In this thesis, we investigate two aspects of one-dimensional interacting quantum
systems. The first one is the effect of explicit antiferromagnetic exchange
interactions on the quantum phase transitions of a one-dimensional itinerant
electron system. The second one is the decoherence of a qubit coupled to a
one-dimensional quantum spin system.
Metal-insulator transitions and other electronic transitionsQuantenphasenübergangNon-Fermi-liquid ground states, electron phase diagrams and phase transitions in model systemsDensity matrix renormalization groupStrongly correlated systemsCritical point phenomenaStark korrelierte SystemeDichtematrixrenormierungsgruppeLattice fermion models (Hubbard model, etc.)Decoherence; open systems; quantum statistical methods (see also 03.67.Pp in quantum information; for decoherence in Bose-Einstein condensates, see 03.75.Gg)Quantum phase transitionsNonconventional mechanisms (spin fluctuations, polarons and bipolarons, resonating valence bond model, anyon mechanism, marginal Fermi liquid, Luttinger liquid, etc.)DekohärenzDecoherenceLattice theory and statistics (Ising, Potts, etc.) (see also 64.60.Cn Order-disorder transformations and statistical mechanics of model systems and 75.10.Hk Classical spin models)Quantum computation
