[Read the OP before voting for special voting rules.]

The many worlds interpretation of quantum mechanics is categorically confused nonsense. Its origins lie in a map/territory confusion, and in the mind projection fallacy. Configuration space is a map, not territory—it is an abstraction used for describing the way that things are laid out in physical space. The density matrix (or in the special case of pure states, the state vector, or the wave function) is a subjective calculational tool used for finding probabilities. It's something that exists in the mind. Any 'interpretation' of quantum mechanics which claims that any of these things exists in reality (e.g. MWI) therefore commits the mind projection fallacy.