic dimer model and the O(3) sigma model with “hedgehog” suppression.

  15. Critical-entanglement spectrum of one-dimensional symmetry-protected topological phases

    NASA Astrophysics Data System (ADS)

    Rao, Wen-Jia; Wan, Xin; Zhang, Guang-Ming

    2014-08-01

    Under an appropriate symmetric extensive bipartition in a one-dimensional symmetry-protected topological (SPT) phase, a bulk critical-entanglement spectrum can be obtained, resembling the excitation spectrum of the critical point separating the SPT phase from the trivial (vacuum) state. Such a critical point is beyond the standard Landau-Ginzburg-Wilson paradigm for symmetry-breaking phase transitions. For the S =1 SPT (Haldane) phase with the Affleck-Kennedy-Lieb-Tasaki exact wave function, the resulting critical-entanglement spectrum has a residual entropy per lattice site sr=0.67602, showing a delocalized version of the edge excitations in the SPT phase. From the wave function corresponding to the lowest entanglement energy level, the central charge of the critical point can be extracted c ≈1.01±0.01. The critical theory can be identified as the same effective field theory as the spin-1/2 antiferromagnetic Heisenberg chain or the spin-1/2 Haldane-Shastry model with inverse-square long-range interaction.

  16. Quantum sensing close to a dissipative phase transition: Symmetry breaking and criticality as metrological resources

    NASA Astrophysics Data System (ADS)

    Fernández-Lorenzo, Samuel; Porras, Diego

    2017-07-01

    We study the performance of a single qubit laser as a quantum sensor to measure the amplitude and phase of a driving field. By using parameter estimation theory we show that certain suitable field quadratures are optimal observables in the lasing phase. The quantum Fisher information scales linearly with the number of bosons and thus the precision can be enhanced by increasing the incoherent pumping acting on the qubit. If we restrict ourselves to measurements of the boson number observable, then the optimal operating point is the critical point of the lasing phase transition. Our results point to an intimate connection between symmetry breaking, dissipative phase transitions, and efficient parameter estimation.

  17. Quantum criticality in an Ising chain: experimental evidence for emergent E8 symmetry.

    PubMed

    Coldea, R; Tennant, D A; Wheeler, E M; Wawrzynska, E; Prabhakaran, D; Telling, M; Habicht, K; Smeibidl, P; Kiefer, K

    2010-01-08

    Quantum phase transitions take place between distinct phases of matter at zero temperature. Near the transition point, exotic quantum symmetries can emerge that govern the excitation spectrum of the system. A symmetry described by the E8 Lie group with a spectrum of eight particles was long predicted to appear near the critical point of an Ising chain. We realize this system experimentally by using strong transverse magnetic fields to tune the quasi-one-dimensional Ising ferromagnet CoNb2O6 (cobalt niobate) through its critical point. Spin excitations are observed to change character from pairs of kinks in the ordered phase to spin-flips in the paramagnetic phase. Just below the critical field, the spin dynamics shows a fine structure with two sharp modes at low energies, in a ratio that approaches the golden mean predicted for the first two meson particles of the E8 spectrum. Our results demonstrate the power of symmetry to describe complex quantum behaviors.

  18. Discrete-Symmetry Breaking and Novel Critical Phenomena in an Antiferromagnetic Planar (XY) Model in Two Dimensions

    NASA Astrophysics Data System (ADS)

    Lee, D. H.; Joannopoulos, J. D.; Negele, J. W.; Landau, D. P.

    1984-02-01

    Landau-Ginzburg-Wilson symmetry analyses and Monte Carlo calculations for the classical antiferromagnetic planar (XY) model on a triangular lattice reveal a wealth of interesting critical phenomena. From this simple model arise a zero-field transition to a state of long-range order, a new mechanism for spin disordering, and a critical point associated with a possible new universality class.

  19. Landau-Ginzburg-Wilson approach to critical phenomena in the presence of gauge symmetries

    NASA Astrophysics Data System (ADS)

    Pelissetto, Andrea; Tripodo, Antonio; Vicari, Ettore

    2017-08-01

    We critically reconsider the Landau-Ginzburg-Wilson (LGW) approach to critical phenomena in the presence of gauge symmetries. In the LGW framework, to obtain the universal features of a continuous transition, one identifies the order parameter Φ and considers the corresponding most general Φ4 field theory that has the same symmetries as the original model. In the presence of gauge symmetries, one usually considers a gauge-invariant order parameter and a LGW field theory that is invariant under the global symmetries of the original model. We show that this approach, in which the gauge dynamics is effectively integrated out, may sometimes lead to erroneous conclusions on the nature of the critical behavior. As an explicit example, we show that the above-described LGW approach generally fails for the three-dimensional ferromagnetic and antiferromagnetic CPN -1 models, which are invariant under global U (N ) and local U(1) transformations. We point out possible implications for the finite-temperature chiral transition of nuclear matter.

  20. Critical point analysis of phase envelope diagram

    NASA Astrophysics Data System (ADS)

    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.

  1. Critical point analysis of phase envelope diagram

    SciTech Connect

    Soetikno, Darmadi; Siagian, Ucok W. R.; Kusdiantara, Rudy Puspita, Dila Sidarto, Kuntjoro A. Soewono, Edy; Gunawan, Agus Y.

    2014-03-24

    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.

  2. Critical points and number of master integrals

    NASA Astrophysics Data System (ADS)

    Lee, Roman N.; Pomeransky, Andrei A.

    2013-11-01

    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 for the typical case, when all critical points are isolated.

  3. Entanglement entropy near Kondo-destruction quantum critical points

    NASA Astrophysics Data System (ADS)

    Pixley, J. H.; Chowdhury, Tathagata; Miecnikowski, M. T.; Stephens, Jaimie; Wagner, Christopher; Ingersent, Kevin

    2015-06-01

    We study the impurity entanglement entropy Se in quantum impurity models that feature a Kondo-destruction quantum critical point (QCP) arising from a pseudogap in the conduction-band density of states or from coupling to a bosonic bath. On the local-moment (Kondo-destroyed) side of the QCP, the entanglement entropy contains a critical component that can be related to the order parameter characterizing the quantum phase transition. In Kondo models describing a spin-Simp,Se assumes its maximal value of ln(2 Simp+1 ) at the QCP and throughout the Kondo phase, independent of features such as particle-hole symmetry and under- or overscreening. In Anderson models, Se is nonuniversal at the QCP and, at particle-hole symmetry, rises monotonically on passage from the local-moment phase to the Kondo phase; breaking this symmetry can lead to a cusp peak in Se due to a divergent charge susceptibility at the QCP. Implications of these results for quantum critical systems and quantum dots are discussed.

  4. Studying Fluid Properties Near the Critical Point

    ERIC Educational Resources Information Center

    Gauthier, J. P.; And Others

    1977-01-01

    Illustrated and described is the design of an apparatus that can be used by students in a short period of time. It gives quantitative results showing evidence of thermoelastic properties of fluids near the critical point. (Author/MA)

  5. Critical point wetting drop tower experiment

    NASA Technical Reports Server (NTRS)

    Kaukler, W. F.; Tcherneshoff, L. M.; Straits, S. R.

    1984-01-01

    Preliminary results for the Critical Point Wetting CPW Drop Tower Experiment are produced with immiscible systems. Much of the observed phenomena conformed to the anticipated behavior. More drops will be needed to test the CPW theory with these immiscible systems.

  6. The Emergence of Dirac points in Photonic Crystals with Mirror Symmetry

    PubMed Central

    He, Wen-Yu; Chan, C. T.

    2015-01-01

    We show that Dirac points can emerge in photonic crystals possessing mirror symmetry when band gap closes. The mechanism of generating Dirac points is discussed in a two-dimensional photonic square lattice, in which four Dirac points split out naturally after the touching of two bands with different parity. The emergence of such nodal points, characterized by vortex structure in momentum space, is attributed to the unavoidable band crossing protected by mirror symmetry. The Dirac nodes can be unbuckled through breaking the mirror symmetry and a photonic analog of Chern insulator can be achieved through time reversal symmetry breaking. Breaking time reversal symmetry can lead to unidirectional helical edge states and breaking mirror symmetry can reduce the band gap to amplify the finite size effect, providing ways to engineer helical edge states. PMID:25640993

  7. Broken symmetry and critical transport properties of random metals

    PubMed Central

    Phillips, J. C.

    1997-01-01

    Recent experimental data on the conductivity σ+(T), T → 0, on the metallic side of the metal–insulator transition in ideally random (neutron transmutation-doped) 70Ge:Ga have shown that σ+(0) ∝ (N − Nc)μ with μ = ½, confirming earlier ultra-low-temperature results for Si:P. This value is inconsistent with theoretical predictions based on diffusive classical scaling models, but it can be understood by a quantum-directed percolative filamentary amplitude model in which electronic basis states exist which have a well-defined momentum parallel but not normal to the applied electric field. The model, which is based on a new kind of broken symmetry, also explains the anomalous sign reversal of the derivative of the temperature dependence in the critical regime. PMID:11038579

  8. Many-body topological invariants in fermionic symmetry-protected topological phases: Cases of point group symmetries

    NASA Astrophysics Data System (ADS)

    Shiozaki, Ken; Shapourian, Hassan; Ryu, Shinsei

    2017-05-01

    We propose the definitions of many-body topological invariants to detect symmetry-protected topological phases protected by point group symmetry, using partial point group transformations on a given short-range entangled quantum ground state. Here, partial point group transformations gD are defined by point group transformations restricted to a spatial subregion D , which is closed under the point group transformations and sufficiently larger than the bulk correlation length ξ . By analytical and numerical calculations, we find that the ground state (GS) expectation value of the partial point group transformations behaves generically as ˜exp [i θ +γ -α Area/(∂ D ) ξd -1] . Here, Area (∂ D ) is the area of the boundary of the subregion D , and α is a dimensionless constant. The complex phase of the expectation value θ is quantized and serves as the topological invariant, and γ is a scale-independent topological contribution to the amplitude. The examples we consider include the Z8 and Z16 invariants of topological superconductors protected by inversion symmetry in (1 +1 ) and (3 +1 ) dimensions, respectively, and the lens space topological invariants in (2 +1 ) -dimensional fermionic topological phases. Connections to topological quantum field theories and cobordism classification of symmetry-protected topological phases are discussed.

  9. Virtual and Printed 3D Models for Teaching Crystal Symmetry and Point Groups

    ERIC Educational Resources Information Center

    Casas, Lluís; Estop, Euge`nia

    2015-01-01

    Both, virtual and printed 3D crystal models can help students and teachers deal with chemical education topics such as symmetry and point groups. In the present paper, two freely downloadable tools (interactive PDF files and a mobile app) are presented as examples of the application of 3D design to study point-symmetry. The use of 3D printing to…

  10. Virtual and Printed 3D Models for Teaching Crystal Symmetry and Point Groups

    ERIC Educational Resources Information Center

    Casas, Lluís; Estop, Euge`nia

    2015-01-01

    Both, virtual and printed 3D crystal models can help students and teachers deal with chemical education topics such as symmetry and point groups. In the present paper, two freely downloadable tools (interactive PDF files and a mobile app) are presented as examples of the application of 3D design to study point-symmetry. The use of 3D printing to…

  11. Controlling superconductivity by tunable quantum critical points.

    PubMed

    Seo, S; Park, E; Bauer, E D; Ronning, F; Kim, J N; Shim, J-H; Thompson, J D; Park, Tuson

    2015-03-04

    The heavy fermion compound CeRhIn5 is a rare example where a quantum critical point, hidden by a dome of superconductivity, has been explicitly revealed and found to have a local nature. The lack of additional examples of local types of quantum critical points associated with superconductivity, however, has made it difficult to unravel the role of quantum fluctuations in forming Cooper pairs. Here, we show the precise control of superconductivity by tunable quantum critical points in CeRhIn5. Slight tin-substitution for indium in CeRhIn5 shifts its antiferromagnetic quantum critical point from 2.3 GPa to 1.3 GPa and induces a residual impurity scattering 300 times larger than that of pure CeRhIn5, which should be sufficient to preclude superconductivity. Nevertheless, superconductivity occurs at the quantum critical point of the tin-doped metal. These results underline that fluctuations from the antiferromagnetic quantum criticality promote unconventional superconductivity in CeRhIn5.

  12. Pions near the chiral critical point

    NASA Astrophysics Data System (ADS)

    Hippert, M.; Fraga, E. S.; Santos, E. M.

    2016-04-01

    It is an exciting possibility that the QCD critical point can be found in ultrarelativistic heavy-ion collision experiments (HICs). While quantities such as some event-by-event moments of specific observables should display strong non-monotonic behavior near the critical point and could, hence, be used as signatures of criticality, it is not clear that this behavior could effectively be observed in the highly non-ideal scenario of HICs. We here employ Monte Carlo simulations to test second-order moments of pion observables as possible signatures of the critical point while taking into account some realistic ingredients, similar to the ones found in HICs. We make use of simplified models to introduce spurious contributions and dynamical effects.

  13. Critical behaviors near the (tri-)critical end point of QCD within the NJL model

    NASA Astrophysics Data System (ADS)

    Lu, Ya; Du, Yi-Lun; Cui, Zhu-Fang; Zong, Hong-Shi

    2015-10-01

    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 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.

  14. Effects of dissipation on a quantum critical point with disorder.

    PubMed

    Hoyos, José A; Kotabage, Chetan; Vojta, Thomas

    2007-12-07

    We study the effects of dissipation on a disordered quantum phase transition with O(N) order-parameter symmetry by applying a strong-disorder renormalization group to the Landau-Ginzburg-Wilson field theory of the problem. We find that Ohmic dissipation results in a nonperturbative infinite-randomness critical point with unconventional activated dynamical scaling while super-Ohmic damping leads to conventional behavior. We discuss applications to the superconductor-metal transition in nanowires and to the Hertz theory of the itinerant antiferromagnetic transition.

  15. Pedagogical systematic derivation of Noether point symmetries in special relativistic field theories and extended gravity cosmology

    NASA Astrophysics Data System (ADS)

    Haas, Fernando

    2016-11-01

    A didactic and systematic derivation of Noether point symmetries and conserved currents is put forward in special relativistic field theories, without a priori assumptions about the transformation laws. Given the Lagrangian density, the invariance condition develops as a set of partial differential equations determining the symmetry transformation. The solution is provided in the case of real scalar, complex scalar, free electromagnetic, and charged electromagnetic fields. Besides the usual conservation laws, a less popular symmetry is analyzed: the symmetry associated with the linear superposition of solutions, whenever applicable. The role of gauge invariance is emphasized. The case of the charged scalar particle under external electromagnetic fields is considered, and the accompanying Noether point symmetries determined. Noether point symmetries for a dynamical system in extended gravity cosmology are also deduced.

  16. Enhancement of superconductivity near a nematic quantum critical point.

    PubMed

    Lederer, S; Schattner, Y; Berg, E; Kivelson, S A

    2015-03-06

    We consider a low T_{c} metallic superconductor weakly coupled to the soft fluctuations associated with proximity to a nematic quantum critical point (NQCP). We show that (1) a BCS-Eliashberg treatment remains valid outside of a parametrically narrow interval about the NQCP, (2) the symmetry of the superconducting state (d wave, s wave, p wave) is typically determined by the noncritical interactions, but T_{c} is enhanced by the nematic fluctuations in all channels, and (3) in 2D, this enhancement grows upon approach to criticality up to the point at which the weak coupling approach breaks down, but in 3D, the enhancement is much weaker.

  17. Hidden symmetry and protection of Dirac points on the honeycomb lattice

    PubMed Central

    Hou, Jing-Min; Chen, Wei

    2015-01-01

    The honeycomb lattice possesses a novel energy band structure, which is characterized by two distinct Dirac points in the Brillouin zone, dominating most of the physical properties of the honeycomb structure materials. However, up till now, the origin of the Dirac points is unclear yet. Here, we discover a hidden symmetry on the honeycomb lattice and prove that the existence of Dirac points is exactly protected by such hidden symmetry. Furthermore, the moving and merging of the Dirac points and a quantum phase transition, which have been theoretically predicted and experimentally observed on the honeycomb lattice, can also be perfectly explained by the parameter dependent evolution of the hidden symmetry. PMID:26639178

  18. Exceptional points and symmetry recovery in a two-state system

    NASA Astrophysics Data System (ADS)

    Zhang, Xu-Lin; Wang, Shubo; Chen, Wen-Jie; Chan, C. T.

    2017-08-01

    We consider a two-state system consisting of a pair of coupled ferromagnetic waveguides. A monotonically increasing bias magnetic field can dynamically manipulate the system to enter a PT -symmetry-broken phase and then reenter a symmetric phase. The symmetry recovery is enabled by the presence of accidental degeneracy points when the system has no loss and each degeneracy point can spawn a pair of exceptional points when asymmetric loss is introduced. We performed microwave experiments to demonstrate the presence of the exceptional point and symmetry recovery.

  19. Hidden symmetry and protection of Dirac points on the honeycomb lattice.

    PubMed

    Hou, Jing-Min; Chen, Wei

    2015-12-07

    The honeycomb lattice possesses a novel energy band structure, which is characterized by two distinct Dirac points in the Brillouin zone, dominating most of the physical properties of the honeycomb structure materials. However, up till now, the origin of the Dirac points is unclear yet. Here, we discover a hidden symmetry on the honeycomb lattice and prove that the existence of Dirac points is exactly protected by such hidden symmetry. Furthermore, the moving and merging of the Dirac points and a quantum phase transition, which have been theoretically predicted and experimentally observed on the honeycomb lattice, can also be perfectly explained by the parameter dependent evolution of the hidden symmetry.

  20. Nonionic reverse micelles near the critical point.

    PubMed

    Shrestha, Lok Kumar; Shrestha, Rekha Goswami

    2013-01-01

    We report shape, size, and internal cross-sectional structure of diglycerol monomyristate (C₁₄G₂) reverse micelles in n-hexadecane near the critical point using small-angle X-ray scattering (SAXS). Pair-distance distribution function, p(r), which gives structural information in real-space, was obtained by indirect Fourier transformation (IFT) method. The p(r) showed a clear picture of rodlike micelles at higher temperatures well above the critical point (micellar solution phase separates into two immiscible liquids at ~ 48°C). At a fixed surfactant concentration (5% C₁₄G₂), decrease in temperature increases the micellar size monotonously and surprisingly shape of the p(r) curve at 50°C; close to the critical point, mimics the shape of the two dimensional disk-like micelles indicating the onset of critical fluctuations (attractive interactions among rodlike micelles forming a weak network). A similar behavior has been observed with normal micelles in aqueous system near the critical point. When the system is heated to 60°C, shape of the p(r) curve regains rodlike structure. At fixed temperature of 60°C, increase in C₁₄G₂ concentration induced one dimensional micellar growth. Maximum length of micelles increases from ca. 23.5 to 46.0 nm upon increasing concentration from 1 to 12% keeping cross section diameter apparently unchanged at ca. 4.0 nm.

  1. Flow Field Classification Using Critical Point Matching

    NASA Astrophysics Data System (ADS)

    Krueger, Paul S.; Williams, Sheila; Hahsler, Michael; Olinick, Eli V.

    2016-11-01

    Classification of flow fields according to topological similarities can help reveal features of the flow generation and evolution for bluff body flows, and characterize different swimming maneuvers in aquatic locomotion, to name a few. Rigorous classification can be challenging, however, especially when complex flows are distorted by measurement uncertainties or variable flow generating conditions. The present work uses critical points of the velocity field to characterize the global flow topology. Flow fields are compared by finding a best match of critical points in two flow fields based on topological and location characteristics of the critical points together with general point set distance measures. The similarity between the flow fields is quantified based on the matched critical points. Applying clustering algorithms to a set of flow fields with quantified similarity can then be used to group flows with similar characteristics. This approach has been applied to generic 2D flow fields constructed using potential flow results and is able to correctly identify similar flow fields even after large distortions (up to 20% of the vortex separation) have been applied to the flows. Support of NSF Grant Nos. 1115139 and 1557698, and the Lyle School of Engineering is gratefully acknowledged.

  2. Quantum critical points in quantum impurity systems

    NASA Astrophysics Data System (ADS)

    Lee, Hyun Jung; Bulla, Ralf

    2005-04-01

    The numerical renormalization group method is used to investigate zero-temperature phase transitions in quantum impurity systems, in particular in the soft-gap Anderson model, where an impurity couples to a non-trivial fermionic bath. In this case, zero-temperature phase transitions occur between two different phases whose fixed points can be built up of non-interacting single-particle states. However, the quantum critical point cannot be described by non-interacting fermionic or bosonic excitations.

  3. Thermodynamic curvature from the critical point to the triple point.

    PubMed

    Ruppeiner, George

    2012-08-01

    I evaluate the thermodynamic curvature R for fourteen pure fluids along their liquid-vapor coexistence curves, from the critical point to the triple point, using thermodynamic input from the NIST Chemistry WebBook. In this broad overview, R is evaluated in both the coexisting liquid and vapor phases. R is an invariant whose magnitude |R| is a measure of the size of mesoscopic organized structures in a fluid, and whose sign specifies whether intermolecular interactions are effectively attractive (R<0) or repulsive (R>0). I discuss five principles for R in pure fluids: (1) Near the critical point, the attractive part of the interactions forms loose structures of size |R| proportional to the correlation volume ξ(3), and the sign of R is negative. (2) In the vapor phase, there are instances of compact clusters of size |R| formed by the attractive part of the interactions and prevented from collapse by the repulsive part of the interactions, and the sign of R is positive. (3) In the asymptotic critical point regime, the R's in the coexisting liquid and vapor phases are equal to each other, i.e., commensurate. (4) Outside the asymptotic critical-point regime incommensurate R's may be associated with metastability. (5) The compact liquid phase has |R| on the order of the volume of a molecule, with the sign of R being negative for a liquidlike state held together by attractive interactions and the sign of R being positive for a solidlike state held up by repulsive interactions. These considerations amplify and extend the application of thermodynamic curvature in pure fluids.

  4. Rigidity of critical points for a nonlocal Ohta–Kawasaki energy

    NASA Astrophysics Data System (ADS)

    Dipierro, Serena; Novaga, Matteo; Valdinoci, Enrico

    2017-04-01

    We investigate the shape of critical points for a free energy consisting of a nonlocal perimeter plus a nonlocal repulsive term. In particular, we prove that a volume-constrained critical point is necessarily a ball if its volume is sufficiently small with respect to its isodiametric ratio, thus extending a result previously known only for global minimizers. We also show that, at least in one-dimension, there exist critical points with arbitrarily small volume and large isodiametric ratio. This example shows that a constraint on the diameter is, in general, necessary to establish the radial symmetry of the critical points.

  5. Asymmetric effects at 3D Ising-like critical points

    NASA Astrophysics Data System (ADS)

    Tsypin, M.

    2003-05-01

    The Standard Model of electroweak interactions has a line of first order phase transition in the plane (higgs mass, temperature) that ends in a critical point belonging to the 3D Ising model universality class [K. Rummukainen et al, hep-lat/9805013. Similar critical points are found in finite-temperature QCD [M. Stephanov et al, hep-ph/9806219; F. Karsch et al, hep-lat/0107020. When these critical points are studied by Monte Carlo simulations on the lattice, one observes certain residual deviations from Z2 symmetry (which is exact for the Ising model). Here we study whether such deviations can be attributed to asymmetric corrections to scaling, which are relatively poorly studied. We compute the critical exponents in the local potential approximation (LPA), that is, in the framework of the Wegner-Houghton equation. We find that the exponent for the leading antisymmetric correction to scaling is approximately 1.691 in the LPA. This high value implies that such corrections cannot explain observed asymmetries.

  6. Critical point fluctuations in supported lipid membranes.

    PubMed

    Connell, Simon D; Heath, George; Olmsted, Peter D; Kisil, Anastasia

    2013-01-01

    In this paper, we demonstrate that it is possible to observe many aspects of critical phenomena in supported lipid bilayers using atomic force microscopy (AFM) with the aid of stable and precise temperature control. The regions of criticality were determined by accurately measuring and calculating phase diagrams for the 2 phase L(d)-L(o) region, and tracking how it moves with temperature, then increasing the sampling density around the estimated critical regions. Compositional fluctuations were observed above the critical temperature (T(c)) and characterised using a spatial correlation function. From this analysis, the phase transition was found to be most closely described by the 2D Ising model, showing it is a critical transition. Below T(c) roughening of the domain boundaries occurred due to the reduction in line tension close to the critical point. Smaller scale density fluctuations were also detected just below T(c). At T(c), we believe we have observed fluctuations on length scales greater than 10 microm. The region of critically fluctuating 10-100 nm nanodomains has been found to extend a considerable distance above T(c) to temperatures within the biological range, and seem to be an ideal candidate for the actual structure of lipid rafts in cell membranes. Although evidence for this idea has recently emerged, this is the first direct evidence for nanoscale domains in the critical region.

  7. The Effect of Instructional Modality and Prior Knowledge on Learning Point Group Symmetry

    ERIC Educational Resources Information Center

    Nottis, Katharyn E. K.; Kastner, Margaret E.

    2005-01-01

    Many topics in chemistry are difficult for learners to understand, including symmetry. Reasons for this difficulty include its multi-level content, instructional methodologies utilized, and learner variables. This study examined the effect of initial instructional modality and prior knowledge on learning of point group symmetry. Forty-four…

  8. On the Number of Generator Sets of the Non-Cubic Symmetry Point Groups.

    ERIC Educational Resources Information Center

    Kouyoumdjian, E. R.

    1983-01-01

    The generator set of a group is the subset of the set of elements of the group. The nature and use of generator sets is discussed, focusing on generator sets for the noncubic symmetry point groups containing one, two, and three symmetry elements. (JN)

  9. The Effect of Instructional Modality and Prior Knowledge on Learning Point Group Symmetry

    ERIC Educational Resources Information Center

    Nottis, Katharyn E. K.; Kastner, Margaret E.

    2005-01-01

    Many topics in chemistry are difficult for learners to understand, including symmetry. Reasons for this difficulty include its multi-level content, instructional methodologies utilized, and learner variables. This study examined the effect of initial instructional modality and prior knowledge on learning of point group symmetry. Forty-four…

  10. Nonequilibrium conductivity at quantum critical points

    NASA Astrophysics Data System (ADS)

    Berridge, A. M.; Green, A. G.

    2013-12-01

    Quantum criticality provides an important route to revealing universal nonequilibrium behavior. A canonical example of a critical point is the Bose-Hubbard model, which we study under the application of an electric field. A Boltzmann transport formalism and ɛ expansion are used to obtain the nonequilibrium conductivity and current noise. This approach allows us to explicitly identify how a universal nonequilibrium steady state is maintained, by identifying the rate-limiting step in balancing Joule heating and dissipation to a heat bath. It also reveals that the nonequilibrium distribution function is very far from a thermal distribution.

  11. The effective QCD phase diagram and the critical end point

    NASA Astrophysics Data System (ADS)

    Ayala, Alejandro; Bashir, Adnan; Cobos-Martínez, J. J.; Hernández-Ortiz, Saúl; Raya, Alfredo

    2015-08-01

    We study the QCD phase diagram on the temperature T and quark chemical potential μ plane, modeling 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 μ taking into account the plasma screening effects. We find the location of the critical end point (CEP) to be (μCEP /Tc, TCEP /Tc) ∼ (1.2, 0.8), where Tc is the (pseudo)critical temperature for the crossover phase transition at vanishing μ. 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 in the QCD phase diagram.

  12. Multiplicity fluctuations near the QCD critical point

    NASA Astrophysics Data System (ADS)

    Hippert, M.; Fraga, E. S.

    2017-08-01

    Statistical moments of particle multiplicities in heavy-ion collision experiments are an important probe in the exploration of the phase diagram of strongly interacting matter and, particularly, in the search for the QCD critical end point. In order to appropriately interpret experimental measures of these moments, however, it is necessary to understand the role of experimental limitations, as well as background contributions, providing expectations on how critical behavior should be affected by them. We here present a framework for calculating moments of particle multiplicities in the presence of correlations of both critical and spurious origins. We also include effects from resonance decay and a limited acceptance window, as well as detector efficiency. Although we focus on second-order moments, for simplicity, an extension to higher-order moments is straightforward.

  13. Correlated fluctuations near the QCD critical point

    NASA Astrophysics Data System (ADS)

    Jiang, Lijia; Li, Pengfei; Song, Huichao

    2016-08-01

    In this article, we introduce a freeze-out scheme for the dynamical models near the QCD critical point through coupling the decoupled classical particles with the order parameter field. With a modified distribution function that satisfies specific static fluctuations, we calculate the correlated fluctuations of net protons on the hydrodynamic freeze-out surface. A comparison with recent STAR data shows that our model calculations could roughly reproduce energy-dependent cumulant C4 and κ σ2 of net protons through tuning the related parameters. However, the calculated C2 and C3 with both Poisson and binomial baselines are always above the experimental data due to the positive contributions from the static critical fluctuations. To qualitatively and quantitatively describe all the related experimental data, the dynamical critical fluctuations and more realistic noncritical fluctuation baselines should be investigated in the near future.

  14. Influence of super-ohmic dissipation on a disordered quantum critical point.

    PubMed

    Vojta, Thomas; Hoyos, José A; Mohan, Priyanka; Narayanan, Rajesh

    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.

  15. Magnetic Rotation and Chirality and X(5) Critical Symmetry in Nucleus

    SciTech Connect

    Zhu, L. H.; Wu, X. G.; He, C. Y.; Hao, X.; Wang, L. L.; Zheng, Y.; Li, G. S.

    2010-05-12

    The magnetic and chiral rotation, the critical symmetry are fundamental problems in the study of nuclear structure. Here we report the recent results from the experiments on the magnetic and electric rotations in {sup 106}Ag, the chiral rotation in {sup 130}Cs and the evolution of X(5) symmetry in {sup 176}Os.

  16. Gene microarray data analysis using parallel point-symmetry-based clustering.

    PubMed

    Sarkar, Anasua; Maulik, Ujjwal

    2015-01-01

    Identification of co-expressed genes is the central goal in microarray gene expression analysis. Point-symmetry-based clustering is an important unsupervised learning technique for recognising symmetrical convex- or non-convex-shaped clusters. To enable fast clustering of large microarray data, we propose a distributed time-efficient scalable approach for point-symmetry-based K-Means algorithm. A natural basis for analysing gene expression data using symmetry-based algorithm is to group together genes with similar symmetrical expression patterns. This new parallel implementation also satisfies linear speedup in timing without sacrificing the quality of clustering solution on large microarray data sets. The parallel point-symmetry-based K-Means algorithm is compared with another new parallel symmetry-based K-Means and existing parallel K-Means over eight artificial and benchmark microarray data sets, to demonstrate its superiority, in both timing and validity. The statistical analysis is also performed to establish the significance of this message-passing-interface based point-symmetry K-Means implementation. We also analysed the biological relevance of clustering solutions.

  17. Dynamical Response near Quantum Critical Points

    NASA Astrophysics Data System (ADS)

    Lucas, Andrew; Gazit, Snir; Podolsky, Daniel; Witczak-Krempa, William

    2017-02-01

    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 quantum 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.

  18. Detecting quantum critical points using bipartite fluctuations.

    PubMed

    Rachel, Stephan; Laflorencie, Nicolas; Song, H Francis; Le Hur, Karyn

    2012-03-16

    We show that the concept of bipartite fluctuations F provides a very efficient tool to detect quantum phase transitions in strongly correlated systems. Using state-of-the-art numerical techniques complemented with analytical arguments, we investigate paradigmatic examples for both quantum spins and bosons. As compared to the von Neumann entanglement entropy, we observe that F allows us to find quantum critical points with much better accuracy in one dimension. We further demonstrate that F can be successfully applied to the detection of quantum criticality in higher dimensions with no prior knowledge of the universality class of the transition. Promising approaches to experimentally access fluctuations are discussed for quantum antiferromagnets and cold gases.

  19. Topological crossovers near a quantum critical point

    NASA Astrophysics Data System (ADS)

    Khodel, V. A.; Clark, J. W.; Zverev, M. V.

    2011-09-01

    We study the temperature evolution of the single-particle spectrum ɛ-( p) and quasiparticle momentum distribution n( p) of homogeneous strongly correlated Fermi systems beyond a point where the necessary condition for stability of the Landau state is violated, and the Fermi surface becomes multi-connected by virtue of a topological crossover. Attention is focused on the different non-Fermi-liquid temperature regimes experienced by a phase exhibiting a single additional hole pocket compared with the conventional Landau state. A critical experiment is proposed to elucidate the origin of NFL behavior in dense films of liquid 3He.

  20. RHIC CRITICAL POINT SEARCH: ASSESSING STARs CAPABILITIES.

    SciTech Connect

    SORENSEN,P.

    2006-07-03

    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.

  1. Sensitivity analysis, optimization, and global critical points

    SciTech Connect

    Cacuci, D.G. )

    1989-11-01

    The title of this paper suggests that sensitivity analysis, optimization, and the search for critical points in phase-space are somehow related; the existence of such a kinship has been undoubtedly felt by many of the nuclear engineering practitioners of optimization and/or sensitivity analysis. However, a unified framework for displaying this relationship has so far been lacking, especially in a global setting. The objective of this paper is to present such a global and unified framework and to suggest, within this framework, a new direction for future developments for both sensitivity analysis and optimization of the large nonlinear systems encountered in practical problems.

  2. Turbulent scaling laws as solutions of the multi-point correlation equation using statistical symmetries

    NASA Astrophysics Data System (ADS)

    Oberlack, Martin; Rosteck, Andreas; Avsarkisov, Victor

    2013-11-01

    Text-book knowledge proclaims that Lie symmetries such as Galilean transformation lie at the heart of fluid dynamics. These important properties also carry over to the statistical description of turbulence, i.e. to the Reynolds stress transport equations and its generalization, the multi-point correlation equations (MPCE). Interesting enough, the MPCE admit a much larger set of symmetries, in fact infinite dimensional, subsequently named statistical symmetries. Most important, theses new symmetries have important consequences for our understanding of turbulent scaling laws. The symmetries form the essential foundation to construct exact solutions to the infinite set of MPCE, which in turn are identified as classical and new turbulent scaling laws. Examples on various classical and new shear flow scaling laws including higher order moments will be presented. Even new scaling have been forecasted from these symmetries and in turn validated by DNS. Turbulence modellers have implicitly recognized at least one of the statistical symmetries as this is the basis for the usual log-law which has been employed for calibrating essentially all engineering turbulence models. An obvious conclusion is to generally make turbulence models consistent with the new statistical symmetries.

  3. Warm unstable asymmetric nuclear matter: Critical properties and the density dependence of the symmetry energy

    NASA Astrophysics Data System (ADS)

    Alam, N.; Pais, H.; Providência, C.; Agrawal, B. K.

    2017-05-01

    The spinodal instabilities in hot asymmetric nuclear matter and some important critical parameters derived thereof are studied by using six different families of relativistic mean-field models. The slopes of the symmetry energy coefficient vary over a wide range within each family. The critical densities and proton fractions are more sensitive to the symmetry energy slope parameter at temperatures much below its critical value (Tc˜14 -16 MeV ). The spread in the critical proton fraction at a given symmetry energy slope parameter is noticeably larger near Tc, indicating that the equation of state of warm asymmetric nuclear matter at subsaturation densities is not sufficiently constrained. The distillation effects are sensitive to the density dependence of the symmetry energy at low temperatures which tend to wash out with increasing temperature.

  4. Pseudogap state near a quantum critical point

    NASA Astrophysics Data System (ADS)

    Efetov, K. B.; Meier, H.; Pépin, C.

    2013-07-01

    In the standard picture of a quantum phase transition, a single quantum critical point separates the phases at zero temperature. Here we show that the two-dimensional case is considerably more complex. Instead of the single point separating the antiferromagnet from the normal metal, we have discovered a broad region between these two phases where the magnetic order is destroyed but certain areas of the Fermi surface are closed by a large gap. This gap reflects the formation of a quantum state characterized by a superposition of d-wave superconductivity and a quadrupole density wave, which builds a chequerboard pattern with a period incommensurate with that of the original spin-density wave. At moderate temperatures both orders coexist over comparatively large distances but thermal fluctuations destroy the long-range order. Below a critical temperature the fluctuations are less essential and superconductivity becomes stable. This phenomenon may help to explain the origin of the mysterious pseudogap state and of the high-temperature transition into the superconducting state in the cuprates. In particular, we show that spectroscopic probes on the oxygen and copper sites reveal chequerboard order.

  5. Symmetry Protection of Critical Phases and a Global Anomaly in 1 +1 Dimensions

    NASA Astrophysics Data System (ADS)

    Furuya, Shunsuke C.; Oshikawa, Masaki

    2017-01-01

    We derive a selection rule among the (1 +1 )-dimensional SU(2) Wess-Zumino-Witten theories, based on the global anomaly of the discrete Z2 symmetry found by Gepner and Witten. In the presence of both the SU(2) and Z2 symmetries, a renormalization-group flow is possible between level-k and level-k' Wess-Zumino-Witten theories only if k ≡k' mod 2 . This classifies the Lorentz-invariant, SU(2)-symmetric critical behavior into two "symmetry-protected" categories corresponding to even and odd levels, restricting possible gapless critical behavior of translation-invariant quantum spin chains.

  6. Determining critical points in organizational learning modes

    NASA Astrophysics Data System (ADS)

    Hamner, Marvine P.

    2002-07-01

    It has been postulated that organizations can be categorized into one of three perspectives that represent the mind-set of managers within organizations with respect to their organization and organizational learning. These are the normative, the developmental and the capability perspectives. Each of these reflects variations among organizational features such as the source of organizational learning, the timeframe for organizational learning and the relationship between organizational learning and organizational culture. However, much like the dynamics experienced by teams, i.e. various stages such as forming, norming, storming and performing, organizations can move through various learning stages, i.e. the three 'perspectives,' often stopping and restarting at different points in their cycles. This means that the three perspectives can be simply viewed as different modes of organizational learning. All organizations operate within one of the three perspectives all the time. And, the perspective through which the organization is best viewed at any point in time changes over time. Because organizations are complex, adaptive systems these modes can be mathematically represented using the output from a neural network model of complex, adaptive systems. This paper briefly describes the organizational science, the neural network model, and the mathematics required to determine critical points in these modes.

  7. Dynamics and Thermodynamics beyond the critical point

    PubMed Central

    Gorelli, F. A.; Bryk, T.; Krisch, M.; Ruocco, G.; Santoro, M.; Scopigno, T.

    2013-01-01

    Sudden changes in the dynamical properties of a supercritical fluid model have been found as a function of pressure and temperature (T/Tc = 2–5 and P/Pc = 10–103), striving with the notion of a single phase beyond the critical point established by thermodynamics. The sound propagation in the Terahertz frequency region reveals a sharp dynamic crossover between the gas like and the liquid like regimes along several isotherms, which involves, at sufficiently low densities, the interplay between purely acoustic waves and heat waves. Such a crossover allows one to determine a dynamic line in the phase diagram which exhibits a very tight correlation with a number of thermodynamic observables, showing that the supercritical state is remarkably more complex than thought so far. PMID:23383373

  8. Viscoelasticity of Xenon near the Critical Point

    NASA Technical Reports Server (NTRS)

    Berg, Robert F.; Moldover, Michael R.; Zimmerli, Gregory A.

    1999-01-01

    Using a novel, overdamped, oscillator flown aboard the Space Shuttle, we measured the viscosity of xenon near the liquid-vapor critical point in the frequency range 2 Hz less than or equal to f less than or equal to 12 Hz. The measured viscosity divergence is characterized by the exponent z(sub eta) = 0.0690 +/- 0.0006, in agreement with the value z(sub eta) = 0.067 +/- 0.002 calculated from a two-loop perturbation expansion. Viscoelastic behavior was evident when t = (T - T(sub c))/T(sub c) less than 10(exp -5) and dominant when t less than 10(exp -6), further from T(sub c) than predicted. Viscoelastic behavior scales as Af(tau) where tau is the fluctuation decay time. The measured value of A is 2.0 +/- 0.3 times the result of a one-loop calculation. (Uncertainties stated are one standard uncertainty.)

  9. Lie and Noether point symmetries for a class of nonautonomous dynamical systems

    NASA Astrophysics Data System (ADS)

    Karpathopoulos, Leonidas; Paliathanasis, Andronikos; Tsamparlis, Michael

    2017-08-01

    We prove two general theorems that determine the Lie and the Noether point symmetries for the equations of motion of a dynamical system that moves in a general Riemannian space under the action of a time dependent potential W (t ,x ) =ω (t ) V (x ) . We apply the theorems to the case of a time dependent central potential and the harmonic oscillator and determine all Lie and Noether point symmetries. Finally we prove that these theorems also apply to the case of a dynamical system with linear dumping and study two examples.

  10. Two critical tests for the Critical Point earthquake

    NASA Astrophysics Data System (ADS)

    Tzanis, A.; Vallianatos, F.

    2003-04-01

    It has been credibly argued that the earthquake generation process is a critical phenomenon culminating with a large event that corresponds to some critical point. In this view, a great earthquake represents the end of a cycle on its associated fault network and the beginning of a new one. The dynamic organization of the fault network evolves as the cycle progresses and a great earthquake becomes more probable, thereby rendering possible the prediction of the cycle’s end by monitoring the approach of the fault network toward a critical state. This process may be described by a power-law time-to-failure scaling of the cumulative seismic release rate. Observational evidence has confirmed the power-law scaling in many cases and has empirically determined that the critical exponent in the power law is typically of the order n=0.3. There are also two theoretical predictions for the value of the critical exponent. Ben-Zion and Lyakhovsky (Pure appl. geophys., 159, 2385-2412, 2002) give n=1/3. Rundle et al. (Pure appl. geophys., 157, 2165-2182, 2000) show that the power-law activation associated with a spinodal instability is essentially identical to the power-law acceleration of Benioff strain observed prior to earthquakes; in this case n=0.25. More recently, the CP model has gained support from the development of more dependable models of regional seismicity with realistic fault geometry that show accelerating seismicity before large events. Essentially, these models involve stress transfer to the fault network during the cycle such, that the region of accelerating seismicity will scale with the size of the culminating event, as for instance in Bowman and King (Geophys. Res. Let., 38, 4039-4042, 2001). It is thus possible to understand the observed characteristics of distributed accelerating seismicity in terms of a simple process of increasing tectonic stress in a region already subjected to stress inhomogeneities at all scale lengths. Then, the region of

  11. QCD diffraction: a critical phenomenon reflecting both confinement and chiral-symmetry breaking

    SciTech Connect

    White, A.R.

    1982-07-01

    Arguments are presented for studying soft diffractive physics at anti p-p colliders in terms of Critical Pomeron Reggeon Field Theory. It is emphasized that both confinement and chiral-symmetry breaking play a vital role in the occurrence of the Critical Pomeron in QCD. SU(3) is the unique strong-interaction gauge group giving the Critical Pomeron and the maximum number of quarks allowed by asymptotic freedom is required for criticality.

  12. Realistic quantum critical point in one-dimensional two-impurity models

    NASA Astrophysics Data System (ADS)

    Lechtenberg, Benedikt; Eickhoff, Fabian; Anders, Frithjof B.

    2017-07-01

    We show that the two-impurity Anderson model exhibits an additional quantum critical point at infinitely many specific distances between both impurities for an inversion symmetric one-dimensional dispersion. Unlike the quantum critical point previously established, it is robust against particle-hole or parity symmetry breaking. The quantum critical point separates a spin doublet from a spin singlet ground state and is, therefore, protected. A finite single-particle tunneling t or an applied uniform gate voltage will drive the system across the quantum critical point. The discriminative magnetic properties of the different phases cause a jump in the spectral functions at low temperature, which might be useful for future spintronics devices. A local parity conservation will prevent the spin-spin correlation function from decaying to its equilibrium value after spin manipulations.

  13. Symmetry and asymmetry of ionospheric weather at magnetic conjugate points for two midlatitude observatories

    NASA Astrophysics Data System (ADS)

    Gulyaeva, T. L.; Arikan, F.; Stanislawska, I.; Poustovalova, L. V.

    2013-11-01

    Variations of the ionospheric weather W-index for two midlatitude observatories, namely, Grahamstown and Hermanus, and their conjugate counterpart locations in Africa are studied for a period from October 2010 to December 2011. The observatories are located in the longitude sector, which has consistent magnetic equator and geographic equator so that geomagnetic latitudes of the line of force are very close to the corresponding geographic latitudes providing opportunity to ignore the impact of the difference of the gravitational field and the geomagnetic field at the conjugate points on the ionosphere structure and dynamics. The ionosondes of Grahamstown and Hermanus provide data of the critical frequency (foF2), and Global Ionospheric Maps (GIM) provide the total electron content (TECgps) along the magnetic field line up to the conjugate point in the opposite hemisphere. The global model of the ionosphere, International Reference Ionosphere, extended to the plasmasphere altitude of 20,200 km (IRI-Plas) is used to deliver the F2 layer peak parameters from TECgps at the magnetic conjugate area. The evidence is obtained that the electron gas heated by day and cooled by night at the summer hemisphere as compared with the opposite features in the conjugate winter hemisphere testifies on a reversal of plasma fluxes along the magnetic field line by the solar terminator. The ionospheric weather W-index is derived from NmF2 (related with foF2) and TECgps data. It is found that symmetry of W-index behavior in the magnetic conjugate hemispheres is dominant for the equinoxes when plasma movement along the magnetic line of force is imposed on symmetrical background electron density and electron content. Asymmetry of the ionospheric storm effects is observed for solstices when the plasma diffuse down more slowly into the colder winter hemisphere than into the warmer summer hemisphere inducing either plasma increase (positive phase) or decrease (negative phase of W-index) in the

  14. Conductivity of metal vapors at the critical point

    SciTech Connect

    Khomkin, A. L. Shumikhin, A. S.

    2016-11-15

    The conductivity of metal vapors at the critical point and near it has been considered. The liquid-metal conductivity originates in this region. The thermodynamic parameters of the critical point, the density of conduction electrons, and the conductivities of various metal vapors have been calculated within the unified approach. It has been proposed to consider the conductivity at the critical point—critical conductivity—as the fourth critical parameter in addition to the density, temperature, and pressure.

  15. Confidence intervals for the symmetry point: an optimal cutpoint in continuous diagnostic tests.

    PubMed

    López-Ratón, Mónica; Cadarso-Suárez, Carmen; Molanes-López, Elisa M; Letón, Emilio

    2016-01-01

    Continuous diagnostic tests are often used for discriminating between healthy and diseased populations. For this reason, it is useful to select an appropriate discrimination threshold. There are several optimality criteria: the North-West corner, the Youden index, the concordance probability and the symmetry point, among others. In this paper, we focus on the symmetry point that maximizes simultaneously the two types of correct classifications. We construct confidence intervals for this optimal cutpoint and its associated specificity and sensitivity indexes using two approaches: one based on the generalized pivotal quantity and the other on empirical likelihood. We perform a simulation study to check the practical behaviour of both methods and illustrate their use by means of three real biomedical datasets on melanoma, prostate cancer and coronary artery disease. Copyright © 2016 John Wiley & Sons, Ltd.

  16. Teaching Molecular Symmetry of Dihedral Point Groups by Drawing Useful 2D Projections

    ERIC Educational Resources Information Center

    Chen, Lan; Sun, Hongwei; Lai, Chengming

    2015-01-01

    There are two main difficulties in studying molecular symmetry of dihedral point groups. One is locating the C[subscript 2] axes perpendicular to the C[subscript n] axis, while the other is finding the s[subscript]d planes which pass through the C[subscript n] axis and bisect the angles formed by adjacent C[subscript 2] axes. In this paper, a…

  17. Teaching Molecular Symmetry of Dihedral Point Groups by Drawing Useful 2D Projections

    ERIC Educational Resources Information Center

    Chen, Lan; Sun, Hongwei; Lai, Chengming

    2015-01-01

    There are two main difficulties in studying molecular symmetry of dihedral point groups. One is locating the C[subscript 2] axes perpendicular to the C[subscript n] axis, while the other is finding the s[subscript]d planes which pass through the C[subscript n] axis and bisect the angles formed by adjacent C[subscript 2] axes. In this paper, a…

  18. Variance-reduced estimator of the connected two-point function in the presence of a broken Z(2)-symmetry.

    PubMed

    Hasenbusch, Martin

    2016-03-01

    The exchange or geometric cluster algorithm allows us to define a variance-reduced estimator of the connected two-point function in the presence of a broken Z(2)-symmetry. We present numerical tests for the improved Blume-Capel model on the simple-cubic lattice. We perform simulations for the critical isotherm, the low-temperature phase at vanishing external field, and, for comparison, also the high-temperature phase. For the connected two-point function, a substantial reduction of the variance can be obtained, allowing us to compute the correlation length ξ with high precision. Based on these results, estimates for various universal amplitude ratios that characterize the universality class of the three-dimensional Ising model are computed.

