Irreversibility Quantum theory 8 Mathematical models 6 Approximation theory 4 Arrow of time 4 Brownian motion 4 Brownian movement 4 Langevin equation 4 Loschmidt echoes 4 Master equation 4 05.40.+j 2 Bunimovich stadium billiard 2 Chaotic systems 2 Coupled harmonic oscillators 2 Foundations of quantum mechanics 2 Function of time 2 Graph theory 2 Ground state 2 Harmonic oscillators 2 Hilbert spaces 2 Hydrostatic pressure 2 Infinite dimensional 2 Integral equations 2 Lyapunov exponent 2 Lyapunov methods 2 Magnetization 2 Manganese compounds 2 Manganites 2 Mesoscopic devices 2 Microstructure 2