Beyond the relaxation time approximation

Relaxation time approximation forelectron - phonon interaction insemiconductorsPeter

A Boltzmann equation for semiconductors is considered. Physical assumptions include the parabolic band approximation and a new relaxation time model for electron-phonon interaction. Thermal equilibrium distributions for this scattering mechanism are products of Maxwellian distributions with periodic functions of the energy, where the period is the energy of a phonon. The hydrodynamic limit is c...

Beyond the Pole Approximation

We present a calculation of the complete electroweak O(α) corrections to p p (−) → W ± → ℓ ± νX (ℓ = e, µ) in the Standard Model of electroweak interactions , focusing on those corrections which do not contribute in the pole approximation. We study in detail the effect of these corrections on the transverse mass distribution, the W-width measurement, and the transverse mass ratio and cross sect...

On the relaxation of a twolevel system: Beyond the weakcoupling approximation

On the Validity of the Relaxation Time Approximation for Macroscopic Transport Models

Although many doubts have been raised concerning its accuracy, the macroscopic relaxation time approximation is often used to approximate the weighted averages of the collision integral. More accurate approaches based on expansions of the distribution function deliver better results. Unfortunately these models depend on the fluxes of the system which causes a coupling of the flux relations. Our...

Variance-reduced particle simulation of the Boltzmann transport equation in the relaxation-time approximation.

We present an efficient variance-reduced particle simulation technique for solving the linearized Boltzmann transport equation in the relaxation-time approximation used for phonon, electron, and radiative transport, as well as for kinetic gas flows. The variance reduction is achieved by simulating only the deviation from equilibrium. We show that in the limit of small deviation from equilibrium...