  19. Validation of acid washes as critical control points in hazard analysis and critical control point systems.

    PubMed

    Dormedy, E S; Brashears, M M; Cutter, C N; Burson, D E

    2000-12-01

    A 2% lactic acid wash used in a large meat-processing facility was validated as an effective critical control point (CCP) in a hazard analysis and critical control point (HACCP) plan. We examined the microbial profiles of beef carcasses before the acid wash, beef carcasses immediately after the acid wash, beef carcasses 24 h after the acid wash, beef subprimal cuts from the acid-washed carcasses, and on ground beef made from acid-washed carcasses. Total mesophilic, psychrotrophic, coliforms, generic Escherichia coli, lactic acid bacteria, pseudomonads, and acid-tolerant microorganisms were enumerated on all samples. The presence of Salmonella spp. was also determined. Acid washing significantly reduced all counts except for pseudomonads that were present at very low numbers before acid washing. All other counts continued to stay significantly lower (P < 0.05) than those on pre-acid-washed carcasses throughout all processing steps. Total bacteria, coliforms, and generic E. coli enumerated on ground beef samples were more than 1 log cycle lower than those reported in the U.S. Department of Agriculture Baseline data. This study suggests that acid washes may be effective CCPs in HACCP plans and can significantly reduce the total number of microorganisms present on the carcass and during further processing.

  20. Assisted finite-rate adiabatic passage across a quantum critical point: exact solution for the quantum Ising model.

    PubMed

    del Campo, Adolfo; Rams, Marek M; Zurek, Wojciech H

    2012-09-14

    The dynamics of a quantum phase transition is inextricably woven with the formation of excitations, as a result of critical slowing down in the neighborhood of the critical point. We design a transitionless quantum driving through a quantum critical point, allowing one to access the ground state of the broken-symmetry phase by a finite-rate quench of the control parameter. The method is illustrated in the one-dimensional quantum Ising model in a transverse field. Driving through the critical point is assisted by an auxiliary Hamiltonian, for which the interplay between the range of the interaction and the modes where excitations are suppressed is elucidated.

  1. Critical point wetting drop tower experiment

    NASA Technical Reports Server (NTRS)

    Kaukler, William F.

    1990-01-01

    The 100 m Drop Tower at NASA-Marshall was used to provide the step change in acceleration from 1.0 to 0.0005 g. An inter-fluid meniscus oscillates vertically within a cylindrical container when suddenly released from earth's gravity and taken into a microgravity environment. Oscillations damp out from energy dissipative mechanisms such as viscosity and interfacial friction. Damping of the oscillations by the later mechanism is affected by the nature of the interfacial junction between the fluid-fluid interface and the container wall. In earlier stages of the project, the meniscus shape which developed during microgravity conditions was applied to evaluations of wetting phenomena near the critical temperature. Variations in equilibrium contact angle against the container wall were expected to occur under critical wetting conditions. However, it became apparent that the meaningful phenomenon was the damping of interfacial oscillations. This latter concept makes up the bulk of this report. Perfluoromethyl cyclohexane and isopropanol in glass were the materials used for the experiment. The wetting condition of the fluids against the wall changes at the critical wetting transition temperature. This change in wetting causes a change in the damping characteristics of the interfacial excursions during oscillation and no measurable change in contact angle. The effect of contact line friction measured above and below the wetting transition temperature was to increase the period of vertical oscillation for the vapor-liquid interface when below the wetting transition temperature.

  2. Critical point wetting drop tower experiment

    NASA Technical Reports Server (NTRS)

    Kaulker, William F.

    1988-01-01

    Experiments with the wetting behavior of immiscible fluids against the container below the critical temperature are being performed in the MSFC Drop Tower Facility. Microgravity conditions extending up to three seconds (of the 4.5 second drop) are generated for the experiment. Specimens consist of glass cylindrical ampoules partially filled with fluid phases. How the fluids develop the meniscus geometry as well as hot the fluid interfaces respond to the microgravity induced oscillations is recorded during the experiment with on-board cameras. Drops are made at various temperatures to determine the interfacial energy variation as a function of temperature.

  3. Singularity of the London Penetration Depth at Quantum Critical Points in Superconductors

    NASA Astrophysics Data System (ADS)

    Chowdhury, Debanjan; Swingle, Brian; Berg, Erez; Sachdev, Subir

    2013-10-01

    We present a general theory of the singularity in the London penetration depth at symmetry-breaking and topological quantum critical points within a superconducting phase. While the critical exponents and ratios of amplitudes on the two sides of the transition are universal, an overall sign depends upon the interplay between the critical theory and the underlying Fermi surface. We determine these features for critical points to spin density wave and nematic ordering, and for a topological transition between a superconductor with Z2 fractionalization and a conventional superconductor. We note implications for recent measurements of the London penetration depth in BaFe2(As1-xPx)2 [K. Hashimoto , Science 336, 1554 (2012)SCIEAS0036-807510.1126/science.1219821].

  4. Singularity of the London penetration depth at quantum critical points in superconductors.

    PubMed

    Chowdhury, Debanjan; Swingle, Brian; Berg, Erez; Sachdev, Subir

    2013-10-11

    We present a general theory of the singularity in the London penetration depth at symmetry-breaking and topological quantum critical points within a superconducting phase. While the critical exponents and ratios of amplitudes on the two sides of the transition are universal, an overall sign depends upon the interplay between the critical theory and the underlying Fermi surface. We determine these features for critical points to spin density wave and nematic ordering, and for a topological transition between a superconductor with Z2 fractionalization and a conventional superconductor. We note implications for recent measurements of the London penetration depth in BaFe2(As(1-x)P(x))2 [K. Hashimoto et al., Science 336, 1554 (2012)].

  5. Pole distribution of PVI transcendents close to a critical point

    NASA Astrophysics Data System (ADS)

    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.

  6. Emergence of a Fermionic Finite-Temperature Critical Point in a Kondo Lattice.

    PubMed

    Chou, Po-Hao; Zhai, Liang-Jun; Chung, Chung-Hou; Mou, Chung-Yu; Lee, Ting-Kuo

    2016-04-29

    The underlying Dirac point is central to the profound physics manifested in a wide class of materials. However, it is often difficult to drive a system with Dirac points across the massless fermionic critical point. Here by exploiting screening of local moments under spin-orbit interactions in a Kondo lattice, we show that below the Kondo temperature, the Kondo lattice undergoes a topological transition from a strong topological insulator to a weak topological insulator at a finite temperature T_{D}. At T_{D}, massless Dirac points emerge and the Kondo lattice becomes a Dirac semimetal. Our analysis indicates that the emergent relativistic symmetry dictates nontrivial thermal responses over large parameter and temperature regimes. In particular, it yields critical scaling behaviors both in magnetic and transport responses near T_{D}.

  7. Universal Postquench Prethermalization at a Quantum Critical Point.

    PubMed

    Gagel, Pia; Orth, Peter P; Schmalian, Jörg

    2014-11-28

    We consider an open system near a quantum critical point that is suddenly moved towards the critical point. The bath-dominated diffusive nonequilibrium dynamics after the quench is shown to follow scaling behavior, governed by a critical exponent that emerges in addition to the known equilibrium critical exponents. We determine this exponent and show that it describes universal prethermalized coarsening dynamics of the order parameter in an intermediate time regime. Implications of this quantum critical prethermalization are: (i) a power law rise of order and correlations after an initial collapse of the equilibrium state and (ii) a crossover to thermalization that occurs arbitrarily late for sufficiently shallow quenches.

  8. Direct Observation of Critical Point Wetting in Microgravity

    NASA Technical Reports Server (NTRS)

    Kaukler, W. F.

    1985-01-01

    The objective of this program is to observe the interface shape in single and multicomponent systems at the onset of critical wetting in microgravity using the MSFC drop tower and KC-135 aircraft. Test cells for the drop facility were built and tested up to critical point of CCl. Low temperature drops were conducted for two-component systems near the critical consolute point. Contact angle seems to approach 90 deg near the critical consolute temperature contrary to expectations. It is suspected that since the interfacial energy becomes vanishingly small at the critical consolute temperature, the interface shape has not reached equilibrium in the available low-gravity time.

  9. Multiple energy scales at a quantum critical point.

    PubMed

    Gegenwart, P; Westerkamp, T; Krellner, C; Tokiwa, Y; Paschen, S; Geibel, C; Steglich, F; Abrahams, E; Si, Q

    2007-02-16

    We report thermodynamic measurements in a magnetic-field-driven quantum critical point of a heavy fermion metal, YbRh2Si2. The data provide evidence for an energy scale in the equilibrium excitation spectrum that is in addition to the one expected from the slow fluctuations of the order parameter. Both energy scales approach zero as the quantum critical point is reached, thereby providing evidence for a new class of quantum criticality.

  10. Exceptional points of degeneracy and P T symmetry in photonic coupled chains of scatterers

    NASA Astrophysics Data System (ADS)

    Othman, Mohamed A. K.; Galdi, Vincenzo; Capolino, Filippo

    2017-03-01

    We demonstrate the existence of exceptional points of degeneracy (EPDs) of periodic eigenstates in non-Hermitian coupled chains of dipolar scatterers. Guided modes supported by these structures can exhibit an EPD in their dispersion diagram at which two or more Bloch eigenstates coalesce, in both their eigenvectors and eigenvalues. We show the emergence of a second-order modal EPD associated with the parity-time (P T ) symmetry condition, at which each particle pair in the double chain exhibits balanced gain and loss. Furthermore, we also demonstrate a fourth-order EPD occurring at the band edge. Such a degeneracy condition was previously referred to as a degenerate band edge in lossless anisotropic photonic crystals. Here, we rigorously show it under the occurrence of gain and loss balance for a discrete guiding system. We identify a more general regime of gain and loss balance showing that P T symmetry is not necessary to attain EPDs. Moreover, we investigate the degree of detuning of the EPD when the geometrical symmetry or balanced condition is broken. Furthermore, we demonstrate a realistic implementation of the EPD in a coupled chain made of pairs of plasmonic nanospheres and active core-shell nanospheres at optical frequencies. These findings open avenues toward superior light localization and transport with application to high-Q resonators utilized in sensors, filters, low-threshold switching and lasing.

  11. Scaling of the magnetic Grüneisen ratio near quantum critical point

    NASA Astrophysics Data System (ADS)

    Tokiwa, Yoshi

    2014-03-01

    The magnetic Grüneisen ratio ΓH = (1/T)dT/dH is the most sensitive probe of quantum criticality. Its divergence signals the underlying instability. We have studied quantum criticality in the frustrated Kondo lattice system YbAgGe and the heavy fermion superconductor CeCoIn5 by high-precision magnetocaloric effect measurements. In the former, NFL behavior appears around a metamagnetic spin-flop transition between two symmetry broken phases. Previously, it was unclear how the two ordered phases are related to the NFL state. Here, we propose a novel quantum bicritical point (QBCP) scenario, which is distinct from either quantum critical end point or ordinary QCPs with single symmetry broken phase. The observed scaling behavior of ΓH and its characteristic asymmetry across the critical field are consistent with a QBCP scenario. We also report a possible violation of Wiedemann-Franz law at the QBCP in YbAgGe. In CeCoIn5 indications of a quantum critical field hidden inside the superconducting (SC) phase have been extensively debated. We show ΓH data and scaling analysis in the normal state, which surprisingly suggests a zero-field QCP. Anomalous behaviors of ΓH and specific heat within the SC state further support this conclusion.

  12. Non-Gaussian fluctuations near the QCD critical point.

    PubMed

    Stephanov, M A

    2009-01-23

    We study the effect of the QCD critical point on non-Gaussian moments (cumulants) of fluctuations of experimental observables in heavy-ion collisions. We find that these moments are very sensitive to the proximity of the critical point, as measured by the magnitude of the correlation length xi. For example, the cubic central moment of multiplicity (deltaN)3 approximately xi4.5 and the quartic cumulant (deltaN)4c approximately xi7. We estimate the magnitude of critical point contributions to non-Gaussian fluctuations of pion and proton multiplicities.

  13. Order parameter fluctuations at a buried quantum critical point

    PubMed Central

    Feng, Yejun; Wang, Jiyang; Jaramillo, R.; van Wezel, Jasper; Haravifard, S.; Srajer, G.; Liu, Y.; Xu, Z.-A.; Littlewood, P. B.; Rosenbaum, T. F.

    2012-01-01

    Quantum criticality is a central concept in condensed matter physics, but the direct observation of quantum critical fluctuations has remained elusive. Here we present an X-ray diffraction study of the charge density wave (CDW) in 2H-NbSe2 at high pressure and low temperature, where we observe a broad regime of order parameter fluctuations that are controlled by proximity to a quantum critical point. X-rays can track the CDW despite the fact that the quantum critical regime is shrouded inside a superconducting phase; and in contrast to transport probes, allow direct measurement of the critical fluctuations of the charge order. Concurrent measurements of the crystal lattice point to a critical transition that is continuous in nature. Our results confirm the long-standing expectations of enhanced quantum fluctuations in low-dimensional systems, and may help to constrain theories of the quantum critical Fermi surface. PMID:22529348

  14. Order parameter fluctuations at a buried quantum critical point.

    PubMed

    Feng, Yejun; Wang, Jiyang; Jaramillo, R; van Wezel, Jasper; Haravifard, S; Srajer, G; Liu, Y; Xu, Z-A; Littlewood, P B; Rosenbaum, T F

    2012-05-08

    Quantum criticality is a central concept in condensed matter physics, but the direct observation of quantum critical fluctuations has remained elusive. Here we present an X-ray diffraction study of the charge density wave (CDW) in 2H-NbSe(2) at high pressure and low temperature, where we observe a broad regime of order parameter fluctuations that are controlled by proximity to a quantum critical point. X-rays can track the CDW despite the fact that the quantum critical regime is shrouded inside a superconducting phase; and in contrast to transport probes, allow direct measurement of the critical fluctuations of the charge order. Concurrent measurements of the crystal lattice point to a critical transition that is continuous in nature. Our results confirm the long-standing expectations of enhanced quantum fluctuations in low-dimensional systems, and may help to constrain theories of the quantum critical Fermi surface.

  15. Lie and Noether point symmetries of a class of quasilinear systems of second-order differential equations

    NASA Astrophysics Data System (ADS)

    Paliathanasis, Andronikos; Tsamparlis, Michael

    2016-09-01

    We study the Lie and Noether point symmetries of a class of systems of second-order differential equations with n independent and m dependent variables (n × m systems). We solve the symmetry conditions in a geometric way and determine the general form of the symmetry vector and of the Noetherian conservation laws. We prove that the point symmetries are generated by the collineations of two (pseudo)metrics, which are defined in the spaces of independent and dependent variables. We demonstrate the general results in two special cases (a) a system of m coupled Laplace equations and (b) the Klein-Gordon equation of a particle in the context of Generalized Uncertainty Principle. In the second case we determine the complete invariant group of point transformations, and we apply the Lie invariants in order to find invariant solutions of the wave function for a spin-0 particle in the two dimensional hyperbolic space.

  16. Cubic Polynomials with Rational Roots and Critical Points

    ERIC Educational Resources Information Center

    Gupta, Shiv K.; Szymanski, Waclaw

    2010-01-01

    If you want your students to graph a cubic polynomial, it is best to give them one with rational roots and critical points. In this paper, we describe completely all such cubics and explain how to generate them.

  17. Cubic Polynomials with Rational Roots and Critical Points

    ERIC Educational Resources Information Center

    Gupta, Shiv K.; Szymanski, Waclaw

    2010-01-01

    If you want your students to graph a cubic polynomial, it is best to give them one with rational roots and critical points. In this paper, we describe completely all such cubics and explain how to generate them.

  18. Electronic in-plane symmetry breaking at field-tuned quantum criticality in CeRhIn5.

    PubMed

    Ronning, F; Helm, T; Shirer, K R; Bachmann, M D; Balicas, L; Chan, M K; Ramshaw, B J; McDonald, R D; Balakirev, F F; Jaime, M; Bauer, E D; Moll, P J W

    2017-08-17

    Electronic nematic materials are characterized by a lowered symmetry of the electronic system compared to the underlying lattice, in analogy to the directional alignment without translational order in nematic liquid crystals. Such nematic phases appear in the copper- and iron-based high-temperature superconductors, and their role in establishing superconductivity remains an open question. Nematicity may take an active part, cooperating or competing with superconductivity, or may appear accidentally in such systems. Here we present experimental evidence for a phase of fluctuating nematic character in a heavy-fermion superconductor, CeRhIn5 (ref. 5). We observe a magnetic-field-induced state in the vicinity of a field-tuned antiferromagnetic quantum critical point at Hc ≈ 50 tesla. This phase appears above an out-of-plane critical field H* ≈ 28 tesla and is characterized by a substantial in-plane resistivity anisotropy in the presence of a small in-plane field component. The in-plane symmetry breaking has little apparent connection to the underlying lattice, as evidenced by the small magnitude of the magnetostriction anomaly at H*. Furthermore, no anomalies appear in the magnetic torque, suggesting the absence of metamagnetism in this field range. The appearance of nematic behaviour in a prototypical heavy-fermion superconductor highlights the interrelation of nematicity and unconventional superconductivity, suggesting nematicity to be common among correlated materials.

  19. Electronic in-plane symmetry breaking at field-tuned quantum criticality in CeRhIn5

    NASA Astrophysics Data System (ADS)

    Ronning, F.; Helm, T.; Shirer, K. R.; Bachmann, M. D.; Balicas, L.; Chan, M. K.; Ramshaw, B. J.; McDonald, R. D.; Balakirev, F. F.; Jaime, M.; Bauer, E. D.; Moll, P. J. W.

    2017-08-01

    Electronic nematic materials are characterized by a lowered symmetry of the electronic system compared to the underlying lattice, in analogy to the directional alignment without translational order in nematic liquid crystals. Such nematic phases appear in the copper- and iron-based high-temperature superconductors, and their role in establishing superconductivity remains an open question. Nematicity may take an active part, cooperating or competing with superconductivity, or may appear accidentally in such systems. Here we present experimental evidence for a phase of fluctuating nematic character in a heavy-fermion superconductor, CeRhIn5 (ref. 5). We observe a magnetic-field-induced state in the vicinity of a field-tuned antiferromagnetic quantum critical point at Hc ≈ 50 tesla. This phase appears above an out-of-plane critical field H* ≈ 28 tesla and is characterized by a substantial in-plane resistivity anisotropy in the presence of a small in-plane field component. The in-plane symmetry breaking has little apparent connection to the underlying lattice, as evidenced by the small magnitude of the magnetostriction anomaly at H*. Furthermore, no anomalies appear in the magnetic torque, suggesting the absence of metamagnetism in this field range. The appearance of nematic behaviour in a prototypical heavy-fermion superconductor highlights the interrelation of nematicity and unconventional superconductivity, suggesting nematicity to be common among correlated materials.

  20. Binary Colloidal Alloy Test-3 and 4: Critical Point

    NASA Technical Reports Server (NTRS)

    Weitz, David A.; Lu, Peter J.

    2007-01-01

    Binary Colloidal Alloy Test - 3 and 4: Critical Point (BCAT-3-4-CP) will determine phase separation rates and add needed points to the phase diagram of a model critical fluid system. Crewmembers photograph samples of polymer and colloidal particles (tiny nanoscale spheres suspended in liquid) that model liquid/gas phase changes. Results will help scientists develop fundamental physics concepts previously cloaked by the effects of gravity.

  1. Inherently unstable networks collapse to a critical point.

    PubMed

    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.

  2. Critical temperature of chiral symmetry restoration for quark matter with a chiral chemical potential

    NASA Astrophysics Data System (ADS)

    Ruggieri, M.; Peng, G. X.

    2016-12-01

    In this article we study the restoration of chiral symmetry at a finite temperature for quark matter with a chiral chemical potential, {μ }5, by means of a nonlocal Nambu-Jona-Lasinio model. This model allows the introduction of, in the simplest way possible, a Euclidean momentum, p E , dependent quark mass function which decays (neglecting logarithms) as 1/{p}{E}2 for large p E , in agreement with the asymptotic behaviour expected in quantum chromodynamics in the presence of a nonperturbative quark condensate. We focus on the critical temperature for chiral symmetry restoration in the chiral limit, T c, versus {μ }5, as well as on the order of the phase transition. We find that T c increases with {μ }5, and that the transition remains of the second order for the whole range of {μ }5 considered.

  3. Implementation of hazard analysis critical control point in jameed production.

    PubMed

    Al-Saed, A K; Al-Groum, R M; Al-Dabbas, M M

    2012-06-01

    The average of standard plate count and coliforms, Staphylococcus aureus and Salmonella counts for three home-made jameed samples, a traditional fermented dairy product, before applying hazard analysis critical control point system were 2.1 × 10(3), 8.9 × 10(1), 4 × 10(1) and less than 10 cfu/g, respectively. The developed hazard analysis critical control point plan resulted in identifying ten critical control points in the flow chart of jameed production. The critical control points included fresh milk receiving, pasteurization, addition of starter, water and salt, straining, personnel hygiene, drying and packaging. After applying hazard analysis critical control point system, there was significant improvement in the microbiological quality of the home-made jameed. The standard plate count was reduced to 3.1 × 10(2) cfu/g whereas coliform and Staphylococcus aureus counts were less than 10 cfu/g and Salmonella was not detected. Sensory evaluation results of color and flavor of sauce prepared from jameed showed a significant increase in the average scores given after hazard analysis critical control point application.

  4. Fingerprints of a Bosonic Symmetry-Protected Topological State in a Quantum Point Contact

    NASA Astrophysics Data System (ADS)

    Zhang, Rui-Xing; Liu, Chao-Xing

    2017-05-01

    In this work, we study the transport through a quantum point contact for bosonic helical liquid that exists at the edge of a bilayer graphene under a strong magnetic field. We identify "smoking gun" transport signatures to distinguish a bosonic symmetry-protected topological (BSPT) state from a fermionic two-channel quantum spin Hall (QSH) state in this system. In particular, a novel charge-insulator-spin-conductor phase is found for the BSPT state, while either the charge-insulator-spin-insulator or the charge-conductor-spin-conductor phase is expected for the two-channel QSH state. Consequently, a simple transport measurement will reveal the fingerprint of bosonic topological physics in bilayer graphene systems.

  5. Critical bifurcation point of the openZ(5)-symmetric spin model

    NASA Astrophysics Data System (ADS)

    Bonnier, B.

    1991-07-01

    The critical behavior of the general isotropic, ferromagnetic two-dimensional spin system with openZ(5) symmetry is studied with use of high-temperature expansions of its mass gap. On the basis of these expansions we propose a simple analytic representation of the mass gap which naturally reproduces all the different phase transitions exhibited by this model (first order and second order of the Ising and of the Kosterlitz-Thouless types). In addition, the bifurcation point where the soft phases originate is clearly identified with the Fateev-Zamolodchikov value.

  6. Existence of a line of critical points in a two-dimensional Lebwohl Lasher model

    NASA Astrophysics Data System (ADS)

    Shabnam, Sabana; DasGupta, Sudeshna; Roy, Soumen Kumar

    2016-02-01

    Controversy regarding transitions in systems with global symmetry group O(3) has attracted the attention of researchers and the detailed nature of this transition is still not well understood. As an example of such a system in this paper we have studied a two-dimensional Lebwohl Lasher model, using the Wolff cluster algorithm. Though we have not been able to reach any definitive conclusions regarding the order present in the system, from finite size scaling analysis, hyperscaling relations and the behavior of the correlation function we have obtained strong indications regarding the presence of quasi-long range order and the existence of a line of critical points in our system.

  7. Finite-Temperature Spin Dynamics in a Perturbed Quantum Critical Ising Chain with an E8 Symmetry

    NASA Astrophysics Data System (ADS)

    Wu, Jianda; Kormos, Márton; Si, Qimiao

    2014-12-01

    A spectrum exhibiting E8 symmetry is expected to arise when a small longitudinal field is introduced in the transverse-field Ising chain at its quantum critical point. Evidence for this spectrum has recently come from neutron scattering measurements in cobalt niobate, a quasi-one-dimensional Ising ferromagnet. Unlike its zero-temperature counterpart, the finite-temperature dynamics of the model has not yet been determined. We study the dynamical spin structure factor of the model at low frequencies and nonzero temperatures, using the form factor method. Its frequency dependence is singular, but differs from the diffusion form. The temperature dependence of the nuclear magnetic resonance (NMR) relaxation rate has an activated form, whose prefactor we also determine. We propose NMR experiments as a means to further test the applicability of the E8 description for CoNb2O6 .

  8. Critical Care Glucose Point-of-Care Testing.

    PubMed

    Narla, S N; Jones, M; Hermayer, K L; Zhu, Y

    Maintaining blood glucose concentration within an acceptable range is a goal for patients with diabetes mellitus. Point-of-care glucose meters initially designed for home self-monitoring in patients with diabetes have been widely used in the hospital settings because of ease of use and quick reporting of blood glucose information. They are not only utilized for the general inpatient population but also for critically ill patients. Many factors affect the accuracy of point-of-care glucose testing, particularly in critical care settings. Inaccurate blood glucose information can result in unsafe insulin delivery which causes poor glucose control and can be fatal. Healthcare professionals should be aware of the limitations of point-of-care glucose testing. This chapter will first introduce glucose regulation in diabetes mellitus, hyperglycemia/hypoglycemia in the intensive care unit, importance of glucose control in critical care patients, and pathophysiological variables of critically ill patients that affect the accuracy of point-of-care glucose testing. Then, we will discuss currently available point-of-care glucose meters and preanalytical, analytical, and postanalytical sources of variation and error in point-of-care glucose testing.

  9. Liquid-liquid critical point: an analytical approach

    NASA Astrophysics Data System (ADS)

    Daanoun, A.

    2006-09-01

    Theoretical simulations and experimental studies have showed that many systems (like liquid metals) can exhibit two phase transitions: gas-liquid and liquid-liquid. Consequently the fluid phase of these systems presents two critical points, namely the usual gas-liquid (G-L) critical point and the liquid-liquid critical point that results from a phase transition between two liquids of different densities: a low density liquid (LDL) and a high density liquid (HDL). The van der Waals theory for simple fluids [Phys. Rev. E 50, 2913 (1994)] is based on taking a system with purely repulsive forces as a reference, is able to describe two stable first-order phase transitions between fluids of different densities. The particles in our system interact via a total pair potential, which splits into a repulsive VR and a density-dependent attractive VA part.

  10. QCD critical point sweep during black hole formation

    SciTech Connect

    Ohnishi, A.; Ueda, H.; Nakano, T. Z.; Ruggieri, M.; Sumiyoshi, K.

    2012-11-12

    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{approx} 90MeV and {mu}{sub B}{approx} 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 {nu} radiation hydrodynamical calculation of the gravitational collapse of a 40M{sub Circled-Dot-Operator} 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.

  11. Odd-Parity Superconductivity and the Ferromagnetic Quantum Critical Point

    NASA Astrophysics Data System (ADS)

    Huxley, A. D.; Yates, S. J. C.; Lévy, F.; Sheikin, I.

    2007-05-01

    The study of the emergence of superconductivity close to quantum critical points affords a powerful means to identify the mechanism that drives the formation of unconventional superconductivity in heavy fermion materials. The recent discovery of superconducting states close to quantum critical points in ferromagnets UGe2 and URhGe is reviewed in this light. For URhGe we examine whether the predominant type of magnetic excitations involved are longitudinal excitations, hitherto considered theoretically to be the most promising candidate to mediate equal-spin-paired superconductivity.

  12. Higgs amplitude mode in a two-dimensional quantum antiferromagnet near the quantum critical point

    NASA Astrophysics Data System (ADS)

    Hong, Tao; Matsumoto, Masashige; Qiu, Yiming; Chen, Wangchun; Gentile, Thomas R.; Watson, Shannon; Awwadi, Firas F.; Turnbull, Mark M.; Dissanayake, Sachith E.; Agrawal, Harish; Toft-Petersen, Rasmus; Klemke, Bastian; Coester, Kris; Schmidt, Kai P.; Tennant, David A.

    2017-07-01

    Spontaneous symmetry-breaking quantum phase transitions play an essential role in condensed-matter physics. The collective excitations in the broken-symmetry phase near the quantum critical point can be characterized by fluctuations of phase and amplitude of the order parameter. The phase oscillations correspond to the massless Nambu-Goldstone modes whereas the massive amplitude mode, analogous to the Higgs boson in particle physics, is prone to decay into a pair of low-energy Nambu-Goldstone modes in low dimensions. Especially, observation of a Higgs amplitude mode in two dimensions is an outstanding experimental challenge. Here, using inelastic neutron scattering and applying the bond-operator theory, we directly and unambiguously identify the Higgs amplitude mode in a two-dimensional S = 1/2 quantum antiferromagnet C9H18N2CuBr4 near a quantum critical point in two dimensions. Owing to an anisotropic energy gap, it kinematically prevents such decay and the Higgs amplitude mode acquires an infinite lifetime.

  13. The search for an E(5) critical-point nucleus among the stable xenon isotopes

    NASA Astrophysics Data System (ADS)

    Peters, E. E.; Ross, T. J.; Chakraborty, A.; Crider, B. P.; Kumar, A.; Prados-Estévez, F. M.; Ashley, S. F.; McEllistrem, M. T.; Yates, S. W.

    2015-10-01

    A critical-point has been proposed to exist within the shape/phase transition of the U(5), spherical, and O(6), γ-soft rotor, limits of the IBM. The xenon isotopes exhibit such a transition and have, therefore, been proposed as a chain in which to search for the E(5) critical-point symmetry. The candidacy for an E(5) nucleus has been largely based on the decays of the excited 0+ states, which for some of the xenon isotopes were not yet known. Inelastic neutron scattering measurements at the University of Kentucky Accelerator Laboratory have been performed using highly enriched (>99.9%) 130Xe, 132Xe, 134Xe and 136Xe gases converted to solid xenon difluorides. From these measurements, new excited 0+ states and their decays were identified, level lifetimes were measured, and transition probabilities were determined. This new information allows definitive conclusions to be drawn about the occurrence of the E(5) symmetry within the stable xenon isotopes. This material is based upon work supported by the U.S. National Science Foundation under Grant No. PHY-1305801.

  14. Natural orbitals renormalization group approach to the two-impurity Kondo critical point

    NASA Astrophysics Data System (ADS)

    He, Rong-Qiang; Dai, Jianhui; Lu, Zhong-Yi

    2015-04-01

    The problem of two magnetic impurities in a normal metal exposes the two opposite tendencies in the formation of a singlet ground state, driven respectively by the single-ion Kondo effect with conduction electrons to screen impurity spins or the Ruderman-Kittel-Kasuya-Yosida interaction between the two impurities to directly form impurity spin singlet. However, whether the competition between these two tendencies can lead to a quantum critical point has been debated over more than two decades. Here, we study this problem by applying the newly proposed natural orbitals renormalization group method to a lattice version of the two-impurity Kondo model with a direct exchange K between the two impurity spins. The method allows for unbiased access to the ground state wave functions and low-lying excitations for sufficiently large system sizes. We demonstrate the existence of a quantum critical point, characterized by the power-law divergence of impurity staggered susceptibility with critical exponent γ =0.60 (1 ) , on the antiferromagnetic side of K when the interimpurity distance R is even lattice spacing, while a crossover behavior is recovered when R is odd lattice spacing. These results have ultimately resolved the long-standing discrepancy between the numerical renormalization group and quantum Monte Carlo studies, confirming a link of this two-impurity Kondo critical point to a hidden particle-hole symmetry predicted by the local Fermi liquid theory.

  15. A critical evaluation of Quintner et al: missing the point.

    PubMed

    Dommerholt, Jan; Gerwin, Robert D

    2015-04-01

    The objective of this article is to critically analyze a recent publication by Quinter, Bove and Cohen, published in Rheumatology, about myofascial pain syndrome and trigger points (Quintner et al., 2014). The authors concluded that the leading trigger point hypothesis is flawed in reasoning and in science. They claimed to have refuted the trigger point hypothesis. The current paper demonstrates that the Quintner et al. paper is a biased review of the literature replete with unsupported opinions and accusations. In summary, Quintner et al. have not presented any convincing evidence to believe that the Integrated TrP Hypothesis should be laid to rest.

  16. Verifying critical control points for Phytophthora introduction into nurseries

    Treesearch

    N.K. Osterbauer; M. Lujan; G. McAninch; A. Trippe; S. Lane

    2013-01-01

    The Oregon Department of Agriculture implemented the Grower Assisted Inspection Program (GAIP) for nurseries in 2007. Participants in GAIP adopted best management practices (BMP) for five critical control points (CCP) (used containers, irrigation water, soil substrate, potting media, and incoming plants), where foliar Phytophthora can be introduced...

  17. Critical end point in a thermomagnetic nonlocal NJL model

    NASA Astrophysics Data System (ADS)

    Márquez, F.; Zamora, R.

    2017-09-01

    In this paper, we explore the critical end point in the T ‑ μ phase diagram of a thermomagnetic nonlocal Nambu-Jona-Lasinio model in the weak field limit. We work with the Gaussian regulator, and find that a crossover takes place at μ, B = 0. The crossover turns to a first-order phase transition as the chemical potential or the magnetic field increases. The critical end point of the phase diagram occurs at a higher temperature and lower chemical potential as the magnetic field increases. This result is in accordance to similar findings in other effective models. We also find that there is a critical magnetic field, for which a first-order phase transition takes place even at μ = 0.

  18. Peculiar thermodynamics of the second critical point in supercooled water.

    PubMed

    Bertrand, C E; Anisimov, M A

    2011-12-08

    On the basis of the principle of critical-point universality, we examine the peculiar thermodynamics of the liquid-liquid critical point in supercooled water. We show that the liquid-liquid criticality in water represents a special kind of critical behavior in fluids, intermediate between two limiting cases: the lattice gas, commonly used to model liquid-vapor transitions, and the lattice liquid, a weakly compressible liquid with an entropy-driven phase separation. While the ordering field in the lattice gas is associated with the chemical potential and the order parameter with the density, in the lattice liquid the ordering field is the temperature and the order parameter is the entropy. The behavior of supercooled water is much closer to lattice-liquid behavior than to lattice-gas behavior. Using new experimental data recently obtained by Mishima [J. Chem. Phys. 2010, 133, 144503], we have revised the parametric scaled equation of state, previously suggested by Fuentevilla and Anisimov [Phys. Rev. Lett. 2006, 97, 195702], and obtain a consistent description of the thermodynamic anomalies of supercooled water by adjusting linear backgrounds, one critical amplitude, and the critical pressure. We also show how the lattice-liquid description affects the finite-size scaling description of supercooled water in confined media.

  19. Integrability from point symmetries in a family of cosmological Horndeski Lagrangians

    NASA Astrophysics Data System (ADS)

    Dimakis, N.; Giacomini, Alex; Paliathanasis, Andronikos

    2017-07-01

    For a family of Horndeski theories, formulated in terms of a generalized Galileon model, we study the integrability of the field equations in a Friedmann-Lemaître-Robertson-Walker space-time. We are interested in point transformations which leave invariant the field equations. Noether's theorem is applied to determine the conservation laws for a family of models that belong to the same general class. The cosmological scenarios with or without an extra perfect fluid with constant equation of state parameter are the two important cases of our study. The de Sitter universe and ideal gas solutions are derived by using the invariant functions of the symmetry generators as a demonstration of our result. Furthermore, we discuss the connection of the different models under conformal transformations while we show that when the Horndeski theory reduces to a canonical field the same holds for the conformal equivalent theory. Finally, we discuss how singular solutions provides nonsingular universes in a different frame and vice versa.

  20. Quantum-to-classical crossover near quantum critical point

    DOE PAGES

    Vasin, M.; Ryzhov, V.; Vinokur, V. M.

    2015-12-21

    A quantum phase transition (QPT) is an inherently dynamic phenomenon. However, while non-dissipative quantum dynamics is described in detail, the question, that is not thoroughly understood is how the omnipresent dissipative processes enter the critical dynamics near a quantum critical point (QCP). Here we report a general approach enabling inclusion of both adiabatic and dissipative processes into the critical dynamics on the same footing. We reveal three distinct critical modes, the adiabatic quantum mode (AQM), the dissipative classical mode [classical critical dynamics mode (CCDM)], and the dissipative quantum critical mode (DQCM). We find that as a result of the transitionmore » from the regime dominated by thermal fluctuations to that governed by the quantum ones, the system acquires effective dimension d+zΛ(T), where z is the dynamical exponent, and temperature-depending parameter Λ(T)ε[0, 1] decreases with the temperature such that Λ(T=0) = 1 and Λ(T →∞) = 0. Lastly, our findings lead to a unified picture of quantum critical phenomena including both dissipation- and dissipationless quantum dynamic effects and offer a quantitative description of the quantum-to-classical crossover.« less

  1. Quantum-to-classical crossover near quantum critical point

    PubMed Central

    Vasin, M.; Ryzhov, V.; Vinokur, V. M.

    2015-01-01

    A quantum phase transition (QPT) is an inherently dynamic phenomenon. However, while non-dissipative quantum dynamics is described in detail, the question, that is not thoroughly understood is how the omnipresent dissipative processes enter the critical dynamics near a quantum critical point (QCP). Here we report a general approach enabling inclusion of both adiabatic and dissipative processes into the critical dynamics on the same footing. We reveal three distinct critical modes, the adiabatic quantum mode (AQM), the dissipative classical mode [classical critical dynamics mode (CCDM)], and the dissipative quantum critical mode (DQCM). We find that as a result of the transition from the regime dominated by thermal fluctuations to that governed by the quantum ones, the system acquires effective dimension d + zΛ(T), where z is the dynamical exponent, and temperature-depending parameter Λ(T) ∈ [0, 1] decreases with the temperature such that Λ(T = 0) = 1 and Λ(T → ∞) = 0. Our findings lead to a unified picture of quantum critical phenomena including both dissipation- and dissipationless quantum dynamic effects and offer a quantitative description of the quantum-to-classical crossover. PMID:26688102

  2. Quantum-to-classical crossover near quantum critical point.

    PubMed

    Vasin, M; Ryzhov, V; Vinokur, V M

    2015-12-21

    A quantum phase transition (QPT) is an inherently dynamic phenomenon. However, while non-dissipative quantum dynamics is described in detail, the question, that is not thoroughly understood is how the omnipresent dissipative processes enter the critical dynamics near a quantum critical point (QCP). Here we report a general approach enabling inclusion of both adiabatic and dissipative processes into the critical dynamics on the same footing. We reveal three distinct critical modes, the adiabatic quantum mode (AQM), the dissipative classical mode [classical critical dynamics mode (CCDM)], and the dissipative quantum critical mode (DQCM). We find that as a result of the transition from the regime dominated by thermal fluctuations to that governed by the quantum ones, the system acquires effective dimension d + zΛ(T), where z is the dynamical exponent, and temperature-depending parameter Λ(T) ∈ [0, 1] decreases with the temperature such that Λ(T = 0) = 1 and Λ(T → ∞) = 0. Our findings lead to a unified picture of quantum critical phenomena including both dissipation- and dissipationless quantum dynamic effects and offer a quantitative description of the quantum-to-classical crossover.

  3. Quantum-to-classical crossover near quantum critical point

    SciTech Connect

    Vasin, M.; Ryzhov, V.; Vinokur, V. M.

    2015-12-21

    A quantum phase transition (QPT) is an inherently dynamic phenomenon. However, while non-dissipative quantum dynamics is described in detail, the question, that is not thoroughly understood is how the omnipresent dissipative processes enter the critical dynamics near a quantum critical point (QCP). Here we report a general approach enabling inclusion of both adiabatic and dissipative processes into the critical dynamics on the same footing. We reveal three distinct critical modes, the adiabatic quantum mode (AQM), the dissipative classical mode [classical critical dynamics mode (CCDM)], and the dissipative quantum critical mode (DQCM). We find that as a result of the transition from the regime dominated by thermal fluctuations to that governed by the quantum ones, the system acquires effective dimension d+zΛ(T), where z is the dynamical exponent, and temperature-depending parameter Λ(T)ε[0, 1] decreases with the temperature such that Λ(T=0) = 1 and Λ(T →∞) = 0. Lastly, our findings lead to a unified picture of quantum critical phenomena including both dissipation- and dissipationless quantum dynamic effects and offer a quantitative description of the quantum-to-classical crossover.

  4. Towards a controlled study of the QCD critical point

    NASA Astrophysics Data System (ADS)

    de Forcrand, Ph; Philipsen, O.

    2008-10-01

    The phase diagram of QCD, as a function of temperature T and quark chemical potential μ, may contain a critical point (μE, TE) whose non-perturbative nature makes it a natural object of lattice studies. However, the sign problem prevents the application of standard Monte Carlo techniques at nonzero baryon density. We have been pursuing an approach free of the sign problem, where the chemical potential is taken as imaginary and the results are Taylor expanded in μ/T about μ = 0, then analytically continued to real μ. Within this approach we have determined the sensitivity of the critical chemical potential μE to the quark mass, d(\\mu_E)^2/dm_q|_{\\mu_E=0} . Our study indicates that the critical point moves to a larger chemical potential as the quark mass decreases. This finding, contrary to common wisdom, implies that the deconfinement crossover, which takes place in QCD at μ = 0 when the temperature is raised, will remain a crossover in the μ-region where our Taylor expansion can be trusted. If this result, obtained on a coarse lattice, is confirmed by simulations on finer lattices now in progress, then we predict that no chiral critical point will be found for μB lsim 500 MeV, unless the phase diagram contains additional transitions.

  5. Hydrodynamical Evolution near the QCD Critical End Point

    NASA Astrophysics Data System (ADS)

    Nonaka, Chiho; Asakawa, Masayuki

    2003-10-01

    Recently, the possibility of the existence of a critical end point (CEP) in the QCD phase diagram has attracted a lot of attention and several experimental signatures have been proposed for it^1. Berdnikov and Rajagopal discussed the growth of the correlation length near the critical end point in heavy-ion collision from the schematic argument^2. However, there has seen, so far, no quantitative study on the hydrodynamic evolution near CEP. Here we quantitatively evaluate the effect of the critical end point on the observables using the hydrodynamical model. First, we construct an equation of state (EOS) that includes critical behavior of CEP. Here we assume that the singular part of EOS near CEP belongs to the same universality class as the 3-d Ising model. Then we match the singular part of EOS with known QGP and hadronic EOS. We found the strong focusing effect near the critical end point in n_B/s trajectories in T-μ plane. This behavior is very different from an EOS of Bag model which is used in usual hydrodynamical models. This suggests that the effect of CEP appears strongly in the time evolution of system and the experimental observables. Next we investigate the time evolution and the behavior of correlation length near CEP along n_B/s trajectories. In addition, we also discuss the consequences of CEP in experimental results such as fluctuations and the kinetic freeze-out temperature. ^1M. Stephanov, K. Rajagopal, and E. Shuryak, Phys. Rev. Lett. 81 (1998) 4816. ^2B. Berdnikov and K. Rajagopal, Phys. Rev. D61 (2000) 105017.

  6. Chemical Kinetics at the Critical Point of Solution

    NASA Astrophysics Data System (ADS)

    Baird, James

    2005-03-01

    We have measured the rate of decomposition of acetone dicarboxylic acid in a mixture of isobutyric acid + water near its consolute point. At temperatures close to the critical solution temperature, the rate constant oscillated in magnitude by about 10 percent as it passed through two complete cycles of slowing down followed by speeding up. This is to be compared with our observations of the rates the SN1 hydrolysis reactions of 2-chloro-2-methylbutane in isobutyric acid + water and 2-bromo-2-methylpropane in triethylamine + water near their respective consolute points. In both mixtures, we observed a single cycle of slowing down above the critical temperature followed by speeding up above it [J. Phys. Chem. A 107, 8435 (2003)]. Whereas we can find no ready explanation for the speeding up, we suggest that because none of these mixtures contains any inert components, the observed slowing down should belong to the Griffiths-Wheeler class of strong critical effects [Phys. Rev. A 2, 1047 (1970)]. To check this hypothesis, we measured the rate of decomposition of ethyl diazoacetate in isobutyric acid + water near the critical solution temperature. In this mixture, isobutyric acid is inert, and no critical effect was observed.

  7. New classes of exact solutions to the Grad-Shafranov equation with arbitrary flow using Lie-point symmetries

    NASA Astrophysics Data System (ADS)

    Kuiroukidis, Ap.; Throumoulopoulos, G. N.

    2016-11-01

    Extending previous work [R. L. White and R. D. Hazeltine, Phys. Plasmas 16, 123101 (2009)] to the case of a generalized Grad-Shafranov equation (GGSE) with incompressible flow of arbitrary direction, we obtain new classes of exact solutions on the basis of Lie-point symmetries. This is done by using a previously found exact generalized Solovév solution to the GGSE. The new solutions containing five free parameters describe D-shaped toroidal configurations with plasma flow non-parallel to the magnetic field. In addition, the full symmetry group is obtained and new group-invariant solutions to the GGSE are presented.

  8. Critical exponents and scaling invariance in the absence of a critical point

    NASA Astrophysics Data System (ADS)

    Saratz, N.; Zanin, D. A.; Ramsperger, U.; Cannas, S.; Pescia, D.; Vindigni, A.

    2016-12-01

    The paramagnetic-to-ferromagnetic phase transition is classified as a critical phenomenon due to the power-law behaviour shown by thermodynamic observables when the Curie point is approached. Here we report the observation of such a behaviour over extraordinarily many decades of suitable scaling variables in ultrathin Fe films, for certain ranges of temperature T and applied field B. This despite the fact that the underlying critical point is practically unreachable because protected by a phase with a modulated domain structure, induced by the dipole-dipole interaction. The modulated structure has a well-defined spatial period and is realized in a portion of the (T, B) plane that extends above the putative critical temperature, where thermodynamic quantities do not display any singularity. Our results imply that scaling behaviour of macroscopic observables is compatible with an avoided critical point.

  9. Critical exponents and scaling invariance in the absence of a critical point

    PubMed Central

    Saratz, N.; Zanin, D. A.; Ramsperger, U.; Cannas, S. A.; Pescia, D.; Vindigni, A.

    2016-01-01

    The paramagnetic-to-ferromagnetic phase transition is classified as a critical phenomenon due to the power-law behaviour shown by thermodynamic observables when the Curie point is approached. Here we report the observation of such a behaviour over extraordinarily many decades of suitable scaling variables in ultrathin Fe films, for certain ranges of temperature T and applied field B. This despite the fact that the underlying critical point is practically unreachable because protected by a phase with a modulated domain structure, induced by the dipole–dipole interaction. The modulated structure has a well-defined spatial period and is realized in a portion of the (T, B) plane that extends above the putative critical temperature, where thermodynamic quantities do not display any singularity. Our results imply that scaling behaviour of macroscopic observables is compatible with an avoided critical point. PMID:27917865

  10. Critical exponents and scaling invariance in the absence of a critical point.

    PubMed

    Saratz, N; Zanin, D A; Ramsperger, U; Cannas, S; Pescia, D; Vindigni, A

    2016-12-05

    The paramagnetic-to-ferromagnetic phase transition is classified as a critical phenomenon due to the power-law behaviour shown by thermodynamic observables when the Curie point is approached. Here we report the observation of such a behaviour over extraordinarily many decades of suitable scaling variables in ultrathin Fe films, for certain ranges of temperature T and applied field B. This despite the fact that the underlying critical point is practically unreachable because protected by a phase with a modulated domain structure, induced by the dipole-dipole interaction. The modulated structure has a well-defined spatial period and is realized in a portion of the (T, B) plane that extends above the putative critical temperature, where thermodynamic quantities do not display any singularity. Our results imply that scaling behaviour of macroscopic observables is compatible with an avoided critical point.

  11. Quantum critical point revisited by dynamical mean-field theory

    DOE PAGES

    Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei M.

    2017-03-31

    Dynamical mean-field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. We characterize the QCP by a universal scaling form of the self-energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low-energy kink and the high-energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high-energy antiferromagnetic paramagnons. Here, we use the frequency-dependent four-point correlation function of spin operators to calculate the momentum-dependent correction to the electron self-energy. Furthermore, by comparing with the calculations basedmore » on the spin-fermion model, our results indicate the frequency dependence of the quasiparticle-paramagnon vertices is an important factor to capture the momentum dependence in quasiparticle scattering.« less

  12. Gravity from entanglement close to a quantum critical point

    NASA Astrophysics Data System (ADS)

    Faulkner, Thomas

    2015-04-01

    Entanglement entropy (EE) in quantum many-body systems reveal interesting non-local aspects of the state or phase of the system. For example, topological order in gapped phases may be characterized in this way. We present calculations of entanglement close to a quantum critical point with relativistic invariance that reveal the existence of an emergent gravitational theory in one higher dimension. The gravitational theory encodes the entanglement of the quantum system in an efficient way. In this way calculations of EE, a usually notoriously difficult quantity to calculate, are reduced to a simple computation in classical gravity. The answer we find is in the spirit of the AdS/CFT duality but goes beyond it since our results apply to any relativistic quantum critical point and not just the known theories with classical gravity duals.

  13. Protecting clean critical points by local disorder correlations

    NASA Astrophysics Data System (ADS)

    Hoyos, J. A.; Laflorencie, Nicolas; Vieira, André.; Vojta, Thomas

    2011-03-01

    We show that a broad class of quantum critical points can be stable against locally correlated disorder even if they are unstable against uncorrelated disorder. Although this result seemingly contradicts the Harris criterion, it follows naturally from the absence of a random-mass term in the associated order-parameter field theory. We illustrate the general concept with explicit calculations for quantum spin-chain models. Instead of the infinite-randomness physics induced by uncorrelated disorder, we find that weak locally correlated disorder is irrelevant. For larger disorder, we find a line of critical points with unusual properties such as an increase of the entanglement entropy with the disorder strength. We also propose experimental realizations in the context of quantum magnetism and cold-atom physics. Financial support: Fapesp, CNPq, NSF, and Research Corporation.

