Search results for "Names"

Model of compact 3D electromagnetic solitons

2019

H-function representations for stretched exponential relaxation and non-Debye susceptibilities in glassy systems.

2001

Analytical expressions in the time and frequency domains are derived for non-Debye relaxation processes. The complex frequency-dependent susceptibility function for the stretched exponential relaxation function is given for general values of the stretching exponent in terms of H-functions. The relaxation functions corresponding to the complex frequency-dependent Cole-Cole, Cole-Davidson, and Havriliak-Negami susceptibilities are given in the time domain in terms of H-functions. It is found that a commonly used correspondence between the stretching exponent of Kohlrausch functions and the stretching parameters of Havriliak-Negami susceptibilities are not generally valid.

The Ground State of the 2-Dimensional Potts Glass

1992

We study the ground state of the 3-state Potts glass in 2 dimensions with a Gaussian distribution of couplings by domain wall renormalization group techniques. We find that the glass correlation function decays to a finite value within a distance of about 2.4 lattice spacings. Thus, there is long-range order in the ground state even though, as found earlier, there is a finite zero-point entropy.

Quantum Criticality of Spin Liquids in Novel Insulators and Magnets

2014

Strongly correlated Fermi systems are among the most intriguing and fundamental systems in physics, whose realization in some compounds is still under consideration. Quantum spin liquids are a promising new phases, where exotic quantum states of matter could be realized. Exotic quantum spin liquid (QSL) made of such hypothetic particles as fermionic spinons which carry spin \(1/2\) and no charge are considered in this chapter. Magnetic insulators with geometrical frustration produce important experimental facts shedding light on the nature of quantum spin liquid composed of spinons. We present a theory of the thermodynamic properties of quantum spin liquids, elucidating how their properties…

Resonant Raman scattering in quantum wells in high magnetic fields: Deformation-potential interaction.

1992

A theoretical study of one-phonon resonant Raman scattering in a quantum well (QW) in high magnetic fields has been performed. The Raman profiles are calculated as a function of magnetic field, quantum-well thickness, and laser frequency. The basic theory is first developed assuming parabolic masses in the plane perpendicular to the growth direction of the QW. Selection rules for deformation-potential-allowed scattering are given and a compact analytical expression for the Raman-scattering efficiency is obtained for infinite barriers. The double-resonance conditions are derived as a function of the magnetic field or well thickness. In a second part of the work, the heavy-hole\char21{}light-…

The Numerical Simulation of Relativistic Fluid Flow with Strong Shocks

2001

In this review we present and analyze the performance of a Go-dunov type method applied to relativistic fluid flow. Our model equations are the corresponding Euler equations for special relativistic hydrodynamics. By choosing an appropriate vector of unknowns, the equations of special relativistic fluid dynamics (RFD) can be written as a hyperbolic system of conservation laws. We give a complete description of the spectral decomposition of the Jacobian matrices associated to the fluxes in each spatial direction, (see (Donat et al., 1998), for details), which is the essential ingredient of the Godunov-type numerical method we propose in this paper. We also review a numerical flux formula tha…

A Second Order Accurate Kinetic Relaxation Scheme for Inviscid Compressible Flows

2013

In this paper we present a kinetic relaxation scheme for the Euler equations of gas dynamics in one space dimension. The method is easily applicable to solve any complex system of conservation laws. The numerical scheme is based on a relaxation approximation for conservation laws viewed as a discrete velocity model of the Boltzmann equation of kinetic theory. The discrete kinetic equation is solved by a splitting method consisting of a convection phase and a collision phase. The convection phase involves only the solution of linear transport equations and the collision phase instantaneously relaxes the distribution function to an equilibrium distribution. We prove that the first order accur…

Asymptotic structure factor for the two-component Ginzburg-Landau equation

1992

We derive an analytic form for the asymptotic time-dependent structure factor for the two-component Ginzburg-Landau equation in arbitrary dimensions. This form is in reasonable agreement with results from numerical simulations in two dimensions. A striking feature of our analytic form is the absence of Porod's law in the tail. This is a consequence of the continuous symmetry of the Hamiltonian, which inhibits the formation of sharp domain walls.

Accurate Nonlinear Optical Properties for Small Molecules

2006

During the last decade it became possible to calculate by quantum chemical ab initio methods not only static but also frequency-dependent properties with high accuracy. Today, the most important tools for such calculations are coupled cluster response methods in combination with systematic hierarchies of correlation consistent basis sets. Coupled cluster response methods combine a computationally efficient treatment of electron correlation with a qualitatively correct pole structure and frequency dispersion of the response functions. Both are improved systematically within a hierarchy of coupled cluster models. The present contribution reviews recent advances in the highly accurate calculat…

Communication: The performance of non-iterative coupled cluster quadruples models

2015

We compare the numerical performance of various non-iterative coupled cluster (CC) quadruples models. The results collectively show how approaches that attempt to correct the CC singles and doubles energy for the combined effect of triple and quadruple excitations all fail at recovering the correlation energy of the full CC singles, doubles, triples, and quadruples (CCSDTQ) model to within sufficient accuracy. Such a level of accuracy is only achieved by models that make corrections to the full CC singles, doubles, and triples (CCSDT) energy for the isolated effect of quadruple excitations of which the CCSDT(Q–3) and CCSDT(Q–4) models of the Lagrangian-based CCSDT(Q–n) perturbation series a…