Stochastic numerical methods play an important role in large scale
computations in the applied sciences. The first goal of this book is to
give a mathematical description of classical direct simulation Monte
Carlo (DSMC) procedures for rarefied gases, using the theory of Markov
processes as a unifying framework. The second goal is a systematic
treatment of an extension of DSMC, called stochastic weighted particle
method. This method includes several new features, which are introduced
for the purpose of variance reduction (rare event simulation). Rigorous
convergence results as well as detailed numerical studies are presented.