  14. Potentials and point symmetries of Klein-Gordon equations in space-time homogenous Gödel-type metrics

    NASA Astrophysics Data System (ADS)

    Jamal, Sameerah

    In this paper, we study the geometric properties of generators for the Klein-Gordon equation on classes of space-time homogeneous Gödel-type metrics. Our analysis complements the study involving the “Symmetries of geodesic motion in Gödel-type spacetimes” by U. Camci (J. Cosmol. Astropart. Phys., doi:10.1088/1475-7516/2014/07/002). These symmetries or Killing vectors (KVs) are used to construct potential functions admitted by the Klein-Gordon equation. The criteria for the potential function originates from three primary sources, viz. through generators that are identically the Killing algebra, or with the KV fields that are recast into linear combinations and third, real subalgebras within the Killing algebra. This leads to a classification of the (1 + 3) Klein-Gordon equation according to the catalogue of infinitesimal Lie and Noether point symmetries admitted. A comprehensive list of group invariant functions is provided and their application to analytic solutions is discussed.

  15. Quaternionic formulation of the two-component Kohn-Sham equations and efficient exploitation of point group symmetry

    NASA Astrophysics Data System (ADS)

    Armbruster, Markus K.

    2017-08-01

    The quaternionic formulation of the time-reversal invariant quasirelativistic Kohn-Sham equations with exact Hartree-Fock exchange leads to hypercomplex one-component equations with half of the dimension compared to the original two-component problem. The combination of the quaternionic equations with point group symmetry exploitation for D2 h and its subgroups by construction of corepresentations leads to quaternionic, complex, or real algorithms depending on the structure of the point group. In this work, the quaternionic approach with point group symmetry exploitation of the relativistic four-component Dirac-Hartree-Fock theory by Saue and Jensen [J. Chem. Phys. 111, 6211 (1999)] will be adopted to the quasirelativistic two-component Kohn-Sham scheme for closed-shell systems. The implementation in the program system TURBOMOLE is applied to the large lead cluster P b56 as a test case.

  16. Turbulence close to the critical point of a fluid

    NASA Astrophysics Data System (ADS)

    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.

  17. Critical points of the anyon-Hubbard model

    NASA Astrophysics Data System (ADS)

    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.

  18. Supergravity instabilities of non-supersymmetric quantum critical points

    NASA Astrophysics Data System (ADS)

    Bobev, Nikolay; Halmagyi, Nick; Pilch, Krzysztof; Warner, Nicholas P.

    2010-12-01

    Motivated by the recent use of certain consistent truncations of M-theory to study condensed matter physics using holographic techniques, we study the SU(3)-invariant sector of four-dimensional, {\\cal N}=8 gauged supergravity and compute the complete scalar spectrum at each of the five non-trivial critical points. We demonstrate that the smaller SU(4)- sector is equivalent to a consistent truncation studied recently by various authors and find that the critical point in this sector, which has been proposed as the ground state of a holographic superconductor, is unstable due to a family of scalars that violate the Breitenlohner-Freedman bound. We also derive the origin of this instability in 11 dimensions and comment on the generalization to other embeddings of this critical point which involve arbitrary Sasaki-Einstein seven manifolds. In the spirit of a resurging interest in consistent truncations, we present a formal treatment of the SU(3)-invariant sector as a U(1) × U(1) gauged {\\cal N}=2 supergravity theory coupled to one hypermultiplet.

  19. Ion exchange at the critical point of solution.

    PubMed

    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.

  20. History Effects and Phase Diagram near the Lower Critical Point in YBa{sub 2}Cu{sub 3}O{sub 7} Single Crystals

    SciTech Connect

    Zhukov, A. A.; de Groot, P. A. J.; Kokkaliaris, S.; di Nicolo, E.; Jansen, A. G. M.; Mossang, E.; Martinez, G.; Wyder, P.; Wolf, T.; Kupfer, H.

    2001-07-02

    Using a sensitive torque magnetometer we have studied magnetization curves for untwinned overdoped YBa{sub 2}Cu {sub 3}O{sub 7 } single crystals in fields of up to 28T. We demonstrate the existence of history effects below the lower critical point and provide a full demarcation of the Bragg-glass phase. A pronounced symmetry is observed in the behavior of the phase lines, irreversible magnetization, and value of the magnetization jump near both critical points.

  1. Possible Signal for Critical Point in Hadronization Process

    NASA Astrophysics Data System (ADS)

    Rybczynski, M.; Wlodarczyk, Z.; Wilk, G.

    2004-02-01

    We argue that recent data on fluctuations observed in heavy ion collisions show non-monotonic behaviour as function of number of participants (or ''wounded nucleons'') NW. When interpreted in thermodynamical approach this result can be associated with a possible structure occurring in the corresponding equation of state (EoS). This in turn could be further interpreted as due to the occurrence of some characteristic points (like softest point or critical point) of EoS discussed in the literature and therefore be regarded as a possible signal of the QGP formation in such collisions. We show, however, that the actual situation is still far from being clear and calls for more investigations of fluctuation phenomena in multiparticle production processes to be performed.

  2. Delirium in Critically Ill Children: An International Point Prevalence Study.

    PubMed

    Traube, Chani; Silver, Gabrielle; Reeder, Ron W; Doyle, Hannah; Hegel, Emily; Wolfe, Heather A; Schneller, Christopher; Chung, Melissa G; Dervan, Leslie A; DiGennaro, Jane L; Buttram, Sandra D W; Kudchadkar, Sapna R; Madden, Kate; Hartman, Mary E; deAlmeida, Mary L; Walson, Karen; Ista, Erwin; Baarslag, Manuel A; Salonia, Rosanne; Beca, John; Long, Debbie; Kawai, Yu; Cheifetz, Ira M; Gelvez, Javier; Truemper, Edward J; Smith, Rebecca L; Peters, Megan E; O'Meara, A M Iqbal; Murphy, Sarah; Bokhary, Abdulmohsen; Greenwald, Bruce M; Bell, Michael J

    2017-04-01

    To determine prevalence of delirium in critically ill children and explore associated risk factors. Multi-institutional point prevalence study. Twenty-five pediatric critical care units in the United States, the Netherlands, New Zealand, Australia, and Saudi Arabia. All children admitted to the pediatric critical care units on designated study days (n = 994). Children were screened for delirium using the Cornell Assessment of Pediatric Delirium by the bedside nurse. Demographic and treatment-related variables were collected. Primary study outcome measure was prevalence of delirium. In 159 children, a final determination of mental status could not be ascertained. Of the 835 remaining subjects, 25% screened positive for delirium, 13% were classified as comatose, and 62% were delirium-free and coma-free. Delirium prevalence rates varied significantly with reason for ICU admission, with highest delirium rates found in children admitted with an infectious or inflammatory disorder. For children who were in the PICU for 6 or more days, delirium prevalence rate was 38%. In a multivariate model, risk factors independently associated with development of delirium included age less than 2 years, mechanical ventilation, benzodiazepines, narcotics, use of physical restraints, and exposure to vasopressors and antiepileptics. Delirium is a prevalent complication of critical illness in children, with identifiable risk factors. Further multi-institutional, longitudinal studies are required to investigate effect of delirium on long-term outcomes and possible preventive and treatment measures. Universal delirium screening is practical and can be implemented in pediatric critical care units.

  3. Universal thermodynamics at the liquid-vapor critical point.

    PubMed

    Sanchez, Isaac C; Boening, Kevin L

    2014-11-26

    For 68 fluids that include hydrogen bonding and quantum fluids, the fugacity coefficient that defines the residual chemical potential adopts a near universal value of 2/3 at the critical point. More precisely, the reciprocal of the fugacity coefficient equals 1.52 ± 0.02 and includes fluids as diverse as helium (1.50), dodecafluoropentane (1.50), and water (1.53). For 65 classical fluids, a dimensionless thermal pressure coefficient and internal pressure attain critical values of 1.88 ± 0.11 and 1.61 ± 0.11, respectively. From equations of state, values of these new critical constants have been calculated and agree favorably with experimental values. Specifically, for the critical fugacity coefficient, the following results were obtained for its reciprocal: van der Waals (1.44), lattice gas (1.43), scaled particle theory (1.46), and the Redlich-Kwong eq (1.50). The semiempirical Redlich-Kwong equation is also the most accurate for the thermal pressure coefficient (1.86) and internal pressure (1.53). Physical interpretations of these results are discussed as well as their implications for other critical phenomena.

  4. [Critical control points in the pasteurized milk processing fluxogram].

    PubMed

    Lopes, A C; Stamford, T L

    1997-12-01

    With the aim of evaluating the microbiological quality of raw and pasteurized milk and confirm the critical control points in a dairy processing industry (Recife-PE, Brazil), 84 samples of milk were collected from four points of the flow-chart considered critical (raw milk storage tank, outlet of the pasteurizer unit, pasteurized milk storage tank and packing filling machine). All samples were evaluated for the presence of mesophilic and psychotrophics microorganisms. The most probable number (MPN) of total and faecal coliforms were determined. Samples of raw and pasteurized milk (collected from the packing filling machine) were also assessed for the presence of Staphylococcus aureus. The preservation temperature of raw and pasteurized milk in the storage tanks and the MPN of total and faecal coliforms present in the water used by the industry were simultaneously evaluated. High counts of mesophilic and psychotrophics microorganisms, total and faecal coliforms and S. aureus were detect in raw milk production and processing. The pasteurization process reduced the microorganisms to acceptable numbers in the Brazilian standards, however, the statistics analysis showed that the number of microorganisms increased significantly (p < 0.01) in the pasteurized milk storage tank, representing an important point of contamination. The probable reason for this findings was the presence of coliforms in 60% samples of water which was used to clean the milk equipment and the inadequate temperatures in the storage tank. Therefore, the results of the microbiological analysis confirm that the milk maintenance temperature in the storage tanks, the pasteurization and the packaging are critical control points in the pasteurized milk processing fluxogram.

  5. Critical Lines in Binary Mixtures of Components with Multiple Critical Points

    NASA Astrophysics Data System (ADS)

    Artemenko, Sergey; Lozovsky, Taras; Mazur, Victor

    The principal aim of this work is a comprehensive analysis of the fluid phase behavior of binary fluid mixtures via the van der Waals like equation of state (EoS) which has a multiplicity of critical points in metastable region. We test the modified van der Waals equation of state (MVDW) proposed by Skibinski et al. (2004) which displays a complex phase behavior including three critical points and identifies four fluid phases (gas, low density liquid (LDL), high density liquid (HDL), and very high density liquid (VHDL)). An improvement of repulsive part doesn't change a topological picture of phase behavior in the wide range of thermodynamic variables. The van der Waals attractive interaction and excluded volume for mixture are calculated from classical mixing rules. Critical lines in binary mixtures of type III of phase behavior in which the components exhibit polyamorphism are calculated and a continuity of fluid-fluid critical line at high pressure is observed.

  6. Critical versus spurious fluctuations in the search for the QCD critical point

    NASA Astrophysics Data System (ADS)

    Hippert, M.; Fraga, E. S.; Santos, E. M.

    2016-01-01

    The neighborhood of the QCD chiral critical point is characterized by intense fluctuations of the chiral field which could, in principle, generate pronounced experimental signatures. However, experimental uncertainties which are inherent to heavy-ion collisions, as well as the modest size and duration of the formed plasma, will severely attenuate these signatures. Using Monte Carlo techniques, we study second-order event-by-event moments of pions as a prototype for signatures of the chiral critical point based on the enhancement of the correlation length and event-by-event analysis. We test their viability against some realistic ingredients, similar to the ones found in the RHIC beam energy scan program.

  7. Critical points for point source pollution in the Yser catchment area (Flanders-France).

    PubMed

    Mestdagh, Inge; Maillet-Mezeray, Julie; Calus, André; Franssens, Vanessa; Röttele, Manfred

    2008-01-01

    In the frame of the European TOPPS project (Train the Operator to prevent Pollution from Point Sources), 200 on farm audits and 300 tele interviews were performed in the Yser catchment area. The objective was to determine the critical points for point source pollution within the spraying process and to inform advisors, intermediaries and farmers on practical measures and achievable solutions to reduce the contamination of the surface water by Plant Protection Products (PPP) due to point source pollution. For the on farm auditing, the Aquasite tool (Arvalis-France) was used. This audit was performed on 100 farms in the Flemish Yser catchment and on 100 farms at the French side. This audit reveals the weak points in infrastructure and technology on the farm in relation to the spraying process. Next, 150 tele interviews were held in the respective catchment areas. These interviews assess the awareness and behaviour of the farmers on point source pollution. The strength of these studies is in giving a view on the real situation on the farms with respect to spraying. The critical points and risks for point source pollution were similar for both regions. Especially the filling and mixing of the sprayer, internal and external cleaning of the sprayer and the management of the waste fraction need specific training, demonstration and advice. However, there is a large difference in the risk perception of point source pollution between farmers on both sides of the border. The transgressing approach of the Yser catchment allows to make a comparison between both regions and allows to assess in which way the legislation had part in explaining the differences between the regions as the agriculture in both regions is similar. Also, the results stress the importance of trainings and sensibilisation at a regional scale.

  8. Resummation of fluctuations near ferromagnetic quantum critical points

    NASA Astrophysics Data System (ADS)

    Pedder, C. J.; Krüger, F.; Green, A. G.

    2013-10-01

    We present a detailed analysis of the nonanalytic structure of the free energy for the itinerant ferromagnet near the quantum critical point in two and three dimensions. We analyze a model of electrons with an isotropic dispersion interacting through a contact repulsion. A fermionic version of the quantum order-by-disorder mechanism allows us to calculate the free energy as a functional of the dispersion in the presence of homogeneous and spiraling magnetic order. We resum the leading divergent contributions to derive an algebraic expression for the nonanalytic contribution to free energy from quantum fluctuations. Using a recursion which relates subleading divergences to the leading term, we calculate the full T=0 contribution in d=3. We propose an interpolating functional form, which allows us to track phase transition lines at temperatures far below the tricritical point and down to T=0. In d=2, quantum fluctuations are stronger, and nonanalyticities are more severe. Using a similar resummation approach, we find that despite the different nonanalytic structures, the phase diagrams in two and three dimensions are remarkably similar, exhibiting an incommensurate spiral phase near the avoided quantum critical point.

  9. A magnetically induced quantum critical point in holography

    DOE PAGES

    Gnecchi, A.; Gursoy, U.; Papadoulaki, O.; ...

    2016-09-15

    Here, we investigate quantum critical points in a 2+1 dimensional gauge theory at finite chemical potential χ and magnetic field B. The gravity dual is based on 4D N = 2 Fayet-Iliopoulos gauged supergravity and the solutions we consider — that are constructed analytically — are extremal, dyonic, asymptotically AdS4 black-branes with a nontrivial radial profile for the scalar field. We discover a line of second order fixed points at B = Bc(χ) between the dyonic black brane and an extremal “thermal gas” solution with a singularity of good-type, according to the acceptability criteria of Gubser. The dual field theorymore » is a strongly coupled nonconformal field theory at finite charge and magnetic field, related to the ABJM theory deformed by a triple trace operator Φ3. This line of fixed points might be useful in studying the various strongly interacting quantum critical phenomena such as the ones proposed to underlie the cuprate superconductors. We also find curious similarities between the behaviour of the VeV <Φ> under B and that of the quark condensate in 2+1 dimensional NJL models.« less

  10. A magnetically induced quantum critical point in holography

    SciTech Connect

    Gnecchi, A.; Gursoy, U.; Papadoulaki, O.; Toldo, C.

    2016-09-15

    Here, we investigate quantum critical points in a 2+1 dimensional gauge theory at finite chemical potential χ and magnetic field B. The gravity dual is based on 4D N = 2 Fayet-Iliopoulos gauged supergravity and the solutions we consider — that are constructed analytically — are extremal, dyonic, asymptotically AdS4 black-branes with a nontrivial radial profile for the scalar field. We discover a line of second order fixed points at B = Bc(χ) between the dyonic black brane and an extremal “thermal gas” solution with a singularity of good-type, according to the acceptability criteria of Gubser. The dual field theory is a strongly coupled nonconformal field theory at finite charge and magnetic field, related to the ABJM theory deformed by a triple trace operator Φ3. This line of fixed points might be useful in studying the various strongly interacting quantum critical phenomena such as the ones proposed to underlie the cuprate superconductors. We also find curious similarities between the behaviour of the VeV <Φ> under B and that of the quark condensate in 2+1 dimensional NJL models.

  11. Field Structure of a Quasisoliton Approaching the Critical Point

    NASA Astrophysics Data System (ADS)

    Gorshkov, K. A.; Soustova, I. A.; Ermoshkin, A. V.

    2016-03-01

    Within the framework of an approximate approach based on the representation of the Gardnerequation solitons as compound structures (different-polarity kinks), the non-quasistationary evolution of such solitary waves, which is stipulated by the variable quadratic-nonlinearity parameter α. The structure of the composite soliton is studied in cases that are critical for the quasistationary description where the predicted increase in the solitary-wave scales becomes unbounded on finite spatio-temporal intervals. The dependence of the spatial scales of the quasisoliton-field distribution on the quadratic-nonlinearity coefficient near the critical point for the power-law time dependence α(t) is studied in detail. The obtained solution is compared with the results of direct numerical simulation of the Gardner equation with variable coefficients.

  12. Dynamical Conductivity near the Superconductor to Insulator Critical Point

    NASA Astrophysics Data System (ADS)

    Auerbach, Assa

    2015-03-01

    I review our results for the dynamical complex conductivity near the two dimensional superconductor to insulator transition. The relativistic field theory is relevant to ordered Jospehson junction arrays and bosons trapped in an optical lattice. In the superconducting phase, the real conductivity reveals the Higgs mode mass as a threshold, with a weak ω5 sub-gap tail. The imaginary conductivity measures the critically vanishing superfluid density. In the insulator phase, the real conductivity has a sharp threshold at the Mott (charge) gap, and the imaginary conductivity goes as - Cω , where the capacitance C measures the inverse of the vortex superfluid density, which vanishes at the critical point. For layered, short coherence length (bosonic), superconductors, the Higgs threshold is raised by the inter-plane plasmon energy. Support of US-Israel Binational Science Foundation is gratefully acknowledged.

  13. Critical Casimir interactions between colloids around the critical point of binary solvents.

    PubMed

    Stuij, S G; Labbé-Laurent, M; Kodger, T E; Maciołek, A; Schall, P

    2017-08-09

    Critical Casimir interactions between colloidal particles arise from the confinement of fluctuations of a near-critical solvent in the liquid gap between closely-spaced particles. So far, the comparison of theoretical predictions and experimental measurements of critical Casimir forces (CCFs) has focused on the critical solvent composition, while it has been lacking for off-critical compositions. We address this issue by investigating CCFs between spherical colloidal particles around the critical point of a binary solvent through a combination of experiments, previous Ising Monte Carlo simulation results and field-theoretical methods. By measuring the correlation length of the near-critical solvent and the pair potentials of the particles in terms of radial distribution functions and by determining the second virial coefficient, we test in detail theoretical predictions. Our results indicate that the critical Casimir theory gives quantitative correct predictions for the interaction potential between particles in a near critical binary mixture if weak preferential adsorption of the particle surface is taken into account.

  14. On the motion of two point vortex pairs with glide-reflective symmetry in a periodic strip

    NASA Astrophysics Data System (ADS)

    Basu, Saikat; Stremler, Mark A.

    2015-10-01

    The motion of four point vortices with zero net circulation in a potential flow contained within a two-dimensional, singly periodic domain (i.e., a periodic strip) is determined under the assumption of a spatial symmetry that is preserved by the dynamics. This symmetry is inspired by the patterns observed in two-pair (2P) vortex wakes, in which four neighboring vortices appear as two pairs with a glide-reflective symmetry: the arrangement of each pair is related to the other by a reflection about the wake centerline and a half-period translation along the wake centerline. Under the assumed constraints, the problem can be reduced to an integrable Hamiltonian system. Vortex motions are classified using a bifurcation analysis of the phase space topology as determined by level curves of the Hamiltonian. Unlike the well-known von Kármán point vortex model, in which a singly periodic system of two point vortices with glide-reflective symmetry is always in relative equilibrium, this four-point-vortex system exhibits a rich variety of relative motions for almost all possible initial conditions. Five distinct classes of relative vortex motion are identified, encompassing a total of 12 different types of motion, suggesting that experimental wakes with four vortices formed per shedding cycle may exhibit behaviors not yet explored in the literature. A finite number of initial conditions do correspond to relative equilibria, in which case the vortex configuration propagates downstream with invariant size and shape. Some of these relative equilibria are neutrally stable to perturbations that preserve the system constraints, while others are unstable, leading to large deviations from the equilibrium configuration.

  15. Pairing correlations near a Kondo-destruction quantum critical point

    NASA Astrophysics Data System (ADS)

    Pixley, J. H.; Deng, Lili; Ingersent, Kevin; Si, Qimiao

    2015-05-01

    Motivated by the unconventional superconductivity observed in heavy-fermion metals, we investigate pairing susceptibilities near a continuous quantum phase transition of the Kondo-destruction type. We solve two-impurity Bose-Fermi Anderson models with Ising and Heisenberg forms of the interimpurity exchange interaction using continuous-time quantum Monte Carlo and numerical renormalization-group methods. Each model exhibits a Kondo-destruction quantum critical point separating Kondo-screened and local-moment phases. For antiferromagnetic interimpurity exchange interactions, singlet pairing is found to be enhanced in the vicinity of the transition. Implications of this result for heavy-fermion superconductivity are discussed.

  16. Itinerant density wave instabilities at classical and quantum critical points

    SciTech Connect

    Feng, Yejun; van Wezel, Jasper; Wang, Jiyang; Flicker, Felix; Silevitch, D. M.; Littlewood, P. B.; Rosenbaum, T. F.

    2015-07-27

    Charge ordering in metals is a fundamental instability of the electron sea, occurring in a host of materials and often linked to other collective ground states such as superconductivity. What is difficult to parse, however, is whether the charge order originates among the itinerant electrons or whether it arises from the ionic lattice. Here in this study we employ high-resolution X-ray diffraction, combined with high-pressure and low-temperature techniques and theoretical modelling, to trace the evolution of the ordering wavevector Q in charge and spin density wave systems at the approach to both thermal and quantum phase transitions. The non-monotonic behaviour of Q with pressure and the limiting sinusoidal form of the density wave point to the dominant role of the itinerant instability in the vicinity of the critical points, with little influence from the lattice. Fluctuations rather than disorder seem to disrupt coherence.

  17. Black holes as critical point of quantum phase transition

    NASA Astrophysics Data System (ADS)

    Dvali, Gia; Gomez, Cesar

    2014-02-01

    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.

  18. Itinerant density wave instabilities at classical and quantum critical points

    NASA Astrophysics Data System (ADS)

    Feng, Yejun; van Wezel, Jasper; Wang, Jiyang; Flicker, Felix; Silevitch, D. M.; Littlewood, P. B.; Rosenbaum, T. F.

    2015-10-01

    Charge ordering in metals is a fundamental instability of the electron sea, occurring in a host of materials and often linked to other collective ground states such as superconductivity. What is difficult to parse, however, is whether the charge order originates among the itinerant electrons or whether it arises from the ionic lattice. Here we employ high-resolution X-ray diffraction, combined with high-pressure and low-temperature techniques and theoretical modelling, to trace the evolution of the ordering wavevector Q in charge and spin density wave systems at the approach to both thermal and quantum phase transitions. The non-monotonic behaviour of Q with pressure and the limiting sinusoidal form of the density wave point to the dominant role of the itinerant instability in the vicinity of the critical points, with little influence from the lattice. Fluctuations rather than disorder seem to disrupt coherence.

  19. Itinerant density wave instabilities at classical and quantum critical points

    DOE PAGES

    Feng, Yejun; van Wezel, Jasper; Wang, Jiyang; ...

    2015-07-27

    Charge ordering in metals is a fundamental instability of the electron sea, occurring in a host of materials and often linked to other collective ground states such as superconductivity. What is difficult to parse, however, is whether the charge order originates among the itinerant electrons or whether it arises from the ionic lattice. Here in this study we employ high-resolution X-ray diffraction, combined with high-pressure and low-temperature techniques and theoretical modelling, to trace the evolution of the ordering wavevector Q in charge and spin density wave systems at the approach to both thermal and quantum phase transitions. The non-monotonic behaviourmore » of Q with pressure and the limiting sinusoidal form of the density wave point to the dominant role of the itinerant instability in the vicinity of the critical points, with little influence from the lattice. Fluctuations rather than disorder seem to disrupt coherence.« less

  20. Black holes as critical point of quantum phase transition.

    PubMed

    Dvali, Gia; Gomez, Cesar

    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.

  1. Liftshitz-point critical behaviour to O(ɛ2)

    NASA Astrophysics Data System (ADS)

    Diehl, H. W.; Shpot, M.

    2001-10-01

    We comment on a recent letter by de Albuquerque and Leite (2001 J. Phys. A: Math. Gen. 34 L327), in which results to the second order in ɛ = 4 - d + m/2 were presented for the critical exponents νL2, ηL2 and γL2 of d-dimensional systems at m-axial Lifshitz points. We point out that their results are at variance with ours. The discrepancy is due to their incorrect computation of momentum-space integrals. Their speculation that the field-theoretic renormalization group approach, if performed in position space, might give results different from when it is performed in momentum space is refuted.

  2. Radial oscillations of thin cylindrical and spherical shells: investigation of Lie point symmetries for arbitrary strain-energy functions

    NASA Astrophysics Data System (ADS)

    Roussos, N.; Mason, D. P.

    2005-03-01

    The Lie point symmetry structure of the second order differential equations which describe non-linear radial oscillations of thin-walled hyperelastic cylindrical and spherical shells is investigated. The differential equations depend on the strain-energy function and on the net applied surface pressure. If the net applied surface pressure is time independent, the differential equations admit the Lie point symmetry corresponding to time translational invariance for arbitrary strain-energy functions. Other Lie point symmetries exist for each equation only for special classes of strain-energy function. For the cylindrical shell the special class includes the Mooney-Rivlin strain-energy function and the differential equation reduces to the Ermakov-Pinney equation. A new solution is obtained for a specific time dependent net applied surface pressure. For the spherical shell the special class does not include the Mooney-Rivlin strain-energy function. For free oscillations the differential equation reduces to the Ermakov-Pinney equation but there also exists a special net applied surface pressure and for this pressure the differential equation is more general than the Ermakov-Pinney equation.

  3. The two-dimensional monatomic Leonard-Jones system: triple point and critical point

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi; Chen, Li-rong

    2001-07-01

    We introduce a Leonard-Jones (L-J) interaction into the two-dimensional (2D) Collins model, and consider the existence of the holes that are called the molecular fraction. The Gibbs free energy of solid, liquid and gas has been derived. From the Gibbs function we have obtained the whole diagram of the 2D monatomic L-J system, which includes the melting line, vaporization line, sublimation line and the triple point. Also, we have discussed a few properties of the critical point.

  4. Universal critical-like scaling of dynamic properties in symmetry-selected glass formers

    NASA Astrophysics Data System (ADS)

    Drozd-Rzoska, Aleksandra; Rzoska, Sylwester J.; Paluch, Marian

    2008-11-01

    Evidence for a possible general validity of the critical-like behavior of dielectric relaxation time or viscosity τ,η∝(T-TC)-ϕ with ϕ →9 and TCsymmetry. The supporting evidence was obtained on the basis of the distortion-sensitive, derivative-based analysis of τ(T ) data for a rodlike liquid crystalline compound (E7), orientationally disordered crystals (plastic crystals), a colloidal nanofluid system, polymer melt (polystyrene), oligomeric liquid (EPON 828), and low molecular weight glass formers (glycerol, threitol, sorbitol, and 1-propanol). Results presented explain the puzzling experimental artifacts supporting the dynamical scaling model [R. H. Colby, Phys. Rev. E 61, 1783 (2000); B. M. Erwin, R. H. Colby, J. Non-Cryst. Solids 307-310, 225 (2002)]. It is suggested that spin-glass-like systems may be linked to the discussed pattern.

  5. Universal critical-like scaling of dynamic properties in symmetry-selected glass formers.

    PubMed

    Drozd-Rzoska, Aleksandra; Rzoska, Sylwester J; Paluch, Marian

    2008-11-14

    Evidence for a possible general validity of the critical-like behavior of dielectric relaxation time or viscosity tau,eta proportional to (T-T(C))(-phi) with phi-->9 and T(C)symmetry. The supporting evidence was obtained on the basis of the distortion-sensitive, derivative-based analysis of tau(T) data for a rodlike liquid crystalline compound (E7), orientationally disordered crystals (plastic crystals), a colloidal nanofluid system, polymer melt (polystyrene), oligomeric liquid (EPON 828), and low molecular weight glass formers (glycerol, threitol, sorbitol, and 1-propanol). Results presented explain the puzzling experimental artifacts supporting the dynamical scaling model [R. H. Colby, Phys. Rev. E 61, 1783 (2000); B. M. Erwin, R. H. Colby, J. Non-Cryst. Solids 307-310, 225 (2002)]. It is suggested that spin-glass-like systems may be linked to the discussed pattern.

  6. Ubiquitous symmetries

    NASA Astrophysics Data System (ADS)

    Nucci, M. C.

    2016-09-01

    We review some of our recent work devoted to the problem of quantization with preservation of Noether symmetries, finding hidden linearity in superintegrable systems, and showing that nonlocal symmetries are in fact local. In particular, we derive the Schrödinger equation for the isochronous Calogero goldfish model using its relation to Darwin equation. We prove the linearity of a classical superintegrable system on a plane of nonconstant curvature. We find the Lie point symmetries that correspond to the nonlocal symmetries (also reinterpreted as λ-symmetries) of the Riccati chain.

  7. On the use of Abelian point group symmetry in density-fitted local MP2 using various types of virtual orbitals

    SciTech Connect

    Köppl, Christoph; Werner, Hans-Joachim

    2015-04-28

    Electron correlation methods based on symmetry-adapted canonical Hartree-Fock orbitals can be speeded up significantly in the well known group theoretical manner, using the fact that integrals vanish unless the integrand is totally symmetric. In contrast to this, local electron correlation methods cannot benefit from such simplifications, since the localized molecular orbitals (LMOs) generally do not transform according to irreducible representations of the underlying point group symmetry. Instead, groups of LMOs become symmetry-equivalent and this can be exploited to accelerate local calculations. We describe an implementation of such a symmetry treatment for density-fitted local Møller-Plesset perturbation theory, using various types of virtual orbitals: Projected atomic orbitals, orbital specific virtuals, and pair natural orbitals. The savings by the symmetry treatment are demonstrated by calculations for several large molecules having different point group symmetries. Benchmarks for the parallel execution efficiency of our method are also presented.

  8. Risk assessment and critical control points from the production perspective.

    PubMed

    Serra, J A; Domenech, E; Escriche, I; Martorell, S

    1999-01-12

    The implementation of a risk analysis program as risk assessment and critical control points (RACCP) is most necessary in order to accomplish the foodborne industries current objective of total quality. The novelty of this technique, when compared to actual hazard analysis and critical control points (HACCP) and its extension to incorporate elements of quantitative risk analysis (QRA), is that RACCP considers the risk of the consequences produced by the production process performance deviations, both inside and outside the company, and also identifies their causative factors. On the other hand, the techniques to be taken in order to prevent or mitigate the consequences of such deviations must be consistent with the former data, but the need for a cost-benefit assessment must not be ignored so that the chosen technique be most profitable for the company. An example developed in a mineral water bottling plant showed that RACCP application is feasible and useful. During this example case, RACCP demonstrated it could obtain a profitable production process that keeps quality and safety of the final product at its maximum, while providing protection to both company and consumer.

  9. Critical point drying: contamination in transitional fluid supply cylinders.

    PubMed

    Hoagland, K D; Rosowski, J R; Cohen, A L

    1980-01-01

    We call attention to the occurrence of an oily residue in the CPD bomb after critical point drying, as well as the presence of rust, dirt, and an oily residue in CO2 and Freon supply cylinders. Bottled gas is often tested for purity once after manufacturing and then is pumped and stored, perhaps several times, before the consumer's cylinders are filled. The cylinders may be in use for over 40 years, and may never be chemically cleaned, although they are hydrostatically pressure tested every five years, with the date of each test stamped on the cylinder. To the bottled gas industry we recommend regular inspection of tanks for bottom contamination, and vacuum and chemical cleaning when contamination is found. To users of bottled gas for critical point drying, we recommend becoming aware of the procedures of cylinder inspection, cleaning, and circulation among users. We suggest reporting to the gas supplier any contamination produced by inadvertently backfilling the supply cylinder. Although a common awareness of the problem of supply cylinder residues should lead to failures, the best assurance of clean, oil-free, dry liquid CO2 and other transitional fluids may be in the development of in-line filters which would remove particles, oil and moisture between the supply cylinder and the CPD bomb. We also suggest the use of gas grades higher than commercial, such as welding anhydrous (CO2) or specialty gases.

  10. Duality between the Deconfined Quantum-Critical Point and the Bosonic Topological Transition

    NASA Astrophysics Data System (ADS)

    Qin, Yan Qi; He, Yuan-Yao; You, Yi-Zhuang; Lu, Zhong-Yi; Sen, Arnab; Sandvik, Anders W.; Xu, Cenke; Meng, Zi Yang

    2017-07-01

    Recently, significant progress has been made in (2 +1 )-dimensional conformal field theories without supersymmetry. In particular, it was realized that different Lagrangians may be related by hidden dualities; i.e., seemingly different field theories may actually be identical in the infrared limit. Among all the proposed dualities, one has attracted particular interest in the field of strongly correlated quantum-matter systems: the one relating the easy-plane noncompact CP1 model (NCCP1 ) and noncompact quantum electrodynamics (QED) with two flavors (N =2 ) of massless two-component Dirac fermions. The easy-plane NCCP1 model is the field theory of the putative deconfined quantum-critical point separating a planar (X Y ) antiferromagnet and a dimerized (valence-bond solid) ground state, while N =2 noncompact QED is the theory for the transition between a bosonic symmetry-protected topological phase and a trivial Mott insulator. In this work, we present strong numerical support for the proposed duality. We realize the N =2 noncompact QED at a critical point of an interacting fermion model on the bilayer honeycomb lattice and study it using determinant quantum Monte Carlo (QMC) simulations. Using stochastic series expansion QMC simulations, we study a planar version of the S =1 /2 J -Q spin Hamiltonian (a quantum X Y model with additional multispin couplings) and show that it hosts a continuous transition between the X Y magnet and the valence-bond solid. The duality between the two systems, following from a mapping of their phase diagrams extending from their respective critical points, is supported by the good agreement between the critical exponents according to the proposed duality relationships. In the J -Q model, we find both continuous and first-order transitions, depending on the degree of planar anisotropy, with deconfined quantum criticality surviving only up to moderate strengths of the anisotropy. This explains previous claims of no deconfined quantum

  11. Measurement of Critical Adsorption of Nitrogen near Its Liquid-vapor Critical Point

    NASA Technical Reports Server (NTRS)

    Chan, Moses

    2003-01-01

    The density profile of a critical fluid near a solid surface is expected to show an universal shape. This is known as critical adsorption. The measurement of this effect, especially close to the critical point, is often obscured by gravity. We were able to separate the gravitational effect from critical adsorption by using two capacitors, one with a large gap and one with a small gap of approximately 2 m. Within the uncertainty in the measurement, our data, which ranges between 10(exp -3) to 2 x 10(exp -6) in reduced temperatures, is consistent with the predicted power law dependence. This work is carried out in collaboration with Rafael Garcia, Sarah Scheidemantel and Klaus Knorr. It is funded by NASA's office of Biological and Physical Researchunder.

  12. Measurement of Critical Adsorption of Nitrogen near Its Liquid-vapor Critical Point

    NASA Technical Reports Server (NTRS)

    Chan, Moses

    2003-01-01

    The density profile of a critical fluid near a solid surface is expected to show an universal shape. This is known as critical adsorption. The measurement of this effect, especially close to the critical point, is often obscured by gravity. We were able to separate the gravitational effect from critical adsorption by using two capacitors, one with a large gap and one with a small gap of approximately 2 m. Within the uncertainty in the measurement, our data, which ranges between 10(exp -3) to 2 x 10(exp -6) in reduced temperatures, is consistent with the predicted power law dependence. This work is carried out in collaboration with Rafael Garcia, Sarah Scheidemantel and Klaus Knorr. It is funded by NASA's office of Biological and Physical Researchunder.

  13. Thermal fluctuation exponents for two near-critical point systems

    NASA Astrophysics Data System (ADS)

    Oprisan, Ana; Bayley, Brittany; Oprisan, Sorinel A.; Hegseth, John J.; Garrabos, Yves; Lecoutre, Carole; Beysens, Daniel

    2010-04-01

    In the supercritical phase, pure fluids have great potential for industrial applications and are increasingly used by industry as nonpolluting solvents of organic materials and media for high yield chemical reactions. The experimental data were recorded in microgravity for sulfur hexafluoride (SF6) and on Earth for density-matching binary mixture of methanol and partially deuterated cyclohexane (CC*-Me). We used small angle light scattering experiments to investigate fluctuations in SF6 near critical point and in density-matched binary mixture CC*-Me in the absence of convective flows. For binary mixture, we used three different filtering methods: bright filed (BF - no filter), phase contrast (PC - quarter wave plate at focal point) and dark field (DF - small opaque object at focal point). The power spectrum of scattered light contains information about local inhomogeneities encountered by light traveling through the sample cell unit (SCU). We found that the spatial correlations revealed by Fourier transforms follow power laws both for SF6 in microgravity and binary mixture on Earth. This is an indication of the universality of fluctuation mechanisms. Temporal correlations of fluctuations were investigated using the correlation time.

  14. Impurities near an antiferromagnetic-singlet quantum critical point

    NASA Astrophysics Data System (ADS)

    Mendes-Santos, T.; Costa, N. C.; Batrouni, G.; Curro, N.; dos Santos, R. R.; Paiva, T.; Scalettar, R. T.

    2017-02-01

    Heavy-fermion systems and other strongly correlated electron materials often exhibit a competition between antiferromagnetic (AF) and singlet ground states. Using exact quantum Monte Carlo simulations, we examine the effect of impurities in the vicinity of such an AF-singlet quantum critical point (QCP), through an appropriately defined "impurity susceptibility" χimp. Our key finding is a connection within a single calculational framework between AF domains induced on the singlet side of the transition and the behavior of the nuclear magnetic resonance (NMR) relaxation rate 1 /T1 . We show that local NMR measurements provide a diagnostic for the location of the QCP, which agrees remarkably well with the vanishing of the AF order parameter and large values of χimp.

  15. Impurities near an antiferromagnetic-singlet quantum critical point

    DOE PAGES

    Mendes-Santos, T.; Costa, N. C.; Batrouni, G.; ...

    2017-02-15

    Heavy-fermion systems and other strongly correlated electron materials often exhibit a competition between antiferromagnetic (AF) and singlet ground states. We examine the effect of impurities in the vicinity of such an AF-singlet quantum critical point (QCP), through an appropriately defined “impurity susceptibility” χimp, using exact quantum Monte Carlo simulations. Our key finding is a connection within a single calculational framework between AF domains induced on the singlet side of the transition and the behavior of the nuclear magnetic resonance (NMR) relaxation rate 1/T1. Furthermore, we show that local NMR measurements provide a diagnostic for the location of the QCP, whichmore » agrees remarkably well with the vanishing of the AF order parameter and large values of χimp.« less

  16. G proteins: critical control points for transmembrane signals.

    PubMed Central

    Neer, E. J.

    1994-01-01

    Heterotrimeric GTP-binding proteins (G proteins) that are made up of alpha and beta gamma subunits couple many kinds of cell-surface receptors to intracellular effector enzymes or ion channels. Every cell contains several types of receptors, G proteins, and effectors. The specificity with which G protein subunits interact with receptors and effectors defines the range of responses a cell is able to make to an external signal. Thus, the G proteins act as a critical control point that determines whether a signal spreads through several pathways or is focused to a single pathway. In this review, I will summarize some features of the structure and function of mammalian G protein subunits, discuss the role of both alpha and beta gamma subunits in regulation of effectors, the role of the beta gamma subunit in macromolecular assembly, and the mechanisms that might make some responses extremely specific and others rather diffuse. PMID:8142895

  17. Rapid microbiological methods with hazard analysis critical control point.

    PubMed

    Griffiths, M W

    1997-01-01

    The proactive approach to ensuring food safety termed hazard analysis critical control point (HACCP) was introduced in the 1960s by the Pillsbury Company, in collaboration with the U.S. Army Natick Laboratories and National Aeronautics and Space Administration, to help guarantee that astronauts would not be incapacitated by the trauma of foodborne illness during space flights. The approach has subsequently been adopted as the standard food safety management system world-wide and is seen as forming the basis for harmonization of food inspection regulations necessitated by trade agreements such as General Agreement on Tariffs and Trade and North American Free Trade Agreement as the move toward globalization of trade in food products gains momentum. The new U.S. Department of Agriculture Mega-Reg requires mandatory introduction of HACCP, and the Food Safety Enhancement Program of Agriculture and Agri-food Canada, as well as the "due diligence" legislation of the European Union, is centered on HACCP principles.

  18. Shear Thinning Near the Critical Point of Xenon

    NASA Technical Reports Server (NTRS)

    Zimmerli, Gregory A.; Berg, Robert F.; Moldover, Michael R.; Yao, Minwu

    2008-01-01

    We measured shear thinning, a viscosity decrease ordinarily associated with complex liquids, near the critical point of xenon. The data span a wide range of reduced shear rate: 10(exp -3) < gamma-dot tau < 700, where gamma-dot tau is the shear rate scaled by the relaxation time tau of critical fluctuations. The measurements had a temperature resolution of 0.01 mK and were conducted in microgravity aboard the Space Shuttle Columbia to avoid the density stratification caused by Earth's gravity. The viscometer measured the drag on a delicate nickel screen as it oscillated in the xenon at amplitudes 3 mu,m < chi (sub 0) >430 mu, and frequencies 1 Hz < omega/2 pi < 5 Hz. To separate shear thinning from other nonlinearities, we computed the ratio of the viscous force on the screen at gamma-dot tau to the force at gamma-dot tau approximates 0: C(sub gamma) is identical with F(chi(sub 0), omega tau, gamma-dot tau )/F)(chi(sub 0, omega tau, 0). At low frequencies, (omega tau)(exp 2) < gamma-dot tau, C(sub gamma) depends only on gamma-dot tau, as predicted by dynamic critical scaling. At high frequencies, (omega tau)(exp 2) > gamma-dot tau, C(sub gamma) depends also on both x(sub 0) and omega. The data were compared with numerical calculations based on the Carreau-Yasuda relation for complex fluids: eta(gamma-dot)/eta(0)=[1+A(sub gamma)|gamma-dot tau|](exp - chi(sub eta)/3+chi(sub eta)), where chi(sub eta) =0.069 is the critical exponent for viscosity and mode-coupling theory predicts A(sub gamma) =0.121. For xenon we find A(sub gamma) =0.137 +/- 0.029, in agreement with the mode coupling value. Remarkably, the xenon data close to the critical temperature T(sub c) were independent of the cooling rate (both above and below T(sub c) and these data were symmetric about T(sub c) to within a temperature scale factor. The scale factors for the magnitude of the oscillator s response differed from those for the oscillator's phase; this suggests that the surface tension of the two

  19. Shear Thinning Near the Critical Point of Xenon

    NASA Technical Reports Server (NTRS)

    Zimmerli, Gregory A.; Berg, Robert F.; Moldover, Michael R.; Yao, Minwu

    2008-01-01

    We measured shear thinning, a viscosity decrease ordinarily associated with complex liquids, near the critical point of xenon. The data span a wide range of reduced shear rate: 10(exp -3) < gamma-dot tau < 700, where gamma-dot tau is the shear rate scaled by the relaxation time tau of critical fluctuations. The measurements had a temperature resolution of 0.01 mK and were conducted in microgravity aboard the Space Shuttle Columbia to avoid the density stratification caused by Earth's gravity. The viscometer measured the drag on a delicate nickel screen as it oscillated in the xenon at amplitudes 3 mu,m < chi (sub 0) >430 mu, and frequencies 1 Hz < omega/2 pi < 5 Hz. To separate shear thinning from other nonlinearities, we computed the ratio of the viscous force on the screen at gamma-dot tau to the force at gamma-dot tau approximates 0: C(sub gamma) is identical with F(chi(sub 0), omega tau, gamma-dot tau )/F)(chi(sub 0, omega tau, 0). At low frequencies, (omega tau)(exp 2) < gamma-dot tau, C(sub gamma) depends only on gamma-dot tau, as predicted by dynamic critical scaling. At high frequencies, (omega tau)(exp 2) > gamma-dot tau, C(sub gamma) depends also on both x(sub 0) and omega. The data were compared with numerical calculations based on the Carreau-Yasuda relation for complex fluids: eta(gamma-dot)/eta(0)=[1+A(sub gamma)|gamma-dot tau|](exp - chi(sub eta)/3+chi(sub eta)), where chi(sub eta) =0.069 is the critical exponent for viscosity and mode-coupling theory predicts A(sub gamma) =0.121. For xenon we find A(sub gamma) =0.137 +/- 0.029, in agreement with the mode coupling value. Remarkably, the xenon data close to the critical temperature T(sub c) were independent of the cooling rate (both above and below T(sub c) and these data were symmetric about T(sub c) to within a temperature scale factor. The scale factors for the magnitude of the oscillator s response differed from those for the oscillator's phase; this suggests that the surface tension of the two

  20. Effective intermolecular potential and critical point for C60 molecule

    NASA Astrophysics Data System (ADS)

    Ramos, J. Eloy

    2017-07-01

    The approximate nonconformal (ANC) theory is applied to the C60 molecule. A new binary potential function is developed for C60, which has three parameters only and is obtained by averaging the site-site carbon interactions on the surface of two C60 molecules. It is shown that the C60 molecule follows, to a good approximation, the corresponding states principle with n-C8H18, n-C4F10 and n-C5F12. The critical point of C60 is estimated in two ways: first by applying the corresponding states principle under the framework of the ANC theory, and then by using previous computer simulations. The critical parameters obtained by applying the corresponding states principle, although very different from those reported in the literature, are consistent with the previous results of the ANC theory. It is shown that the Girifalco potential does not correspond to an average of the site-site carbon-carbon interaction.

  1. Influence of intermolecular forces at critical-point wedge filling

    NASA Astrophysics Data System (ADS)

    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.

  2. Phase separation in polymer solutions near the critical point

    NASA Astrophysics Data System (ADS)

    Cherayil, Binny J.

    1991-08-01

    The Edwards path-integral description of chain statistics is used to derive an effective φ4 field theory of polymer solutions that is applicable near the temperature of critical phase separation Tc. The present formalism, an extension of the mean-field approach discussed in paper I [R. E. Goldstein and B. J. Cherayil, J. Chem. Phys. 90, 7448 (1989)], makes use of standard results from the theory of continuous phase transitions to account for the effects of previously neglected density fluctuations, and to obtain thereby, among other results, estimates for the temperature and molecular weight-scaling exponents of the coexistence curve in the vicinity of Tc. The critical monomer volume fraction ρc of the solution is shown to scale as the osmotic second virial coefficient below the theta point, providing a rigorous approach to the calculation of the molecular weight dependence of ρc. Experimental data on the phase separation of solutions of polystyrene in methylcyclohexane are shown to lie on a single universal curve when expressed in terms of the scaling variables suggested by the present analysis.

  3. Entanglement entropy near Kondo-destruction quantum critical points

    NASA Astrophysics Data System (ADS)

    Chowdhury, Tathagata; Wagner, Christopher; Ingersent, Kevin; Pixley, Jedediah

    Entanglement entropy is a measure of quantum-mechanical entanglement across the boundary created by partitioning a system into two subsystems. We study this quantity in Kondo impurity models that feature Kondo-destruction quantum critical points (QCPs). Recent work has shown that the entanglement entropy between a Kondo impurity of spin Simp and its environment is pinned at its maximum possible value Se = ln (2Simp + 1) throughout the Kondo phase. In the Kondo-destroyed phase, where the impurity spin acquires a nonzero expectation value Mloc, Se = ln (2Simp + 1) - a (Simp) Mloc2 irrespective of the properties of the host. Here, we report numerical renormalization-group results for Kondo models with a pseudogapped density of states under a different partition that separates the impurity and on-site conduction electrons from the rest of the system. Now, the entanglement entropy is affected by the nature of the environment beyond the information contained in Mloc, but Se still contains a critical part that exhibits power-law behavior in the vicinity of the Kondo-destruction QCP

  4. Influence of intermolecular forces at critical-point wedge filling.

    PubMed

    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.

  5. Entropy excess in strongly correlated Fermi systems near a quantum critical point

    SciTech Connect

    Clark, J.W.; Zverev, M.V.; Khodel, V.A.

