Search results for "Criticality"
showing 10 items of 39 documents
Dynamical phase transitions and their relation to structural and thermodynamic aspects of glass physics.
2020
We review recent developments in structural–dynamical phase transitions in trajectory space based on dynamic facilitation theory. An open question is how the dynamic facilitation perspective on the glass transition may be reconciled with thermodynamic theories that posit collective reorganization accompanied by a growing static length scale and, eventually, a vanishing configurational entropy. In contrast, dynamic facilitation theory invokes a dynamical phase transition between an active phase (close to the normal liquid) and an inactive phase, which is glassy and whose order parameter is either a time-averaged dynamic or structural quantity. In particular, the dynamical phase transition in…
On the sure criticality of tasks in activity networks with imprecise durations
2002
BB; International audience; The notion of the necessary criticality (both with respect to path and to activity) of a network with imprecisely defined (by means of intervals or fuzzy intervals) activity duration times is introduced and analyzed. It is shown, in the interval case, that both the problem of asserting whether a given path is necessarily critical and the problem of determining an arbitrary necessarily critical path (more exactly, a subnetwork covering all the necessarily critical. paths) are easy. The corresponding solution algorithms are proposed. However, the problem. of evaluating whether a given activity is necessarily critical does not seem to be such. Certain conditions are…
Artificial multiple criticality and phase equilibria: an investigation of the PC-SAFT approach
2005
The perturbed-chain statistical associating fluid theory (PC-SAFT) is studied for a wide range of temperature, T, pressure, p, and (effective) chain length, m, to establish the generic phase diagram of polymers according to this theory. In addition to the expected gas-liquid coexistence, two additional phase separations are found, termed "gas-gas" equilibrium (at very low densities) and "liquid-liquid" equilibrium (at densities where the system is expected to be solid already). These phase separations imply that in one-component polymer systems three critical points occur, as well as equilibria of three fluid phases at triple points. However, Monte Carlo simulations of the corresponding sys…
Rotor—frame contact in a centrifuge installed on board a ship
2009
The criticality of rotor and stator contact in a large-size marine separator is studied by numerical modelling. Two plausible mechanisms leading to such contact, namely rolling of a ship in steady-state motion and a suddenly occurring unbalance in the rotor, are considered. It is found that contact due to sea motion may be tolerable, while sudden development of unbalance at operating speed can lead to unacceptably high contact forces. This agrees with experience of centrifugal separators operating on board of ships.
Temperature dependence of single chain properties in a binary polymer blend
1996
The temperature dependence of the correlation length of composition fluctuations and single chain statics and dynamics is studied in a symmetric, binary polymer blend. Our Monte Carlo simulation reveals a pronounced shrinking of the chain in the minority phase at low temperatures. However, only a weak temperature dependence of the single chain properties is found above criticality. Especially there is only a weak coupling between the correlation length of composition fluctuations and the relaxation of the internal chain structure. The coherent dynamic structure factor does not show any signs of a spatial restricted motion for our chain length N = 16, which is far below the entanglement leng…
A coupled map as a model of the dynamics of the magnetotail current sheet
2001
Abstract A magnetic field model of the magnetotail current sheet in the form of a coupled-map lattice (CML) is presented. It is continuously driven (“running”) and based on the MHD diffusion equation. Solar wind vBS data (solar wind speed multiplied by the southward component of IMF) are used for driving the model, and it is shown to exhibit perturbations (avalanches) with power-law scalings in their distributions of duration and size. Such distributions may indicate self-organized critical (SOC) behavior. Furthermore, it is shown that the power spectra of the model outputs are of bicolor power-law form with different slopes for high and low frequencies. Although the “running” model gives p…
Entanglement Properties and Phase Diagram of the Two-Orbital Atomic Hubbard Model
2009
We study the two-orbital Hubbard model in the limit of vanishing kinetic energy. The phase diagram in the $V-J$ plane, with $V$ and $J$ denoting the interorbital hybridization and exchange coupling respectively, at half filling is obtained. A singlet(dimer)-triplet transition is found for a critical value of the ratio $V/J.$ The entropy of formation, both in the mode and in the particle picture, presents a jump as the same critical line in conformity with the suggested relation between criticality and entanglement.
Coupling MCNP-DSP and LAHET Monte Carlo Codes for Designing Subcriticality Monitors for Accelerator-Driven Systems
2001
The design of reactivity monitoring systems for accelerator-driven systems must be investigated to ensure that such systems remain subcritical during operation. The Monte Carlo codes LAHET and MCNP-DSP were combined together to facilitate the design of reactivity monitoring systems. The coupling of LAHET and MCNP-DSP provides a tool that can be used to simulate a variety of subcritical measurements such as the pulsed neutron, Rossi-α, or noise analysis measurements.
Quasi-classical Physics Within Quantum Criticality in HF Compounds
2014
In this chapter, we explore how the fermion condensation paves the road for quasi-classical physics in HF compounds. This means simply that systems with FC admit partly the quasi-classical description of their thermodynamic and transport properties. This, in turn, simplifies a lot not only of their description but permits to gain more insights both in the puzzling NFL physics of HF compounds and of the physics of FC itself. The quasi-classical physics starts to be applicable near FCQPT, at which FC generates flat bands and quantum criticality, and makes the density of electron states in strongly correlated metals diverge. As we shall see, due to the formation of flat bands the strongly corr…
Unconstrained periodic boundary conditions for solid state elasticity
2004
We introduce a method to implement dynamics on an elastic lattice without imposing constraints via boundary or loading conditions. Using this method we are able to examine fracture processes in two-dimensional systems previously inaccessible for reliable computer simulations. We show the validity of the method by benchmarking and report a few preliminary results.