ABSTRACT
This chapter summarizes the localisation theory for electrons in solids. It presents application of localisation theory to the investigation of the quantum behaviour of the kicked rotor. The scaling theory for localisation enables one to describe properties of the system on large scales in terms of few parameters. The property of physical interest that is being calculated is the conductance on various scales. Exponential localisation of the quasi-energies results in suppression of diffusion in momentum space. The chapter demonstrates the interplay between adiabatic localisation, that takes place also in classical mechanics and quantum localisation that results from interference. One problem where classical diffusion is suppressed by quantum interference is the electronic motion in disordered solids. The chapter deals with the investigation of electronic motion in disordered solids at low temperature. The spectrum that one finds when the wave functions are localised in a random system is a dense point spectrum.