    2012-12-15

    A system of interacting, identical fermions described by standard Landau Fermi-liquid (FL) theory can experience a rearrangement of its Fermi surface if the correlations grow sufficiently strong, as occurs at a quantum critical point where the effective mass diverges. As yet, this phenomenon defies full understanding, but salient aspects of the non-Fermi-liquid (NFL) behavior observed beyond the quantum critical point are still accessible within the general framework of the Landau quasiparticle picture. Self-consistent solutions of the coupled Landau equations for the quasiparticle momentum distribution n(p) and quasiparticle energy spectrum {epsilon}(p) are shown to exist in two distinct classes, depending on coupling strength and on whether the quasiparticle interaction is regular or singular at zero momentum transfer. One class of solutions maintains the idempotency condition n{sup 2}(p)=n(p) of standard FL theory at zero temperature T while adding pockets to the Fermi surface. The other solutions are characterized by a swelling of the Fermi surface and a flattening of the spectrum {epsilon}(p) over a range of momenta in which the quasiparticle occupancies lie between 0 and 1 even at T=0. The latter, non-idempotent solution is revealed by analysis of a Poincare mapping associated with the fundamental Landau equation connecting n(p) and {epsilon}(p) and validated by solution of a variational condition that yields the symmetry-preserving ground state. Significantly, this extraordinary solution carries the burden of a large temperature-dependent excess entropy down to very low temperatures, threatening violation of the Nernst Theorem. It is argued that certain low-temperature phase transitions, notably those involving Cooper-pair formation, offer effective mechanisms for shedding the entropy excess. Available measurements in heavy-fermion compounds provide concrete support for such a scenario. - Highlights: Black-Right-Pointing-Pointer Extension of Landau

  6. Lie symmetry analysis of the Lundgren-Monin-Novikov equations for multi-point probability density functions of turbulent flow

    NASA Astrophysics Data System (ADS)

    Wacławczyk, M.; Grebenev, V. N.; Oberlack, M.

    2017-04-01

    The problem of turbulence statistics described by the Lundgren-Monin-Novikov (LMN) hierarchy of integro-differential equations is studied in terms of its group properties. For this we perform a Lie group analysis of a truncated LMN chain which presents the first two equations in an infinite set of integro-differential equations for the multi-point probability density functions (pdf’s) of velocity. A complete set of point transformations is derived for the one-point pdf’s and the independent variables: sample space of velocity, space and time. For this purpose we use a direct method based on the canonical Lie-Bäcklund operator. Due to the one-way coupling of correlation equations, the present results are complete in the sense that no additional symmetries exist for the first leading equation, even if the full infinite hierarchy is considered.

  7. Theory of the nematic quantum critical point in a nodal superconductor

    NASA Astrophysics Data System (ADS)

    Kim, Eun-Ah

    2008-03-01

    In the last several years, experimental evidence has accumulated in a variety of highly correlated electronic systems of new quantum phases which (for purely electronic reasons) spontaneously break the rotational (point group) symmetry of the underlying crystal. Such electron ``nematic'' phases have been seen in quantum Hall systems[1], in the metamagnetic metal Sr3Ru2O7[2], and more recently in magnetic neutron scattering studies of the high temperature superconductor, YBCO[3]. In the case of a high Tc superconductor, the quantum dynamics of nematic order parameter naturally couples strongly to quasiparticle (qp) excitations. In this talk, I will discuss our recent results on the effects of the coupling between quantum critical nematic fluctuations and the nodal qp's of a d-wave superconductor in the vicinity of a putative quantum critical point inside the superconducting phase. We solve a model system with N flavors of quasiparticles in the large N limit[4]. To leading order in 1/N, quantum fluctuations enhance the dispersion anisotropy of the nodal excitations, and cause strong scattering which critically broadens the quasiparticle peaks in the spectral function, except in the vicinity of ``the tips of the banana,'' where the qp's remain sharp. We will discuss the possible implications of our results to ARPES and STM experiments. [1] M.P. Lilly, K.B. Cooper, J.P. Eisenstein, L.N. Pfeiffer, and K.W. West, PRL 83, 824 (1999). [2] R. A. Borzi and S. A. Grigera and J. Farrell and R. S. Perry and S. J. S. Lister and S. L. Lee and D. A. Tennant and Y. Maeno and A. P. Mackenzie, Science 315, 214 (2007). [3] V. Hinkov, D. Haug, B. Fauqu'e, P. Bourges, Y. Sidis, A. Ivanov, C. Bernhard, C. T. Lin, B. Keimer, unpublished. [4] E.-A. Kim, M. Lawler, P. Oreto, E. Fradkin, S. Kivelson, cond-mat/0705.4099.

  8. Critical limits for the control points for halal poultry slaughter.

    PubMed

    Shahdan, Intan Azura; Regenstein, Joe Mac; Rahman, Mohammad Tariqur

    2016-12-13

    This study proposes critical limits (CL) for control points for halal slaughter (CPHS). Previously, 6 control points (CP) were determined, and CL for these 6 CPHS are suggested based on: 1) a literature survey for the CL for CP 1 (poultry breeding, rearing, and poultry feed) and CP 2 (welfare of poultry during transportation and lairage); 2) a field survey of slaughter plants in Kuantan (Malaysia) for CP 3 (immobilization), CP 4 (slaughter), CP 5 (time for full bleed-out), and CP 6 (washing and packaging); and 3) controlled experiments to refine the CL for CP 3, 4, and 5. The CL for CP 1 focused on stress reduction during rearing and use of substances that could compromise poultry meat wholesomeness. The CL for CP 2 emphasizes humane best-practices for handling poultry during lairage. The CL for CP 3 suggests a gap of 5 s between 2 shackles if only one shackler is employed and shackling times of <1 min for live chickens. In countries permitting water-bath electrical stunning of halal poultry, the stunning current needed to induce unconsciousness must be defined for the breed and bird size but not cause any chicken deaths. The CL for CP 4 mandates the recitation of the tasmiyah (the invocation), which if done for every chicken, will require ≥5 s between stunning and neck cutting. The CL for CP 4 also includes information about the slaughter knife. In CP 5 the recommended minimum time between neck cutting and scalding is 9.5 min. Finally, the CL for CP 6 emphasizes good supply chain hygiene and zero adulteration from haram species and substances.

  9. A critical appraisal of point-of-care coagulation testing in critically ill patients.

    PubMed

    Levi, M; Hunt, B J

    2015-11-01

    Derangement of the coagulation system is a common phenomenon in critically ill patients, who may present with severe bleeding and/or conditions associated with a prothrombotic state. Monitoring of this coagulopathy can be performed with conventional coagulation assays; however, point-of-care tests have become increasingly attractive, because not only do they yield a more rapid result than clinical laboratory testing, but they may also provide a more complete picture of the condition of the hemostatic system. There are many potential areas of study and applications of point-of-care hemostatic testing in critical care, including patients who present with massive blood loss, patients with a hypercoagulable state (such as in disseminated intravascular coagulation), and monitoring of antiplatelet treatment for acute arterial thrombosis, mostly acute coronary syndromes. However, the limitations of near-patient hemostatic testing has not been fully appreciated, and are discussed here. The currently available evidence indicates that point-of-care tests may be applied to guide appropriate blood product transfusion and the use of hemostatic agents to correct the hemostatic defect or to ameliorate antithrombotic treatment. Disappointingly, however, only in cardiac surgery is there adequate evidence to show that application of near-patient thromboelastography leads to an improvement in clinically relevant outcomes, such as reductions in bleeding-related morbidity and mortality, and cost-effectiveness. More research is required to validate the utility and cost-effectiveness of near-patient hemostatic testing in other areas, especially in traumatic bleeding and postpartum hemorrhage.

  10. Remembrance of things past: non-equilibrium effects and the evolution of critical fluctuations near the QCD critical point

    NASA Astrophysics Data System (ADS)

    Mukherjee, Swagato; Venugopalan, Raju; Yin, Yi

    2016-12-01

    We report on recent progress in the study of the evolution of non-Gaussian cumulants of critical fluctuations. We explore the implications of non-equilibrium effects on the search for the QCD critical point.

  11. Superuniversal transport near a (2 +1 ) -dimensional quantum critical point

    NASA Astrophysics Data System (ADS)

    Rose, F.; Dupuis, N.

    2017-09-01

    We compute the zero-temperature conductivity in the two-dimensional quantum O (N ) model using a nonperturbative functional renormalization-group approach. At the quantum critical point we find a universal conductivity σ*/σQ (with σQ=q2/h the quantum of conductance and q the charge) in reasonable quantitative agreement with quantum Monte Carlo simulations and conformal bootstrap results. In the ordered phase the conductivity tensor is defined, when N ≥3 , by two independent elements, σA(ω ) and σB(ω ) , respectively associated with SO (N ) rotations which do and do not change the direction of the order parameter. Whereas σA(ω →0 ) corresponds to the response of a superfluid (or perfect inductance), the numerical solution of the flow equations shows that limω→0σB(ω ) /σQ=σB*/σQ is a superuniversal (i.e., N -independent) constant. These numerical results, as well as the known exact value σB*/σQ=π /8 in the large-N limit, allow us to conjecture that σB*/σQ=π /8 holds for all values of N , a result that can be understood as a consequence of gauge invariance and asymptotic freedom of the Goldstone bosons in the low-energy limit.

  12. CARS spectroscopy of carbon dioxide in the critical point vicinity

    SciTech Connect

    Arakcheev, V G; Valeev, A A; Gordienko, Vyacheslav M; Kireev, Vyacheslav V; Morozov, V B; Olenin, A N; Tunkin, V G; Yakovlev, D V; Bagratashvili, Viktor N; Popov, Vladimir K

    2004-01-31

    The transformation of the Q-band of the low-frequency 1285-cm{sup -1} component of the 2v{sub 2}/v{sub 1} Fermi doublet of a CO{sub 2} molecule is studied in the critical point vicinity (T{sub c}=31.03 {sup 0}C, P{sub c}=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 36{sup 0}C. At the temperature above 29{sup 0}C, 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)

  13. Stochastic approximation of dynamical exponent at quantum critical point

    NASA Astrophysics Data System (ADS)

    Yasuda, Shinya; Suwa, Hidemaro; Todo, Synge

    2015-09-01

    We have developed a unified finite-size scaling method for quantum phase transitions that requires no prior knowledge of the dynamical exponent z . During a quantum Monte Carlo simulation, the temperature is automatically tuned by the Robbins-Monro stochastic approximation method, being proportional to the lowest gap of the finite-size system. The dynamical exponent is estimated in a straightforward way from the system-size dependence of the temperature. As a demonstration of our novel method, the two-dimensional S =1 /2 quantum X Y model in uniform and staggered magnetic fields is investigated in the combination of the world-line quantum Monte Carlo worm algorithm. In the absence of a uniform magnetic field, we obtain the fully consistent result with the Lorentz invariance at the quantum critical point, z =1 , i.e., the three-dimensional classical X Y universality class. Under a finite uniform magnetic field, on the other hand, the dynamical exponent becomes two, and the mean-field universality with effective dimension (2 +2 ) governs the quantum phase transition.

  14. Critical point of the solar wind by radio sounding data

    NASA Technical Reports Server (NTRS)

    Lotova, N. A.; Oraevsky, V. N.; Pisarenko, Ya. V.; Vladimirskii, K. V.

    1995-01-01

    Results of the close-to-Sun plasmas sounding at the transonic region of the solar wind, where the sub-to supersonic flow transition proceeds (at 10 to 40 solar radii from the Sun), are presented. Natural sources of two types were used, water vapour maser sources at 1.35 cm and guasars at 2.9 m wavelength. scattering observations cover the period of 1986 to 1993, Russian Academy of Sciences telescopes RT-22 and DCR-1000 were used, IPS index and scattering angle being the immediate results of observations. Extensive studies of the scintillation index and scattering angle radial profiles reveal a remarkable structural detail, 'transonic region forrunner'-narrow region of diminished scattering close to the internal border of the extended transonic region with its characteristic enhanced scattering. Comparisons of the scattering and plasma velocity profiles let it possible to determine the critical point positions by the comparatively simple scattering observations. This new possibility widely improves the process of the basic data accumulation in the fundamental problem of the solar wind acceleration mechanism.

  15. Stochastic Approximation of Dynamical Exponent at Quantum Critical Point

    NASA Astrophysics Data System (ADS)

    Suwa, Hidemaro; Yasuda, Shinya; Todo, Synge

    We have developed a unified finite-size scaling method for quantum phase transitions that requires no prior knowledge of the dynamical exponent z. During a quantum Monte Carlo simulation, the temperature is automatically tuned by the Robbins-Monro stochastic approximation method, being proportional to the lowest gap of the finite-size system. The dynamical exponent is estimated in a straightforward way from the system-size dependence of the temperature. As a demonstration of our novel method, the two-dimensional S = 1 / 2 quantum XY model, or equivalently the hard-core boson system, in uniform and staggered magnetic fields is investigated in the combination of the world-line quantum Monte Carlo worm algorithm. In the absence of a uniform magnetic field, we obtain the fully consistent result with the Lorentz invariance at the quantum critical point, z = 1 . Under a finite uniform magnetic field, on the other hand, the dynamical exponent becomes two, and the mean-field universality with effective dimension (2+2) governs the quantum phase transition. We will discuss also the system with random magnetic fields, or the dirty boson system, bearing a non-trivial dynamical exponent.Reference: S. Yasuda, H. Suwa, and S. Todo Phys. Rev. B 92, 104411 (2015); arXiv:1506.04837

  16. Anomalous parity-time-symmetry transition away from an exceptional point

    NASA Astrophysics Data System (ADS)

    Ge, Li

    2016-07-01

    Parity-time (PT ) symmetric systems have two distinguished phases, e.g., one with real-energy eigenvalues and the other with complex-conjugate eigenvalues. To enter one phase from the other, it is believed that the system must pass through an exceptional point, which is a non-Hermitian degenerate point with coalesced eigenvalues and eigenvectors. Here we reveal an anomalous PT transition that takes place away from an exceptional point in a nonlinear system: as the nonlinearity increases, the original linear system evolves along two distinct PT -symmetric trajectories, each of which can have an exceptional point. However, the two trajectories collide and vanish away from these exceptional points, after which the system is left with a PT -broken phase. We first illustrate this phenomenon using a coupled-mode theory and then exemplify it using paraxial wave propagation in a transverse periodic potential.

  17. 21 CFR 120.8 - Hazard Analysis and Critical Control Point (HACCP) plan.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 2 2010-04-01 2010-04-01 false Hazard Analysis and Critical Control Point (HACCP... SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION HAZARD ANALYSIS AND CRITICAL CONTROL POINT (HACCP) SYSTEMS General Provisions § 120.8 Hazard Analysis and Critical Control Point (HACCP) plan. (a) HACCP plan....

  18. Critical integer quantum Hall topology and the integrable Maryland model as a topological quantum critical point

    NASA Astrophysics Data System (ADS)

    Ganeshan, Sriram; Kechedzhi, K.; Das Sarma, S.

    2014-07-01

    One-dimensional tight binding models such as the Aubry-André-Harper (AAH) model (with an on-site cosine potential) and the integrable Maryland model (with an on-site tangent potential) have been the subject of extensive theoretical research in localization studies. AAH can be directly mapped onto the two-dimensional (2D) Hofstadter model which manifests the integer quantum Hall topology on a lattice. However, such a connection needs to be made for the Maryland model (MM). Here we describe a generalized model that contains AAH and MM as the limiting cases with the MM lying precisely at a topological quantum phase transition (TQPT) point. A remarkable feature of this critical point is that the one-dimensional MM retains well defined energy gaps whereas the equivalent 2D model becomes gapless, signifying the 2D nature of the TQPT.

  19. γ -rigid solution of the Bohr Hamiltonian for the critical point description of the spherical to γ -rigidly deformed shape phase transition

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Pan, Feng; Liu, Yu-Xin; Luo, Yan-An; Draayer, J. P.

    2017-09-01

    The γ -rigid solution of the Bohr Hamiltonian with the β -soft potential and 0∘≤γ ≤30∘ is worked out. The resulting model, called T(4), provides a natural dynamical connection between the X(4) and the Z(4) critical-point symmetries, which thus serves as the critical-point symmetry of the spherical to γ -rigidly deformed shape phase transition. This point is further justified through comparing the model dynamics with those of the interacting boson model. As a preliminary test, the low-lying structures of 158Er are taken to compare the theoretical calculations, and the results indicate that this nucleus could be considered as the candidate of the T(4) model with an intermediate γ deformation.

  20. The effect of disorder on the critical points in the vortex phase diagram of YBCO

    SciTech Connect

    Crabtree, G. W.; Kwok, W. K.; Paulius, L. M.; Petrean, A. M.; Olsson, R. J.; Karapetrov, G.; Tobos, V.; Moulton, W. G.

    2000-01-19

    The effect of line disorder induced by heavy ion irradiation and of point disorder induced by proton and electron irradiation on the upper and lower critical points in the vortex phase diagram of YBCO is presented. The authors find that dilute line disorder induces a Bose glass transition at low fields which is replaced at the lower critical point by first order melting at higher fields. Strong pinning point defects raise the lower critical point, while weak pinning point defects have little or no effect on the lower critical point. The upper critical point is lowered by point disorder, but raised by line disorder. First order melting is suppressed by point disorder in two ways, by lowering of the upper critical point only for weak point pins, or by merging of the upper and lower critical points for strong point pins. The differing responses of the upper and lower critical points to line and point disorder can be understood in a picture of transverse and longitudinal spatial fluctuations.

  1. Entropy excess in strongly correlated Fermi systems near a quantum critical point

    NASA Astrophysics Data System (ADS)

    Clark, J. W.; Zverev, M. V.; Khodel, V. A.

    2012-12-01

    A system of interacting, identical fermions described by standard Landau Fermi-liquid (FL) theory can experience a rearrangement of its Fermi surface if the correlations grow sufficiently strong, as occurs at a quantum critical point where the effective mass diverges. As yet, this phenomenon defies full understanding, but salient aspects of the non-Fermi-liquid (NFL) behavior observed beyond the quantum critical point are still accessible within the general framework of the Landau quasiparticle picture. Self-consistent solutions of the coupled Landau equations for the quasiparticle momentum distribution n(p) and quasiparticle energy spectrum ɛ(p) are shown to exist in two distinct classes, depending on coupling strength and on whether the quasiparticle interaction is regular or singular at zero momentum transfer. One class of solutions maintains the idempotency condition n2(p)=n(p) of standard FL theory at zero temperature T while adding pockets to the Fermi surface. The other solutions are characterized by a swelling of the Fermi surface and a flattening of the spectrum ɛ(p) over a range of momenta in which the quasiparticle occupancies lie between 0 and 1 even at T=0. The latter, non-idempotent solution is revealed by analysis of a Poincaré mapping associated with the fundamental Landau equation connecting n(p) and ɛ(p) and validated by solution of a variational condition that yields the symmetry-preserving ground state. Significantly, this extraordinary solution carries the burden of a large temperature-dependent excess entropy down to very low temperatures, threatening violation of the Nernst Theorem. It is argued that certain low-temperature phase transitions, notably those involving Cooper-pair formation, offer effective mechanisms for shedding the entropy excess. Available measurements in heavy-fermion compounds provide concrete support for such a scenario.

  2. Self-organized criticality as Witten-type topological field theory with spontaneously broken Becchi-Rouet-Stora-Tyutin symmetry

    SciTech Connect

    Ovchinnikov, Igor V.

    2011-05-15

    Here, a scenario is proposed, according to which a generic self-organized critical (SOC) system can be looked upon as a Witten-type topological field theory (W-TFT) with spontaneously broken Becchi-Rouet-Stora-Tyutin (BRST) symmetry. One of the conditions for the SOC is the slow driving noise, which unambiguously suggests Stratonovich interpretation of the corresponding stochastic differential equation (SDE). This, in turn, necessitates the use of Parisi-Sourlas-Wu stochastic quantization procedure, which straightforwardly leads to a model with BRST-exact action, i.e., to a W-TFT. In the parameter space of the SDE, there must exist full-dimensional regions where the BRST symmetry is spontaneously broken by instantons, which in the context of SOC are essentially avalanches. In these regions, the avalanche-type SOC dynamics is liberated from overwise a rightful dynamics-less W-TFT, and a Goldstone mode of Fadeev-Popov ghosts exists. Goldstinos represent moduli of instantons (avalanches) and being gapless are responsible for the critical avalanche distribution in the low-energy, long-wavelength limit. The above arguments are robust against moderate variations of the SDE's parameters and the criticality is 'self-tuned'. The proposition of this paper suggests that the machinery of W-TFTs may find its applications in many different areas of modern science studying various physical realizations of SOC. It also suggests that there may in principle exist a connection between some SOC's and the concept of topological quantum computing.

  3. Anomalous discontinuity at the percolation critical point of active gels.

    PubMed

    Sheinman, M; Sharma, A; Alvarado, J; Koenderink, G H; MacKintosh, F C

    2015-03-06

    We develop a percolation model motivated by recent experimental studies of gels with active network remodeling by molecular motors. This remodeling was found to lead to a critical state reminiscent of random percolation (RP), but with a cluster distribution inconsistent with RP. Our model not only can account for these experiments, but also exhibits an unusual type of mixed phase transition: We find that the transition is characterized by signatures of criticality, but with a discontinuity in the order parameter.

  4. Gravity dual to a quantum critical point with spontaneous symmetry breaking.

    PubMed

    Gubser, Steven S; Rocha, Fábio D

    2009-02-13

    We consider zero-temperature solutions to the Abelian Higgs model coupled to gravity with a negative cosmological constant. With appropriate choices of parameters, the geometry contains two copies of anti-de Sitter space, one describing conformal invariance in the ultraviolet, and one in the infrared. The effective speed of signal propagation is smaller in the infrared. Green's functions and associated transport coefficients can have unusual power-law scaling in the infrared. We provide an example in which the real part of the conductivity scales approximately as omega;{3.5} for small omega.

  5. Gravity Dual to a Quantum Critical Point with Spontaneous Symmetry Breaking

    SciTech Connect

    Gubser, Steven S.; Rocha, Fabio D.

    2009-02-13

    We consider zero-temperature solutions to the Abelian Higgs model coupled to gravity with a negative cosmological constant. With appropriate choices of parameters, the geometry contains two copies of anti-de Sitter space, one describing conformal invariance in the ultraviolet, and one in the infrared. The effective speed of signal propagation is smaller in the infrared. Green's functions and associated transport coefficients can have unusual power-law scaling in the infrared. We provide an example in which the real part of the conductivity scales approximately as {omega}{sup 3.5} for small {omega}.

  6. Critical point relascope sampling for unbiased volume estimation of downed coarse woody debris

    Treesearch

    Jeffrey H. Gove; Michael S. Williams; Goran Stahl; Mark J. Ducey; Mark J. Ducey

    2005-01-01

    Critical point relascope sampling is developed and shown to be design-unbiased for the estimation of log volume when used with point relascope sampling for downed coarse woody debris. The method is closely related to critical height sampling for standing trees when trees are first sampled with a wedge prism. Three alternative protocols for determining the critical...

  7. Rotational symmetry breaking in the topological superconductor SrxBi2Se3 probed by upper-critical field experiments.

    PubMed

    Pan, Y; Nikitin, A M; Araizi, G K; Huang, Y K; Matsushita, Y; Naka, T; de Visser, A

    2016-06-28

    Recently it was demonstrated that Sr intercalation provides a new route to induce superconductivity in the topological insulator Bi2Se3. Topological superconductors are predicted to be unconventional with an odd-parity pairing symmetry. An adequate probe to test for unconventional superconductivity is the upper critical field, Bc2. For a standard BCS layered superconductor Bc2 shows an anisotropy when the magnetic field is applied parallel and perpendicular to the layers, but is isotropic when the field is rotated in the plane of the layers. Here we report measurements of the upper critical field of superconducting SrxBi2Se3 crystals (Tc = 3.0 K). Surprisingly, field-angle dependent magnetotransport measurements reveal a large anisotropy of Bc2 when the magnet field is rotated in the basal plane. The large two-fold anisotropy, while six-fold is anticipated, cannot be explained with the Ginzburg-Landau anisotropic effective mass model or flux flow induced by the Lorentz force. The rotational symmetry breaking of Bc2 indicates unconventional superconductivity with odd-parity spin-triplet Cooper pairs (Δ4-pairing) recently proposed for rhombohedral topological superconductors, or might have a structural nature, such as self-organized stripe ordering of Sr atoms.

  8. Rotational symmetry breaking in the topological superconductor SrxBi2Se3 probed by upper-critical field experiments

    PubMed Central

    Pan, Y.; Nikitin, A. M.; Araizi, G. K.; Huang, Y. K.; Matsushita, Y.; Naka, T.; de Visser, A.

    2016-01-01

    Recently it was demonstrated that Sr intercalation provides a new route to induce superconductivity in the topological insulator Bi2Se3. Topological superconductors are predicted to be unconventional with an odd-parity pairing symmetry. An adequate probe to test for unconventional superconductivity is the upper critical field, Bc2. For a standard BCS layered superconductor Bc2 shows an anisotropy when the magnetic field is applied parallel and perpendicular to the layers, but is isotropic when the field is rotated in the plane of the layers. Here we report measurements of the upper critical field of superconducting SrxBi2Se3 crystals (Tc = 3.0 K). Surprisingly, field-angle dependent magnetotransport measurements reveal a large anisotropy of Bc2 when the magnet field is rotated in the basal plane. The large two-fold anisotropy, while six-fold is anticipated, cannot be explained with the Ginzburg-Landau anisotropic effective mass model or flux flow induced by the Lorentz force. The rotational symmetry breaking of Bc2 indicates unconventional superconductivity with odd-parity spin-triplet Cooper pairs (Δ4-pairing) recently proposed for rhombohedral topological superconductors, or might have a structural nature, such as self-organized stripe ordering of Sr atoms. PMID:27350295

  9. Rotational symmetry breaking in the topological superconductor SrxBi2Se3 probed by upper-critical field experiments

    NASA Astrophysics Data System (ADS)

    Pan, Y.; Nikitin, A. M.; Araizi, G. K.; Huang, Y. K.; Matsushita, Y.; Naka, T.; de Visser, A.

    2016-06-01

    Recently it was demonstrated that Sr intercalation provides a new route to induce superconductivity in the topological insulator Bi2Se3. Topological superconductors are predicted to be unconventional with an odd-parity pairing symmetry. An adequate probe to test for unconventional superconductivity is the upper critical field, Bc2. For a standard BCS layered superconductor Bc2 shows an anisotropy when the magnetic field is applied parallel and perpendicular to the layers, but is isotropic when the field is rotated in the plane of the layers. Here we report measurements of the upper critical field of superconducting SrxBi2Se3 crystals (Tc = 3.0 K). Surprisingly, field-angle dependent magnetotransport measurements reveal a large anisotropy of Bc2 when the magnet field is rotated in the basal plane. The large two-fold anisotropy, while six-fold is anticipated, cannot be explained with the Ginzburg-Landau anisotropic effective mass model or flux flow induced by the Lorentz force. The rotational symmetry breaking of Bc2 indicates unconventional superconductivity with odd-parity spin-triplet Cooper pairs (Δ4-pairing) recently proposed for rhombohedral topological superconductors, or might have a structural nature, such as self-organized stripe ordering of Sr atoms.

  10. Continuous symmetry measures for complex symmetry group.

    PubMed

    Dryzun, Chaim

    2014-04-05

    Symmetry is a fundamental property of nature, used extensively in physics, chemistry, and biology. The Continuous symmetry measures (CSM) is a method for estimating the deviation of a given system from having a certain perfect symmetry, which enables us to formulate quantitative relation between symmetry and other physical properties. Analytical procedures for calculating the CSM of all simple cyclic point groups are available for several years. Here, we present a methodology for calculating the CSM of any complex point group, including the dihedral, tetrahedral, octahedral, and icosahedral symmetry groups. We present the method and analyze its performances and errors. We also introduce an analytical method for calculating the CSM of the linear symmetry groups. As an example, we apply these methods for examining the symmetry of water, the symmetry maps of AB4 complexes, and the symmetry of several Lennard-Jones clusters.

  11. Estimate of beryllium critical point on the basis of correspondence between the critical and the Zeno-line parameters.

    PubMed

    Apfelbaum, E M

    2012-12-20

    The critical-point coordinates of Beryllium have been calculated by means of recently found similarity relations between the Zeno-line and the critical-point parameters. We have used the NVT MC simulations and pseudopotential theory to calculate the Zeno-line parameters together with the data of isobaric measurements to construct the liquid branch of Beryllium binodal. The critical-point coordinates, determined this way, are lower than earlier estimates. We have shown that these previous estimates are in evident contradiction with available measurements data. Present investigation can resolve this contradiction if the measurements data are supposed to be reliable.

  12. Metamagnetic behavior near the quantum critical point in UGe 2

    NASA Astrophysics Data System (ADS)

    Huxley, A.; Sheikin, I.; Braithwaite, D.

    2000-07-01

    We have discovered a low-field metamagnetic transition in UGe 2 close to the critical pressure at which the Curie temperature is suppressed to zero. The systematic evolution of the transition with pressure provides a unique opportunity to test theoretical models of metamagnetism.

  13. Critical-point analysis of the liquid-vapor interfacial surface tension

    NASA Technical Reports Server (NTRS)

    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.

  14. 75 FR 8239 - School Food Safety Program Based on Hazard Analysis and Critical Control Point Principles (HACCP...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-24

    ... Critical Control Point Principles (HACCP); Approval of Information Collection Request AGENCY: Food and... rule entitled School Food Safety Program Based on Hazard Analysis and Critical Control Point...

  15. Universal Entanglement Entropy in 2D Conformal Quantum Critical Points

    SciTech Connect

    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.

  16. Discrete Holomorphicity at Two-Dimensional Critical Points

    NASA Astrophysics Data System (ADS)

    Cardy, John

    2009-12-01

    After a brief review of the historical role of analyticity in the study of critical phenomena, an account is given of recent discoveries of discretely holomorphic observables in critical two-dimensional lattice models. These are objects whose correlation functions satisfy a discrete version of the Cauchy-Riemann relations. Their existence appears to have a deep relation with the integrability of the model, and they are presumably the lattice versions of the truly holomorphic observables appearing in the conformal field theory (CFT) describing the continuum limit. This hypothesis sheds light on the connection between CFT and integrability, and, if verified, can also be used to prove that the scaling limit of certain discrete curves in these models is described by Schramm-Loewner evolution (SLE).

  17. Topology of Functions with Isolated Critical Points on the Boundary of a 2-Dimensional Manifold

    NASA Astrophysics Data System (ADS)

    Hladysh, Bohdana I.; Prishlyak, Aleksandr O.

    2017-07-01

    This paper focuses on the problem of topological equivalence of functions with isolated critical points on the boundary of a compact surface M which are also isolated critical points of their restrictions to the boundary. This class of functions we denote by Ω(M). Firstly, we've obtained the topological classification of above-mentioned functions in some neighborhood of their critical points. Secondly, we've constructed a chord diagram from the neighborhood of a critical level. Also the minimum number of critical points of such functions is being considered. And finally, the criterion of global topological equivalence of functions which belong to Ω(M) and have three critical points has been developed.

  18. Phenomenological consequences of enhanced bulk viscosity near the QCD critical point

    NASA Astrophysics Data System (ADS)

    Monnai, Akihiko; Mukherjee, Swagato; Yin, Yi

    2017-03-01

    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 nonzero baryon density. We demonstrate that the critically enhanced bulk viscosity induces a substantial nonequilibrium 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 complementary information to facilitate searches for the QCD critical point.

  19. Dynamical Crossing of an Infinitely Degenerate Critical Point

    NASA Astrophysics Data System (ADS)

    Bachmann, Sven; Fraas, Martin; Graf, Gian Michele

    2017-05-01

    We study the evolution of a driven harmonic oscillator with a time-dependent frequency $\\omega_t \\propto |t|$. At time $t=0$ the Hamiltonian undergoes a point of infinite spectral degeneracy. If the system is initialized in the instantaneous vacuum in the distant past then the asymptotic future state is a squeezed state whose parameters are explicitly determined. We show that the squeezing is independent on the sweeping rate. This manifests the failure of the adiabatic approximation at points where infinitely many eigenvalues collide. We extend our analysis to the situation where the gap at $t=0$ remains finite. We also discuss the natural geometry of the manifold of squeezed states. We show that it is realized by the Poincar\\'e disk model viewed as a K\\"ahler manifold.

  20. Locating the quantum critical point of the Bose-Hubbard model through singularities of simple observables

    NASA Astrophysics Data System (ADS)

    Łącki, Mateusz; Damski, Bogdan; Zakrzewski, Jakub

    2016-12-01

    We show that the critical point of the two-dimensional Bose-Hubbard model can be easily found through studies of either on-site atom number fluctuations or the nearest-neighbor two-point correlation function (the expectation value of the tunnelling operator). Our strategy to locate the critical point is based on the observation that the derivatives of these observables with respect to the parameter that drives the superfluid-Mott insulator transition are singular at the critical point in the thermodynamic limit. Performing the quantum Monte Carlo simulations of the two-dimensional Bose-Hubbard model, we show that this technique leads to the accurate determination of the position of its critical point. Our results can be easily extended to the three-dimensional Bose-Hubbard model and different Hubbard-like models. They provide a simple experimentally-relevant way of locating critical points in various cold atomic lattice systems.

  1. Locating the quantum critical point of the Bose-Hubbard model through singularities of simple observables

    PubMed Central

    Łącki, Mateusz; Damski, Bogdan; Zakrzewski, Jakub

    2016-01-01

    We show that the critical point of the two-dimensional Bose-Hubbard model can be easily found through studies of either on-site atom number fluctuations or the nearest-neighbor two-point correlation function (the expectation value of the tunnelling operator). Our strategy to locate the critical point is based on the observation that the derivatives of these observables with respect to the parameter that drives the superfluid-Mott insulator transition are singular at the critical point in the thermodynamic limit. Performing the quantum Monte Carlo simulations of the two-dimensional Bose-Hubbard model, we show that this technique leads to the accurate determination of the position of its critical point. Our results can be easily extended to the three-dimensional Bose-Hubbard model and different Hubbard-like models. They provide a simple experimentally-relevant way of locating critical points in various cold atomic lattice systems. PMID:27910915

  2. Locating the quantum critical point of the Bose-Hubbard model through singularities of simple observables.

    PubMed

    Łącki, Mateusz; Damski, Bogdan; Zakrzewski, Jakub

    2016-12-02

    We show that the critical point of the two-dimensional Bose-Hubbard model can be easily found through studies of either on-site atom number fluctuations or the nearest-neighbor two-point correlation function (the expectation value of the tunnelling operator). Our strategy to locate the critical point is based on the observation that the derivatives of these observables with respect to the parameter that drives the superfluid-Mott insulator transition are singular at the critical point in the thermodynamic limit. Performing the quantum Monte Carlo simulations of the two-dimensional Bose-Hubbard model, we show that this technique leads to the accurate determination of the position of its critical point. Our results can be easily extended to the three-dimensional Bose-Hubbard model and different Hubbard-like models. They provide a simple experimentally-relevant way of locating critical points in various cold atomic lattice systems.

  3. Bulk viscosity of stirred xenon near the critical point

    NASA Astrophysics Data System (ADS)

    Gillis, K. A.; Shinder, I. I.; Moldover, M. R.

    2005-11-01

    We deduce the thermophysical properties of near-critical xenon from measurements of the frequencies and half-widths of the acoustic resonances of xenon maintained at its critical density in centimeter-sized cavities. In the reduced temperature range 1×10-3<(T-Tc)/Tc<7×10-6 , we measured the resonance frequency and quality factor (Q) for each of six modes spanning a factor of 27 in frequency. As Tc was approached, the frequencies decreased by a factor of 2.2 and the Q ’s decreased by as much as a factor of 140. Remarkably, these results are predicted (within ±2% of the frequency and within a factor of 1.4 of Q ) by a model for the resonator and a model for the frequency-dependent bulk viscosity ζ(ω) that uses no empirically determined parameters. The resonator model is based on a theory of acoustics in near-critical fluids developed by Gillis, Shinder, and Moldover [Phys. Rev. E 70, 021201 (2004)]. In addition to describing the present low-frequency data (from 120Hzto7.5kHz ), the model for ζ(ω) is consistent with ultrasonic (0.4-7MHz) velocity and attenuation data from the literature. However, the model predicts a peak in the temperature dependence of the dissipation in the boundary layer that we did not detect. This suggests that the model overestimates the effect of the bulk viscosity on the thermal boundary layer. In this work, the acoustic cavities were heated from below to stir the xenon, thereby reducing the density stratification resulting from Earth’s gravity. The stirring reduced the apparent equilibration time from several hours to a few minutes, and it reduced the effective temperature resolution from 60mK to approximately 2mK , which corresponds to (T-Tc)/Tc≈7×10-6 .

  4. Hydrogen bond breaking in aqueous solutions near the critical point

    USGS Publications Warehouse

    Mayanovic, Robert A.; Anderson, Alan J.; Bassett, William A.; Chou, I.-Ming

    2001-01-01

    The nature of water-anion bonding is examined using X-ray absorption fine structure spectroscopy on a 1mZnBr2/6m NaBr aqueous solution, to near critical conditions. Analyses show that upon heating the solution from 25??C to 500??C, a 63% reduction of waters occurs in the solvation shell of ZnBr42-, which is the predominant complex at all pressure-temperature conditions investigated. A similar reduction in the hydration shell of waters in the Br- aqua ion was found. Our results indicate that the water-anion and water-water bond breaking mechanisms occurring at high temperatures are essentially the same. This is consistent with the hydration waters being weakly hydrogen bonded to halide anions in electrolyte solutions. ?? 2001 Elsevier Science B.V.

  5. Non-Equilibrium Conductivity at Quantum Critical Points

    NASA Astrophysics Data System (ADS)

    Berridge, Andrew; Bhaseen, M. J.; Green, A. G.

    2013-03-01

    The behaviour of quantum systems driven out of equilibrium is a field in which we are still searching for general principles and universal results. Quantum critical systems are useful in this search as their out of equilibrium steady states may inherit universal features from equilibrium. While this has been shown in some cases, the calculational techniques used often involve simplified models or calculational tricks, which can obscure some of the underlying physical processes. Here we use a Boltzmann transport approach to study the steady-state non-equilibrium properties - conductivity and current noise, of the Bose-Hubbard model head-on. We must explicitly consider heat-flow and rate limiting processes in the establishment of the steady-state to show that it can indeed be universal. Our analysis reveals the importance of the hydrodynamic limit and the limitations of current approaches.

  6. Near-critical point phenomena in fluids (19-IML-1)

    NASA Technical Reports Server (NTRS)

    Beysens, D.

    1992-01-01

    Understanding the effects of gravity is essential if the behavior of fluids is to be predicted in spacecraft and orbital stations, and, more generally, to give a better understanding of the hydrodynamics in these systems. An understanding is sought of the behavior of fluids in space. What should emerge from the International Microgravity Lab (IML-1) mission is a better understanding of the kinetics of growth in off-critical conditions, in both liquid mixtures and pure fluids. This complex phenomenon is the object of intensive study in physics and materials sciences area. It is also expected that the IML-1 flight will procure key results to provide a better understanding of how a pure fluid can be homogenized without gravity induced convections, and to what extent the 'Piston Effect' is effective in thermalizing the compressible fluids.

  7. Universality class of replica symmetry breaking, scaling behavior, and the low-temperature fixed-point order function of the Sherrington-Kirkpatrick model.

    PubMed

    Oppermann, R; Schmidt, M J

    2008-12-01

    A scaling theory of replica symmetry breaking (RSB) in the Sherrington-Kirkpatrick (SK) model is presented in the framework of critical phenomena for the scaling regime of large RSB orders kappa , small temperatures T , and small (homogeneous) magnetic fields H . We employ the pseudodynamical picture [R. Oppermann, M. J. Schmidt, and D. Sherrington, Phys. Rev. Lett. 98, 127201 (2007)], where two critical points CP1 and CP2 are associated with the order function's pseudodynamical limits lim_{a-->infinity}q(a)=1 and lim_{a-->0}q(a)=0 at (T=0 , H=0 , 1kappa=0) . CP1 - and CP2 -dominated contributions to the free energy functional F[q(a)] require an unconventional scaling hypothesis. We determine the scaling contributions in accordance with detailed numerical self-consistent solutions for up to 200 orders of RSB. Power laws, scaling functions, and crossover lines are obtained. CP1 -dominated behavior is found for the nonequilibrium susceptibility, which decays like chi_{1}=kappa;{-53}f_{1}(Tkappa;{-53}) , for the entropy, which obeys S(T=0) approximately chi_{1};{2} , and for the subclass of diverging parameters a_{i}=kappa;{53}f_{a_{i}}(Tkappa;{-53}) [describing Parisi box sizes m_{i}(T) identical witha_{i}(T)T ], with f_{1}(zeta) approximately zeta and f_{a_{i}}(zeta) approximately 1zeta for zeta-->infinity , while f(0) is finite. CP2 -dominated behavior, controlled by the magnetic field H while temperature is irrelevant, is retrieved in the plateau height (or width) of the order function q(a) according to q_{pl}(H)=kappa;{-1}f_{pl}(H;{23}kappa;{-1}) with f_{pl}mid R:(zeta)mid R:_{zeta-->infinity} approximately zeta and f_{pl}(0) finite. Divergent characteristic RSB orders kappa_{CP1}(T) approximately T;{-35} and kappa_{CP2}(H) approximately H;{-23} , respectively, describe the crossover from mean field SK- to RSB-critical behavior with rational-valued exponents extracted with high precision from our RSB data. The order function q(a) is obtained as a fixed-point

  8. 21 CFR 120.8 - Hazard Analysis and Critical Control Point (HACCP) plan.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... General Provisions § 120.8 Hazard Analysis and Critical Control Point (HACCP) plan. (a) HACCP plan. Each.... Sanitation controls may be included in the HACCP plan. However, to the extent that they are monitored in... 21 Food and Drugs 2 2011-04-01 2011-04-01 false Hazard Analysis and Critical Control Point...

  9. Perturbation theory of N point-mass gravitational lens systems without symmetry: small mass-ratio approximation

    NASA Astrophysics Data System (ADS)

    Asada, H.

    2009-04-01

    This paper makes the first systematic attempt to determine using perturbation theory the positions of images by gravitational lensing due to arbitrary number of coplanar masses without any symmetry on a plane, as a function of lens and source parameters. We present a method of Taylor-series expansion to solve the lens equation under a small mass-ratio approximation. First, we investigate perturbative structures of a single-complex-variable polynomial, which has been commonly used. Perturbative roots are found. Some roots represent positions of lensed images, while the others are unphysical because they do not satisfy the lens equation. This is consistent with a fact that the degree of the polynomial, namely the number of zeros, exceeds the maximum number of lensed images if N = 3 (or more). The theorem never tells which roots are physical (or unphysical). In this paper, unphysical ones are identified. Secondly, to avoid unphysical roots, we re-examine the lens equation. The advantage of our method is that it allows a systematic iterative analysis. We determine image positions for binary lens systems up to the third order in mass ratios and for arbitrary N point masses up to the second order. This clarifies the dependence on parameters. Thirdly, the number of the images that admit a small mass-ratio limit is less than the maximum number. It is suggested that positions of extra images could not be expressed as Maclaurin series in mass ratios. Magnifications are finally discussed.

  10. Polynomial Graphs and Symmetry

    ERIC Educational Resources Information Center

    Goehle, Geoff; Kobayashi, Mitsuo

    2013-01-01

    Most quadratic functions are not even, but every parabola has symmetry with respect to some vertical line. Similarly, every cubic has rotational symmetry with respect to some point, though most cubics are not odd. We show that every polynomial has at most one point of symmetry and give conditions under which the polynomial has rotational or…

  11. Polynomial Graphs and Symmetry

    ERIC Educational Resources Information Center

    Goehle, Geoff; Kobayashi, Mitsuo

    2013-01-01

    Most quadratic functions are not even, but every parabola has symmetry with respect to some vertical line. Similarly, every cubic has rotational symmetry with respect to some point, though most cubics are not odd. We show that every polynomial has at most one point of symmetry and give conditions under which the polynomial has rotational or…

  12. Robustness of critical points in a complex adaptive system: Effects of hedge behavior

    NASA Astrophysics Data System (ADS)

    Liang, Yuan; Huang, Ji-Ping

    2013-08-01

    In our recent papers, we have identified a class of phase transitions in the market-directed resource-allocation game, and found that there exists a critical point at which the phase transitions occur. The critical point is given by a certain resource ratio. Here, by performing computer simulations and theoretical analysis, we report that the critical point is robust against various kinds of human hedge behavior where the numbers of herds and contrarians can be varied widely. This means that the critical point can be independent of the total number of participants composed of normal agents, herds and contrarians, under some conditions. This finding means that the critical points we identified in this complex adaptive system (with adaptive agents) may also be an intensive quantity, similar to those revealed in traditional physical systems (with non-adaptive units).

  13. Breaking axi-symmetry in stenotic flow lowers the critical transition Reynolds number

    NASA Astrophysics Data System (ADS)

    Samuelsson, J.; Tammisola, O.; Juniper, M. P.

    2015-10-01

    Flow through a sinuous stenosis with varying degrees of non-axisymmetric shape variations and at Reynolds number ranging from 250 to 750 is investigated using direct numerical simulation (DNS) and global linear stability analysis. At low Reynolds numbers (Re < 390), the flow is always steady and symmetric for an axisymmetric geometry. Two steady state solutions are obtained when the Reynolds number is increased: a symmetric steady state and an eccentric, non-axisymmetric steady state. Either one can be obtained in the DNS depending on the initial condition. A linear global stability analysis around the symmetric and non-axisymmetric steady state reveals that both flows are linearly stable for the same Reynolds number, showing that the first bifurcation from symmetry to antisymmetry is subcritical. When the Reynolds number is increased further, the symmetric state becomes linearly unstable to an eigenmode, which drives the flow towards the non-axisymmetric state. The symmetric state remains steady up to Re = 713, while the non-axisymmetric state displays regimes of periodic oscillations for Re ≥ 417 and intermittency for Re ≳ 525. Further, an offset of the stenosis throat is introduced through the eccentricity parameter E. When eccentricity is increased from zero to only 0.3% of the pipe diameter, the bifurcation Reynolds number decreases by more than 50%, showing that it is highly sensitive to non-axisymmetric shape variations. Based on the resulting bifurcation map and its dependency on E, we resolve the discrepancies between previous experimental and computational studies. We also present excellent agreement between our numerical results and previous experimental results.

  14. Smectic-C* alpha-smectic-C* Phase Transition and Critical Point in Binary Mixtures

    SciTech Connect

    Liu,Z.; Wang, S.; McCoy, B.; Cady, A.; Pindak, R.; Caliebe, W.; Takekoshi, K.; Ema, K.; Nguyen, H.; Huang, C.

    2006-01-01

    We have investigated the smectic-C*{sub {alpha}}-smectic-C* (SmC*{sub {alpha}}-SmC*) transition in a series of binary mixtures with resonant x-ray diffraction, differential optical reflectivity, and heat capacity measurements. Results show that the phases are separated by a first-order transition that ends at a critical point. We report the observation of such a critical point. We have proposed the appropriate order parameter and obtained values of two critical exponents associated with this transition. The values of the critical exponents suggest that long-range intersections are present in the SmC*{sub {alpha}}-SmC* critical regions.

  15. Whole wafer critical point drying of MEMS devices

    NASA Astrophysics Data System (ADS)

    Resnick, Paul J.; Clews, Peggy J.

    2001-10-01

    Stiction induced by capillary forces during the post-release drying step of MEMS fabrication can substantially limit the functional yield of complex devices. Supercritical CO2 drying provides a method to remove liquid from the device surface without creating a liquid/vapor interface, thereby mitigating stiction. We show that a continuous stirred-tank reactor (CSTR) model can be applied as a method to estimate the volume of liquid CO2 required to effectively displace the post release solvent. The CSTR model predicts that about 8 volume exchanges is sufficient to effectively displace the methanol to a concentration below the saturation point. Experimental data indicate that about 10 exchanges are adequate for repeatable drying of complex devices, which is in reasonable agreement to the model prediction. In addition to drying devices without inducing stiction, the process must be inherently non-contaminating. Data indicate that the majority of contaminants deposited during the drying process can be attributed to contaminants originating in the post-release solvent, rather than the supercritical CO2 process.

  16. Rheumatoid arthritis: scientific development from a critical point of view.

    PubMed

    Schöffel, Norman; Mache, Stefanie; Quarcoo, David; Scutaru, Cristian; Vitzthum, Karin; Groneberg, David A; Spallek, Michael

    2010-02-01

    Rheumatoid arthritis (RA) is classified as a chronic, progressive, systemic autoimmune disorder leading to inflammation, stiffness, defective position and destruction of joints. Finally a complete loss of mobility and functioning can be the result. The fraction of disability varies strongly, for example, a systematic review shows a 50% disability in a period from first occurrence to disability from 4.5 to 22 years. Scientific efforts focused strongly on therapeutic and diagnostic methods during recent years. So far, there is no scientometric approach of the topic rheumatoid arthritis available although there is an increased need to evaluate quality and quantity of scientific research. Density-equalizing algorithms, scientometric methods and large scale data analysis were applied to evaluate the quality and quantity of scientific efforts in the field of rheumatoid arthritis. Data were gained from Pubmed and ISI-Web. During the period 1901-2007, 78,128 items were published by 129 countries including the USA, UK and Germany being the most productive suppliers, representing 45.7% of all publications. Another 23 countries published more than 100 items. In terms of international cooperation the USA proved to be the most successful partner. "Arthritis and Rheumatism", "Annals of the Rheumatic Diseases" and the "Journal of Rheumatology" are the most prolific journals. The current study is the first analysis of "rheumatoid arthritis" research activities and output. Our analysis revealed single areas of interest, the most prolific journals, authors and institutions dealing with the topic. Nevertheless, statements concerning the scientific quality should be considered critical due to a bias according to self-citation and co-authorship.

  17. Frequency-Dependent Viscosity of Xenon Near the Critical Point

    NASA Technical Reports Server (NTRS)

    Berg, Robert F.; Moldover, Michael R.; Zimmerli, Gregory A.

