Universal Wavefunction

The Universal Wavefunction or Universal Wave Function is a term introduced by Hugh Everett in his Princeton PhD thesis The Theory of the Universal Wave Function, and forms a core concept in the relative state interpretation or many-worlds interpretation of quantum mechanics. It has also received more recent investigation from James Hartle and Stephen Hawking in which they derive a specific solution to the Wheeler-deWitt equation to explain the initial conditions of the Big Bang cosmology.

Everett's thesis introduction reads:

Since the universal validity of the state function description is asserted, one can regard the state functions themselves as the fundamental entities, and one can even consider the state function of the entire universe. In this sense this theory can be called the theory of the "universal wave function," since all of physics is presumed to follow from this function alone.

The universal wave function is the wavefunction or quantum state of the totality of existence, regarded as the "basic physical entity" or "the fundamental entity, obeying at all times a deterministic wave equation"