Hi, I've been reading some (very) basic texts on decoherence and have some questions about it: 1. What is the difference between decoherence and dephasing? 2. Assuming decoherence, can we completely do away with collapse theories (i.e. theories in which wavefunction collapse must be postulated)? 3. Could decoherence deal with a completely isolated system (no idea if this is experimentally possible, but assuming it is)? Or will decoherence then be induced by vacuum fluctuations? Or what happens if we measure very quickly after the preparation of a pure state, such that no considerable decoherence could have taken place? 4. If I understand correctly, decoherence explains how the density operator of a system transforms from a pure to a mixed state by interaction with its environment. So if we look at a system without environment, i.e. the quantum state of the whole universe, what can we say about that? Is it pure and remains pure, or could it be mixed? What difference would it make? 5. The many-worlds interpretation in combination with decoherence is pretty popular. But where exactly does many-worlds come in? Decoherence transforms a quantum superposition into a state that can completely be represented with classical probability theory, i.e. statistical physics, where, as far as I know, no interpretational questions arise. So where do we still need interpretations? Thanks!