    1999-01-01

    We used a novel, overdamped oscillator aboard the Space Shuttle to measure the viscosity eta of xenon near its critical density rho(sub c), and temperature T(sub c). In microgravity, useful data were obtained within 0.1 mK of T(sub c), corresponding to a reduced temperature t = (T -T(sub c))/T(sub c) = 3 x 10(exp -7). The data extend two decades closer to T(sub c) than the best ground measurements, and they directly reveal the expected power-law behavior eta proportional to t(sup -(nu)z(sub eta)). Here nu is the correlation length exponent, and our result for the small viscosity exponent is z(sub eta) = 0.0690 +/- 0.0006. (All uncertainties are one standard uncertainty.) Our value for z(sub eta) depends only weakly on the form of the viscosity crossover function, and it agrees with the value 0.067 +/- 0.002 obtained from a recent two-loop perturbation expansion. The measurements spanned the frequency range 2 Hz less than or equal to f less than or equal to 12 Hz and revealed viscoelasticity when t less than or equal to 10(exp -1), further from T(sub c) than predicted. The viscoelasticity scales as Af(tau), where tau is the fluctuation-decay time. The fitted value of the viscoelastic time-scale parameter A is 2.0 +/- 0.3 times the result of a one-loop perturbation calculation. Near T(sub c), the xenon's calculated time constant for thermal diffusion exceeded days. Nevertheless, the viscosity results were independent of the xenon's temperature history, indicating that the density was kept near rho(sub c), by judicious choices of the temperature vs. time program. Deliberately bad choices led to large density inhomogeneities. At t greater than 10(exp -5), the xenon approached equilibrium much faster than expected, suggesting that convection driven by microgravity and by electric fields slowly stirred the sample.

  18. A chemical test of critical point isomorphism: reactive dissolution of ionic solids in isobutyric acid + water near the consolute point.

    PubMed

    Baird, James K; Baker, Jonathan D; Hu, Baichuan; Lang, Joshua R; Joyce, Karen E; Sides, Alison K; Richey, Randi D

    2015-03-12

    Binary liquid mixtures having a consolute point can be used as solvents for chemical reactions. When excess cerium(IV) oxide is brought into equilibrium with a mixture of isobutyric acid + water, and the concentration of cerium in the liquid phase is plotted in van't Hoff form, a straight line results for temperatures sufficiently in excess of the critical solution temperature. Within 1 K of the critical temperature, however, the concentration becomes substantially suppressed, and the van't Hoff slope diverges toward negative infinity. According to the phase rule, one mole fraction can be fixed. Given this restriction, the temperature behavior of the data is in exact agreement with the predictions of both the principle of critical point isomorphism and the Gibbs-Helmholtz equation. In addition, we have determined the concentration of lead in the liquid phase when crystalline lead(II) sulfate reacts with potassium iodide in isobutyric acid + water. When plotted in van't Hoff form, the data lie on a straight line for all temperatures including the critical region. The phase rule indicates that two mole fractions can be fixed. With this restriction, the data are in exact agreement with the principle of critical point isomorphism.

  19. Transport properties of gases and binary liquids near the critical point

    NASA Technical Reports Server (NTRS)

    Sengers, J. V.

    1972-01-01

    A status report is presented on the anomalies observed in the behavior of transport properties near the critical point of gases and binary liquids. The shear viscosity exhibits a weak singularity near the critical point. An analysis is made of the experimental data for those transport properties, thermal conductivity and thermal diffusivity near the gas-liquid critical point and binary diffusion coefficient near the critical mixing point, that determine the critical slowing down of the thermodynamic fluctuations in the order parameter. The asymptotic behavior of the thermal conductivity appears to be closely related to the asymptotic behavior of the correlation length. The experimental data for the thermal conductivity and diffusivity are shown to be in substantial agreement with current theoretical predictions.

  20. Theory of finite-entanglement scaling at one-dimensional quantum critical points.

    PubMed

    Pollmann, Frank; Mukerjee, Subroto; Turner, Ari M; Moore, Joel E

    2009-06-26

    Studies of entanglement in many-particle systems suggest that most quantum critical ground states have infinitely more entanglement than noncritical states. Standard algorithms for one-dimensional systems construct model states with limited entanglement, which are a worse approximation to quantum critical states than to others. We give a quantitative theory of previously observed scaling behavior resulting from finite entanglement at quantum criticality. Finite-entanglement scaling in one-dimensional systems is governed not by the scaling dimension of an operator but by the "central charge" of the critical point. An important ingredient is the universal distribution of density-matrix eigenvalues at a critical point [P. Calabrese and A. Lefevre, Phys. Rev. A 78, 032329 (2008)10.1103/PhysRevA.78.032329]. The parameter-free theory is checked against numerical scaling at several quantum critical points.

  1. Symmetry adaptation of spherical tensor quantities in cubic point groups: comments on a paper by M. Rey et al.

    NASA Astrophysics Data System (ADS)

    Michelot, F.

    2004-04-01

    We underline some inconsistencies in the work [J. Mol. Spectrosc. 219 (2003) 313] concerning symmetry adaptation in cubic groups. Also we show that some rather complicated methods presented can be easily avoided.

  2. 8x8 and 10x10 Hyperspace Representations of SU(3) and 10-fold Point-Symmetry Group of Quasicrystals

    NASA Astrophysics Data System (ADS)

    Animalu, Alexander

    2012-02-01

    In order to further elucidate the unexpected 10-fold point-symmetry group structure of quasi-crystals for which the 2011 Nobel Prize in chemistry was awarded to Daniel Shechtman, we explore a correspondence principle between the number of (projective) geometric elements (points[vertices] + lines[edges] + planes[faces]) of primitive cells of periodic or quasi-periodic arrangement of hard or deformable spheres in 3-dimensional space of crystallography and elements of quantum field theory of particle physics [points ( particles, lines ( particles, planes ( currents] and hence construct 8x8 =64 = 28+36 = 26 + 38, and 10x10 =100= 64 + 36 = 74 + 26 hyperspace representations of the SU(3) symmetry of elementary particle physics and quasicrystals of condensed matter (solid state) physics respectively, As a result, we predict the Cabibbo-like angles in leptonic decay of hadrons in elementary-particle physics and the observed 10-fold symmetric diffraction pattern of quasi-crystals.

  3. Self-organization of plants in a dryland ecosystem: Symmetry breaking and critical cluster size.

    PubMed

    Meyra, Ariel G; Zarragoicoechea, Guillermo J; Kuz, Victor A

    2015-05-01

    Periodical patterns of vegetation in an arid or semiarid ecosystem are described using statistical mechanics and Monte Carlo numerical simulation technique. Plants are characterized by the area that each individual occupies and a facilitation-competition pairwise interaction. Assuming that external resources (precipitation, solar radiation, nutrients, etc.) are available to the ecosystem, it is possible to obtain the persistent configurations of plants compatible with an equitable distribution of resources maximizing the Shannon entropy. Variation of vegetation patterns with density, critical cluster size, and facilitation distance are predicted. Morphological changes of clusters are shown to be a function of the external resources. As a final remark, it is proposed that an early warning of desertification could be detected from the coefficient of variation of the mean cluster size together with the distribution of cluster sizes.

  4. Self-organization of plants in a dryland ecosystem: Symmetry breaking and critical cluster size

    NASA Astrophysics Data System (ADS)

    Meyra, Ariel G.; Zarragoicoechea, Guillermo J.; Kuz, Victor A.

    2015-05-01

    Periodical patterns of vegetation in an arid or semiarid ecosystem are described using statistical mechanics and Monte Carlo numerical simulation technique. Plants are characterized by the area that each individual occupies and a facilitation-competition pairwise interaction. Assuming that external resources (precipitation, solar radiation, nutrients, etc.) are available to the ecosystem, it is possible to obtain the persistent configurations of plants compatible with an equitable distribution of resources maximizing the Shannon entropy. Variation of vegetation patterns with density, critical cluster size, and facilitation distance are predicted. Morphological changes of clusters are shown to be a function of the external resources. As a final remark, it is proposed that an early warning of desertification could be detected from the coefficient of variation of the mean cluster size together with the distribution of cluster sizes.

  5. Critical-Point Drying: Rapid Method for the Determination of Bacterial Extracellular Polymer and Surface Structures

    PubMed Central

    Cagle, Gerald D.

    1974-01-01

    The relative amount of extracellular polymer which remains about Azotobacter vinelandii, Zoogloea ramigera, Klebsiella pneumoniae, and Diplococcus pneumoniae after critical-point drying was studied by electron microscopy. The results obtained with this technique are compared to those obtained with methods that illustrate extracellular polymer, such as freeze-etching and ruthenium red staining. Comparative results indicate critical-point drying to be a rapid, reliable method for the determination of capsule-like polymer surrounding bacterial cells. In addition, critical-point drying can be used to observe morphogenetic changes, such as vesicle production. Images PMID:4136617

  6. Quantum critical point in the Sc-doped itinerant antiferromagnet TiAu

    NASA Astrophysics Data System (ADS)

    Svanidze, E.; Besara, T.; Wang, J. K.; Geiger, D.; Prochaska, L.; Santiago, J. M.; Lynn, J. W.; Paschen, S.; Siegrist, T.; Morosan, E.

    2017-06-01

    We present an experimental realization of a quantum critical point in an itinerant antiferromagnet composed of nonmagnetic constituents, TiAu. By partially substituting Ti with Sc in Ti1 -xScxAu , a doping amount of xc=0.13 ±0.01 induces a quantum critical point with minimal disorder effects. The accompanying non-Fermi liquid behavior is observed in both the resistivity ρ ∝T and specific heat Cp/T ∝-ln T , characteristic of a two-dimensional antiferromagnet. The quantum critical point is accompanied by an enhancement of the spin fluctuations, as indicated by the diverging Sommerfeld coefficient γ at x =xc .

  7. Evidence for a Disordered Critical Point in a Glass-Forming Liquid

    NASA Astrophysics Data System (ADS)

    Berthier, Ludovic; Jack, Robert L.

    2015-05-01

    Using computer simulations of an atomistic glass-forming liquid, we investigate the fluctuations of the overlap between a fluid configuration and a quenched reference system. We find that large fluctuations of the overlap develop as temperature decreases, consistent with the existence of the random critical point that is predicted by effective field theories. We discuss the scaling of fluctuations near the presumed critical point, comparing the observed behavior with that of the random-field Ising model. We argue that this critical point directly reveals the existence of an interfacial tension between amorphous metastable states, a quantity relevant both for equilibrium relaxation and for nonequilibrium melting of stable glass configurations.

  8. Evidence for a Disordered Critical Point in a Glass-Forming Liquid.

    PubMed

    Berthier, Ludovic; Jack, Robert L

    2015-05-22

    Using computer simulations of an atomistic glass-forming liquid, we investigate the fluctuations of the overlap between a fluid configuration and a quenched reference system. We find that large fluctuations of the overlap develop as temperature decreases, consistent with the existence of the random critical point that is predicted by effective field theories. We discuss the scaling of fluctuations near the presumed critical point, comparing the observed behavior with that of the random-field Ising model. We argue that this critical point directly reveals the existence of an interfacial tension between amorphous metastable states, a quantity relevant both for equilibrium relaxation and for nonequilibrium melting of stable glass configurations.

  9. Thermoacoustic wave propagation and reflection near the liquid-gas critical point.

    PubMed

    Zhang, P; Shen, B

    2009-06-01

    We study the thermoacoustic wave propagation and reflection near the liquid-gas critical point. Specifically, we perform a numerical investigation of the acoustic responses in a near-critical fluid to thermal perturbations based on the same setup of a recent ultrasensitive interferometry measurement in CO2 [Y. Miura, Phys. Rev. E 74, 010101(R) (2006)]. The numerical results agree well with the experimental data. Different features regarding the reflection pattern of thermoacoustic waves near the critical point under pulse perturbations are revealed by the proper inclusion of the critically diverging bulk viscosity.

  10. Enhancement of superconductivity near the ferromagnetic quantum critical point in UCoGe.

    PubMed

    Slooten, E; Naka, T; Gasparini, A; Huang, Y K; de Visser, A

    2009-08-28

    We report a high-pressure single crystal study of the superconducting ferromagnet UCoGe. Measurements of the ac susceptibility and resistivity 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 over the whole pressure range. The obtained p-T phase diagram reveals superconductivity is closely connected to a ferromagnetic quantum-critical point hidden under the superconducting "dome."

  11. Splitting of the zero-energy Landau level and universal dissipative conductivity at critical points in disordered graphene.

    PubMed

    Ortmann, Frank; Roche, Stephan

    2013-02-22

    We report on robust features of the longitudinal conductivity (σ(xx)) of the graphene zero-energy Landau level in the presence of disorder and varying magnetic fields. By mixing an Anderson disorder potential with a low density of sublattice impurities, the transition from metallic to insulating states is theoretically explored as a function of Landau-level splitting, using highly efficient real-space methods to compute the Kubo conductivities (both σ(xx) and Hall σ(xy)). As long as valley degeneracy is maintained, the obtained critical conductivity σ(xx) =/~ 1.4e(2)/h is robust upon an increase in disorder (by almost 1 order of magnitude) and magnetic fields ranging from about 2 to 200 T. When the sublattice symmetry is broken, σ(xx) eventually vanishes at the Dirac point owing to localization effects, whereas the critical conductivities of pseudospin-split states (dictating the width of a σ(xy) = 0 plateau) change to σ(xx) =/~ e(2)/h, regardless of the splitting strength, superimposed disorder, or magnetic strength. These findings point towards the nondissipative nature of the quantum Hall effect in disordered graphene in the presence of Landau level splitting.

  12. Variation of critical point of aging transition in a networked oscillators system.

    PubMed

    Huang, Wenwen; Zhang, Xiyun; Hu, Xin; Zou, Yong; Liu, Zonghua; Guan, Shuguang

    2014-06-01

    In this work, we study the variation of critical point in aging transition in a networked system consisting of both active and inactive oscillators. By theoretical analysis and numerical simulations, we show that the critical point of aging transition actually is determined by the (normalized) cross links between active and inactive subpopulations of oscillators. This reveals how specific configuration of active and inactive oscillators in the network can lead to the variation of transition point. In particular, we investigate how different strategies of targeted inactivation influence the transition point based on the theory. Our results theoretically explain why the low-degree nodes are crucial regarding dynamical robustness in such systems.

  13. An Introduction to Critical Points for Biophysicists; Observations of Compositional Heterogeneity in Lipid Membranes

    PubMed Central

    Honerkamp-Smith, Aurelia R.; Veatch, Sarah L.; Keller, Sarah L.

    2011-01-01

    Scaling laws associated with critical points have the power to greatly simplify our description of complex biophysical systems. For the general reader, we first review basic concepts and equations associated with critical phenomena for the general reader. We then apply these concepts to the specific biophysical system of lipid membranes. We recently reported that lipid membranes can contain composition fluctuations that behave in a manner consistent with the two-dimensional Ising universality class. Near the membrane’s critical point, these fluctuations are micron-sized, clearly observable by fluorescence microscopy. At higher temperatures, above the critical point, we expect to find submicron fluctuations. In separate work, we have reported that plasma membranes isolated directly from cells exhibit the same Ising behavior as model membranes do. We review other models describing submicron lateral inhomogeneity in membranes, including microemulsions, nanodomains, and mean field critical fluctuations, and we describe experimental tests that may distinguish these models. PMID:18930706

  14. Histogram-based methodology for the determination of the critical point in condensation-evaporation systems

    NASA Astrophysics Data System (ADS)

    dos Santos, G. J.; Linares, D. H.; Ramirez-Pastor, A. J.

    2017-07-01

    A methodology based on a combination of the histogram reweighting technique and the fourth order Binder cumulant was developed to determine the critical point in generalized condensation-evaporation systems. This methodology was applied, particularly, to the study of the critical point of the condensation transition for linear molecules adsorbed on square lattices. The results were obtained by means of grand canonical Monte Carlo simulations within the lattice gas model, along with finite size scaling. The method was tested in a system of interacting monomers, in which the critical point can be determined exactly. Furthermore, the application of this method to the determination of the critical point in dimer systems with attractive interactions, gave better results than the previous reported studies. In addition, the adsorption isotherms at different temperatures, as well as the phase diagrams for monomer and dimer systems were obtained, achieving significant improvements in the phase diagram for dimers.

  15. Is the critical point for aperture crossing adapted to the person-plus-object system?

    PubMed

    Hackney, Amy L; Cinelli, Michael E; Frank, Jim S

    2014-01-01

    When passing through apertures, individuals scale their actions to their shoulder width and rotate their shoulders or avoid apertures that are deemed too small for straight passage. Carrying objects wider than the body produces a person-plus-object system that individuals must account for in order to pass through apertures safely. The present study aimed to determine whether individuals scale their critical point to the widest horizontal dimension (shoulder or object width). Two responses emerged: Fast adapters adapted to the person-plus-object system by maintaining a consistent critical point regardless of whether the object was carried while slow adapters initially increased their critical point (overestimated) before adapting back to their original critical point. The results suggest that individuals can account for increases in body width by scaling actions to the size of the object width but people adapt at different rates.

  16. Impact of resonance decays on critical point signals in net-proton fluctuations

    DOE PAGES

    Bluhm, Marcus; Nahrgang, Marlene; Bass, Steffen A.; ...

    2017-04-03

    The non-monotonic beam energy dependence of the higher cumulants of net-proton fluctuations is a widely studied signature of the conjectured presence of a critical point in the QCD phase diagram. In this work we study the effect of resonance decays on critical fluctuations. We show that resonance effects reduce the signatures of critical fluctuations, but that for reasonable parameter choices critical effects in the net-proton cumulants survive. The relative role of resonance decays has a weak dependence on the order of the cumulants studied with a slightly stronger suppression of critical effects for higher-order cumulants.

  17. Hazard analysis and critical control point systems applied to public health risks: the example of seafood.

    PubMed

    Williams, R A; Zorn, D J

    1997-08-01

    The authors describe the way in which the two components of risk analysis--risk assessment and risk management--can be used in conjunction with the hazard analysis and critical control points concept to determine the allocation of resources at potential critical control points. This approach is examined in the context of risks to human health associated with seafood, and in particular with regard to ciguatera poisoning.

  18. Critical point representations of electron density maps for the comparison of benzodiazepine-type ligands.

    PubMed

    Leherte, L; Meurice, N; Vercauteren, D P

    2000-01-01

    A procedure for the comparison of three-dimensional electron density distributions is proposed for similarity searches between pharmacological ligands at various levels of crystallographic resolution. First, a graph representation of molecular electron density distributions is generated using a critical point analysis approach. Pairwise as well as multiple comparisons between the obtained graphs of critical points are then carried out using a Monte Carlo/simulated annealing technique, and results are compared with genetic algorithm solutions.

  19. Critical point drying for scanning electron microscopy: a semi-automatic method of preparing biological specimens.

    PubMed

    Hall, D J; Skerrett, E J; Thomas, W D

    1978-08-01

    Slow, controlled, rates of critical point bomb heating and of gas venting have been shown to improve the preservation of biological specimens in critical point drying. A procedure that represents a balance between avoidance of specimen damage and speed of operation has been developed for use with CO2 as the transitional fluid. Bomb heating is automated and controlled electronically, and manual venting of the gaseous CO2 is monitored using a gas flow meter.

  20. Searching critical-point nuclei in Te- and Xe-isotopic chains using sextic oscillator potential

    SciTech Connect

    Kharb, S.; Chand, F.

    2012-02-15

    We have identified the nuclei in the Te- and Xe-isotopic chains lying close to the critical point, through which the shape phase transition occurs, by using the sextic oscillator potential formalism. It has been found that {sup 110}Te, {sup 124}Te, and {sup 124}Xe isotopes are the most promising candidates for the critical-point nuclei slightly above the Z = 50 proton shell closure.

  1. Bulk singularities at critical end points: a field-theory analysis

    NASA Astrophysics Data System (ADS)

    Diehl, H. W.; Smock, M.

    2001-06-01

    A class of continuum models with a critical end point is considered whose Hamiltonian [φ,ψ] involves two densities: a primary order-parameter field, φ, and a secondary (noncritical) one, ψ. Field-theoretic methods (renormalization group results in conjunction with functional methods) are used to give a systematic derivation of singularities occurring at critical end points. Specifically, the thermal singularity | t|2 - α of the first-order line on which the disordered or ordered phase coexists with the noncritical spectator phase, and the coexistence singularity | t|1 - α or | t|β of the secondary density <ψ> are derived. It is clarified how the renormalization group (RG) scenario found in position-space RG calculations, in which the critical end point and the critical line are mapped onto two separate fixed points CEP* and λ*, translates into field theory. The critical RG eigenexponents of CEP* and λ* are shown to match. CEP* is demonstrated to have a discontinuity eigenperturbation (with eigenvalue y = d), tangent to the unstable trajectory that emanates from CEP* and leads to λ*. The nature and origin of this eigenperturbation as well as the role redundant operators play are elucidated. The results validate that the critical behavior at the end point is the same as on the critical line.

  2. Phase diagram and critical end point in nonlocal PNJL models with wavefunction renormalization

    SciTech Connect

    Contrera, Gustavo A.; Orsaria, Milva G.; Scoccola, Norberto N.

    2010-11-12

    We study the chiral phase transition at finite temperature and chemical potential considering a non-local chiral quark model which includes wave-function renormalization and coupling to the Polyakov loop. In particular, we determine the position of the Critical End Point as well as the value of the associated critical exponents for different model parameterizations.

  3. Simple reusable hermetically-sealed spectrophotometer cuvette for turbidity studies near binary liquid critical points

    NASA Astrophysics Data System (ADS)

    Eden, Don

    1982-01-01

    Simple cells were designed for measuring the turbidity of binary liquids near their critical point. The cells were constructed by fusing a general purpose, high-vacuum, high-pressure, Teflon and glass stopcock to a commercial cuvette. No sample contamination, as indicated by a shift in critical temperature, has been observed in a sample immersed in a water bath for six months.

  4. Performance enhancement of the branch length similarity entropy descriptor for shape recognition by introducing critical points

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Hee; Kang, Seung-Ho

    2016-10-01

    In previous studies, we showed that the branch length similarity (BLS) entropy profile could be used successfully for the recognition of shapes such as battle tanks, facial expressions, and butterflies. In the present study, we introduce critical points defined as a set of distinguishing points with high curvature to the BLS entropy profile in order to improve the shape recognition. In order to generate a given number of critical points from the shape, we propose a critical point detection method. Furthermore, we show the invariant properties of the BLS entropy descriptor. To evaluate the effects of critical points on the shape recognition of the BLS entropy descriptor, we performed a butterfly classification experiment against a real image data set, and we conducted performance comparisons with other point detection methods. In addition, the performance of the BLS entropy descriptor computed using the critical points was compared with those of other well-known descriptors such as the Fourier descriptor using three machine learning techniques, the Bayesian classifier, the multi-layer perceptron and the support vector machine. The results show that the BLS entropy descriptor outperforms other well-known descriptors.

  5. Fermi-surface collapse and dynamical scaling near a quantum-critical point

    PubMed Central

    Friedemann, Sven; Oeschler, Niels; Wirth, Steffen; Krellner, Cornelius; Geibel, Christoph; Steglich, Frank; Paschen, Silke; Kirchner, Stefan; Si, Qimiao

    2010-01-01

    Quantum criticality arises when a macroscopic phase of matter undergoes a continuous transformation at zero temperature. While the collective fluctuations at quantum-critical points are being increasingly recognized as playing an important role in a wide range of quantum materials, the nature of the underlying quantum-critical excitations remains poorly understood. Here we report in-depth measurements of the Hall effect in the heavy-fermion metal YbRh2Si2, a prototypical system for quantum criticality. We isolate a rapid crossover of the isothermal Hall coefficient clearly connected to the quantum-critical point from a smooth background contribution; the latter exists away from the quantum-critical point and is detectable through our studies only over a wide range of magnetic field. Importantly, the width of the critical crossover is proportional to temperature, which violates the predictions of conventional theory and is instead consistent with an energy over temperature, E/T, scaling of the quantum-critical single-electron fluctuation spectrum. Our results provide evidence that the quantum-dynamical scaling and a critical Kondo breakdown simultaneously operate in the same material. Correspondingly, we infer that macroscopic scale-invariant fluctuations emerge from the microscopic many-body excitations associated with a collapsing Fermi-surface. This insight is expected to be relevant to the unconventional finite-temperature behavior in a broad range of strongly correlated quantum systems. PMID:20668246

  6. Fermi-surface collapse and dynamical scaling near a quantum-critical point.

    PubMed

    Friedemann, Sven; Oeschler, Niels; Wirth, Steffen; Krellner, Cornelius; Geibel, Christoph; Steglich, Frank; Paschen, Silke; Kirchner, Stefan; Si, Qimiao

    2010-08-17

    Quantum criticality arises when a macroscopic phase of matter undergoes a continuous transformation at zero temperature. While the collective fluctuations at quantum-critical points are being increasingly recognized as playing an important role in a wide range of quantum materials, the nature of the underlying quantum-critical excitations remains poorly understood. Here we report in-depth measurements of the Hall effect in the heavy-fermion metal YbRh(2)Si(2), a prototypical system for quantum criticality. We isolate a rapid crossover of the isothermal Hall coefficient clearly connected to the quantum-critical point from a smooth background contribution; the latter exists away from the quantum-critical point and is detectable through our studies only over a wide range of magnetic field. Importantly, the width of the critical crossover is proportional to temperature, which violates the predictions of conventional theory and is instead consistent with an energy over temperature, E/T, scaling of the quantum-critical single-electron fluctuation spectrum. Our results provide evidence that the quantum-dynamical scaling and a critical Kondo breakdown simultaneously operate in the same material. Correspondingly, we infer that macroscopic scale-invariant fluctuations emerge from the microscopic many-body excitations associated with a collapsing Fermi-surface. This insight is expected to be relevant to the unconventional finite-temperature behavior in a broad range of strongly correlated quantum systems.

  7. Long-term mortality after critical care: what is the starting point?

    PubMed

    Ranzani, Otavio T; Zampieri, Fernando G; Park, Marcelo; Salluh, Jorge If

    2013-09-27

    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 sepsis, who showed high ongoing long-term mortality rates after severe sepsis, reaching 61% at 5 years (from a starting point of ICU admission). Follow-up may start at ICU admission, after ICU discharge, or after hospital discharge. Using ICU admission as a starting point will include patients with a wide range of illness severities and reasons for ICU admission. As a result, important consequences of the ICU, such as rehabilitation and reduced quality of life, may be diluted in an unselected population. ICU discharge is another frequently used starting point. ICU discharge is a marker of better outcome and reduced risk for acute deterioration, making this an interesting starting point for studying long-term mortality, need for ICU readmission, and critical illness rehabilitation. Finally, using hospital discharge as the starting point will include patients with the minimal requirements to sustain an adequate condition in a non-monitored environment but will add a ?survivors bias?; that is, patients who survive critical illness are a special group among the critically ill. In this commentary, we discuss the heterogeneity in long-term mortality from recent studies in critical care medicine ? heterogeneity that may be a consequence simply of changing the follow-up starting point ? and propose a standardized follow-up starting point for future studies according to the outcome of interest.

  8. Molecular dynamics simulation of a binary mixture near the lower critical point.

    PubMed

    Pousaneh, Faezeh; Edholm, Olle; Maciołek, Anna

    2016-07-07

    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.

  9. Can we approach the gas-liquid critical point using slab simulations of two coexisting phases?

    PubMed

    Goujon, Florent; Ghoufi, Aziz; Malfreyt, Patrice; Tildesley, Dominic J

    2016-09-28

    In this paper, we demonstrate that it is possible to approach the gas-liquid critical point of the Lennard-Jones fluid by performing simulations in a slab geometry using a cut-off potential. In the slab simulation geometry, it is essential to apply an accurate tail correction to the potential energy, applied during the course of the simulation, to study the properties of states close to the critical point. Using the Janeček slab-based method developed for two-phase Monte Carlo simulations [J. Janec̆ek, J. Chem. Phys. 131, 6264 (2006)], the coexisting densities and surface tension in the critical region are reported as a function of the cutoff distance in the intermolecular potential. The results obtained using slab simulations are compared with those obtained using grand canonical Monte Carlo simulations of isotropic systems and the finite-size scaling techniques. There is a good agreement between these two approaches. The two-phase simulations can be used in approaching the critical point for temperatures up to 0.97 TC(∗) (T(∗) = 1.26). The critical-point exponents describing the dependence of the density, surface tension, and interfacial thickness on the temperature are calculated near the critical point.

  10. Nonsingular absorption of ultrasound near the critical mixing point of a binary liquid

    NASA Astrophysics Data System (ADS)

    Fenner, D. B.

    1981-04-01

    The absorption and velocity of ultrasound and the critical opalescence have been measured for a critical-composition mixture of nitrobenzene and 2,2,4-trimethylpentane along the critical isochore in the homogeneous phase of the system. The measurements cover the relatively wide range of temperature interval of 30 K to 7 mK from the critical value. The nearness of approach to the critical point was affirmed by the critical-opalescence measurements. The measurements of acoustic absorption covered the range of 1 to 91 MHz, and the strong frequency dependence observed can be satisfactorily described by the Fixman-Kawasaki theory with the adjustment of three parameters. Singular behavior for the sound absorption, consistent with critical slowing down, was observed when the mixture was more than about 3 K away from the critical point. When within about 0.3 K of the critical temperature the sound absorption was observed to become constant. The absence of any effects on the critical sound absorption, while the mixture was under a large electric field, is also reported.

  11. Extra gauge symmetries in BHT gravity

    NASA Astrophysics Data System (ADS)

    Blagojević, M.; Cvetković, B.

    2011-03-01

    We study the canonical structure of the Bergshoeff-Hohm-Townsend massive gravity, linearized around a maximally symmetric background. At the critical point in the space of parameters, defined by Λ 0/ m 2 = -1, we discover an extra gauge symmetry, which reflects the existence of the partially massless mode. The number of the Lagrangian degrees of freedom is found to be 1. We show that the canonical structure of the theory at the critical point is unstable under linearization.

  12. Phenomenological consequences of enhanced bulk viscosity near the QCD critical point

    DOE PAGES

    Monnai, Akihiko; Mukherjee, Swagato; Yin, Yi

    2017-03-06

    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. Here, 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 nonzero baryon density. We demonstrate that the critically enhanced bulk viscosity induces a substantial nonequilibrium pressure, effectively softening themore » equation of state, and leads to sizable effects in the flow velocity and single-particle distributions at the freeze-out. In conclusion, the observable effects that may arise due to the enhanced bulk viscosity in the vicinity of the QCD critical point can be used as complementary information to facilitate searches for the QCD critical point.« less

  13. Behavior of the dielectric constant of Ar near the critical point.

    PubMed

    Hidalgo, Marcelo; Coutinho, Kaline; Canuto, Sylvio

    2015-03-01

    The fundamental question of the behavior of the dielectric constant near the critical point is addressed using Ar as the probe system. The neighborhood of the liquid-vapor critical point of Ar is accessed by classical Monte Carlo simulation and then explicit quantum mechanics calculations are performed to study the behavior of the dielectric constant. The theoretical critical temperature is determined by calculating the position of the discontinuity of the specific heat and is found to be at T(c)Theor=148.7K, only 2 K below the experimental value. The large fluctuations and the inhomogeneity of the density that characterize the critical point rapidly disappear and are not seen at T=T(c)Theor+2K. The structure of Ar obtained by the radial distribution function is found to be in very good agreement with experiment both in the liquid phase and 2 K above the critical temperature. The behavior of the dielectric constant is then analyzed after calculating the static dipole polarizability and using a many-body Clausius-Mossotti equation. The dielectric constant shows a density-independent behavior around the critical density, 2 K above the critical temperature. At this point, the calculated value of the dielectric constant is 1.173±0.005 in excellent agreement with the experimental value of 1.179.

  14. Odd-Parity Superconductivity near an Inversion Breaking Quantum Critical Point in One Dimension.

    PubMed

    Ruhman, Jonathan; Kozii, Vladyslav; Fu, Liang

    2017-06-02

    We study how an inversion-breaking quantum critical point affects the ground state of a one-dimensional electronic liquid with repulsive interaction and spin-orbit coupling. We find that regardless of the interaction strength, the critical fluctuations always lead to a gap in the electronic spin sector. The origin of the gap is a two-particle backscattering process, which becomes relevant due to renormalization of the Luttinger parameter near the critical point. The resulting spin-gapped state is topological and can be considered as a one-dimensional version of a spin-triplet superconductor. Interestingly, in the case of a ferromagnetic critical point, the Luttinger parameter is renormalized in the opposite manner, such that the system remains nonsuperconducting.

  15. Odd-Parity Superconductivity near an Inversion Breaking Quantum Critical Point in One Dimension

    NASA Astrophysics Data System (ADS)

    Ruhman, Jonathan; Kozii, Vladyslav; Fu, Liang

    2017-06-01

    We study how an inversion-breaking quantum critical point affects the ground state of a one-dimensional electronic liquid with repulsive interaction and spin-orbit coupling. We find that regardless of the interaction strength, the critical fluctuations always lead to a gap in the electronic spin sector. The origin of the gap is a two-particle backscattering process, which becomes relevant due to renormalization of the Luttinger parameter near the critical point. The resulting spin-gapped state is topological and can be considered as a one-dimensional version of a spin-triplet superconductor. Interestingly, in the case of a ferromagnetic critical point, the Luttinger parameter is renormalized in the opposite manner, such that the system remains nonsuperconducting.

  16. Energy of the quasi-free electron in supercritical krypton near the critical point.

    PubMed

    Li, Luxi; Evans, C M; Findley, G L

    2005-12-01

    Field ionization measurements of high-n CH(3)I and C(2)H(5)I Rydberg states doped into krypton are presented as a function of krypton number density along the critical isotherm. These data exhibit a decrease in the krypton-induced shift of the dopant ionization energy near the critical point. This change in shift is modeled to within +/-0.2% of experiment using a theory that accounts for the polarization of krypton by the dopant ion, the polarization of krypton by the quasi-free electron that arises from field ionization of the dopant, and the zero point kinetic energy of the free electron. The overall decrease in the shift of the dopant ionization energy near the critical point of krypton, which is a factor of 2 larger than that observed in argon, is dominated by the increase in the zero point kinetic energy of the quasi-free electron.

  17. Strong enhancement of s -wave superconductivity near a quantum critical point of Ca3Ir4Sn13

    DOE PAGES

    Biswas, P. K.; Guguchia, Z.; Khasanov, R.; ...

    2015-11-11

    We repormore » t microscopic studies by muon spin rotation/relaxation as a function of pressure of the Ca3Ir4Sn13 and Sr3Ir4Sn13 system displaying superconductivity and a structural phase transition associated with the formation of a charge density wave (CDW). Our findings show a strong enhancement of the superfluid density and a dramatic increase of the pairing strength above a pressure of ≈ 1.6 GPa giving direct evidence of the presence of a quantum critical point separating a superconducting phase coexisting with CDW from a pure superconducting phase. The superconducting order parameter in both phases has the same s-wave symmetry. In spite of the conventional phonon-mediated BCS character of the weakly correlated (Ca1-xSrx)3Ir4Sn13 system the dependence of the effective superfluid density on the critical temperature puts this compound in the “Uemura” plot close to unconventional superconductors. This system exemplifies that conventional BCS superconductors in the presence of competing orders or multi-band structure can also display characteristics of unconventional superconductors.« less

  18. Critical points in the 16-moment approximation. [plasma flow in laboratory and space plasmas study

    NASA Technical Reports Server (NTRS)

    Yasseen, F.; Retterer, J. M.

    1991-01-01

    The singular points in steady state, field-aligned plasma transport models based on velocity moment theory are examined. In particular, two separate singular points in the equations obtained from the 16-moment approximation are identified. These equations are presented in a form that makes the singularities apparent, and they are solved in a simple illustrative case. The singular points, one occurring at the sonic point and the other at a critical value of the parallel heat flux, give rise to different outflow regimes, characterized generically by different asymptotic behavior. The existence of the different outflow regimes separated by the heat flux critical point has been only hinted at in previous discussions of numerical simulation of the polar wind.

  19. Complex systems analysis of series of blackouts: cascading failure, critical points, and self-organization.

    PubMed

    Dobson, Ian; Carreras, Benjamin A; Lynch, Vickie E; Newman, David E

    2007-06-01

    We give an overview of a complex systems approach to large blackouts of electric power transmission systems caused by cascading failure. Instead of looking at the details of particular blackouts, we study the statistics and dynamics of series of blackouts with approximate global models. Blackout data from several countries suggest that the frequency of large blackouts is governed by a power law. The power law makes the risk of large blackouts consequential and is consistent with the power system being a complex system designed and operated near a critical point. Power system overall loading or stress relative to operating limits is a key factor affecting the risk of cascading failure. Power system blackout models and abstract models of cascading failure show critical points with power law behavior as load is increased. To explain why the power system is operated near these critical points and inspired by concepts from self-organized criticality, we suggest that power system operating margins evolve slowly to near a critical point and confirm this idea using a power system model. The slow evolution of the power system is driven by a steady increase in electric loading, economic pressures to maximize the use of the grid, and the engineering responses to blackouts that upgrade the system. Mitigation of blackout risk should account for dynamical effects in complex self-organized critical systems. For example, some methods of suppressing small blackouts could ultimately increase the risk of large blackouts.

  20. Complex systems analysis of series of blackouts: cascading failure, critical points, and self-organization

    SciTech Connect

    Dobson, Ian; Carreras, Benjamin A; Lynch, Vickie E; Newman, David E

    2007-01-01

    We give an overview of a complex systems approach to large blackouts of electric power transmission systems caused by cascading failure. Instead of looking at the details of particular blackouts, we study the statistics and dynamics of series of blackouts with approximate global models. Blackout data from several countries suggest that the frequency of large blackouts is governed by a power law. The power law makes the risk of large blackouts consequential and is consistent with the power system being a complex system designed and operated near a critical point. Power system overall loading or stress relative to operating limits is a key factor affecting the risk of cascading failure. Power system blackout models and abstract models of cascading failure show critical points with power law behavior as load is increased. To explain why the power system is operated near these critical points and inspired by concepts from self-organized criticality, we suggest that power system operating margins evolve slowly to near a critical point and confirm this idea using a power system model. The slow evolution of the power system is driven by a steady increase in electric loading, economic pressures to maximize the use of the grid, and the engineering responses to blackouts that upgrade the system. Mitigation of blackout risk should account for dynamical effects in complex self-organized critical systems. For example, some methods of suppressing small blackouts could ultimately increase the risk of large blackouts.

  1. Theoretical Analysis of Thermodynamic Measurements near a Liquid-Gas Critical Point

    NASA Technical Reports Server (NTRS)

    Barmatz, M.; Zhong, Fang; Hahn, Inseob

    2003-01-01

    Over the years, many ground-based studies have been performed near liquid-gas critical points to elucidate the expected divergences in thermodynamic quantities. The unambiguous interpretation of these studies very near the critical point is hindered by a gravity-induced density stratification. However, these ground-based measurements can give insight into the crossover behavior between the asymptotic critical region near the transition and the mean field region farther away. We have completed a detailed analysis of heat capacity, susceptibility and coexistence curve measurements near the He-3 liquid-gas critical point using the minimal-subtraction renormalization (MSR) scheme within the phi(exp 4) model. This MSR scheme, using only two adjustable parameters, provides a reasonable global fit to all of these experimental measurements in the gravity-free region out to a reduced temperature of |t| approx. 2x10(exp -2). Recently this approach has also been applied to the earlier microgravity measurements of Haupt and Straub in SF(sub 6) with surprising results. The conclusions drawn from the MSR analyses will be presented. Measurements in the gravity-affected region closer to the He-3 critical point have also been analyzed using the recent crossover parametric model (CPM) of the equation-of-state. The results of fitting heat capacity measurements to the CPM model along the He-3 critical isochore in the gravity-affected region will also be presented.

  2. Evaluation of critical points in technology transfer of cryopreservation protocols to international plant conservation laboratories.

    PubMed

    Reed, Barbara M; Kovalchuk, Irina; Kushnarenko, Svetlana; Meier-Dinkel, Andreas; Schoenweiss, Katja; Pluta, Stanislaw; Straczynska, Krystyna; Benson, Erica E

    2004-01-01

    Cryopreservation of plant tissues in liquid nitrogen is now used for long-term conservation of vegetatively-propagated crops. Development of standard techniques for cryopreservation is important to the international plant-conservation community for successful implementation of storage protocols in diverse and internationally dispersed laboratories. Evaluation of the critical points of each preservation technique will greatly assist in developing and validating internationally-used cryopreservation protocols. The goals of this project were to assess critical points of two major cryopreservation techniques (PVS2 vitrification and encapsulation dehydration) during their transfer to international laboratories; analyze post-storage viability for each technique and location; and develop recommendations based on the assessments and data from the participating laboratories. Investigators from Germany, Kazakhstan, Poland and UK participated in a 2-week training workshop in cryopreservation methods after which the techniques were tested in the home laboratories of the participants. After one-year site visits by the technology trainers identified critical points in the protocols. Critical points were identified as 1) Cryogenic (cryoprotection, LN exposure, rewarming); 2) Non-cryogenic (plant health status, pre- and post-storage culture); 3) Operational (skills transfer, training, interpretation of procedures); 4) Facility (growth room, ambient conditions, media preparation, equipment). The most critical factors in all laboratories were culture health, operator skills and experience, and clarification of the technical details of the procedures. Final results showed that correction of critical factors improved the post-storage recovery in all the laboratories.

  3. Theoretical Analysis of Thermodynamic Measurements near a Liquid-Gas Critical Point

    NASA Technical Reports Server (NTRS)

    Barmatz, M.; Zhong, Fang; Hahn, Inseob

    2003-01-01

    Over the years, many ground-based studies have been performed near liquid-gas critical points to elucidate the expected divergences in thermodynamic quantities. The unambiguous interpretation of these studies very near the critical point is hindered by a gravity-induced density stratification. However, these ground-based measurements can give insight into the crossover behavior between the asymptotic critical region near the transition and the mean field region farther away. We have completed a detailed analysis of heat capacity, susceptibility and coexistence curve measurements near the He-3 liquid-gas critical point using the minimal-subtraction renormalization (MSR) scheme within the phi(exp 4) model. This MSR scheme, using only two adjustable parameters, provides a reasonable global fit to all of these experimental measurements in the gravity-free region out to a reduced temperature of |t| approx. 2x10(exp -2). Recently this approach has also been applied to the earlier microgravity measurements of Haupt and Straub in SF(sub 6) with surprising results. The conclusions drawn from the MSR analyses will be presented. Measurements in the gravity-affected region closer to the He-3 critical point have also been analyzed using the recent crossover parametric model (CPM) of the equation-of-state. The results of fitting heat capacity measurements to the CPM model along the He-3 critical isochore in the gravity-affected region will also be presented.

  4. Pseudo-critical point in anomalous phase diagrams of simple plasma models

    NASA Astrophysics Data System (ADS)

    Chigvintsev, A. Yu; Iosilevskiy, I. L.; Noginova, L. Yu

    2016-11-01

    Anomalous phase diagrams in subclass of simplified (“non-associative”) Coulomb models is under discussion. The common feature of this subclass is absence on definition of individual correlations for charges of opposite sign. It is e.g. modified OCP of ions on uniformly compressible background of ideal Fermi-gas of electrons OCP(∼), or a superposition of two non-ideal OCP(∼) models of ions and electrons etc. In contrast to the ordinary OCP model on non-compressible (“rigid”) background OCP(#) two new phase transitions with upper critical point, boiling and sublimation, appear in OCP(∼) phase diagram in addition to the well-known Wigner crystallization. The point is that the topology of phase diagram in OCP(∼) becomes anomalous at high enough value of ionic charge number Z. Namely, the only one unified crystal- fluid phase transition without critical point exists as continuous superposition of melting and sublimation in OCP(∼) at the interval (Z 1 < Z < Z 2). The most remarkable is appearance of pseudo-critical points at both boundary values Z = Z 1 ≈ 35.5 and Z = Z 2 ≈ 40.0. It should be stressed that critical isotherm is exactly cubic in both these pseudo-critical points. In this study we have improved our previous calculations and utilized more complicated model components equation of state provided by Chabrier and Potekhin (1998 Phys. Rev. E 58 4941).

  5. Critical Point Cancellation in 3D Vector Fields: Robustness and Discussion.

    PubMed

    Skraba, Primoz; Rosen, Paul; Wang, Bei; Chen, Guoning; Bhatia, Harsh; Pascucci, Valerio

    2016-02-29

    Vector field topology has been successfully applied to represent the structure of steady vector fields. Critical points, one of the essential components of vector field topology, play an important role in describing the complexity of the extracted structure. Simplifying vector fields via critical point cancellation has practical merit for interpreting the behaviors of complex vector fields such as turbulence. However, there is no effective technique that allows direct cancellation of critical points in 3D. This work fills this gap and introduces the first framework to directly cancel pairs or groups of 3D critical points in a hierarchical manner with a guaranteed minimum amount of perturbation based on their robustness, a quantitative measure of their stability. In addition, our framework does not require the extraction of the entire 3D topology, which contains non-trivial separation structures, and thus is computationally effective. Furthermore, our algorithm can remove critical points in any subregion of the domain whose degree is zero and handle complex boundary configurations, making it capable of addressing challenging scenarios that may not be resolved otherwise. We apply our method to synthetic and simulation datasets to demonstrate its effectiveness.

  6. CETF Space Station payload pointing system design and analysis feasibility study. [Critical Evaluation Task Force

    NASA Technical Reports Server (NTRS)

    Smagala, Tom; Mcglew, Dave

    1988-01-01

    The expected pointing performance of an attached payload coupled to the Critical Evaluation Task Force Space Station via a payload pointing system (PPS) is determined. The PPS is a 3-axis gimbal which provides the capability for maintaining inertial pointing of a payload in the presence of disturbances associated with the Space Station environment. A system where the axes of rotation were offset from the payload center of mass (CM) by 10 in. in the Z axis was studied as well as a system having the payload CM offset by only 1 inch. There is a significant improvement in pointing performance when going from the 10 in. to the 1 in. gimbal offset.

  7. Necessary Condition for Emergent Symmetry from the Conformal Bootstrap.

    PubMed

    Nakayama, Yu; Ohtsuki, Tomoki

    2016-09-23

    We use the conformal bootstrap program to derive the necessary conditions for emergent symmetry enhancement from discrete symmetry (e.g., Z_{n}) to continuous symmetry [e.g., U(1)] under the renormalization group flow. In three dimensions, in order for Z_{2} symmetry to be enhanced to U(1) symmetry, the conformal bootstrap program predicts that the scaling dimension of the order parameter field at the infrared conformal fixed point must satisfy Δ_{1}>1.08. We also obtain the similar necessary conditions for Z_{3} symmetry with Δ_{1}>0.580 and Z_{4} symmetry with Δ_{1}>0.504 from the simultaneous conformal bootstrap analysis of multiple four-point functions. As applications, we show that our necessary conditions impose severe constraints on the nature of the chiral phase transition in QCD, the deconfinement criticality in Néel valence bond solid transitions, and anisotropic deformations in critical O(n) models. We prove that some fixed points proposed in the literature are unstable under the perturbation that cannot be forbidden by the discrete symmetry. In these situations, the second-order phase transition with enhanced symmetry cannot happen.

  8. Fate of the one-dimensional Ising quantum critical point coupled to a gapless boson

    NASA Astrophysics Data System (ADS)

    Alberton, Ori; Ruhman, Jonathan; Berg, Erez; Altman, Ehud

    2017-02-01

    The problem of a quantum Ising degree of freedom coupled to a gapless bosonic mode appears naturally in many one-dimensional systems, yet surprisingly little is known how such a coupling affects the Ising quantum critical point. We investigate the fate of the critical point in a regime, where the weak coupling renormalization group (RG) indicates a flow toward strong coupling. Using a renormalization group analysis and numerical density matrix renormalization group (DMRG) calculations we show that, depending on the ratio of velocities of the gapless bosonic mode and the Ising critical fluctuations, the transition may remain continuous or become fluctuation-driven first order. The two regimes are separated by a tricritical point of a novel type.

  9. Critical points and transitions in an electric power transmission model for cascading failure blackouts.

    PubMed

    Carreras, B. A.; Lynch, V. E.; Dobson, I.; Newman, D. E.

    2002-12-01

    Cascading failures in large-scale electric power transmission systems are an important cause of blackouts. Analysis of North American blackout data has revealed power law (algebraic) tails in the blackout size probability distribution which suggests a dynamical origin. With this observation as motivation, we examine cascading failure in a simplified transmission system model as load power demand is increased. The model represents generators, loads, the transmission line network, and the operating limits on these components. Two types of critical points are identified and are characterized by transmission line flow limits and generator capability limits, respectively. Results are obtained for tree networks of a regular form and a more realistic 118-node network. It is found that operation near critical points can produce power law tails in the blackout size probability distribution similar to those observed. The complex nature of the solution space due to the interaction of the two critical points is examined.(c) 2002 American Institute of Physics.

  10. Hazard analysis and critical control point (HACCP) history and conceptual overview.

    PubMed

    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.

  11. QCD Critical End Point: How it started, How it grew, and Where it goes

    SciTech Connect

    Asakawa, Masayuki

    2011-05-06

    The presence of a critical end point in the QCD phase diagram can deform the trajectories describing the evolution of the expanding fireball in the {mu}{sub B}-T phase diagram. If the average emission time of hadrons is a function of transverse velocity, as microscopic simulations of the hadronic freezeout dynamics suggest, the deformation of the hydrodynamic trajectories will change the transverse velocity ({beta}{sub T}) dependence of the antiproton-to-proton ratio when the fireball passes in the vicinity of the critical end point. An unusual {beta}{sub T}-dependence of the p-bar/p ratio in a narrow beam energy window would thus signal the presence of the critical end point.

