Imaginary time quantum Monte Carlo simulations of many fermion systems

This dissertation contains all the knowledge of Imaginary Time Quantum Monte Carlo (QMC) methods I have acquired during the years of my graduate studies.;It discusses the problems common to QMC simulations of many fermion systems and the way these problems can be solved.;It starts with a description of a simple noninteracting model and goes on to a discussion of lattice systems of interacting fermions. From 1-d system of interacting fermions we move on to 2-d systems. We discuss the problems arising from the change of special dimensionality and the way these problems can be solved. Limitations of the methods are discussed along the way. Then, the lattice models are used to describe quantum conductivity processes through short molecular wires. Results of these studies are compared with experimental data.;From the lattice models we move to continuous many fermion systems. We discuss the blocking idea and Multi-Level Blocking (MLB) algorithm derived from it. We use Quantum Monte Carlo empowered by MLB algorithm to calculate electron distributions in small molecules and discuss the results.;Discussions of the success achieved in the field as well as the problems yet to be solved concludes the thesis.