Search results for "model [interaction]"

Scaling behavior in the dynamics of a supercooled Lennard-Jones mixture

1994

We present the results of a large scale molecular dynamics computer simulation of a binary, supercooled Lennard-Jones fluid. At low temperatures and intermediate times the time dependence of the intermediate scattering function is well described by a von Schweidler law. The von Schweidler exponent is independent of temperature and depends only weakly on the type of correlator. For long times the correlation functions show a Kohlrausch behavior with an exponent $\beta$ that is independent of temperature. This dynamical behavior is in accordance with the mode-coupling theory of supercooled liquids.

Types I and II intermittencies in a cascade laser model

1995

Abstract We report on types I and II intermittencies found in a cascade laser model. A continuous transition from one to another type of intermittency, which involves the coexistence of both types of laminar phases within the same time series, is found. Type II intermittency has special characteristics such as its origin at a frequency locked two-torus. When frequency unlocked this torus bifurcates to a three-torus, further giving rise to a type II intermittent like behaviour with new features during the laminar phases.

AB Doradus C: age, spectral type, orbit, and comparison to evolutionary models

2005

We expand upon the results of Close et al. 2005 regarding the young, low-mass object AB Dor C and its role as a calibration point for theoretical tracks. We present an improved spectral reduction and a new orbital solution with two additional epochs. Our improved analysis confirms our spectral type of M8 (+/- 1) and mass of 0.090+/-0.003 solar masses for AB Dor C. Comparing the results for AB Dor C with other young, low-mass objects with dynamical masses we find a general trend where current evolutionary models tend to over-predict the temperature (or under-predict the mass) for low mass stars and brown dwarfs. Given our precision, there is a ~99% chance that the mass of AB Dor C is underes…

Transient Reversible Growth and Percolation During Phase Separation

1988

Binary mixtures when quenched into the two-phase region exhibit transient percolation phenomena. These transient percolation phenomena and the underlying mechanism of transient reversible growth are investigated. In particular, one of the possible dynamical percolation lines between the dynamical spinodal and the line of macroscopic percolation is traced out. Analyzing the finite size effects with the usual scaling theory one finds exponents which seem to be inconsistent with the universality class of percolation. However, at zero temperature, where the growth is non-reversible and the transition of a sol-gel type, the exponents are consistent with those of random percolation.

Activity, colour anomalies and temperature determination in solar-type stars

2008

Low-energy fixed points of random Heisenberg models

2002

The effect of quenched disorder on the low-energy and low-temperature properties of various two- and three-dimensional Heisenberg models is studied by a numerical strong disorder renormalization group method. For strong enough disorder we have identified two relevant fixed points, in which the gap exponent, omega, describing the low-energy tail of the gap distribution, P(Delta) ~ Delta^omega is independent of disorder, the strength of couplings and the value of the spin. The dynamical behavior of non-frustrated random antiferromagnetic models is controlled by a singlet-like fixed point, whereas for frustrated models the fixed point corresponds to a large spin formation and the gap exponent …

Higher-order correlation functions and nonlinear response functions in a gaussian trap model.

2012

The four-time correlation function of a general dynamical variable obeying Gaussian statistics is calculated for the trap model with a Gaussian density of states. It is argued that for energy-independent variables this function is reminiscent of the four-time functions that have been discussed earlier in the interpretation of the results of four-dimensional NMR experiments on supercooled liquids. Using an approximative relation between the four-time correlation function and the cubic response function the nonlinear susceptibility is calculated and the results are compared with the corresponding ones resulting from an exact calculation. It is found that the results of the approximation chang…

Sterile Neutrinos with Secret Interactions -- Cosmological Discord?

2018

Several long-standing anomalies from short-baseline neutrino oscillation experiments -- most recently corroborated by new data from MiniBooNE -- have led to the hypothesis that extra, 'sterile', neutrino species might exist. Models of this type face severe cosmological constraints, and several ideas have been proposed to avoid these constraints. Among the most widely discussed ones are models with so-called 'secret interactions' in the neutrino sector. In these models, sterile neutrinos are hypothesized to couple to a new interaction, which dynamically suppresses their production in the early Universe through finite-temperature effects. Recently, it has been argued that the original calcula…

Future CEvNS experiments as probes of lepton unitarity and light-sterile neutrinos

2020

We determine the sensitivities of short-baseline coherent elastic neutrino-nucleus scattering (CE$\nu$NS) experiments using a pion decay at rest neutrino source as a probe for nonunitarity in the lepton sector, as expected in low-scale type-I seesaw schemes. We also identify the best configuration for probing light sterile neutrinos at future ton-scale liquid argon CE$\nu$NS experiments, estimating the projected sensitivities on the sterile neutrino parameters. Possible experimental setups at the Spallation Neutron Source, Lujan facility and the European Spallation Source are discussed. Provided that systematic uncertainties remain under control, we find that CE$\nu$NS experiments will be c…

Momentum-space structure of surface states in a topological semimetal with a nexus point of Dirac lines

2016

Three-dimensional topological semimetals come in different variants, either containing Weyl points or Dirac lines. Here we describe a more complicated momentum-space topological defect where several separate Dirac lines connect with each other, forming a momentum-space equivalent of the real-space nexus considered before for helium-3. Close to the nexus the Dirac lines exhibit a transition from type I to type II lines. We consider a general model of stacked honeycomb lattices with the symmetry of Bernal (AB) stacked graphite and show that the structural mirror symmetries in such systems protect the presence of the Dirac lines, and also naturally lead to the formation of the nexus. By the bu…