  12. The QCD critical point: an exciting Odyssey in the Femto-world

    NASA Astrophysics Data System (ADS)

    Gavai, Rajiv V.

    2016-07-01

    Strongly interacting matter, which makes up the nuclei of atoms, is described by a theory called quantum chromodynamics (QCD). A critical point in the phase diagram of QCD, if established either theoretically or experimentally, would be as profound a discovery as the familiar gas-liquid critical point discovered in the nineteenth century. Due to the extremely 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 which can fit the bill to do so. Theoretical techniques of Lattice QCD, which is QCD defined on a discrete space-time lattice, have provided glimpses into where the QCD critical point may be, and how to search for it in the experimental data. A brief overview of the theoretical and experimental attempts is provided.

  13. Determination of liquid-liquid critical point composition using 90∘ laser light scattering

    NASA Astrophysics Data System (ADS)

    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.

  14. Determination of liquid-liquid critical point composition using 90^{∘} laser light scattering.

    PubMed

    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.

  15. Communication: Analytic continuation of the virial series through the critical point using parametric approximants.

    PubMed

    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.

  16. Communication: Nonexistence of a critical point within the Kirkwood superposition approximation

    NASA Astrophysics Data System (ADS)

    Piasecki, Jarosław; Szymczak, Piotr; Kozak, John J.

    2013-10-01

    An analytic argument is given to show that the application of the Kirkwood superposition approximation to the description of fluid correlation functions precludes the existence of a critical point. The argument holds irrespective of the dimension of the system and the specific form of the interaction potential and settles a long-standing controversy surrounding the nature of the critical behavior predicted within the approximation.

  17. Communication: Analytic continuation of the virial series through the critical point using parametric approximants

    SciTech Connect

    Barlow, Nathaniel S.; Schultz, Andrew J. Kofke, David A.; Weinstein, Steven J.

    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.

  18. Scaling in driven dynamics starting in the vicinity of a quantum critical point

    NASA Astrophysics Data System (ADS)

    Yin, Shuai; Lo, Chung-Yu; Chen, Pochung

    2016-08-01

    Driven dynamics across a quantum critical point is usually described by the Kibble-Zurek scaling. Although the original Kibble-Zurek scaling requires an adiabatic initial state, it has been shown that scaling behaviors exist even when the driven dynamics is triggered from a thermal equilibrium state exactly at the critical point, in spite of the breakdown of the initial adiabaticity. In this paper, we show that the existence of the scaling behavior can be generalized to the case of the initial state being a thermal equilibrium state near the critical point. We propose a scaling theory in which the initial parameters are included as additional scaling variables due to the breakdown of the initial adiabaticity. In particular, we demonstrate that for the driven critical dynamics in a closed system, the nontrivial thermal effects are closely related to the initial distance to the critical point. We numerically confirm the scaling theory by simulating the real-time dynamics of the one-dimensional quantum Ising model at both zero and finite temperatures.

  19. Anomalous waves in gas-liquid mixtures near gas critical point in Gardner equation approximation

    NASA Astrophysics Data System (ADS)

    Gasenko, V. G.

    2016-10-01

    The waves in a bubbled incompressible liquid with Van der Waals gas in a bubbles being near critical points is considered in a frame of Gardner equation. It is shown that both coefficients on quadratic and cubic nonlinear terms in Gardner equation change the sign near gas critical point and it results the anomalous waves: negative and limited solitons, kinks, antikinks and breathers. The dynamics and interactions of these waves was studied numerically by high accuracy Fourier methods with periodically boundary conditions. In particular it is revealed that limited solitons always arise from initial distribution with a few identical soliton's pair and stand stable in their form after numerous interactions.

  20. Evolution of the critical points with the density of bosons under local three-body interactions

    NASA Astrophysics Data System (ADS)

    Avila, C. A.; Franco, R.; Silva-Valencia, J.

    2014-12-01

    We study the quantum phase transition in the one-dimensional Bose-Hubbard model with three-body local interactions for densities ρ = 2, 3, 4 and 5 by implementing the Density Matrix Renormalization Group method. This system shows two types of phases. One phase is incompressible (corresponding to the Mott insulator state) and the other compressible (the superfluid state). The critical points found correspond to a value of the hopping parameter for which the gap energy is equal to zero. We found that the critical point increases slowly as the density of the system increases.

  1. Universal free-energy distribution in the critical point of a random Ising ferromagnet.

    PubMed

    Dotsenko, Victor; Holovatch, Yurij

    2014-11-01

    We discuss the non-self-averaging phenomena in the critical point of weakly disordered Ising ferromagnet. In terms of the renormalized replica Ginzburg-Landau Hamiltonian in dimensions D<4, we derive an explicit expression for the probability distribution function (PDF) of the critical free-energy fluctuations. In particular, using known fixed-point values for the renormalized coupling parameters, we obtain the universal curve for such PDF in the dimension D=3. It is demonstrated that this function is strongly asymmetric: its left tail is much slower than the right one.

  2. Noise levels at critical points in the municipality of Guadalajara, Jalisco, Mexico

    NASA Astrophysics Data System (ADS)

    Figueroa, Arturo; Garcia, Jesus; Macias, Jorge; Orozco, Martha; Garcia, Javier; Delgadillo, Alan

    2002-11-01

    Studies of acoustic conditions are planning tools on which we can diagnose the problem of noise pollution in the cities. The first study on noise pollution made in the city was made by the University of Guadalajara in 1995 and updated in 1998 covering with measuring points the city center. This paper discusses the problem of noise pollution by motor vehicles at critical points and covers a total of 105 points. The study also analyzes the problem of noise pollution base on the community annoyance from which a regulation policy should derive. Results of the study show that the most critical points are located within zone 1 (center) where Leq levels within the range of 70-85 dB were found. Such levels exceed by far the international standard of 65 dB as recommended for ambient noise by the World Health Organization.

  3. The critical points of alloys of iron and cobalt during rapid heating

    NASA Technical Reports Server (NTRS)

    Gridnev, V. N.; Oshkaderov, S. P.

    1980-01-01

    The influence of the rate of heating on the position of the critical points of iron-cobalt alloys was studied. It is shown that when an alloy with 8% Co by weight is heated at the rate of 7000 deg/sec, a shift in the temperature of phase conversion of almost 30 deg occurs. When an alloy with 15% Co by weight is heated at the same rate, the conversion temperature is shifted by approximately 20 deg. For an alloy with 15% Co by weight, for which under ordinary conditions of heating the points of phase conversion and magnetic randomization (the Curie point) coincide, it was possible to show that for high rates of heating, a separation with respect to temperature occurs which clearly confirms the fact of the shift in the critical points of phase conversion.

  4. Determining the Critical Point of a Sigmoidal Curve via its Fourier Transform

    NASA Astrophysics Data System (ADS)

    Humeyra Bilge, Ayse; Ozdemir, Yunus

    2016-08-01

    A sigmoidal curve y(t) is a monotone increasing curve such that all derivatives vanish at infinity. Let tn be the point where the nth derivative of y(t) reaches its global extremum. In the previous work on sol-gel transition modelled by the Susceptible-Infected- Recovered (SIR) system, we observed that the sequence {tn } seemed to converge to a point that agrees qualitatively with the location of the gel point [2]. In the present work we outline a proof that for sigmoidal curves satisfying fairly general assumptions on their Fourier transform, the sequence {tn } is convergent and we call it “the critical point of the sigmoidal curve”. In the context of phase transitions, the limit point is interpreted as a junction point of two different regimes where all derivatives undergo their highest rate of change.

  5. Zero-Field Quantum Critical Point in CeCoIn5

    NASA Astrophysics Data System (ADS)

    Tokiwa, Y.; Bauer, E. D.; Gegenwart, P.

    2013-09-01

    Quantum criticality in the normal and superconducting states of the heavy-fermion metal CeCoIn5 is studied by measurements of the magnetic Grüneisen ratio ΓH and specific heat in different field orientations and temperatures down to 50 mK. A universal temperature over magnetic field scaling of ΓH in the normal state indicates a hidden quantum critical point at zero field. Within the superconducting state, the quasiparticle entropy at constant temperature increases upon reducing the field towards zero, providing additional evidence for zero-field quantum criticality.

  6. Influence of the ferroelectric quantum critical point on SrTiO3 interfaces

    NASA Astrophysics Data System (ADS)

    Atkinson, W. A.; Lafleur, P.; Raslan, A.

    2017-02-01

    We study a model SrTiO3 interface in which conduction t2 g electrons couple to the ferroelectric (FE) phonon mode. We treat the FE mode within a self-consistent phonon theory that captures its quantum critical behavior and show that proximity to the quantum critical point leads to universal tails in the electron density of the form n (z ) ˜(λ+z ) -2 , where λ ˜T2 -d /z , with d =3 the dimensionality and z =1 the dynamical critical exponent. Implications for the metal-insulator transition at low electron density are discussed.

  7. Behavior of the finite-sized, three-dimensional, Ising model near the critical point

    SciTech Connect

    Baker, G.A. Jr.; Gupta, R.

    1996-05-01

    Recent work showing the validity of hyperscaling involved results for finite size systems very near the critical point. The authors study this problem in more detail, and give estimators related to the Binder cumulant ratio which seem to approach the critical temperature from above and below. Based on these results, they estimate that the renormalized coupling constant, computed for the temperature fixed at the critical temperature and then taking the large system-size limit, is about 4.9 {+-} 0.1, and give a likely lower bound for it of 4.5. These estimates are argued to suffice to show the validity of hyperscaling.

  8. Two-scale-factor universality near the critical point of fluids

    NASA Technical Reports Server (NTRS)

    Sengers, J. V.; Moldover, M. R.

    1978-01-01

    Thermodynamic data from interferometric density profile studies and light-scattering experiments near the critical isochore of Xe, CO2 and SF6 provide a basis for examining the hypothesized two-scale-factor universality for the correlation function of fluids near the gas-liquid critical point. For the investigation, three-scale-factor universality is assumed, with Ising-like critical exponent values obtained through the renormalization group technique. The two thermodynamic scale factors are found from the density profiles, while the scale factor for the correlation length is obtained from the light-scattering data.

  9. Zero-field quantum critical point in CeCoIn5.

    PubMed

    Tokiwa, Y; Bauer, E D; Gegenwart, P

    2013-09-06

    Quantum criticality in the normal and superconducting states of the heavy-fermion metal CeCoIn5 is studied by measurements of the magnetic Grüneisen ratio ΓH and specific heat in different field orientations and temperatures down to 50 mK. A universal temperature over magnetic field scaling of ΓH in the normal state indicates a hidden quantum critical point at zero field. Within the superconducting state, the quasiparticle entropy at constant temperature increases upon reducing the field towards zero, providing additional evidence for zero-field quantum criticality.

  10. Exploring Symmetry Breaking at the Dicke Quantum Phase Transition

    SciTech Connect

    Baumann, K.; Mottl, R.; Brennecke, F.; Esslinger, T.

    2011-09-30

    We study symmetry breaking at the Dicke quantum phase transition by coupling a motional degree of freedom of a Bose-Einstein condensate to the field of an optical cavity. Using an optical heterodyne detection scheme, we observe symmetry breaking in real time and distinguish the two superradiant phases. We explore the process of symmetry breaking in the presence of a small symmetry-breaking field and study its dependence on the rate at which the critical point is crossed. Coherent switching between the two ordered phases is demonstrated.

  11. Applications of chiral symmetry

    SciTech Connect

    Pisarski, R.D.

    1995-03-01

    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 T{sub {chi}} implies that the {rho} and a{sub 1} vector mesons are degenerate in mass. In a gauged linear sigma model the {rho} mass increases with temperature, m{sub {rho}}(T{sub {chi}}) > m{sub {rho}}(0). The author conjectures that at T{sub {chi}} the thermal {rho} - a{sub 1}, peak is relatively high, at about {approximately}1 GeV, with a width approximately that at zero temperature (up to standard kinematic factors). The {omega} meson also increases in mass, nearly degenerate with the {rho}, but its width grows dramatically with temperature, increasing to at least {approximately}100 MeV by T{sub {chi}}. 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}quenched{close_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.

  12. The essential role of information management in point-of-care/critical care testing.

    PubMed

    Blick, K E

    2001-05-01

    Laboratory medicine is undergoing tremendous change in recent years driven primarily by technology, regulations, reimbursement, and market forces. In this paradigm shift, the laboratory is under tremendous pressure to adapt to new requirements for critical care testing. Indeed, laboratories have entered the information age where chemical data is being extracted from specimens in totally automated fashion. In the past, laboratory data has played a more historical role in the care of critically ill patients, arriving at the bedside too late to be of significant use in the active, ongoing care of the patient. However, today's physicians taking care of critically ill patients now require that laboratory results are made available in real-time and, if possible, at the patient's point-of-care. Many new testing point-of-care testing (POCT) devices have been developed to address this need however often laboratories implement such distributed devices with little or no attention to the information technology requirements. In fact, as little as 10% of point-of-care testing is actually managed by the central laboratory computer hence critically importance results are not found on the patient's electronic medical record. In addition, the billing and management data for point-of-care testing is often handled manually with no plans to interface point-of-care devices to the laboratory billing and management systems. Because of recent improvements of information handling and interface capability, such shortcomings in data management are no longer acceptable. Indeed, the demands for laboratories to utilize information technology are such that those laboratories with no overall plan for data management of critical care testing will probably not survive this market-driven paradigm. We present a discussion of the various approaches to computerization of point-of-care testing including the advantages and the disadvantages of each approach.

  13. Triple point of Lennard-Jones fluid in slit nanopore: solidification of critical condensate.

    PubMed

    Kanda, Hideki; Miyahara, Minoru; Higashitani, Ko

    2004-04-01

    We report the results of a molecular dynamics simulation that looked for the triple point of Lennard-Jones fluid in slit-shaped nanopores. The simulation method employed for this purpose is able to maintain vapor-liquid coexistence in a nanopore at a specific equilibrium bulk-phase pressure. The triple point is the freezing point of the critical condensate. The triple-point temperature could be higher or lower than the bulk triple point, depending on the pore size. This is thought to be due to two opposing factors: the elevating effect of the pore-wall potential energy, and the depressing effect of the capillary condensate's tensile condition. Because of the cancellation, the deviation of the triple-point temperature from the bulk triple-point temperature was not considered significant. The pressure of the triple point, however, was significantly different from that of the bulk triple point. A simple model to describe the triple point is developed and shown to agree well with the results of the simulation. The importance of the two factors in nanoscale pores, which cannot be described by the classic Gibbs-Thomson equation, is emphasized.

  14. Study of the ST2 model of water close to the liquid-liquid critical point.

    PubMed

    Sciortino, Francesco; Saika-Voivod, Ivan; Poole, Peter H

    2011-11-28

    We perform successive umbrella sampling grand canonical Monte Carlo computer simulations of the original ST2 model of water in the vicinity of the proposed liquid-liquid critical point, at temperatures above and below the critical temperature. Our results support the previous work of Y. Liu, A. Z. Panagiotopoulos and P. G. Debenedetti [J. Chem. Phys., 2009, 131, 104508], who provided evidence for the existence and location of the critical point for ST2 using the Ewald method to evaluate the long-range forces. Our results therefore demonstrate the robustness of the evidence for critical behavior with respect to the treatment of the electrostatic interactions. In addition, we verify that the liquid is equilibrated at all densities on the Monte Carlo time scale of our simulations, and also that there is no indication of crystal formation during our runs. These findings demonstrate that the processes of liquid-state relaxation and crystal nucleation are well separated in time. Therefore, the bimodal shape of the density of states, and hence the critical point itself, is a purely liquid-state phenomenon that is distinct from the crystal-liquid transition.

  15. Critical-Point Description of the Transition from Vibrational to Rotational Regimes in the Pairing Phase

    SciTech Connect

    Clark, R.M.; Macchiavelli, A.O.; Fortunato, L.; Kruecken, R.

    2006-01-27

    An approximate solution at the critical point of the pairing transition from harmonic vibration to deformed rotation in gauge space is found by analytic solution of the collective pairing Hamiltonian. The eigenvalues are expressed in terms of the zeros of Bessel functions of integer order. The results are compared to the pairing bands based on the Pb isotopes.

  16. Improved Criteria for Acceptable Yield Point Elongation in Surface Critical Steels

    SciTech Connect

    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.

  17. Euler Strut: A Mechanical Analogy for Dynamics in the Vicinity of a Critical Point

    ERIC Educational Resources Information Center

    Bobnar, Jaka; Susman, Katarina; Parsegian, V. Adrian; Rand, Peter R.; Cepic, Mojca; Podgornik, Rudolf

    2011-01-01

    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…

  18. One-norm geometric quantum discord and critical point estimation in the XY spin chain

    SciTech Connect

    Cheng, Chang-Cheng; Wang, Yao; Guo, Jin-Liang

    2016-11-15

    In contrast with entanglement and quantum discord (QD), we investigate the thermal quantum correlation in terms of Schatten one-norm geometric quantum discord (GQD) in the XY spin chain, and analyze their capabilities in detecting the critical point of quantum phase transition. We show that the one-norm GQD can reveal more properties about quantum correlation between two spins, especially for the long-range quantum correlation at finite temperature. Under the influences of site distance, anisotropy and temperature, one-norm GQD and its first derivative make it possible to detect the critical point efficiently for a general XY spin chain. - Highlights: • Comparing with entanglement and QD, one-norm GQD is more robust versus the temperature. • One-norm GQD is more efficient in characterization of long-range quantum correlation between two distant qubits. • One-norm GQD performs well in highlighting the critical point of QPT at zero or low finite temperature. • One-norm GQD has a number of advantages over QD in detecting the critical point of the spin chain.

  19. Euler Strut: A Mechanical Analogy for Dynamics in the Vicinity of a Critical Point

    ERIC Educational Resources Information Center

    Bobnar, Jaka; Susman, Katarina; Parsegian, V. Adrian; Rand, Peter R.; Cepic, Mojca; Podgornik, Rudolf

    2011-01-01

    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…

  20. Towards sustaining women through critical transition points in scientific careers: a workshop summary.

    USDA-ARS?s Scientific Manuscript database

    This invited editorial summarizes and comments on discussions from a workshop entitled “From Doctorate to Dean or Director: Sustaining Women through Critical Transition Points in Science, Engineering, and Medicine” held by the Committee on Women in Science, Engineering, and Medicine of the National ...

  1. The application of the nonsmooth critical point theory to the stationary electrorheological fluids

    NASA Astrophysics Data System (ADS)

    Qian, Chenyin

    2016-06-01

    In this paper, we prove the existence of variational solutions to systems modeling electrorheological fluids in the stationary case. Our method of proof is based on the nonsmooth critical point theory for locally Lipschitz functional and the properties of the generalized Lebesgue-Sobolev space.

  2. Using bioluminescent biosensors for hazard analysis and critical control point (HACCP) in wastewater control.

    PubMed

    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.

  3. Using change-point models to estimate empirical critical loads for nitrogen in mountain ecosystems.

    PubMed

    Roth, Tobias; Kohli, Lukas; Rihm, Beat; Meier, Reto; Achermann, Beat

    2017-01-01

    To protect ecosystems and their services, the critical load concept has been implemented under the framework of the Convention on Long-range Transboundary Air Pollution (UNECE) to develop effects-oriented air pollution abatement strategies. Critical loads are thresholds below which damaging effects on sensitive habitats do not occur according to current knowledge. Here we use change-point models applied in a Bayesian context to overcome some of the difficulties when estimating empirical critical loads for nitrogen (N) from empirical data. We tested the method using simulated data with varying sample sizes, varying effects of confounding variables, and with varying negative effects of N deposition on species richness. The method was applied to the national-scale plant species richness data from mountain hay meadows and (sub)alpine scrubs sites in Switzerland. Seven confounding factors (elevation, inclination, precipitation, calcareous content, aspect as well as indicator values for humidity and light) were selected based on earlier studies examining numerous environmental factors to explain Swiss vascular plant diversity. The estimated critical load confirmed the existing empirical critical load of 5-15 kg N ha(-1) yr(-1) for (sub)alpine scrubs, while for mountain hay meadows the estimated critical load was at the lower end of the current empirical critical load range. Based on these results, we suggest to narrow down the critical load range for mountain hay meadows to 10-15 kg N ha(-1) yr(-1).

  4. Second-order magnetic critical points at finite magnetic fields: Revisiting Arrott plots

    NASA Astrophysics Data System (ADS)

    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.

  5. IMAGE-PLANE ANALYSIS OF n-POINT-MASS LENS CRITICAL CURVES AND CAUSTICS

    SciTech Connect

    Danek, Kamil; Heyrovský, David E-mail: heyrovsky@utf.mff.cuni.cz

    2015-06-10

    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. Utilizing this property further, we introduce the cusp curve to identify cusp-image positions on all contours simultaneously. In order to track cusp-number changes in caustic metamorphoses, we define the morph curve, which pinpoints the positions of metamorphosis-point images along the cusp curve. We demonstrate the usage of both curves on simple two- and three-point-mass lens examples. For the three simplest caustic metamorphoses we illustrate the local structure of the image and source planes.

  6. Acute enhancement of the upper critical field for superconductivity approaching a quantum critical point in URhGe

    NASA Astrophysics Data System (ADS)

    Lévy, F.; Sheikin, I.; Huxley, A.

    2007-07-01

    When a pure material is tuned to the point where a continuous phase-transition line is crossed at zero temperature, known as a quantum critical point (QCP), completely new correlated quantum ordered states can form. These phases include exotic forms of superconductivity. However, as superconductivity is generally suppressed by a magnetic field, the formation of superconductivity ought not to be possible at extremely high field. Here, we report that as we tune the ferromagnet, URhGe, towards a QCP by applying a component of magnetic field in the material's easy magnetic plane, superconductivity survives in progressively higher fields applied simultaneously along the material's magnetic hard axis. Thus, although superconductivity never occurs above a temperature of 0.5K, we find that it can survive in extremely high magnetic fields, exceeding 28T.

  7. Functional renormalization group analysis of the soft mode at the QCD critical point

    NASA Astrophysics Data System (ADS)

    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.

  8. Equation of state and critical point behavior of hard-core double-Yukawa fluids

    NASA Astrophysics Data System (ADS)

    Montes, J.; Robles, M.; López de Haro, M.

    2016-02-01

    A theoretical study on the equation of state and the critical point behavior of hard-core double-Yukawa fluids is presented. Thermodynamic perturbation theory, restricted to first order in the inverse temperature and having the hard-sphere fluid as the reference system, is used to derive a relatively simple analytical equation of state of hard-core multi-Yukawa fluids. Using such an equation of state, the compressibility factor and phase behavior of six representative hard-core double-Yukawa fluids are examined and compared with available simulation results. The effect of varying the parameters of the hard-core double-Yukawa intermolecular potential on the location of the critical point is also analyzed using different perspectives. The relevance of this analysis for fluids whose molecules interact with realistic potentials is also pointed out.

  9. Equation of state and critical point behavior of hard-core double-Yukawa fluids.

    PubMed

    Montes, J; Robles, M; López de Haro, M

    2016-02-28

    A theoretical study on the equation of state and the critical point behavior of hard-core double-Yukawa fluids is presented. Thermodynamic perturbation theory, restricted to first order in the inverse temperature and having the hard-sphere fluid as the reference system, is used to derive a relatively simple analytical equation of state of hard-core multi-Yukawa fluids. Using such an equation of state, the compressibility factor and phase behavior of six representative hard-core double-Yukawa fluids are examined and compared with available simulation results. The effect of varying the parameters of the hard-core double-Yukawa intermolecular potential on the location of the critical point is also analyzed using different perspectives. The relevance of this analysis for fluids whose molecules interact with realistic potentials is also pointed out.

  10. A Model for Hydrogen Thermal Conductivity and Viscosity Including the Critical Point

    NASA Technical Reports Server (NTRS)

    Wagner, Howard A.; Tunc, Gokturk; Bayazitoglu, Yildiz

    2001-01-01

    In order to conduct a thermal analysis of heat transfer to liquid hydrogen near the critical point, an accurate understanding of the thermal transport properties is required. A review of the available literature on hydrogen transport properties identified a lack of useful equations to predict the thermal conductivity and viscosity of liquid hydrogen. The tables published by the National Bureau of Standards were used to perform a series of curve fits to generate the needed correlation equations. These equations give the thermal conductivity and viscosity of hydrogen below 100 K. They agree with the published NBS tables, with less than a 1.5 percent error for temperatures below 100 K and pressures from the triple point to 1000 KPa. These equations also capture the divergence in the thermal conductivity at the critical point

  11. Theory of First Order Chemical Kinetics at the Critical Point of Solution.

    PubMed

    Baird, James Kern; Lang, Joshua R

    2017-09-27

    Liquid mixtures, which have a phase diagram exhibiting a miscibility gap ending in a critical point of solution, have been used as solvents for chemical reactions. The reaction rate in the forward direction has often been observed to slow down as a function of temperature in the critical region. Theories based upon the Gibbs free energy of reaction as the driving force for chemical change have been invoked to explain this behavior. With the assumption that the reaction is proceeding under relaxation conditions, these theories expand the free energy in a Taylor series about the position of equilibrium. Since the free energy is zero at equilibrium, the leading term in the Taylor series is proportional to the first derivative of the free energy with respect to the extent of reaction. To analyze the critical behavior of this derivative, the theories invoke the principle of critical point isomorphism, which is thought to govern all critical phenomena. They find that the derivative goes to zero in the critical region, which accounts for the slowing down observed in the reaction rate. As has been pointed out, however, most experimental rate investigations have been carried out under irreversible conditions as opposed to relaxation conditions [Shen et al. J. Phys. Chem. A 2015, 119, 8784 - 8791]. Below, we consider a reaction governed by first order kinetics and invoke transition state theory to take into account the irreversible conditions. We express the apparent activation energy in terms of thermodynamic derivatives evaluated under standard conditions as well as the pseudo-equilibrium conditions associated with the reactant and the activated complex. We show that these derivatives approach infinity in the critical region. The apparent activation energy follows this behavior, and its divergence accounts for the slowing down of the reaction rate.

  12. Polymer Conformation near the Critical Demixing Point of a Binary Solution

    NASA Astrophysics Data System (ADS)

    He, Lilin; Cheng, Gang; Melnichenko, Yuri

    2012-02-01

    We have used Contrast Matching Small Angle Neutron Scattering (CMSANS) to probe directly the conformation change of polyethylene glycerol (PEO) chains in the critical demixing region of Acetonitrile-d3 in (D2O + H2O) at concentration of the components corresponding to zero-average contrast condition. The d-PEO and h-PEO were mixed to match the scattering length density (SLD) of the critical liquid solution, which allowed us to extract single-chain dimension of polymer molecules in the aggregates near the critical point of the solvent. A non-monotonic variation of Rg was detected as temperature approached the critical temperature of phase demixing of acetonitrile- water solution, which was attributed to the interaction asymmetry of the solvent molecules with polymers predicted by Brochard and de Gennes two decades ago. To our best knowledge, this is the first direct experimental evidence supporting this prediction.

  13. Metal-insulator quantum critical point beneath the high Tc superconducting dome

    PubMed Central

    Sebastian, Suchitra E.; Harrison, N.; Altarawneh, M. M.; Mielke, C. H.; Liang, Ruixing; Bonn, D. A.; Lonzarich, G. G.; Hardy, W. N.

    2010-01-01

    An enduring question in correlated systems concerns whether superconductivity is favored at a quantum critical point (QCP) characterized by a divergent quasiparticle effective mass. Despite such a scenario being widely postulated in high Tc cuprates and invoked to explain non-Fermi liquid transport signatures, experimental evidence is lacking for a critical divergence under the superconducting dome. We use ultrastrong magnetic fields to measure quantum oscillations in underdoped YBa2Cu3O6+x, revealing a dramatic doping-dependent upturn in quasiparticle effective mass at a critical metal-insulator transition beneath the superconducting dome. Given the location of this QCP under a plateau in Tc in addition to a postulated QCP at optimal doping, we discuss the intriguing possibility of two intersecting superconducting subdomes, each centered at a critical Fermi surface instability. PMID:20304800

  14. Reaction kinetics and critical phenomena: iodination of acetone in isobutyric acid + water near the consolute point.

    PubMed

    Hu, Baichuan; Baird, James K

    2010-01-14

    The rate of iodination of acetone has been measured as a function of temperature in the binary solvent isobutyric acid (IBA) + water near the upper consolute point. The reaction mixture was prepared by the addition of acetone, iodine, and potassium iodide to IBA + water at its critical composition of 38.8 mass % IBA. The value of the critical temperature determined immediately after mixing was 25.43 degrees C. Aliquots were extracted from the mixture at regular intervals in order to follow the time course of the reaction. After dilution of the aliquot with water to quench the reaction, the concentration of triiodide ion was determined by the measurement of the optical density at a wavelength of 565 nm. These measurements showed that the kinetics were zeroth order. When at the end of 24 h the reaction had come to equilibrium, the critical temperature was determined again and found to be 24.83 degrees C. An Arrhenius plot of the temperature dependence of the observed rate constant, k(obs), was linear over the temperature range 27.00-38.00 degrees C, but between 25.43 and 27.00 degrees C, the values of k(obs) fell below the extrapolation of the Arrhenius line. This behavior is evidence in support of critical slowing down. Our experimental method and results are significant in three ways: (1) In contrast to in situ measurements of optical density, the determination of the optical density of diluted aliquots avoided any interference from critical opalescence. (2) The measured reaction rate exhibited critical slowing down. (3) The rate law was pseudo zeroth order both inside and outside the critical region, indicating that the reaction mechanism was unaffected by the presence of the critical point.

  15. Stationary and transient Soret separation in a binary mixture with a consolute critical point.

    PubMed

    Ryzhkov, Ilya I; Kozlova, Sofia V

    2016-12-01

    The stationary and transient Soret separation in a binary mixture with a consolute critical point is studied theoretically. The mixture is placed between two parallel plates kept at different temperatures. A polymer blend is used as a model system. Analytical solutions are constructed to describe the stationary separation in a binary mixture with variable Soret coefficient. The latter strongly depends on temperature and concentration and enhances near a consolute critical point due to reduced diffusion. As a result, a large concentration gradient is observed locally, while much smaller concentration variations are found in the rest of the layer. It is shown that complete separation can be obtained by applying a small temperature difference first, waiting for the establishment of stationary state, and then increasing this difference again. In this case, the critical temperature lies between hot and cold wall temperatures, while the mixture still remains in the one-phase region. When the initial (mean) temperature or concentration are shifted away from the near-critical values, the separation decreases. The analysis of transient behavior shows that the Soret separation occurs much faster than diffusion to the homogeneous state when the initial concentration is close to the critical one. It happens due to the decrease (increase) of the local relaxation time during the Soret (Diffusion) steps. The transient times of these steps become comparable for small temperature differences or off-critical initial concentrations. An unusual (non-exponential) separation dynamics is observed when the separation starts in the off-critical domain, and then enhances greatly when the system enters into the near-critical region. It is also found that the transient time decreases with increasing the applied temperature difference.

  16. Symmetry operation measures.

    PubMed

    Pinsky, Mark; Casanova, David; Alemany, Pere; Alvarez, Santiago; Avnir, David; Dryzun, Chaim; Kizner, Ziv; Sterkin, Alexander

    2008-01-30

    We introduce a new mathematical tool for quantifying the symmetry contents of molecular structures: the Symmetry Operation Measures. In this approach, we measure the minimal distance between a given structure and the structure which is obtained after applying a selected symmetry operation on it. If the given operation is a true symmetry operation for the structure, this distance is zero; otherwise it gives an indication of how different the transformed structure is from the original one. Specifically, we provide analytical solutions for measures of all the improper rotations, S n p, including mirror symmetry and inversion, as well as for all pure rotations, C n p. These measures provide information complementary to the Continuous Symmetry Measures (CSM) that evaluate the distance between a given structure and the nearest structure which belongs to a selected symmetry point-group.

  17. Critical Casimir interactions around the consolute point of a binary solvent.

    PubMed

    Mohry, T F; Kondrat, S; Maciołek, A; Dietrich, S

    2014-08-14

    Spatial confinement of a near-critical medium changes its fluctuation spectrum and modifies the corresponding order parameter distribution, resulting in effective, so-called critical Casimir forces (CCFs) acting on the confining surfaces. These forces are attractive for like boundary conditions of the order parameter at the opposing surfaces of the confinement. For colloidal particles dissolved in a binary liquid mixture acting as a solvent close to its critical point of demixing, one thus expects the emergence of phase segregation into equilibrium colloidal liquid and gas phases. We analyze how such phenomena occur asymmetrically in the whole thermodynamic neighborhood of the consolute point of the binary solvent. By applying field-theoretical methods within mean-field approximation and the semi-empirical de Gennes-Fisher functional, we study the CCFs acting between planar parallel walls as well as between two spherical colloids and their dependence on temperature and on the composition of the near-critical binary mixture. We find that for compositions slightly poor in the molecules preferentially adsorbed at the surfaces, the CCFs are significantly stronger than at the critical composition, thus leading to pronounced colloidal segregation. The segregation phase diagram of the colloid solution following from the calculated effective pair potential between the colloids agrees surprisingly well with experiments and simulations.

  18. Nonsymmorphic symmetry-required band crossings in topological semimetals

    NASA Astrophysics Data System (ADS)

    Zhao, Y. X.; Schnyder, Andreas P.

    2016-11-01

    We show that for two-band systems nonsymmorphic symmetries may enforce the existence of band crossings in the bulk, which realize Fermi surfaces of reduced dimensionality. We find that these unavoidable crossings originate from the momentum dependence of the nonsymmorphic symmetry, which puts strong restrictions on the global structure of the band configurations. Three different types of nonsymmorphic symmetries are considered: (i) a unitary nonsymmorphic symmetry, (ii) a nonsymmorphic magnetic symmetry, and (iii) a nonsymmorphic symmetry combined with inversion. For nonsymmorphic symmetries of the latter two types, the band crossings are located at high-symmetry points of the Brillouin zone, with their exact positions being determined by the algebra of the symmetry operators. To characterize these band degeneracies we introduce a global topological charge and show that it is of Z2 type, which is in contrast to the local topological charge of Fermi points in, say, Weyl semimetals. To illustrate these concepts, we discuss the π -flux state as well as the Su-Schrieffer-Heeger model at its critical point and show that these two models fit nicely into our general framework of nonsymmorphic two-band systems.

  19. Superconductivity and non-Fermi liquid behavior near a nematic quantum critical point.

    PubMed

    Lederer, Samuel; Schattner, Yoni; Berg, Erez; Kivelson, Steven A

    2017-05-09

    Using determinantal quantum Monte Carlo, we compute the properties of a lattice model with spin [Formula: see text] itinerant electrons tuned through a quantum phase transition to an Ising nematic phase. The nematic fluctuations induce superconductivity with a broad dome in the superconducting [Formula: see text] enclosing the nematic quantum critical point. For temperatures above [Formula: see text], we see strikingly non-Fermi liquid behavior, including a "nodal-antinodal dichotomy" reminiscent of that seen in several transition metal oxides. In addition, the critical fluctuations have a strong effect on the low-frequency optical conductivity, resulting in behavior consistent with "bad metal" phenomenology.

  20. Probing Wnt Receptor Turnover: A Critical Regulatory Point of Wnt Pathway.

    PubMed

    Jiang, Xiaomo; Cong, Feng

    2016-01-01

    Wnt pathways are critical for embryonic development and adult tissue homeostasis in all multicellular animals. Many regulatory mechanisms exist to control proper signaling output. Recent studies suggest that cell surface Wnt receptor level is controlled by ubiquitination, and serve as a critical regulatory point of Wnt pathway activity as it determines the responsiveness of cells to Wnt signal. Here, we describe flow cytometry, cell surface protein biotinylation, and immunofluorescence pulse-chase methods to probe the surface expression, ubiquitination, and internalization of the Wnt receptors FZD and LRP6.

  1. Replica symmetry breaking for anisotropic magnets with quenched disorder

    NASA Astrophysics Data System (ADS)

    Kogan, E.; Kaveh, M.

    2017-01-01

    We study critical behaviour of a magnet with cubic anisotropy and quenched scalar disorder which is taken into account by replica method. We derive to first order in ε approximation the renormalization group equations taking into account possible replica symmetry breaking. We study the stability of the replica symmetric fixed points with respect to perturbations without (in general case) replica symmetry. However, we find that if a fixed point is stable with respect to replica symmetric deviations, it is also stable with respect to deviations without replica symmetry.

  2. Intrinsic low pass filtering improves signal-to-noise ratio in critical-point flexure biosensors

    SciTech Connect

    Jain, Ankit; Alam, Muhammad Ashraful

    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.

  3. Universal organization of resting brain activity at the thermodynamic critical point.

    PubMed

    Yu, Shan; Yang, Hongdian; Shriki, Oren; Plenz, Dietmar

    2013-01-01

    Thermodynamic criticality describes emergent phenomena in a wide variety of complex systems. In the mammalian cortex, one type of complex dynamics that spontaneously emerges from neuronal interactions has been characterized as neuronal avalanches. Several aspects of neuronal avalanches such as their size and life time distributions are described by power laws with unique exponents, indicating an underlying critical branching process that governs avalanche formation. Here, we show that neuronal avalanches also reflect an organization of brain dynamics 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 a distinct, yet universal organization of brain dynamics. Our results demonstrate that normal brain dynamics at rest resides near or at criticality, which maximizes several aspects of information processing such as input sensitivity and dynamic range.

  4. Nanoporous Materials Can Tune the Critical Point of a Pure Substance

    SciTech Connect

    Braun, Efrem; Chen, Joseph J.; Schnell, Sondre K.; Lin, Li-Chiang; Reimer, Jeffrey A.; Smit, Berend

    2015-09-30

    Molecular simulations and NMR relaxometry experiments demonstrate that pure benzene or xylene confined in isoreticular metal–organic frameworks (IRMOFs) exhibit true vapor–liquid phase equilibria where the effective critical point may be reduced by tuning the structure of the MOF. Our results are consistent with vapor and liquid phases extending over many MOF unit cells. These results are counterintuitive since the MOF pore diameters are approximately the same length scale as the adsorbate molecules. Lastly, as applications of these materials in catalysis, separations, and gas storage rely on the ability to tune the properties of adsorbed molecules, we anticipate that the ability to systematically control the critical point, thereby preparing spatially inhomogeneous local adsorbate densities, could add a new design tool for MOF applications.

  5. Nanoporous Materials Can Tune the Critical Point of a Pure Substance

    DOE PAGES

    Braun, Efrem; Chen, Joseph J.; Schnell, Sondre K.; ...

    2015-09-30

    Molecular simulations and NMR relaxometry experiments demonstrate that pure benzene or xylene confined in isoreticular metal–organic frameworks (IRMOFs) exhibit true vapor–liquid phase equilibria where the effective critical point may be reduced by tuning the structure of the MOF. Our results are consistent with vapor and liquid phases extending over many MOF unit cells. These results are counterintuitive since the MOF pore diameters are approximately the same length scale as the adsorbate molecules. Lastly, as applications of these materials in catalysis, separations, and gas storage rely on the ability to tune the properties of adsorbed molecules, we anticipate that the abilitymore » to systematically control the critical point, thereby preparing spatially inhomogeneous local adsorbate densities, could add a new design tool for MOF applications.« less

  6. Athermal domain-wall creep near a ferroelectric quantum critical point

    PubMed Central

    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

  7. Akara Ogbomoso: microbiological examination and identification of hazards and critical control points.

    PubMed

    Lateef, A; Davies, T E; Adelekan, A; Adelere, I A; Adedeji, A A; Fadahunsi, A H

    2010-10-01

    Akara Ogbomoso was examined toward the establishment of hazard analysis and critical control point (HACCP). The akara was produced in residential buildings with the attendant consequence of contamination. There was ample growth of aerobes, coliforms, staphylococci, Shigella and yeast/mold from the samples, water and cowpea pastes. Microbial contaminations occur through the processing, which can be corrected through education by adopting good hygienic and manufacturing practices. The critical control points were identified as frying, storage and refrying. It may be heated in the microwave for 10 s before consumption. Akara, prepared in the laboratory through the implementation of HACCP was not contaminated. Several bacterial isolates, namely; Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, Citrobacter freundii, Serratia marcescens, Proteus vulgaris, Bacillus cereus, Streptococcus pyogenes, Bacillus sp. and Shigella sp., showed multiple resistance to antibiotics ranging from two to nine. Seven strains were not resistant to the antibiotics, while five were resistant to one type of antibiotic.

  8. Nanoporous Materials Can Tune the Critical Point of a Pure Substance

    PubMed Central

    Braun, Efrem; Chen, Joseph J; Schnell, Sondre K; Lin, Li-Chiang; Reimer, Jeffrey A; Smit, Berend

    2015-01-01

    Molecular simulations and NMR relaxometry experiments demonstrate that pure benzene or xylene confined in isoreticular metal–organic frameworks (IRMOFs) exhibit true vapor–liquid phase equilibria where the effective critical point may be reduced by tuning the structure of the MOF. Our results are consistent with vapor and liquid phases extending over many MOF unit cells. These results are counterintuitive since the MOF pore diameters are approximately the same length scale as the adsorbate molecules. As applications of these materials in catalysis, separations, and gas storage rely on the ability to tune the properties of adsorbed molecules, we anticipate that the ability to systematically control the critical point, thereby preparing spatially inhomogeneous local adsorbate densities, could add a new design tool for MOF applications. PMID:26419318

  9. Athermal domain-wall creep near a ferroelectric quantum critical point

    NASA Astrophysics Data System (ADS)

    Kagawa, Fumitaka; Minami, Nao; Horiuchi, Sachio; Tokura, Yoshinori

    2016-02-01

    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.

  10. Entanglement at a two-dimensional quantum critical point: a numerical linked-cluster expansion study.

    PubMed

    Kallin, Ann B; Hyatt, Katharine; Singh, Rajiv R P; Melko, Roger G

    2013-03-29

    We develop a method to calculate the bipartite entanglement entropy of quantum models, in the thermodynamic limit, using a numerical linked-cluster expansion (NLCE) involving only rectangular clusters. It is based on exact diagonalization of all n×m rectangular clusters at the interface between entangled subsystems A and B. We use it to obtain the Renyi entanglement entropy of the two-dimensional transverse field Ising model, for arbitrary real Renyi index α. Extrapolating these results as a function of the order of the calculation, we obtain universal pieces of the entanglement entropy associated with lines and corners at the quantum critical point. They show NLCE to be one of the few methods capable of accurately calculating universal properties of arbitrary Renyi entropies at higher dimensional critical points.

  11. Extraction of the Density Fluctuations in Diatomic Fluids Around the Critical Points Using Molecular Dynamics Simulation.

    PubMed

    Tsuda, Shin-Ichi; Tomi, Masato; Tsuboi, Nobuyuki; Ikawa, Shohei; Tokumasu, Takashi

    2015-04-01

    The objective in this study is the investigation of the principle of corresponding state for the density fluctuation around the critical points of non-polar diatomic fluids. In this paper, we conducted Molecular Dynamics (MD) simulation for the extraction of the fluctuation structure around the critical points of 2-Center-Lennard-Jones (2CLJ) fluids, which have anisotropy depending on the molecular elongation. As a result, in the 2CLJ fluids which have comparatively shorter molecular elongations, the principle of corresponding state can be satisfied because almost all density fluctuations in each elongation showed the similar values. On the other hand, some of the results suggested that the 2CLJ fluids which have the longer elongation decrease the density fluctuation although the further detailed investigation is necessary.

  12. Self-assembly in chains, rings, and branches: a single component system with two critical points.

    PubMed

    Rovigatti, Lorenzo; Tavares, José Maria; Sciortino, Francesco

    2013-10-18

    We study the interplay between phase separation and self-assembly in chains, rings, and branched structures in a model of particles with dissimilar patches. We extend Wertheim's first order perturbation theory to include the effects of ring formation and to theoretically investigate the thermodynamics of the model. We find a peculiar shape for the vapor-liquid coexistence, featuring reentrant behavior in both phases and two critical points, despite the single-component nature of the system. The emergence of the lower critical point is caused by the self-assembly of rings taking place in the vapor, generating a phase with lower energy and lower entropy than the liquid. Monte Carlo simulations of the same model fully support these unconventional theoretical predictions.

  13. Nanoporous Materials Can Tune the Critical Point of a Pure Substance.

    PubMed

    Braun, Efrem; Chen, Joseph J; Schnell, Sondre K; Lin, Li-Chiang; Reimer, Jeffrey A; Smit, Berend

    2015-11-23

    Molecular simulations and NMR relaxometry experiments demonstrate that pure benzene or xylene confined in isoreticular metal-organic frameworks (IRMOFs) exhibit true vapor-liquid phase equilibria where the effective critical point may be reduced by tuning the structure of the MOF. Our results are consistent with vapor and liquid phases extending over many MOF unit cells. These results are counterintuitive since the MOF pore diameters are approximately the same length scale as the adsorbate molecules. As applications of these materials in catalysis, separations, and gas storage rely on the ability to tune the properties of adsorbed molecules, we anticipate that the ability to systematically control the critical point, thereby preparing spatially inhomogeneous local adsorbate densities, could add a new design tool for MOF applications.

  14. Second virial coefficient at the critical point in a fluid of colloidal spheres plus depletants.

    PubMed

    Tuinier, Remco; Feenstra, Maartje S

    2014-11-11

    Vliegenthart-Lekkerkerker (VL) criterion B2 = -6vc for second virial coefficient B2 at the critical (colloidal) gas-liquid point is considered for a mixture of spheres with volume vc plus depletants. For the onset of fluid-phase instability, the VL criterion holds for a wide range of shapes of direct attractive forces between hard-core spheres (Vliegenthart, G. A.; Lekkerkerker, H. N. W. J. Chem. Phys. 2000, 112, 5364). In the case of long-ranged attractions imposed indirectly via depletants, it is found that the VL relation fails. Instead, B2/vc at the critical point depends strongly on the sphere/depletant size ratio. By making the hard spheres sticky, we find that B2 moves gradually toward the VL criterion upon increasing the stickiness.

  15. Athermal domain-wall creep near a ferroelectric quantum critical point.

    PubMed

    Kagawa, Fumitaka; Minami, Nao; Horiuchi, Sachio; Tokura, Yoshinori

    2016-02-16

    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.

  16. Doping-Induced Quantum Critical Point in an Itinerant Antiferromagnet TiAu

    NASA Astrophysics Data System (ADS)

    Santiago, Jessica; Svanidze, Eteri; Besara, Tiglet; Siegrist, Theo; Morosan, Emilia

    The recently discovered itinerant magnet TiAu is the first antiferromagnet composed of non-magnetic constituents. The spin density wave ground state develops below TN ~36 K, about an order of magnitude smaller than in Cr. Achieving a quantum critical point in this material would provide a better understanding of weak itinerant antiferromagnets, while giving long sought-after insights into the effects of spin fluctuations in itinerant electron systems. While the application of pressure increases the ordering temperature TN, partial substitution of Ti provides an alternative avenue towards achieving a quantum critical point. The non-Fermi liquid behavior accompanies the quantum phase transition, as evidenced by the divergent specific heat coefficient and linear temperature dependence of the resistivity. The transition is accompanied by enhanced electron-electron correlations as well as strong spin-fluctuations, providing an experimental avenue for the verification of the self-consistent theory of spin fluctuations.

  17. A constructive method for finding critical point of the Ginzburg-Landau energy functional

    NASA Astrophysics Data System (ADS)

    Kazemi, Parimah

    In this work I present a constructive method for finding critical points of the Ginzburg-Landau energy functional using the method of Sobolev gradients. I give a description of the construction of the Sobolev gradient and obtain convergence results for continuous steepest descent with this gradient. I study the Ginzburg-Landau functional with magnetic field and the Ginzburg-Landau functional without magnetic field. I then present the numerical results I obtained by using steepest descent with the discretized Sobolev gradient.

  18. Overview of point-of-care abdominal ultrasound in emergency and critical care.

    PubMed

    Kameda, Toru; Taniguchi, Nobuyuki

    2016-01-01

    Point-of-care abdominal ultrasound (US), which is performed by clinicians at bedside, is increasingly being used to evaluate clinical manifestations, to facilitate accurate diagnoses, and to assist procedures in emergency and critical care. Methods for the assessment of acute abdominal pain with point-of-care US must be developed according to accumulated evidence in each abdominal region. To detect hemoperitoneum, the methodology of a focused assessment with sonography for a trauma examination may also be an option in non-trauma patients. For the assessment of systemic hypoperfusion and renal dysfunction, point-of-care renal Doppler US may be an option. Utilization of point-of-care US is also considered in order to detect abdominal and pelvic lesions. It is particularly useful for the detection of gallstones and the diagnosis of acute cholecystitis. Point-of-case US is justified as the initial imaging modality for the diagnosis of ureterolithiasis and the assessment of pyelonephritis. It can be used with great accuracy to detect the presence of abdominal aortic aneurysm in symptomatic patients. It may also be useful for the diagnoses of digestive tract diseases such as appendicitis, small bowel obstruction, and gastrointestinal perforation. Additionally, point-of-care US can be a modality for assisting procedures. Paracentesis under US guidance has been shown to improve patient care. US appears to be a potential modality to verify the placement of the gastric tube. The estimation of the amount of urine with bladder US can lead to an increased success rate in small children. US-guided catheterization with transrectal pressure appears to be useful in some male patients in whom standard urethral catheterization is difficult. Although a greater accumulation of evidences is needed in some fields, point-of-care abdominal US is a promising modality to improve patient care in emergency and critical care settings.

  19. Weak phase stiffness and nature of the quantum critical point in underdoped cuprates

    DOE PAGES

    Yildirim, Yucel; Ku, Wei

    2015-11-02

    We demonstrate that the zero-temperature superconducting phase diagram of underdoped cuprates can be quantitatively understood in the strong binding limit, using only the experimental spectral function of the “normal” pseudogap phase without any free parameter. In the prototypical (La1–xSrx)2CuO4, a kinetics-driven d-wave superconductivity is obtained above the critical doping δc ~ 5.2%, below which complete loss of superfluidity results from local quantum fluctuation involving local p-wave pairs. Near the critical doping, an enormous mass enhancement of the local pairs is found responsible for the observed rapid decrease of phase stiffness. Lastly, a striking mass divergence is predicted at δc thatmore » dictates the occurrence of the observed quantum critical point and the abrupt suppression of the Nernst effects in the nearby region.« less

  20. Weak phase stiffness and nature of the quantum critical point in underdoped cuprates

    SciTech Connect

    Yildirim, Yucel; Ku, Wei

    2015-11-02

    We demonstrate that the zero-temperature superconducting phase diagram of underdoped cuprates can be quantitatively understood in the strong binding limit, using only the experimental spectral function of the “normal” pseudogap phase without any free parameter. In the prototypical (La1–xSrx)2CuO4, a kinetics-driven d-wave superconductivity is obtained above the critical doping δc ~ 5.2%, below which complete loss of superfluidity results from local quantum fluctuation involving local p-wave pairs. Near the critical doping, an enormous mass enhancement of the local pairs is found responsible for the observed rapid decrease of phase stiffness. Lastly, a striking mass divergence is predicted at δc that dictates the occurrence of the observed quantum critical point and the abrupt suppression of the Nernst effects in the nearby region.

  1. Superconductivity near a Quantum-Critical Point: The Special Role of the First Matsubara Frequency

    NASA Astrophysics Data System (ADS)

    Wang, Yuxuan; Abanov, Artem; Altshuler, Boris L.; Yuzbashyan, Emil A.; Chubukov, Andrey V.

    2016-10-01

    Near a quantum-critical point in a metal strong fermion-fermion interaction mediated by a soft collective boson gives rise to incoherent, non-Fermi liquid behavior. It also often gives rise to superconductivity which masks the non-Fermi liquid behavior. We analyze the interplay between the tendency to pairing and fermionic incoherence for a set of quantum-critical models with effective dynamical interaction between low-energy fermions. We argue that superconducting Tc is nonzero even for strong incoherence and/or weak interaction due to the fact that the self-energy from dynamic critical fluctuations vanishes for the two lowest fermionic Matsubara frequencies ωm=±π T . We obtain the analytic formula for Tc, which reproduces well earlier numerical results for the electron-phonon model at vanishing Debye frequency.

  2. Ising nematic quantum critical point in a metal: a Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Lederer, Samuel

    The Ising nematic quantum critical point (QCP) associated with the zero temperature transition from a symmetric to a nematic metal is an exemplar of metallic quantum criticality. We have carried out a minus sign-free quantum Monte Carlo study of this QCP for a two dimensional lattice model with sizes up to 24 × 24 sites. The system remains non-superconducting down to the lowest accessible temperatures. The results exhibit critical scaling behavior over the accessible ranges of temperature, (imaginary) time, and distance. This scaling behavior has remarkable similarities with recently measured properties of the Fe-based superconductors proximate to their putative nematic QCP. With Yoni Schattner, Steven A. Kivelson, and Erez Berg.

  3. Pre-Yield Non-Affine Fluctuations and A Hidden Critical Point in Strained Crystals

    PubMed Central

    Das, Tamoghna; Ganguly, Saswati; Sengupta, Surajit; Rao, Madan

    2015-01-01

    A crystalline solid exhibits thermally induced localised non-affine droplets in the absence of external stress. Here we show that upon an imposed shear, the size of these droplets grow until they percolate at a critical strain, well below the value at which the solid begins to yield. This critical point does not manifest in most thermodynamic or mechanical properties, but is hidden and reveals itself in the onset of inhomogeneities in elastic moduli, marked changes in the appearance and local properties of non-affine droplets and a sudden enhancement in defect pair concentration. Slow relaxation of stress and an-elasticity appear as observable dynamical consequences of this hidden criticality. Our results may be directly verified in colloidal crystals with video microscopy techniques but are expected to have more general validity. PMID:26039380

  4. Magnetocaloric effect and magnetic cooling near a field-induced quantum-critical point

    PubMed Central

    Wolf, Bernd; Tsui, Yeekin; Jaiswal-Nagar, Deepshikha; Tutsch, Ulrich; Honecker, Andreas; Remović-Langer, Katarina; Hofmann, Georg; Prokofiev, Andrey; Assmus, Wolf; Donath, Guido; Lang, Michael

    2011-01-01

    The presence of a quantum-critical point (QCP) can significantly affect the thermodynamic properties of a material at finite temperatures T. This is reflected, e.g., in the entropy landscape S(T,r) in the vicinity of a QCP, yielding particularly strong variations for varying the tuning parameter r such as pressure or magnetic field B. Here we report on the determination of the critical enhancement of ∂S/∂B near a B-induced QCP via absolute measurements of the magnetocaloric effect (MCE), (∂T/∂B)S and demonstrate that the accumulation of entropy around the QCP can be used for efficient low-temperature magnetic cooling. Our proof of principle is based on measurements and theoretical calculations of the MCE and the cooling performance for a Cu2+-containing coordination polymer, which is a very good realization of a spin-½ antiferromagnetic Heisenberg chain—one of the simplest quantum-critical systems.

  5. Superconductivity near a Quantum-Critical Point: The Special Role of the First Matsubara Frequency.

    PubMed

    Wang, Yuxuan; Abanov, Artem; Altshuler, Boris L; Yuzbashyan, Emil A; Chubukov, Andrey V

    2016-10-07

    Near a quantum-critical point in a metal strong fermion-fermion interaction mediated by a soft collective boson gives rise to incoherent, non-Fermi liquid behavior. It also often gives rise to superconductivity which masks the non-Fermi liquid behavior. We analyze the interplay between the tendency to pairing and fermionic incoherence for a set of quantum-critical models with effective dynamical interaction between low-energy fermions. We argue that superconducting T_{c} is nonzero even for strong incoherence and/or weak interaction due to the fact that the self-energy from dynamic critical fluctuations vanishes for the two lowest fermionic Matsubara frequencies ω_{m}=±πT. We obtain the analytic formula for T_{c}, which reproduces well earlier numerical results for the electron-phonon model at vanishing Debye frequency.

  6. Kinetic stability analysis of protein assembly on the center manifold around the critical point.

    PubMed

    Tsuruyama, Tatsuaki

    2017-02-02

    Non-linear kinetic analysis is a useful method for illustration of the dynamic behavior of cellular biological systems. To date, center manifold theory (CMT) has not been sufficiently applied for stability analysis of biological systems. The aim of this study is to demonstrate the application of CMT to kinetic analysis of protein assembly and disassembly, and to propose a novel framework for nonlinear multi-parametric analysis. We propose a protein assembly model with nonlinear kinetics provided by the fluctuation in monomer concentrations during their diffusion. When the diffusion process of a monomer is self-limited to give kinetics non-linearity, numerical simulations suggest the probability that the assembly and disassembly oscillate near the critical point. We applied CMT to kinetic analysis of the center manifold around the critical point in detail, and successfully demonstrated bifurcation around the critical point, which explained the observed oscillation. The stability kinetics of the present model based on CMT illustrates a unique feature of protein assembly, namely non-linear behavior. Our findings are expected to provide methodology for analysis of biological systems.

  7. Overlapping Modularity at the Critical Point of k-Clique Percolation

    NASA Astrophysics Data System (ADS)

    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.

  8. Measurements of the Coexistence Curve near the Liquid-Gas Critical Point

    NASA Technical Reports Server (NTRS)

    Hahn, Inseob

    2003-01-01

    The shape of the liquid-gas coexistence curve of He-3 very near the critical point (-2x10(exp -6) < t < -5x10(exp -3) was measured using the quasi-static thermogram method. The study was performed in Earth s gravitational field using two different height calorimetry cells, both originally designed for simultaneous measurements of the isochoric heat capacity, isothermal compressibility, and PVT. The heights of two cells were 0.5 mm and 4.8 cm. The uncertainty in measuring the phase transition temperature was typically +/-2 micro-K. The measured coexistence curve near the critical point was strongly affected by the gravitational field. Away from the critical point, the coexistence curve obtained using this technique was also consistent with the earlier work using the local density measurements of Pittman et al. The recent crossover parametric model of the equation-of-state are used to analyze the height-dependent measured coexistence curves. Data analyses have indicated that microgravity will permit measurements within two additional decades in reduced temperatures beyond the best gravity-free data obtained in Earth-bound experiments.

  9. Numerical renormalization group for impurity quantum phase transitions: structure of critical fixed points

    NASA Astrophysics Data System (ADS)

    Lee, Hyun-Jung; Bulla, Ralf; Vojta, Matthias

    2005-11-01

    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.

  10. Mechanical parts range-image segmentation by locating critical points of one-dimensional curves

    NASA Astrophysics Data System (ADS)

    Lee, Ji-Chun; Fan, Kuang-Chao

    1996-02-01

    A modified edge-based segmentation algorithm specially designed for mechanical parts is proposed. The technique used is based on a concept of 3-views of engineering drawings and is a partial parallel algorithm. Mechanical parts considered here are composed of planes, cylindrical and spherical surfaces. At first, a set of critical points is extracted from each row and column of range image by one dimensional curves' segmentation technique. Edge linking process is performed on the map of critical points by morphological dilation, thinning and edge tracking. After that, a connected component labeling procedure is done and all pixels belonging to the same 4-connected region are assigned a unique label. An efficient run-length implementation of local table method is used to do the connected components' analysis. Finally, a robust least squares surface fitting is employed for each label to accommodate the error of previous steps, and outliers are discarded according to errors. Experiments are presented for numerous scenes of both real and synthetic range images of mechanical parts including concave and convex surfaces, noiseless and noisy. The results show that the proposed one dimensional critical point locating method segments the range image of mechanical parts fast and accurately.

  11. Estimating the Critical Point of Crowding in the Emergency Department for the Warning System

    NASA Astrophysics Data System (ADS)

    Chang, Y.; Pan, C.; Tseng, C.; Wen, J.

    2011-12-01

    The purpose of this study is to deduce a function from the admissions/discharge rate of patient flow to estimate a "Critical Point" that provides a reference for warning systems in regards to crowding in the emergency department (ED) of a hospital or medical clinic. In this study, a model of "Input-Throughput-Output" was used in our established mathematical function to evaluate the critical point. The function is defined as dPin/dt=dwait/dt+Cp×B+ dPout/dt where Pin= number of registered patients, Pwait= number of waiting patients, Cp= retention rate per bed (calculated for the critical point), B= number of licensed beds in the treatment area, and Pout= number of patients discharged from the treatment area. Using the average Cp of ED crowding, we could start the warning system at an appropriate time and then plan for necessary emergency response to facilitate the patient process more smoothly. It was concluded that ED crowding could be quantified using the average value of Cp and the value could be used as a reference for medical staff to give optimal emergency medical treatment to patients. Therefore, additional practical work should be launched to collect more precise quantitative data.

  12. Influence of the critical point on the electrocaloric response of relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Rožič, Brigita; Kosec, Marija; Uršič, Hana; Holc, Janez; Malič, Barbara; Zhang, Q. M.; Blinc, Robert; Pirc, Raša; Kutnjak, Zdravko

    2011-09-01

    The electrocaloric effect (ECE), i.e., the conversion of electric energy into heat, is of great importance for application in new generation cooling or heating devices that would be friendlier to the environment. Here, utilizing direct measurements of the ECE change of the temperature ΔT via a high resolution calorimeter, we study the ECE as a function of the magnitude of the electric-field step E in the vicinity of the critical point in several bulk relaxor ferroelectric ceramic systems. Relatively large ΔT of ˜2 to 3 K were obtained at modest fields of 90 kV/cm, even in the case of ceramic materials. The effective responsivity ΔT/E as a function of the electric field shows a characteristic peak near the critical point, which demonstrates the importance of proximity to the critical point for the enhancement of the electrocaloric effect. Experimental results are in good agreement with the theoretical calculations based on the spherical random-bond random-field model.

  13. Searching for the QCD critical point using particle ratio fluctuations and higher moments of multiplicity distributions

    NASA Astrophysics Data System (ADS)

    Tarnowsky, Terence J.; STAR Collaboration

    2011-12-01

    Dynamical fluctuations in global conserved quantities such as baryon number, strangeness or charge may be observed near a QCD critical point. Results from new measurements of dynamical K/π, p/π and K/p ratio fluctuations are presented. The commencing of a QCD critical point search at the RHIC has extended the reach of possible measurements of dynamical K/π, p/π and K/p ratio fluctuations from Au+Au collisions to lower energies. The STAR experiment has performed a comprehensive study of the energy dependence of these dynamical fluctuations in Au+Au collisions at the energies \\sqrt{s_{NN}} = 7.7, 11.5, 39, 62.4 and 200 GeV. New results are compared to previous measurements and to theoretical predictions from several models. The measured dynamical K/π fluctuations are found to be independent of collision energy, while dynamical p/π and K/p fluctuations have a negative value that increases toward zero at top RHIC energy. Fluctuations of the higher moments of conserved quantities (net-proton and net-charge) distributions, which are predicted to be sensitive to the presence of a critical point, are also presented.

  14. Measurements of the Coexistence Curve near the Liquid-Gas Critical Point

    NASA Technical Reports Server (NTRS)

    Hahn, Inseob

    2003-01-01

    The shape of the liquid-gas coexistence curve of He-3 very near the critical point (-2x10(exp -6) < t < -5x10(exp -3) was measured using the quasi-static thermogram method. The study was performed in Earth s gravitational field using two different height calorimetry cells, both originally designed for simultaneous measurements of the isochoric heat capacity, isothermal compressibility, and PVT. The heights of two cells were 0.5 mm and 4.8 cm. The uncertainty in measuring the phase transition temperature was typically +/-2 micro-K. The measured coexistence curve near the critical point was strongly affected by the gravitational field. Away from the critical point, the coexistence curve obtained using this technique was also consistent with the earlier work using the local density measurements of Pittman et al. The recent crossover parametric model of the equation-of-state are used to analyze the height-dependent measured coexistence curves. Data analyses have indicated that microgravity will permit measurements within two additional decades in reduced temperatures beyond the best gravity-free data obtained in Earth-bound experiments.

  15. Quantum critical point in the superconducting transition on the surface of a topological insulator

    NASA Astrophysics Data System (ADS)

    Li, Dingping; Rosenstein, Baruch; Shapiro, B. Ya.; Shapiro, I.

    2014-08-01

    Pairing in the Weyl semimetal appearing on the surface of a topological insulator is considered. It is shown that due to an "ultrarelativistic" dispersion relation there is a quantum critical point governing the zero-temperature transition to a superconducting state. Starting from the microscopic Hamiltonian with local attraction, we calculated using the Gor'kov equations, the phase diagram of the superconducting transition at arbitrary chemical potential, and its magnetic properties and critical exponents close to the quantum critical point. The Ginzburg-Landau (GL) effective theory is derived for small chemical potential, allowing us to consider effects of spatial dependence of order parameters in a magnetic field. The GL equations are very different from the conventional ones reflecting the chiral universality class of the quantum phase transition. The order-parameter distribution of a single vortex is found to be different as well. The magnetization near the upper critical field is found to be quadratic, not linear as usual. We discuss the application of these results to recent experiments in which surface superconductivity was found for some three-dimensional topological insulators, and we estimate feasibility of the phonon pairing.

  16. Indications for a critical point in the phase diagram for hot and dense nuclear matter

    NASA Astrophysics Data System (ADS)

    Lacey, Roy A.

    2016-12-01

    Two-pion interferometry measurements are studied for a broad range of collision centralities in Au+Au (√{sNN} = 7.7- 200 GeV) and Pb+Pb (√{sNN} = 2.76 TeV) collisions. They indicate non-monotonic excitation functions for the Gaussian emission source radii difference (Rout -Rside), 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 Tcep ∼ 165 MeV and μBcep ∼ 95 MeV for its location in the (T ,μB)-plane of the phase diagram. The static critical exponents (ν ≈ 0.66 and γ ≈ 1.2) extracted via the same FSS analysis, place this CEP in the 3D Ising model (static) universality class. A Dynamic Finite-Size Scaling analysis of the excitation functions, gives the estimate z ∼ 0.87 for the dynamic critical exponent, suggesting that the associated critical expansion dynamics is dominated by the hydrodynamic sound mode.

  17. Study of the critical points of experimental HPMC-NaCMC hydrophilic matrices.

    PubMed

    Contreras, L; Melgoza, L M; Villalobos, R; Caraballo, I

    2010-02-15

    The purpose of the present work was to study the existence of critical points on the drug release and water uptake behaviour of ternary hydrophilic matrix tablets and to study the possibility of simplifying a ternary to a binary system. The ternary hydrophilic matrix tablets were prepared between 40 and 100% (w/w) of KCl, HPMC and NaCMC. Dissolution studies were carried out using the paddle method and the water uptake studies were measured using the modified Enslin apparatus and the behaviour of the kinetic parameters was studied. According to the percolation theory, both studies confirm the existence of critical points; those were related to the excipients percolation tresholds. The percolation thresholds for the binary hydrophilic matrix tablets were found between 28.7-40.7% (v/v) of HPMC and 38.6-53.9% (v/v) of NaCMC. For the ternary hydrophilic matrix tablets, the existence of a critical barrier between 54 and 61% (v/v) KCl (60-70%, w/w of KCl) was found. In the studied ternary systems HPMC and NaCMC showed that is not possible to simplify the system but they present a partial collaboration in order to establish the gel layer. The knowledge of this critical barrier will be useful in order to optimize the design of the ternary hydrophilic matrix systems. Copyright 2009 Elsevier B.V. All rights reserved.

  18. Field theory of bicritical and tetracritical points. IV. Critical dynamics including reversible terms

    NASA Astrophysics Data System (ADS)

    Folk, R.; Holovatch, Yu.; Moser, G.

    2012-02-01

    This article concludes a series of papers [Folk, Holovatch, and Moser, Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.78.04112478, 041124 (2008); Folk, Holovatch, and Moser, Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.78.04112578, 041125 (2008); Folk, Holovatch, and Moser, Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.79.03110979, 031109 (2009)] where the tools of the field theoretical renormalization group were employed to explain and quantitatively describe different types of static and dynamic behavior in the vicinity of multicritical points. Here we give the complete two-loop calculation and analysis of the dynamic renormalization-group flow equations at the multicritical point in anisotropic antiferromagnets in an external magnetic field. We find that the time scales of the order parameters characterizing the parallel and perpendicular ordering with respect to the external field scale in the same way. This holds independent whether the Heisenberg fixed point or the biconical fixed point in statics is the stable one. The nonasymptotic analysis of the dynamic flow equations shows that due to cancellation effects the critical behavior is described, in distances from the critical point accessible to experiments, by the critical behavior qualitatively found in one-loop order. Although one may conclude from the effective dynamic exponents (taking almost their one-loop values) that weak scaling for the order parameter components is valid, the flow of the time-scale ratios is quite different, and they do not reach their asymptotic values.

  19. Assessment of hygiene standards and Hazard Analysis Critical Control Points implementation on passenger ships.

    PubMed

    Mouchtouri, Varavara; Malissiova, Eleni; Zisis, Panagiotis; Paparizou, Evina; Hadjichristodoulou, Christos

    2013-01-01

    The level of hygiene on ferries can have impact on travellers' health. The aim of this study was to assess the hygiene standards of ferries in Greece and to investigate whether Hazard Analysis Critical Control Points (HACCP) implementation contributes to the hygiene status and particularly food safety aboard passenger ships. Hygiene inspections on 17 ferries in Greece were performed using a standardized inspection form, with a 135-point scale. Thirty-four water and 17 food samples were collected and analysed. About 65% (11/17) of ferries were scored with >100 points. Ferries with HACCP received higher scores during inspection compared to those without HACCP (p value <0.001). All 34 microbiological water test results were found negative and, from the 17 food samples, only one was found positive for Salmonella spp. Implementation of management systems including HACCP principles can help to raise the level of hygiene aboard passenger ships.

  20. Asymptotic Behavior of the Magnetization Near Critical and Tricritical Points via Ginzburg Landau Polynomials

    NASA Astrophysics Data System (ADS)

    Ellis, Richard S.; Machta, Jonathan; Otto, Peter Tak-Hun

    2008-10-01

    The purpose of this paper is to prove connections among the asymptotic behavior of the magnetization, the structure of the phase transitions, and a class of polynomials that we call the Ginzburg-Landau polynomials. The model under study is a mean-field version of a lattice spin model due to Blume and Capel. It is defined by a probability distribution that depends on the parameters β and K, which represent, respectively, the inverse temperature and the interaction strength. Our main focus is on the asymptotic behavior of the magnetization m( β n , K n ) for appropriate sequences ( β n , K n ) that converge to a second-order point or to the tricritical point of the model and that lie inside various subsets of the phase-coexistence region. The main result states that as ( β n , K n ) converges to one of these points ( β, K), m(βn,Kn)˜ bar{x}|β -βn|^{γ}→ 0 . In this formula γ is a positive constant, and bar{x} is the unique positive, global minimum point of a certain polynomial g. We call g the Ginzburg-Landau polynomial because of its close connection with the Ginzburg-Landau phenomenology of critical phenomena. For each sequence the structure of the set of global minimum points of the associated Ginzburg-Landau polynomial mirrors the structure of the set of global minimum points of the free-energy functional in the region through which ( β n , K n ) passes and thus reflects the phase-transition structure of the model in that region. This paper makes rigorous the predictions of the Ginzburg-Landau phenomenology of critical phenomena and the tricritical scaling theory for the mean-field Blume-Capel model.

  1. Appearance of symmetry, beauty, and health in human faces.

    PubMed

    Zaidel, Dahlia W; Aarde, Shawn M; Baig, Kiran

    2005-04-01

    Symmetry is an important concept in biology, being related to mate selection strategies, health, and survival of species. In human faces, the relevance of left-right symmetry to attractiveness and health is not well understood. We compared the appearance of facial attractiveness, health, and symmetry in three separate experiments. Participants inspected front views of faces on the computer screen and judged them on a 5-point scale according to their attractiveness in Experiment 1, health in Experiment 2, and symmetry in Experiment 3. We found that symmetry and attractiveness were not strongly related in faces of women or men while health and symmetry were related. There was a significant difference between attractiveness and symmetry judgments but not between health and symmetry judgments. Moreover, there was a significant difference between attractiveness and health. Facial symmetry may be critical for the appearance of health but it does not seem to be critical for the appearance of attractiveness, not surprisingly perhaps because human faces together with the human brain have been shaped by adaptive evolution to be naturally asymmetrical.

  2. Neural avalanches at the critical point between replay and non-replay of spatiotemporal patterns.

    PubMed

    Scarpetta, Silvia; de Candia, Antonio

    2013-01-01

    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.

  3. Laboratory testing during critical care transport: point-of-care testing in air ambulances.

    PubMed

    Di Serio, Francesca; Petronelli, Maria Antonia; Sammartino, Eugenio

    2010-07-01

    Air and ground transport are used for prehospital transport of patients in acute life-threatening situations, and increasingly, critically ill patients undergo interhospital transportation. Results from clinical studies suggest that critical tests performed during the transport of critically ill patients presents a potential opportunity to improve patient care. Our project was to identify, according to the recommendations published at this time, a model of point-of-care testing (POCT) (arterial blood gases analysis and glucose, sodium, potassium, ionized calcium, hematocrit/hemoglobin measurements) in air ambulances. In order to identify the key internal and external factors that are important to achieving our objective, an analysis of the Strengths, Weaknesses, Opportunities, and Threats (SWOT analysis) was incorporated into our planning model prior to starting the project. To allow the entire POCT process (pre-, intra-, and post-analytic steps) to be under the control of the reference laboratory, an experimental model of information technology was applied. Real-time results during transport of critically ill patients must be considered to be an integral part of the patient care process and excellent channels of communication are needed between the intensive care units, emergency medical services and laboratories. With technological and computer advances, POCT during critical care transport will certainly increase in the future: this will be a challenge from a laboratory and clinical context.

  4. Thermal properties of ionic systems near the liquid-liquid critical point

    NASA Astrophysics Data System (ADS)

    Méndez-Castro, Pablo; Troncoso, Jacobo; Pérez-Sánchez, Germán; Peleteiro, José; Romaní, Luis

    2011-12-01

    Isobaric heat capacity per unit volume, Cp, and excess molar enthalpy, hE, were determined in the vicinity of the critical point for a set of binary systems formed by an ionic liquid and a molecular solvent. Moreover, and, since critical composition had to be accurately determined, liquid-liquid equilibrium curves were also obtained using a calorimetric method. The systems were selected with a view on representing, near room temperature, examples from clearly solvophobic to clearly coulombic behavior, which traditionally was related with the electric permittivity of the solvent. The chosen molecular compounds are: ethanol, 1-butanol, 1-hexanol, 1,3-dichloropropane, and diethylcarbonate, whereas ionic liquids are formed by imidazolium-based cations and tetrafluoroborate or bis-(trifluromethylsulfonyl)amide anions. The results reveal that solvophobic critical behavior—systems with molecular solvents of high dielectric permittivity—is very similar to that found for molecular binary systems. However, coulombic systems—those with low permittivity molecular solvents—show strong deviations from the results usually found for these magnitudes near the liquid-liquid phase transition. They present an extremely small critical anomaly in Cp—several orders of magnitude lower than those typically obtained for binary mixtures—and extremely low hE—for one system even negative, fact not observed, up to date, for any liquid-liquid transition in the nearness of an upper critical solution temperature.

  5. [Theses on critical gerontology from a social science point of view].

    PubMed

    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.

  6. Symmetry impedes symmetry discrimination.

    PubMed

    Tjan, Bosco S; Liu, Zili

    2005-12-16

    Objects in the world, natural and artificial alike, are often bilaterally symmetric. The visual system is likely to take advantage of this regularity to encode shapes for efficient object recognition. The nature of encoding a symmetric shape, and of encoding any departure from it, is therefore an important matter in visual perception. We addressed this issue of shape encoding empirically, noting that a particular encoding scheme necessarily leads to a specific profile of sensitivity in perceptual discriminations. We studied symmetry discrimination using human faces and random dots. Each face stimulus was a frontal view of a three-dimensional (3-D) face model. The 3-D face model was a linearly weighted average (a morph) between the model of an original face and that of the corresponding mirror face. Using this morphing technique to vary the degree of asymmetry, we found that, for faces and analogously generated random-dot patterns alike, symmetry discrimination was worst when the stimuli were nearly symmetric, in apparent opposition to almost all studies in the literature. We analyzed the previous work and reconciled the old and new results using a generic model with a simple nonlinearity. By defining asymmetry as the minimal difference between the left and right halves of an object, we found that the visual system was disproportionately more sensitive to larger departures from symmetry than to smaller ones. We further demonstrated that our empirical and modeling results were consistent with Weber-Fechner's and Stevens's laws.

  7. Event-by-event fluctuations in heavy ion collisions and the QCD critical point

    NASA Astrophysics Data System (ADS)

    Stephanov, M.; Rajagopal, K.; Shuryak, E.

    1999-12-01

    The event-by-event fluctuations of suitably chosen observables in heavy ion collisions at CERN SPS, BNL RHIC, and CERN LHC can tell us about the thermodynamic properties of the hadronic system at freeze-out. By studying these fluctuations as a function of varying control parameters, it is possible to learn much about the phase diagram of QCD. As a timely example, we stress the methods by which present experiments at the CERN SPS can locate the second-order critical end point of the first-order transition between quark-gluon plasma and hadron matter. Those event-by-event signatures which are characteristic of freeze-out in the vicinity of the critical point will exhibit nonmonotonic dependence on control parameters. We focus on observables constructed from the multiplicity and transverse momenta of charged pions. We first consider how the event-by-event fluctuations of such observables are affected by Bose-Einstein correlations, by resonances which decay after freeze-out, and by fluctuations in the transverse flow velocity. We compare our thermodynamic predictions for such noncritical event-by-event fluctuations with NA49 data, finding broad agreement. We then focus on effects due to thermal contact between the observed pions and a heat bath with a given (possibly singular) specific heat, due to the direct coupling between the critical fluctuations of the sigma field and the observed pions. We also discuss the effect of the pions produced in the decay of sigma particles just above threshold after freeze-out on the inclusive pion spectrum and on multiplicity fluctuations. We estimate the size of these nonmonotonic effects, which appear near the critical point, including restrictions imposed by finite size and finite time, and conclude that they should be easily observable.

  8. Solid-like features in dense vapors near the fluid critical point

    NASA Astrophysics Data System (ADS)

    Ruppeiner, George; Dyjack, Nathan; McAloon, Abigail; Stoops, Jerry

    2017-06-01

    The phase diagram (pressure versus temperature) of the pure fluid is typically envisioned as being featureless apart from the presence of the liquid-vapor coexistence curve terminating at the critical point. However, a number of recent authors have proposed that this simple picture misses important features, such as the Widom line, the Fisher-Widom line, and the Frenkel line. In our paper, we discuss another way of augmenting the pure fluid phase diagram, lines of zero thermodynamic curvature R = 0 separating regimes of fluid solid-like behavior (R > 0) from gas-like or liquid-like behavior (R < 0). We systematically evaluate R for the 121 pure fluids in the NIST/REFPROP (version 9.1) fluid database near the saturated vapor line from the triple point to the critical point. Our specific goal was to identify regions of positive R abutting the saturated vapor line ("feature D"). We found the following: (i) 97/121 of the NIST/REFPROP fluids have feature D. (ii) The presence and character of feature D correlates with molecular complexity, taken to be the number of atoms Q per molecule. (iii) The solid-like properties of feature D might be attributable to a mesoscopic model based on correlations among coordinated spinning molecules, a model that might be testable with computer simulations. (iv) There are a number of correlations between thermodynamic quantities, including the acentric factor ω , but we found little explicit correlation between ω and the shape of a molecule. (v) Feature D seriously constrains the size of the asymptotic fluid critical point regime, possibly resolving a long-standing mystery about why these are so small. (vi) Feature D correlates roughly with regimes of anomalous sound propagation.

  9. Analytic description of critical-point actinides in a transition from octupole deformation to octupole vibrations

    SciTech Connect

    Bonatsos, Dennis; Lenis, D.; Petrellis, D.; Minkov, N.; Yotov, P.

    2005-06-01

    An analytic collective model in which the relative presence of the quadrupole and octupole deformations is determined by a parameter ({phi}{sub 0}), while axial symmetry is obeyed, is developed. The model [to be called the analytic quadrupole octupole axially symmetric model (AQOA)] involves an infinite well potential, provides predictions for energy and B(EL) ratios, which depend only on {phi}{sub 0}, draws the border between the regions of octupole deformation and octupole vibrations in an essentially parameter-independent way, and describes well {sup 226}Th and {sup 226}Ra, for which experimental energy data are shown to suggest that they lie close to this border. The similarity of the AQOA results with {phi}{sub 0}=45 deg. for ground-state band spectra and B(E2) transition rates to the predictions of the X(5) model is pointed out. Analytic solutions are also obtained for Davidson potentials of the form {beta}{sup 2}+{beta}{sub 0}{sup 4}/{beta}{sup 2}, leading to the AQOA spectrum through a variational procedure.

  10. Phenomenological Equations Relating Various Critical Anomalies above a Cubic-to-Tetragonal Phase Transition Point

    NASA Astrophysics Data System (ADS)

    Hamano, Katsumi; Hirotsu, Shunsuke

    1980-01-01

    Phenomenological equations are derived which interrelate the anomalies in various thermodynamic quantities above the transition point of a cubic-to-tetragonal phase transition caused by an instability of a triply degenerate soft mode. The anomalous part of the Gibbs free energy is assumed to be a simple sum of the three parts which represent the contributions from the three fluctuation components. A cylindrical approximation is adopted to each of the three contributions by taking into account the symmetry of the fluctuations. The theory predicts that the adiabatic elastic compliances, s11s, s12s, and also s11s-s12s should exhibit anomalies proportional to the anomaly in the specific heat at constant pressure. This is in marked contrast with the result of the generalized Pippard equations derived by Garland, and by Janovec. The new equations are successfully tested for KMnF3, CsPbCl3, and CsPbBr3. The β-γ transition of NH4Br is also discussed.

  11. Influences of depletion potential on vapor-liquid critical point metastability

    NASA Astrophysics Data System (ADS)

    Zhou, S.; Liu, G.

    2016-04-01

    Phase behavior of a neutral colloid dispersion is investigated based on an improved Asakura-Oosawa (AO) model. Several observations are made: (i) an increase of solvent fugacity can enlarge the fluid-solid (FS) coexistence region, and this makes fugacity become a powerful factor in tuning a vapor-liquid transition (VLT) critical point metastability. (ii) A reducing of size ratio of the solvent versus colloid particle can enlarge the FS coexistence region as well as lower the VLT critical temperature, and a combination of the two effects makes the size ratio an extremely powerful factor adjusting the VLT critical point metastability. (iii) Existence of a long-range attraction term in the effective colloid potential is not a necessary condition for occurrence of a vapor-solid transition (VST), and short-ranged oscillatory depletion potential also can induce the VST over an even broader temperature range. (iv) Sensitivity of the freezing line on the size ratio is disclosed, and one can make use of the sensitivity to prepare mono-disperse colloid of well-controlled diameter by following a fractionated crystallization scheme; moreover, broadening of the FST coexistence region by raising the solvent fugacity and/or lowering the size ratio has important implication for crystallization process.

  12. Vegetation community change points suggest that critical loads of nutrient nitrogen may be too high

    NASA Astrophysics Data System (ADS)

    Wilkins, Kayla; Aherne, Julian; Bleasdale, Andy

    2016-12-01

    It is widely accepted that elevated nitrogen deposition can have detrimental effects on semi-natural ecosystems, including changes to plant diversity. Empirical critical loads of nutrient nitrogen have been recommended to protect many sensitive European habitats from significant harmful effects. In this study, we used Threshold Indicator Taxa Analysis (TITAN) to investigate shifts in vegetation communities along an atmospheric nitrogen deposition gradient for twenty-two semi-natural habitat types (as described under Annex I of the European Union Habitats Directive) in Ireland. Significant changes in vegetation community, i.e., change points, were determined for twelve habitats, with seven habitats showing a decrease in the number of positive indicator species. Community-level change points indicated a decrease in species abundance along a nitrogen deposition gradient ranging from 3.9 to 15.3 kg N ha-1 yr-1, which were significantly lower than recommended critical loads (Wilcoxon signed-rank test; V = 6, p < 0.05). These results suggest that lower critical loads of empirical nutrient nitrogen deposition may be required to protect many European habitats. Changes to vegetation communities may mean a loss of sensitive indicator species and potentially rare species in these habitats, highlighting how emission reductions policies set under the National Emissions Ceilings Directive may be directly linked to meeting the goal set out under the European Union's Biodiversity Strategy of "halting the loss of biodiversity" across Europe by 2020.

  13. Scaling dimensions of higher-charge monopoles at deconfined critical points

    NASA Astrophysics Data System (ADS)

    Sreejith, G. J.; Powell, Stephen

    2015-11-01

    The classical cubic dimer model has a columnar ordering transition that is continuous and described by a critical Anderson-Higgs theory containing an SU (2 ) -symmetric complex field minimally coupled to a noncompact U (1 ) gauge theory. Defects in the dimer constraints correspond to monopoles of the gauge theory, with charge determined by the deviation from unity of the dimer occupancy. By introducing such defects into Monte Carlo simulations of the dimer model at its critical point, we determine the scaling dimensions y2=1.48 ±0.07 and y3=0.20 ±0.03 for the operators corresponding to defects of charge q =2 and 3, respectively. These results, which constitute the first direct determination of the scaling dimensions, shed light on the deconfined critical point of spin-1/2 quantum antiferromagnets, thought to belong to the same universality class. In particular, the positive value of y3 implies that the transition in the J Q model on the honeycomb lattice is of first order.

  14. Quantum critical point and spin fluctuations in lower-mantle ferropericlase

    PubMed Central

    Lyubutin, Igor S.; Struzhkin, Viktor V.; Mironovich, A. A.; Gavriliuk, Alexander G.; Naumov, Pavel G.; Lin, Jung-Fu; Ovchinnikov, Sergey G.; Sinogeikin, Stanislav; Chow, Paul; Xiao, Yuming; Hemley, Russell J.

    2013-01-01

    Ferropericlase [(Mg,Fe)O] is one of the most abundant minerals of the earth’s lower mantle. The high-spin (HS) to low-spin (LS) transition in the Fe2+ ions may dramatically alter the physical and chemical properties of (Mg,Fe)O in the deep mantle. To understand the effects of compression on the ground electronic state of iron, electronic and magnetic states of Fe2+ in (Mg0.75Fe0.25)O have been investigated using transmission and synchrotron Mössbauer spectroscopy at high pressures and low temperatures (down to 5 K). Our results show that the ground electronic state of Fe2+ at the critical pressure Pc of the spin transition close to T = 0 is governed by a quantum critical point (T = 0, P = Pc) at which the energy required for the fluctuation between HS and LS states is zero. Analysis of the data gives Pc = 55 GPa. Thermal excitation within the HS or LS states (T > 0 K) is expected to strongly influence the magnetic as well as physical properties of ferropericlase. Multielectron theoretical calculations show that the existence of the quantum critical point at temperatures approaching zero affects not only physical properties of ferropericlase at low temperatures but also its properties at P-T of the earth’s lower mantle. PMID:23589892

  15. Infinite-randomness critical point in the two-dimensional disordered contact process.

    PubMed

    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.

  16. Heat capacity singularity of binary liquid mixtures at the liquid-liquid critical point.

    PubMed

    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.

  17. Change of carrier density at the pseudogap critical point of a cuprate superconductor.

    PubMed

    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.

  18. Indications for a critical end point in the phase diagram for hot and dense nuclear matter.

    PubMed

    Lacey, Roy A

    2015-04-10

    Excitation functions for the Gaussian emission source radii difference (R_{out}^{2}-R_{side}^{2}) 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 nonmonotonic excitation functions validate the finite-size scaling patterns expected for the deconfinement phase transition and the critical end point (CEP), in the temperature versus baryon chemical potential (T,μ_{B}) plane of the nuclear matter phase diagram. A finite-size scaling (FSS) analysis of these data suggests a second order phase transition with the estimates T^{cep}∼165  MeV and μ_{B}^{cep}∼95  MeV for the location of the critical end point. The critical exponents (ν≈0.66 and γ≈1.2) extracted via the same FSS analysis place this CEP in the 3D Ising model universality class.

  19. Quantum critical point and spin fluctuations in lower-mantle ferropericlase.

    PubMed

    Lyubutin, Igor S; Struzhkin, Viktor V; Mironovich, A A; Gavriliuk, Alexander G; Naumov, Pavel G; Lin, Jung-Fu; Ovchinnikov, Sergey G; Sinogeikin, Stanislav; Chow, Paul; Xiao, Yuming; Hemley, Russell J

    2013-04-30

    Ferropericlase [(Mg,Fe)O] is one of the most abundant minerals of the earth's lower mantle. The high-spin (HS) to low-spin (LS) transition in the Fe(2+) ions may dramatically alter the physical and chemical properties of (Mg,Fe)O in the deep mantle. To understand the effects of compression on the ground electronic state of iron, electronic and magnetic states of Fe(2+) in (Mg0.75Fe0.25)O have been investigated using transmission and synchrotron Mössbauer spectroscopy at high pressures and low temperatures (down to 5 K). Our results show that the ground electronic state of Fe(2+) at the critical pressure Pc of the spin transition close to T = 0 is governed by a quantum critical point (T = 0, P = P(c)) at which the energy required for the fluctuation between HS and LS states is zero. Analysis of the data gives P(c) = 55 GPa. Thermal excitation within the HS or LS states (T > 0 K) is expected to strongly influence the magnetic as well as physical properties of ferropericlase. Multielectron theoretical calculations show that the existence of the quantum critical point at temperatures approaching zero affects not only physical properties of ferropericlase at low temperatures but also its properties at P-T of the earth's lower mantle.

  20. Criticality in large-scale brain FMRI dynamics unveiled by a novel point process analysis.

    PubMed

    Tagliazucchi, Enzo; Balenzuela, Pablo; Fraiman, Daniel; Chialvo, Dante R

    2012-01-01

    Functional magnetic resonance imaging (fMRI) techniques have contributed significantly to our understanding of brain function. Current methods are based on the analysis of gradual and continuous changes in the brain blood oxygenated level dependent (BOLD) signal. Departing from that approach, recent work has shown that equivalent results can be obtained by inspecting only the relatively large amplitude BOLD signal peaks, suggesting that relevant information can be condensed in discrete events. This idea is further explored here to demonstrate how brain dynamics at resting state can be captured just by the timing and location of such events, i.e., in terms of a spatiotemporal point process. The method allows, for the first time, to define a theoretical framework in terms of an order and control parameter derived from fMRI data, where the dynamical regime can be interpreted as one corresponding to a system close to the critical point of a second order phase transition. The analysis demonstrates that the resting brain spends most of the time near the critical point of such transition and exhibits avalanches of activity ruled by the same dynamical and statistical properties described previously for neuronal events at smaller scales. Given the demonstrated functional relevance of the resting state brain dynamics, its representation as a discrete process might facilitate large-scale analysis of brain function both in health and disease.

  1. Critical control points of complementary food preparation and handling in eastern Nigeria.

    PubMed Central

    Ehiri, J. E.; Azubuike, M. C.; Ubbaonu, C. N.; Anyanwu, E. C.; Ibe, K. M.; Ogbonna, M. O.

    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 acceptable levels. Food samples were collected and tested microbiologically at different stages of preparation and handling. FINDINGS: During cooking, all foods attained temperatures capable of destroying vegetative forms of food-borne pathogens. However, the risk of contamination increased by storage of food at ambient temperature, by using insufficiently high temperatures to reheat the food, and by adding contaminated ingredients such as dried ground crayfish and soybean powder at stages where no further heat treatment was applied. The purchasing of contaminated raw foodstuffs and ingredients, particularly raw akamu, from vendors in open markets is also a CCP. CONCLUSION: Although an unsafe environment poses many hazards for children's food, the hygienic quality of prepared food can be assured if basic food safety principles are observed. When many factors contribute to food contamination, identification of CCPs becomes particularly important and can facilitate appropriate targeting of resources and prevention efforts. PMID:11417038

  2. Another Broken Symmetry

    ERIC Educational Resources Information Center

    Groetsch, C. W.

    2005-01-01

    Resistance destroys symmetry. In this note, a graphical exploration serves as a guide to a rigorous elementary proof of a specific asymmetry in the trajectory of a point projectile in a medium offering linear resistance.

  3. Anesthetics lower Tc of a 2D miscibility critical point in the plasma membrane

    NASA Astrophysics Data System (ADS)

    Machta, Benjamin; Gray, Elly; Veatch, Sarah

    2014-03-01

    Many small hydrophobic molecules induce general anesthesia. Their efficacy as anesthetics has been shown to correlate both with their hydrophobicity and with their potency in inhibiting certain ligand gated ion channels. I will first report on our experiments on the effects that these molecules have on the two-dimensional miscibility critical point observed in cell derived vesicles (GPMVs). We show that anesthetics depress the critical temperature (Tc) of these GPMVs but do not strongly affect the ratio of phases found below Tc. The magnitude of this affect is consistent across the n-alcohols only when their concentration is rescaled by the median anesthetic concentration (AC50) for tadpole anesthesia and at AC50 we see a 4K downward shift in Tc. I will next present a model in which anesthetics interfere with native allosteric regulation of ligand gated channels by the critical membrane, showing that our observed change in critical properties could lead to the previously observed changes in channel conductance without a direct interaction between anesthetic molecules and their target proteins. Finally, I will discuss ongoing experiments that will clarify the role of this membrane effect in mediating the organism level anesthetic response.

  4. Susceptibility Measurements Near the He-3 Liquid-Gas Critical Point

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin; Zhong, Fang; Hahn, Inseob

    2000-01-01

    An experiment is now being developed to measure both the linear susceptibility and specific heat at constant volume near the liquid-gas critical point of He-3 in a microgravity environment. An electrostriction technique for measuring susceptibility will be described. Initial electrostriction measurements were performed on the ground along the critical isochore in a 0.5 mm high measurement cell filled to within 0.1 % of the critical density. These measurements agreed with the susceptibility determined from pressure-density measurements along isotherms. The critical temperature, T(sub c), determined separately from specific heat and susceptibility measurements was self-consistent. Susceptibility measurements in the range t = T/T(sub c) - 1 > 10(exp -4)were fit to Chi(sup *)(sub T) = Gamma(sup +)t(exp -lambda)(1 + Gamma(sup +)(sub 1)t(sup delta). Best fit parameters for the asymptotic amplitude Gamma(sup +) and the first Wegner amplitude Gamma(sup +)(sub 1) will be presented and compared to previous measurements.

  5. Superconductivity and non-Fermi liquid behavior near a nematic quantum critical point

    NASA Astrophysics Data System (ADS)

    Lederer, Samuel; Schattner, Yoni; Berg, Erez; Kivelson, Steven A.

    2017-05-01

    Using determinantal quantum Monte Carlo, we compute the properties of a lattice model with spin 1212 itinerant electrons tuned through a quantum phase transition to an Ising nematic phase. The nematic fluctuations induce superconductivity with a broad dome in the superconducting TcTc enclosing the nematic quantum critical point. For temperatures above TcTc, we see strikingly non-Fermi liquid behavior, including a “nodal-antinodal dichotomy” reminiscent of that seen in several transition metal oxides. In addition, the critical fluctuations have a strong effect on the low-frequency optical conductivity, resulting in behavior consistent with “bad metal” phenomenology.

  6. Anomalous Reduction of the Lorenz Ratio at the Quantum Critical Point in YbAgGe

    NASA Astrophysics Data System (ADS)

    Dong, J. K.; Tokiwa, Y.; Bud'ko, S. L.; Canfield, P. C.; Gegenwart, P.

    2013-04-01

    We report measurements of the electrical and thermal transport on the hexagonal heavy-fermion metal YbAgGe for temperatures T≥40mK and in magnetic fields H∥ab up to 14 T. This distorted kagome-lattice system displays a series of magnetic states and a quantum critical point at Hc=4.5T. The Lorenz ratio L(T)/L0 displays a marked reduction only close to Hc. A T-linear contribution below 120 mK, present at all different fields, allows us to extrapolate the Lorenz ratio towards T=0. At the critical field this yields L/L0=0.92±0.03, suggesting a violation of the Wiedemann-Franz law due to strong inelastic scattering.

  7. Anomalous reduction of the Lorenz ratio at the quantum critical point in YbAgGe.

    PubMed

    Dong, J K; Tokiwa, Y; Bud'ko, S L; Canfield, P C; Gegenwart, P

    2013-04-26

    We report measurements of the electrical and thermal transport on the hexagonal heavy-fermion metal YbAgGe for temperatures T ≥ 40  mK and in magnetic fields H∥ab up to 14 T. This distorted kagome-lattice system displays a series of magnetic states and a quantum critical point at H(c) = 4.5  T. The Lorenz ratio L(T)/L0 displays a marked reduction only close to H(c). A T-linear contribution below 120 mK, present at all different fields, allows us to extrapolate the Lorenz ratio towards T = 0. At the critical field this yields L/L0 = 0.92±0.03, suggesting a violation of the Wiedemann-Franz law due to strong inelastic scattering.

  8. Universality in eight-arm star polystyrene and methylcyclohexane mixtures near the critical point.

    PubMed

    Jacobs, D T; Braganza, Clinton I; Brinck, Andy P; Cohen, Adam B; Lightfoot, Mark A; Locke, Christopher J; Suddendorf, Sarah J; Timmers, Henry R; Triplett, Angela L; Venkataraman, Nithya L; Wellons, Mark T

    2007-09-28

    Measurements of the coexistence curve and turbidity were made on different molecular mass samples of the branched polymer-solvent system eight-arm star polystyrene in methylcyclohexane near its critical point. We confirmed that these systems belong in the Ising universality class. The location of the critical temperature and composition as well as the correlation length, susceptibility, and coexistence curve amplitudes were found to depend on molecular mass and the degree of branching. The coexistence curve diameter had an asymmetry that followed a "complete scaling" approach. All the coexistence curve data could be scaled onto a common curve with one adjustable parameter. We found the coexistence curve amplitude to be about 12% larger for branched than linear polystyrenes of the same molecular mass in either solvent cyclohexane or methylcyclohexane. The two-scale-factor universality ratio R was found to be independent of molecular mass or degree of branching.

  9. Candidate Elastic Quantum Critical Point in LaCu6-xAux

    DOE PAGES

    Poudel, Lekh; May, Andrew F.; Koehler, Michael R.; ...

    2016-11-30

    In this paper, the structural properties of LaCu6-xAux are studied using neutron diffraction, x-ray diffraction, and heat capacity measurements. The continuous orthorhombic-monoclinic structural phase transition in LaCu6 is suppressed linearly with Au substitution until a complete suppression of the structural phase transition occurs at the critical composition xc=0.3. Heat capacity measurements at low temperatures indicate residual structural instability at xc. The instability is ferroelastic in nature, with density functional theory calculations showing negligible coupling to electronic states near the Fermi level. Finally, the data and calculations presented here are consistent with the zero temperature termination of a continuous structural phasemore » transition suggesting that the LaCu6-xAux series hosts an elastic quantum critical point.« less

  10. Time-resolved spectral density of interacting fermions following a quench to a superconducting critical point

    NASA Astrophysics Data System (ADS)

    Lemonik, Yonah; Mitra, Aditi

    2017-09-01

    Results are presented for the time evolution of fermions initially in a nonzero temperature normal phase, following the switch on of an attractive interaction. The dynamics are studied in the disordered phase close to the critical point, where the superfluid fluctuations are large. The analysis is conducted within a two-particle irreducible, large N approximation. The system is considered from the perspective of critical quenches where it is shown that the fluctuations follow universal model A dynamics. A signature of this universality is found in a singular correction to the fermion lifetime, given by a scaling form t(3 -d )/2Sd(ɛ2t ) , where d is the spatial dimension, t is the time since the quench, and ɛ is the fermion energy. The singular behavior of the spectral density is interpreted as arising due to incoherent Andreev reflections off superfluid fluctuations.

  11. Shear viscosity at the Ising-nematic quantum critical point in two-dimensional metals

    NASA Astrophysics Data System (ADS)

    Eberlein, Andreas; Patel, Aavishkar A.; Sachdev, Subir

    2017-02-01

    In an isotropic strongly interacting quantum liquid without quasiparticles, general scaling arguments imply that the dimensionless ratio (kB/ℏ )η /s , where η 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: η scales in the same manner as a chiral conductivity, and the ratio η /s diverges at low temperature (T ) as T-2 /z, where z is the dynamic critical exponent for fermionic excitations dispersing normal to the Fermi surface.

  12. The Cambrian explosion triggered by critical turning point in genome size evolution.

    PubMed

    Li, Dirson Jian; Zhang, Shengli

    2010-02-05

    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.

  13. Mapping the current–current correlation function near a quantum critical point

    SciTech Connect

    Prodan, Emil; Bellissard, Jean

    2016-05-15

    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.

  14. Candidate Elastic Quantum Critical Point in LaCu_{6-x}Au_{x}.

    PubMed

    Poudel, L; May, A F; Koehler, M R; McGuire, M A; Mukhopadhyay, S; Calder, S; Baumbach, R E; Mukherjee, R; Sapkota, D; de la Cruz, C; Singh, D J; Mandrus, D; Christianson, A D

    2016-12-02

    The structural properties of LaCu_{6-x}Au_{x} are studied using neutron diffraction, x-ray diffraction, and heat capacity measurements. The continuous orthorhombic-monoclinic structural phase transition in LaCu_{6} is suppressed linearly with Au substitution until a complete suppression of the structural phase transition occurs at the critical composition x_{c}=0.3. Heat capacity measurements at low temperatures indicate residual structural instability at x_{c}. The instability is ferroelastic in nature, with density functional theory calculations showing negligible coupling to electronic states near the Fermi level. The data and calculations presented here are consistent with the zero temperature termination of a continuous structural phase transition suggesting that the LaCu_{6-x}Au_{x} series hosts an elastic quantum critical point.

  15. Octupole degree of freedom for the critical-point candidate nucleus Sm152 in a reflection-asymmetric relativistic mean-field approach

    NASA Astrophysics Data System (ADS)

    Zhang, W.; Li, Z. P.; Zhang, S. Q.; Meng, J.

    2010-03-01

    The potential energy surfaces of even-even Sm146-156 are investigated in the constrained reflection-asymmetric relativistic mean-field approach with parameter set PK1. It is shown that the critical-point candidate nucleus Sm152 marks the shape/phase transition not only from U(5) to SU(3) symmetry, but also from the octupole-deformed ground state in Sm150 to the quadrupole-deformed ground state in Sm154. By including the octupole degree of freedom, an energy gap near the Fermi surface for single-particle levels in Sm152 with β2=0.14~0.26 is found and the important role of the octupole deformation driving pair ν2f7/2 and ν1i13/2 is demonstrated.

  16. Octupole degree of freedom for the critical-point candidate nucleus {sup 152}Sm in a reflection-asymmetric relativistic mean-field approach

    SciTech Connect

    Zhang, W.; Li, Z. P.; Zhang, S. Q.; Meng, J.

    2010-03-15

    The potential energy surfaces of even-even {sup 146-156}Sm are investigated in the constrained reflection-asymmetric relativistic mean-field approach with parameter set PK1. It is shown that the critical-point candidate nucleus {sup 152}Sm marks the shape/phase transition not only from U(5) to SU(3) symmetry, but also from the octupole-deformed ground state in {sup 150}Sm to the quadrupole-deformed ground state in {sup 154}Sm. By including the octupole degree of freedom, an energy gap near the Fermi surface for single-particle levels in {sup 152}Sm with beta{sub 2}=0.14approx0.26 is found and the important role of the octupole deformation driving pair nu2f{sub 7/2} and nu1i{sub 13/2} is demonstrated.

  17. Higher-order moments at the critical point of the Ziff-Gulari-Barshad model.

    PubMed

    Leite, V S; Hoenicke, G L; Figueiredo, W

    2001-09-01

    We studied the continuous phase transition between the active and the absorbing state of the Ziff-Gulari-Barshad (ZGB) model. Through Monte Carlo simulations we determined all the moments of the order parameter up to fourth order and their ratios at the critical point. We show that the ratios we found are in agreement with those of the contact and pair contact processes in two dimensions, which give support to the idea that the ZGB model is in the directed percolation universality class in (2+1) dimensions.

  18. Higher-order moments at the critical point of the Ziff-Gulari-Barshad model

    NASA Astrophysics Data System (ADS)

    Leite, Vanessa S.; Hoenicke, Gilberto L.; Figueiredo, Wagner

    2001-09-01

    We studied the continuous phase transition between the active and the absorbing state of the Ziff-Gulari-Barshad (ZGB) model. Through Monte Carlo simulations we determined all the moments of the order parameter up to fourth order and their ratios at the critical point. We show that the ratios we found are in agreement with those of the contact and pair contact processes in two dimensions, which give support to the idea that the ZGB model is in the directed percolation universality class in (2+1) dimensions.

  19. Spontaneous formation of large clusters in a lattice gas above the critical point.

    PubMed

    Khain, Evgeniy; Khasin, Michael; Sander, Leonard M

    2014-12-01

    We consider clustering of particles in the lattice gas model above the critical point. We find the probability for large density fluctuations over scales much larger than the correlation length. This fundamental problem is of interest in various biological contexts such as quorum sensing and clustering of motile, adhesive, cancer cells. In the latter case, it may give a clue to the problem of growth of recurrent tumors. We develop a formalism for the analysis of this rare event employing a phenomenological master equation and measuring the transition rates in numerical simulations. The spontaneous clustering is treated in the framework of the eikonal approximation to the master equation.

  20. Examination of two methods of describing the thermodynamic properties of oxygen near the critical point

    NASA Technical Reports Server (NTRS)

    Rees, T. H.; Suttles, J. T.

    1972-01-01

    A computer study was conducted to compare the numerical behavior of two approaches to describing the thermodynamic properties of oxygen near the critical point. Data on the relative differences between values of specific heats at constant pressure (sub p) density, and isotherm and isochor derivatives of the equation of state are presented for selected supercritical pressures at temperatures in the range 100 to 300 K. The results of a more detailed study of the sub p representations afforded by the two methods are also presented.

  1. Spontaneous formation of large clusters in a lattice gas above the critical point

    NASA Astrophysics Data System (ADS)

    Khain, Evgeniy; Khasin, Michael; Sander, Leonard M.

    2014-12-01

    We consider clustering of particles in the lattice gas model above the critical point. We find the probability for large density fluctuations over scales much larger than the correlation length. This fundamental problem is of interest in various biological contexts such as quorum sensing and clustering of motile, adhesive, cancer cells. In the latter case, it may give a clue to the problem of growth of recurrent tumors. We develop a formalism for the analysis of this rare event employing a phenomenological master equation and measuring the transition rates in numerical simulations. The spontaneous clustering is treated in the framework of the eikonal approximation to the master equation.

  2. Scaled Correlations of Critical Points of Random Sections on Riemann Surfaces

    NASA Astrophysics Data System (ADS)

    Baber, John

    2012-08-01

    In this paper we prove that as N goes to infinity, the scaling limit of the correlation between critical points z 1 and z 2 of random holomorphic sections of the N-th power of a positive line bundle over a compact Riemann surface tends to 2/(3 π 2) for small sqrt{N}|z1-nobreak z2|. The scaling limit is directly calculated using a general form of the Kac-Rice formula and formulas and theorems of Pavel Bleher, Bernard Shiffman, and Steve Zelditch.

  3. Critical points of the Bose-Hubbard model with three-body local interaction

    NASA Astrophysics Data System (ADS)

    Avila, C. A.; Franco, R.; Souza, A. M. C.; Figueira, M. S.; Silva-Valencia, J.

    2014-09-01

    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.

  4. Microscopic study on magnetocaloric and electrocaloric effects near the critical point

    NASA Astrophysics Data System (ADS)

    Honmi, Hitoshi; Hashizume, Yoichiro; Nakajima, Takashi; Okamura, Soichiro

    2015-09-01

    Adiabatic temperature changes of magnetocaloric/electrocaloric effects are analytically investigated. The analytical studies are based on the microscopic statistical models such as Husimi-Temperley model and Slater model. As a result, we show the characteristic scales of the adiabatic processes correspond to microscopic parameters, namely exchange couplings and Slater energy. The scaled parameter dependence become stronger near the critical point. Furthermore, using a general Hamiltonian method, we clarify the adiabatic temperature changes depend on the relative ratio of characteristic scales. The present study may propose a useful aspect for applications.

  5. Pathogen Reduction and Hazard Analysis and Critical Control Point (HACCP) systems for meat and poultry. USDA.

    PubMed

    Hogue, A T; White, P L; Heminover, J A

    1998-03-01

    The United States Department of Agriculture (USDA) Food Safety Inspection Service (FSIS) adopted Hazard Analysis and Critical Control Point Systems and established finished product standards for Salmonella in slaughter plants to improve food safety for meat and poultry. In order to make significant improvements in food safety, measures must be taken at all points in the farm-to-table chain including production, transportation, slaughter, processing, storage, retail, and food preparation. Since pathogens can be introduced or multiplied anywhere along the continuum, success depends on consideration and comparison of intervention measures throughout the continuum. Food animal and public health veterinarians can create the necessary preventative environment that mitigates risks for food borne pathogen contamination.

  6. On the critical temperature, normal boiling point, and vapor pressure of ionic liquids.

    PubMed

    Rebelo, Luis P N; Canongia Lopes, José N; Esperança, José M S S; Filipe, Eduardo

    2005-04-07

    One-stage, reduced-pressure distillations at moderate temperature of 1-decyl- and 1-dodecyl-3-methylimidazolium bistriflilamide ([Ntf(2)](-)) ionic liquids (ILs) have been performed. These liquid-vapor equilibria can be understood in light of predictions for normal boiling points of ILs. The predictions are based on experimental surface tension and density data, which are used to estimate the critical points of several ILs and their corresponding normal boiling temperatures. In contrast to the situation found for relatively unstable ILs at high-temperature such as those containing [BF(4)](-) or [PF(6)](-) anions, [Ntf(2)](-)-based ILs constitute a promising class in which reliable, accurate vapor pressure measurements can in principle be performed. This property is paramount for assisting in the development and testing of accurate molecular models.

  7. Critical decision points in the management of impaired doctors: the New South Wales Medical Board program.

    PubMed

    Wilhelm, Kay A; Reid, Alison M

    2004-10-04

    The New South Wales Medical Board has developed the Impaired Registrants Program to deal with impaired registrants (doctors and medical students) in a constructive and non-disciplinary manner; the program is now well established. The Program enables the Board to protect the public, while maintaining doctors in practice whenever possible. Disorders that commonly lead to referral of impaired doctors include alcohol and drug misuse, major depression, bipolar disorder, cognitive impairment and, less commonly, psychotic and personality disorders and anorexia nervosa. Pathways in the program are individualised according to the impact of the specific disorder, the registrant's career stage, stage of involvement in the program, insight and motivation. Critical points in the program include entry, easing of conditions, breach of conditions, return to work after suspension, and exit from the program. Decision-making at these points takes into account the nature of the impairment, compliance, professional and personal support available and the registrant's insight and motivation.

  8. Probing Critical Point Energies of Transition Metal Dichalcogenides: Surprising Indirect Gap of Single Layer WSe2.

    PubMed

    Zhang, Chendong; Chen, Yuxuan; Johnson, Amber; Li, Ming-Yang; Li, Lain-Jong; Mende, Patrick C; Feenstra, Randall M; Shih, Chih-Kang

    2015-10-14

    By using a comprehensive form of scanning tunneling spectroscopy, we have revealed detailed quasi-particle electronic structures in transition metal dichalcogenides, including the quasi-particle gaps, critical point energy locations, and their origins in the Brillouin zones. We show that single layer WSe2 surprisingly has an indirect quasi-particle gap with the conduction band minimum located at the Q-point (instead of K), albeit the two states are nearly degenerate. We have further observed rich quasi-particle electronic structures of transition metal dichalcogenides as a function of atomic structures and spin-orbit couplings. Such a local probe for detailed electronic structures in conduction and valence bands will be ideal to investigate how electronic structures of transition metal dichalcogenides are influenced by variations of local environment.

  9. Experimental and Theoretical Bond Critical Point Properties for Model Electron Density Distributions for Earth Materials

    SciTech Connect

    Gibbs, Gerald V.; Cox, David F.; Rosso, Kevin M.; Kirfel, Armin; Lippmann, Thomas; Blaha, Peter; Schwarz, Karlheinz

    2005-06-01

    Generalized X-ray scattering factor model experimental electron density distributions and bond critical point, bcp, properties generated in recent studies for the earth materials stishovite, forsterite, fayalite and cuprite with high energy single crystal synchrotron X-ray diffraction data and those generated with high resolution diffraction data for coesite and senarmonite were found to be adequate and in relatively good agreement, ~5% on average, with those calculated with quantum chemical methods with relatively robust basis sets. High resolution low energy single crystal diffraction data, recorded for the molecular sieve AlPO4-15, were also found to yield model electron density distribution values at the bcp points for the AlO and PO bonded interactions that are in relatively good to moderately good agreement with the theoretical values, but the Laplacian values of the distribution at the points for the two bonded interactions were found to be in relatively poor agreement. In several cases, experimental bcp properties, generated with conventional low energy X-ray diffraction data for several rock forming minerals, were found overall to be in poorer agreement with the theoretical properties. The overall agreement between theoretical bcp properties generated with computational quantum methods and experimental properties generated with synchrotron high energy radiation not only provides a basis for using computational strategies for studying and modeling structures and their electron density distributions, but it also provides a basis for improving our understanding of the crystal chemistry and bonded interactions for earth materials. Theoretical bond critical point properties generated with computational quantum methods are believed to rival the accuracy of those determined experimentally. As such the calculations provide a powerful and efficient method for evaluating electron density distributions and the bonded interactions for a wide range of earth materials.

  10. Broken Symmetry

    ScienceCinema

    None

    2016-07-12

    - Physics, as we know it, attempts to interpret the diverse natural phenomena as particular manifestations of general laws. This vision of a world ruled by general testable laws is relatively recent in the history of mankind. Basically it was initiated by the Galilean inertial principle. The subsequent rapid development of large-scale physics is certainly tributary to the fact that gravitational and electromagnetic forces are long-range and hence can be perceived directly without the mediation of highly sophisticated technical devices. - The discovery of subatomic structures and of the concomitant weak and strong short-range forces raised the question of how to cope with short-range forces in relativistic quantum field theory. The Fermi theory of weak interactions, formulated in terms of point-like current-current interaction, was well-defined in lowest order perturbation theory and accounted for existing experimental data.However, it was inconsistent in higher orders because of uncontrollable divergent quantum fluctuations. In technical terms, in contradistinction to quantum electrodynamics, the Fermi theorywas not “renormalizable”. This difficulty could not be solved by smoothing the point-like interaction by a massive, and therefore short-range, charged “vector” particle exchange: theories with massive charged vector bosons were not renormalizable either. In the early nineteen sixties, there seemed to be insuperable obstacles to formulating a consistent theory with short-range forces mediated by massive vectors. - The breakthrough came from the notion of spontaneous symmetry breaking which arose in the study of phase transitions and was introduced in field theory by Nambu in 1960. - Ferromagnets illustrate the notion in phase transitions. Although no direction is dynamically preferred, the magnetization selects a global orientation. This is a spontaneous broken symmetry(SBS)of rotational invariance. Such continuous SBS imply the existence of

  11. Broken Symmetry

    SciTech Connect

    2011-02-24

    - Physics, as we know it, attempts to interpret the diverse natural phenomena as particular manifestations of general laws. This vision of a world ruled by general testable laws is relatively recent in the history of mankind. Basically it was initiated by the Galilean inertial principle. The subsequent rapid development of large-scale physics is certainly tributary to the fact that gravitational and electromagnetic forces are long-range and hence can be perceived directly without the mediation of highly sophisticated technical devices. - The discovery of subatomic structures and of the concomitant weak and strong short-range forces raised the question of how to cope with short-range forces in relativistic quantum field theory. The Fermi theory of weak interactions, formulated in terms of point-like current-current interaction, was well-defined in lowest order perturbation theory and accounted for existing experimental data.However, it was inconsistent in higher orders because of uncontrollable divergent quantum fluctuations. In technical terms, in contradistinction to quantum electrodynamics, the Fermi theorywas not “renormalizable”. This difficulty could not be solved by smoothing the point-like interaction by a massive, and therefore short-range, charged “vector” particle exchange: theories with massive charged vector bosons were not renormalizable either. In the early nineteen sixties, there seemed to be insuperable obstacles to formulating a consistent theory with short-range forces mediated by massive vectors. - The breakthrough came from the notion of spontaneous symmetry breaking which arose in the study of phase transitions and was introduced in field theory by Nambu in 1960. - Ferromagnets illustrate the notion in phase transitions. Although no direction is dynamically preferred, the magnetization selects a global orientation. This is a spontaneous broken symmetry(SBS)of rotational invariance. Such continuous SBS imply the existence of

  12. Physical observables of the Ising spin glass in 6 -ɛ dimensions: Asymptotical behavior around the critical fixed point

    NASA Astrophysics Data System (ADS)

    Temesvári, T.

    2017-07-01

    The asymptotical behavior of physical quantities, like the order parameter, the replicon, and longitudinal masses, is studied around the zero-field spin-glass transition point when a small external magnetic field is applied. An effective field theory to model this asymptotics contains a small perturbation in its Lagrangian which breaks the zero-field symmetry. A first-order renormalization group supplemented by perturbational results provides the scaling functions. The perturbative zero of the scaling function for the replicon mass defines a generic Almeida-Thouless surface stemming from the zero-field fixed point.

  13. Critical end point in the presence of a chiral chemical potential

    NASA Astrophysics Data System (ADS)

    Cui, Z.-F.; Cloët, I. C.; Lu, Y.; Roberts, C. D.; Schmidt, S. M.; Xu, S.-S.; Zong, H.-S.

    2016-10-01

    A class of Polyakov-loop-modified Nambu-Jona-Lasinio models has been used to support a conjecture that numerical simulations of lattice-regularized QCD defined with a chiral chemical potential can provide information about the existence and location of a critical end point 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 Polyakov-loop-modified Nambu-Jona-Lasinio 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-loop dynamics. With the lQCD and DSE predictions thus confirmed, it seems unlikely that simulations of lQCD with μ5>0 can shed any light on a critical end point in the regular QCD phase diagram.

  14. Multiple critical points and liquid liquid equilibria from the van der Waals like equations of state

    NASA Astrophysics Data System (ADS)

    Artemenko, Sergey; Lozovsky, Taras; Mazur, Victor

    2008-06-01

    The principal aim of this work is a comprehensive analysis of the phase diagram of water via the van der Waals like equations of state (EoSs) which are considered as superpositions of repulsive and attractive forces. We test more extensively the modified van der Waals EoS (MVDW) proposed by Skibinski et al (2004 Phys. Rev. E 69 061206) and refine this model by introducing instead of the classical van der Waals repulsive term a very accurate hard sphere EoS over the entire stable and metastable regions (Liu 2006 Preprint cond-mat/0605392). It was detected that the simplest form of MVDW EoS displays a complex phase behavior, including three critical points, and identifies four fluid phases (gas, low density liquid (LDL), high density liquid (HDL), and very high density liquid (VHDL)). Moreover the experimentally observed (Mallamace et al 2007 Proc. Natl Acad. Sci. USA 104 18387) anomalous behavior of the density of water in the deeply supercooled region (a density minimum) is reproduced by the MWDW EoS. An improvement of the repulsive part does not change the topological picture of the phase behavior of water in the wide range of thermodynamic variables. The new parameters set for second and third critical points are recognized by thorough analysis of experimental data for the loci of thermodynamic response function extrema.

  15. Fluid adsorption up to the critical point. Experimental study of a wetting fluid/solid interface

    NASA Astrophysics Data System (ADS)

    Findenegg, G. H.; Löring, R.

    1984-10-01

    We have measured multilayer adsorption isotherms of propane on graphitized carbon black over a wide temperature range, corresponding to reduced temperatures T/Tc of the fluid from 0.7 to 1.004 and reduced densities ρ/ρc up to 1.4. Experimental isotherms of the surface excess concentration Γgs are analyzed in terms of the Frenkel-Halsey-Hill (FHH) model. The exponent n is somewhat less than 3 (2.55±0.30) and the amplitude parameter Δɛ/kT becomes nearly independent of temperature, up to T/Tc=0.98, when the simple one-step density profile of the original FHH model is replaced by a two-step profile, to account for the compression of the layer next to the solid substrate. Evidence for a compression of the liquid boundary layer comes from measurements of the surface excess concentration Γls at the liquid/substrate interface. Along the liquid-vapor coexistence curve, Γls0 diverges as T approaches Tc, in qualitative agreement with scaling law theory. The analogy of the present one-component fluid/solid-substrate interface near the critical point of the fluid, with a two-component liquid/vapor interface near the critical solution point of the liquid mixture is discussed.

  16. Motor hysteresis in a sequential grasping and pointing task is absent in task-critical joints.

    PubMed

    Schütz, Christoph; Weigelt, Matthias; Schack, Thomas

    2017-03-01

    In a prior study (Schütz et al. in Exp Brain Res 2016. doi: 10.1007/s00221-016-4608-6 ), we demonstrated that the cognitive cost of motor planning did not differ in a vertical pointing and grasping task. It was unclear whether the similar cost implied that both tasks required the same number of independent degrees of freedom (IDOFs) or that the number of IDOFs did not affect motor planning. To differentiate between both cases, a reanalysis of the prior data was conducted. The number of IDOFs in the pointing and grasping tasks was computed by factor analysis. In both tasks, two IDOFs were used, which was the minimum number required for position control. This indicates that hand alignment in the grasping task did not require an additional IDOF. No conclusions regarding the link between the cognitive cost of motor planning and the number of IDOFs could be drawn. A subset of task-critical joint angles was not affected by motor hysteresis. This indicates that a joint's susceptibility to motor hysteresis depends on its relevance to the task goal. In task-critical joints, planning cost minimization by motor plan reuse is suppressed in favor of the task goal.

  17. Search for a liquid-liquid critical point in models of silica

    NASA Astrophysics Data System (ADS)

    Lascaris, Erik; Hemmati, Mahin; Buldyrev, Sergey V.; Stanley, H. Eugene; Angell, C. Austen

    2014-06-01

    Previous research has indicated the possible existence of a liquid-liquid critical point (LLCP) in models of silica at high pressure. To clarify this interesting question we run extended molecular dynamics simulations of two different silica models (WAC and BKS) and perform a detailed analysis of the liquid at temperatures much lower than those previously simulated. We find no LLCP in either model within the accessible temperature range, although it is closely approached in the case of the WAC potential near 4000 K and 5 GPa. Comparing our results with those obtained for other tetrahedral liquids, and relating the average Si-O-Si bond angle and liquid density at the model glass temperature to those of the ice-like β-cristobalite structure, we conclude that the absence of a critical point can be attributed to insufficient "stiffness" in the bond angle. We hypothesize that a modification of the potential to mildly favor larger average bond angles will generate a LLCP in a temperature range that is accessible to simulation. The tendency to crystallize in these models is extremely weak in the pressure range studied, although this tendency will undoubtedly increase with increasing stiffness.

  18. The phase and critical point of quantum Einstein-Cartan gravity

    NASA Astrophysics Data System (ADS)

    Xue, She-Sheng

    2012-05-01

    By introducing diffeomorphism and local Lorentz gauge invariant holonomy fields, we study in the recent article [S.-S. Xue, Phys. Rev. D 82 (2010) 064039] the quantum Einstein-Cartan gravity in the framework of Regge calculus. On the basis of strong coupling expansion, mean-field approximation and dynamical equations satisfied by holonomy fields, we present in this Letter calculations and discussions to show the phase structure of the quantum Einstein-Cartan gravity, (i) the order phase: long-range condensations of holonomy fields in strong gauge couplings; (ii) the disorder phase: short-range fluctuations of holonomy fields in weak gauge couplings. According to the competition of the activation energy of holonomy fields and their entropy, we give a simple estimate of the possible ultra-violet critical point and correlation length for the second-order phase transition from the order phase to disorder one. At this critical point, we discuss whether the continuum field theory of quantum Einstein-Cartan gravity can be possibly approached when the macroscopic correlation length of holonomy field condensations is much larger than the Planck length.

  19. Critical Points and Bifurcations of the Three-Dimensional Onsager Model for Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Vollmer, Michaela A. C.

    2017-07-01

    We study the bifurcation diagram of the Onsager free-energy functional for liquid crystals with orientation parameter on the sphere. In particular, we concentrate on the bifurcations from the isotropic solution for a general class of two-body interaction potentials including the Onsager kernel. Reformulating the problem as a non-linear eigenvalue problem for the kernel operator, we prove that spherical harmonics are the corresponding eigenfunctions and we present a direct relationship between the coefficients of the Taylor expansion of this class of interaction potentials and their eigenvalues. We find explicit expressions for all bifurcation points corresponding to bifurcations from the isotropic state of the Onsager free-energy functional equipped with the Onsager interaction potential. A substantial amount of our analysis is based on the use of spherical harmonics and a special algorithm for computing expansions of products of spherical harmonics in terms of spherical harmonics is presented. Using a Lyapunov-Schmidt reduction, we derive a bifurcation equation depending on five state variables. The dimension of this state space is further reduced to two dimensions by using the rotational symmetry of the problem and the invariant theory of groups. On the basis of these results, we show that the first bifurcation from the isotropic state of the Onsager interaction potential is a transcritical bifurcation and that the corresponding solution is uniaxial. In addition, we prove some global properties of the bifurcation diagram such as the fact that the trivial solution is the unique local minimiser if the bifurcation parameter is high, that it is not a local minimiser if the bifurcation parameter is small, the boundedness of all equilibria of the functional and that the bifurcation branches are either unbounded or that they meet another bifurcation branch.

  20. Universal Scaling in the Fan of an Unconventional Quantum Critical Point

    SciTech Connect

    Melko, Roger G; Kaul, Ribhu

    2008-01-01

    We present the results of extensive finite-temperature Quantum Monte Carlo simulati ons on a SU(2) symmetric, $S=1/2$ quantum antiferromagnet with a frustrating four-s pin interaction -- the so-called 'JQ' model~[Sandvik, Phys. Rev. Lett. {\\bf 98}, 22 7202 (2007)]. Our simulations, which are unbiased, free of the sign-problem and car ried out on lattice sizes containing in excess of $1.6\\times 10^4$ spins, indicate that N\\'eel order is destroyed through a continuous quantum transition at a critica l value of the frustrating interaction. At larger values of this coupling the param agnetic state obtained has valence-bond solid order. The scaling behavior in the 'q uantum critical fan' above the putative critical point confirms a $z=1$ quantum pha se transition that is not in the conventional $O(3)$ universality class. Our result s are consistent with the predictions of the 'deconfined quantum criticality' scena rio.

  1. Criticality as a Set-Point for Adaptive Behavior in Neuromorphic Hardware.

    PubMed

    Srinivasa, Narayan; Stepp, Nigel D; Cruz-Albrecht, Jose

    2015-01-01

    Neuromorphic hardware are designed by drawing inspiration from biology to overcome limitations of current computer architectures while forging the development of a new class of autonomous systems that can exhibit adaptive behaviors. Several designs in the recent past are capable of emulating large scale networks but avoid complexity in network dynamics by minimizing the number of dynamic variables that are supported and tunable in hardware. We believe that this is due to the lack of a clear understanding of how to design self-tuning complex systems. It has been widely demonstrated that criticality appears to be the default state of the brain and manifests in the form of spontaneous scale-invariant cascades of neural activity. Experiment, theory and recent models have shown that neuronal networks at criticality demonstrate optimal information transfer, learning and information processing capabilities that affect behavior. In this perspective article, we argue that understanding how large scale neuromorphic electronics can be designed to enable emergent adaptive behavior will require an understanding of how networks emulated by such hardware can self-tune local parameters to maintain criticality as a set-point. We believe that such capability will enable the design of truly scalable intelligent systems using neuromorphic hardware that embrace complexity in network dynamics rather than avoiding it.

  2. Weak phase stiffness and nature of the quantum critical point in underdoped cuprates

    NASA Astrophysics Data System (ADS)

    Ku, Wei; Yildirim, Yucel

    We demonstrate that the zero-temperature superconducting phase diagram of underdoped cuprates can be quantitatively understood in the strong binding limit, using only the experimental spectral function of the ``normal'' pseudo-gap phase without any free parameter. In the prototypical (La1-xSrx)2CuO4, a kinetics-driven d-wave superconductivity is obtained above the critical doping δc ~ 5 . 2 % , below which complete loss of superfluidity results from local quantum fluctuation involving local p-wave pairs. Near the critical doping, a enormous mass enhancement of the local pairs is found responsible for the observed rapid decrease of phase stiffness. Finally, a striking mass divergence is predicted at δc that dictates the occurrence of the observed quantum critical point and the abrupt suppression of the Nernst effects in the nearby region. * Phys. Rev. B 92, 180501(R) (2015); Phys. Rev. X 1, 011011 (2011). Work supported by U.S. Department of Energy, Office of Basic Energy Science, under Contract No. DE-AC02-98CH10886.

  3. Weak phase stiffess and nature of the quantum critical point in underdoped cuprates

    NASA Astrophysics Data System (ADS)

    Ku, Wei; Yildirim, Yucel

    2014-03-01

    We demonstrate that the zero-temperature superconducting phase diagram of underdoped cuprates can be quantitatively understood in the strong binding limit, using only the experimental spectral function of the ``normal'' pseudo-gap phase without any free parameter. In the prototypical (La1-xSrx)2CuO4, a kinetics-driven d-wave superconductivity is obtained above the critical doping δc ~ 5 . 2 % , below which complete loss of superfluidity results from local quantum fluctuation involving local p-wave pairs. Near the critical doping, a enormous mass enhancement of the local pairs is found responsible for the observed rapid decrease of phase stiffness. Finally, a striking mass divergence is predicted at δc that dictates the occurrence of the observed quantum critical point and the sudden suppression of the Nernst effects in the nearby region. Work supported by U.S. Department of Energy, Office of Basic Energy Science, under Contract No. DE-AC02-98CH10886.

  4. Critical point scaling of Ising spin glasses in a magnetic field

    NASA Astrophysics Data System (ADS)

    Yeo, Joonhyun; Moore, M. A.

    2015-03-01

    Critical point scaling in a field H applies for the limits t →0 (where t =T /Tc-1 ) and H →0 but with the ratio R =t /H2 /Δ finite. Δ is a critical exponent of the zero-field transition. We study the replicon correlation length ξ and from it the crossover scaling function f (R ) defined via 1 /(ξ H4 /(d +2 -η )) ˜f (R ) . We have calculated analytically f (R ) for the mean-field limit of the Sherrington-Kirkpatrick model. In dimension d =3 , we have determined the exponents and the critical scaling function f (R ) within two versions of the Migdal-Kadanoff (MK) renormalization group procedure. One of the MK versions gives results for f (R ) in d =3 in reasonable agreement with those of the Monte Carlo simulations at the values of R for which they can be compared. If there were a de Almeida-Thouless (AT) line for d ≤6 , it would appear as a zero of the function f (R ) at some negative value of R , but there is no evidence for such behavior. This is consistent with the arguments that there should be no AT line for d ≤6 , which we review.

  5. Criticality as a Set-Point for Adaptive Behavior in Neuromorphic Hardware

    PubMed Central

    Srinivasa, Narayan; Stepp, Nigel D.; Cruz-Albrecht, Jose

    2015-01-01

    Neuromorphic hardware are designed by drawing inspiration from biology to overcome limitations of current computer architectures while forging the development of a new class of autonomous systems that can exhibit adaptive behaviors. Several designs in the recent past are capable of emulating large scale networks but avoid complexity in network dynamics by minimizing the number of dynamic variables that are supported and tunable in hardware. We believe that this is due to the lack of a clear understanding of how to design self-tuning complex systems. It has been widely demonstrated that criticality appears to be the default state of the brain and manifests in the form of spontaneous scale-invariant cascades of neural activity. Experiment, theory and recent models have shown that neuronal networks at criticality demonstrate optimal information transfer, learning and information processing capabilities that affect behavior. In this perspective article, we argue that understanding how large scale neuromorphic electronics can be designed to enable emergent adaptive behavior will require an understanding of how networks emulated by such hardware can self-tune local parameters to maintain criticality as a set-point. We believe that such capability will enable the design of truly scalable intelligent systems using neuromorphic hardware that embrace complexity in network dynamics rather than avoiding it. PMID:26648839

  6. Quasiparticle interaction function in a two-dimensional Fermi liquid near an antiferromagnetic critical point

    NASA Astrophysics Data System (ADS)

    Chubukov, Andrey V.; Wölfle, Peter

    2014-01-01

    We present the expression for the quasiparticle vertex function Γω(KF,PF) (proportional to the Landau interaction function) in a 2D Fermi liquid (FL) near an instability towards antiferromagnetism. This function is relevant in many ways in the context of metallic quantum criticality. Previous studies have found that near a quantum critical point, the system enters into a regime in which the fermionic self-energy is large near hot spots on the Fermi surface [points on the Fermi surface connected by the antiferromagnetic ordering vector qπ=(π,π)] and has much stronger dependence on frequency than on momentum. We show that in this regime, which we termed a critical FL, the conventional random-phase-approximation- (RPA) type approach breaks down, and to properly calculate the vertex function one has to sum up an infinite series of terms which were explicitly excluded in the conventional treatment. Besides, we show that, to properly describe the spin component of Γω(KF,PF) even in an ordinary FL, one has to add Aslamazov-Larkin (AL) terms to the RPA vertex. We show that the total Γω(KF,PF) is larger in a critical FL than in an ordinary FL, roughly by an extra power of magnetic correlation length ξ, which diverges at the quantum critical point. However, the enhancement of Γω(KF,PF) is highly nonuniform: It holds only when, for one of the two momentum variables, the distance from a hot spot along the Fermi surface is much larger than for the other one. This fact renders our case different from quantum criticality at small momentum, where the enhancement of Γω(KF,PF) was found to be homogeneous. We show that the charge and spin components of the total vertex function satisfy the universal relations following from the Ward identities related to the conservation of the particle number and the total spin. We show that in a critical FL, the Ward identity involves Γω(KF,PF) taken between particles on the FS. We find that the charge and spin components of

  7. Comparison of preparation techniques of mixed samples (fungi-helminth eggs) for scanning electron microscopy by critical point drying.

    PubMed

    Sarmiento, P L; Ciarmela, María L; Sánchez Thevenet, P; Minvielle, M C; Basualdo, J A

    2006-09-01

    We compared three preparation techniques for critical point drying of fungus Paecilomyces lilacinus (Thom) Samson with Toxocara canis (Werner) Johnston and Taenia hydatigena Linneo eggs by scanning electron microscopy. We evaluated filtration (first), centrifugation (second), and phytoplankton network (third) in critical point drying methods. The first and third methods were advantageous for T. canis eggs because they preserved the quantity and quality of samples to obtain better images definition. The best technique for T. hydatigena eggs was the addition of phytoplankton network in critical point drying which preserved these helminth eggs.

  8. Critical current scaling and the pivot-point in Nb3Sn strands

    NASA Astrophysics Data System (ADS)

    Tsui, Y.; Hampshire, D. P.

    2012-05-01

    Detailed measurements are provided of the engineering critical current density (Jc) and the index of transition (n-value) of two different types of advanced ITER Nb3Sn superconducting strand for fusion applications. The samples consist of one internal-tin strand (OST) and two bronze-route strands (BEAS I and BEAS II—reacted using different heat treatments). Tests on different sections of these wires show that prior to applying strain, Jc is homogeneous to better than 2% along the length of each strand. Jc data have been characterized as a function of magnetic field (B ≤ 14.5 T), temperature (4.2 K ≤ T ≤ 12 K) and applied axial strain ( - 1% ≤ ɛA ≤ 0.8%). Strain-cycling tests demonstrate that the variable strain Jc data are reversible to better than 2% when the applied axial strain is in the range of - 1% ≤ ɛA ≤ 0.5%. The wires are damaged when the intrinsic strain (ɛI) is ɛI ≥ 0.55% and ɛI ≥ 0.23% for the OST and BEAS strands, respectively. The strain dependences of the normalized Jc for each type of strand are similar to those of prototype strands of similar design measured in 2005 and 2008 to about 2% which makes them candidate strands for a round-robin interlaboratory comparison. The Jc data are described by Durham, ITER and Josephson-junction parameterizations to an accuracy of about 4%. For all of these scaling laws, the percentage difference between the data and the parameterization is larger when Jc is small, caused by high B, T or |ɛI|. The n-values can be described by a modified power law of the form n=1+r{I}_{{c}}^{s}, where r and s are approximately constant and Ic is the critical current. It has long been known that pivot-points (or cross-overs) in Jc occur at high magnetic field and temperature. Changing the magnetic field or temperature from one side of the pivot-point to the other changes the highest Jc sample to the lowest Jc sample and vice versa. The pivot-point follows the B-T phase boundary associated with the upper

  9. A First Test of the E(5/4) Bose-Fermi Symmetry : 135Ba

    NASA Astrophysics Data System (ADS)

    Cakirli, R. B.; Fetea, M. S.; Casten, R. F.; Warner, D. D.; McCutchan, E. A.; Meyer, D. A.; Heinz, A.; Ai, H.; Gurdal, G.; Qian, J.; Winkler, R.

    2007-04-01

    There has been intense recent interest in equilibrium shape / phase transitions in nuclei and the concept of critical point symmetries to describe them. The first critical point symmetry for an odd-mass nucleus has been recently proposed, namely, the E(5/4) Bose-Fermi critical point symmetry, it corresponds to coupling between an odd particle in a j = 3/2 orbit and the E(5) critical point symmetry, at the transition between the O(6) gamma-soft and the U(5) vibrator symmetries. Since 134Ba is a candidate for the E(5) critical point symmetry, we carried out a β-decay experiment on 135Ba whose last neutron can occupy a 2d3/2 orbit as a first test of E(5/4). The experimental results were compared to E(5/4) and also with the Interacting Boson-Fermion Approximation Model (IBFA) and Shell Model calculations. We see fair agreement with E(5/4) for B(E2) values but not for all energies. The IBFA shows better agreement with data than E(5/4) and the Shell model shows the best agreement.

  10. The Subtle Balance between Lipolysis and Lipogenesis: A Critical Point in Metabolic Homeostasis.

    PubMed

    Saponaro, Chiara; Gaggini, Melania; Carli, Fabrizia; Gastaldelli, Amalia

    2015-11-13

    Excessive accumulation of lipids can lead to lipotoxicity, cell dysfunction and alteration in metabolic pathways, both in adipose tissue and peripheral organs, like liver, heart, pancreas and muscle. This is now a recognized risk factor for the development of metabolic disorders, such as obesity, diabetes, fatty liver disease (NAFLD), cardiovascular diseases (CVD) and hepatocellular carcinoma (HCC). The causes for lipotoxicity are not only a high fat diet but also excessive lipolysis, adipogenesis and adipose tissue insulin resistance. The aims of this review are to investigate the subtle balances that underlie lipolytic, lipogenic and oxidative pathways, to evaluate critical points and the complexities of these processes and to better understand which are the metabolic derangements resulting from their imbalance, such as type 2 diabetes and non alcoholic fatty liver disease.

  11. The Subtle Balance between Lipolysis and Lipogenesis: A Critical Point in Metabolic Homeostasis

    PubMed Central

    Saponaro, Chiara; Gaggini, Melania; Carli, Fabrizia; Gastaldelli, Amalia

    2015-01-01

    Excessive accumulation of lipids can lead to lipotoxicity, cell dysfunction and alteration in metabolic pathways, both in adipose tissue and peripheral organs, like liver, heart, pancreas and muscle. This is now a recognized risk factor for the development of metabolic disorders, such as obesity, diabetes, fatty liver disease (NAFLD), cardiovascular diseases (CVD) and hepatocellular carcinoma (HCC). The causes for lipotoxicity are not only a high fat diet but also excessive lipolysis, adipogenesis and adipose tissue insulin resistance. The aims of this review are to investigate the subtle balances that underlie lipolytic, lipogenic and oxidative pathways, to evaluate critical points and the complexities of these processes and to better understand which are the metabolic derangements resulting from their imbalance, such as type 2 diabetes and non alcoholic fatty liver disease. PMID:26580649

  12. Fate of the Wiedemann-Franz Law near Quantum Critical Points of Electron Systems in Solids

    NASA Astrophysics Data System (ADS)

    Khodel, V. A.; Clark, J. W.; Shaginyan, V. R.; Zverev, M. V.

    2015-12-01

    We introduce and analyze two different scenarios for violation of the Wiedemann-Franz law in strongly correlated electron systems of solids, close to a topological quantum critical point (TQCP) where the density of states N(0) diverges. The first, applicable to the Fermi-liquid (FL) side of the TQCP, involves a transverse zero-sound collective mode that opens a new channel for the thermal conductivity, thereby enhancing the Lorenz number L(0) relative to the value L0 =π2 k B 2/3 e 2 dictated by conventional FL theory. The second mechanism for violation of the WF law, relevant to the non-Fermi-liquid (NFL) side of the TQCP, involves the formation of a flat band and leads instead to a reduction of the Lorenz number.

  13. Classical Behavior of Two-Dimensional Liquid 3He Near a Quantum Critical Point

    NASA Astrophysics Data System (ADS)

    Clark, J. W.; Khodel, V. A.; Zverev, M. V.

    2013-11-01

    Non-Fermi-liquid (NFL) behavior of the specific heat C(T) of two-dimensional (2D) liquid 3He, first uncovered in measurements almost 20 years ago, is explained in terms of intrinsic properties of this system that emerge when its density rises and the liquid becomes strongly correlated. The occurrence of a T-independent β term in C(T) is attributed to satisfaction of the conditions for Dulong-Petit behavior by the boson part of the free energy. This unexpected classicality stems from softening of the transverse zero-sound mode (TZSM) in the density region where the anomaly in C(T), associated with a quantum critical point (QCP), is observed.

  14. Critical Point Facility (CPF) Team in the Spacelab Payload Operations Control Center (SL POCC)

    NASA Technical Reports Server (NTRS)

    1982-01-01

    The primary payload for Space Shuttle Mission STS-42, launched January 22, 1992, was the International Microgravity Laboratory-1 (IML-1), a pressurized manned Spacelab module. The goal of IML-1 was to explore in depth the complex effects of weightlessness of living organisms and materials processing. Around-the-clock research was performed on the human nervous system's adaptation to low gravity and effects of microgravity on other life forms such as shrimp eggs, lentil seedlings, fruit fly eggs, and bacteria. Materials processing experiments were also conducted, including crystal growth from a variety of substances such as enzymes, mercury iodide, and a virus. The Huntsville Operations Support Center (HOSC) Spacelab Payload Operations Control Center (SL POCC) at the Marshall Space Flight Center (MSFC) was the air/ground communication channel used between the astronauts and ground control teams during the Spacelab missions. Featured is the Critical Point Facility (CPF) team in the SL POCC during the IML-1 mission.

  15. Time delay of critical images in the vicinity of cusp point of gravitational-lens systems

    NASA Astrophysics Data System (ADS)

    Alexandrov, A.; Zhdanov, V.

    2016-12-01

    We consider approximate analytical formulas for time-delays of critical images of a point source in the neighborhood of a cusp-caustic. We discuss zero, first and second approximations in powers of a parameter that defines the proximity of the source to the cusp. These formulas link the time delay with characteristics of the lens potential. The formula of zero approximation was obtained by Congdon, Keeton & Nordgren (MNRAS, 2008). In case of a general lens potential we derived first order correction thereto. If the potential is symmetric with respect to the cusp axis, then this correction is identically equal to zero. For this case, we obtained second order correction. The relations found are illustrated by a simple model example.

  16. [The Hazard Analysis Critical Control Point approach (HACCP) in meat production].

    PubMed

    Berends, B R; Snijders, J M

    1994-06-15

    The Hazard Analysis Critical Control Point (HACCP) approach is a method that could transform the current system of safety and quality assurance of meat into a really effective and flexible integrated control system. This article discusses the origin and the basic principles of the HACCP approach. It also discusses why the implementation of the approach is not as widespread as might be expected. It is concluded that a future implementation of the approach in the entire chain of meat production, i.e. from conception to consumption, is possible. Prerequisites are, however, that scientifically validated risk analyses become available, that future legislation forms a framework that actively supports the approach, and that all parties involved in meat production not only become convinced of the advantages, but also are trained to implement the HACCP approach with insight.

  17. [Monitoring of a HACCP (Hazard Analysis Critical Control Point) plan for Listeria monocytogenes control].

    PubMed

    Mengoni, G B; Apraiz, P M

    2003-01-01

    The monitoring of a HACCP (Hazard Analysis Critical Control Point) plan for the Listeria monocytogenes control in the cooked and frozen meat section of a thermo-processing meat plant was evaluated. Seventy "non-product-contact" surface samples and fourteen finished product samples were examined. Thirty eight positive sites for the presence of Listeria sp. were obtained. Twenty-two isolates were identified as L. monocytogenes, two as L. seeligeri and fourteen as L. innocua. Non isolates were obtained from finished product samples. The detection of L. monocytogenes in cooked and frozen meat section environment showed the need for the HACCP plan to eliminate or prevent product contamination in the post-thermal step.

  18. [Economic aspects of the Italian food industry: critical points and perspectives].

    PubMed

    Casati, D

    2012-01-01

    The Italian food industry represents 2% of GDP and employment. Its role grows considering the whole food supply chain to 3.7% of GDP and 5.7% of employment, reaching 12.5% of the European one. In terms of value added, it reaches 25% of private sector expenditure, at the second places after the house one, but 8 times more than health. The european food industry is the leading sector. Italian industry is at the 3rd place for its value added, at 5th for employment, but the first for productivity together with the French food industry. Critical points of Italian food industry are mainly connected with its structure, production composition, dependence on consumer evolution, crisis impact, internationalization of firms and leading groups, innovation.

  19. Critical Point Facility (CPF) Team in the Spacelab Payload Operations Control Center (SL POCC)

    NASA Technical Reports Server (NTRS)

    1982-01-01

    The primary payload for Space Shuttle Mission STS-42, launched January 22, 1992, was the International Microgravity Laboratory-1 (IML-1), a pressurized manned Spacelab module. The goal of IML-1 was to explore in depth the complex effects of weightlessness of living organisms and materials processing. Around-the-clock research was performed on the human nervous system's adaptation to low gravity and effects of microgravity on other life forms such as shrimp eggs, lentil seedlings, fruit fly eggs, and bacteria. Materials processing experiments were also conducted, including crystal growth from a variety of substances such as enzymes, mercury iodide, and a virus. The Huntsville Operations Support Center (HOSC) Spacelab Payload Operations Control Center (SL POCC) at the Marshall Space Flight Center (MSFC) was the air/ground communication channel used between the astronauts and ground control teams during the Spacelab missions. Featured is the Critical Point Facility (CPF) team in the SL POCC during the IML-1 mission.

  20. Structural Stability of Planar Homogeneous Polynomial Vector Fields: Applications to Critical Points and to Infinity

    NASA Astrophysics Data System (ADS)

    Llibre, Jaume; Pérez del Río, Jesús S.; Rodríguez, José Angel

    1996-03-01

    LetHmbe the space of planar homogeneous polynomial vector fields of degreemendowed with the coefficient topology. We characterize the setΩmof the vector fields ofHmthat are structurally stable with respect to perturbations inHmand we determine the exact number of the topological equivalence classes inΩm. The study of structurally stable homogeneous polynomial vector fields is very useful for understanding some interesting features of inhomogeneous vector fields. Thus, by using this characterization we can do first an extension of the Hartman-Grobman Theorem which allows us to study the critical points of planar analytical vector fields whosek-jets are zero for allk