The universal wavefunction or the wavefunction of the universe is the wavefunction or quantum state of the entire universe.[1] It is regarded as the basic physical entity[2] in the many-worlds interpretation of quantum mechanics,[3] [4] [5] [6] and finds applications in quantum cosmology. It evolves deterministically according to a wave equation.[7]
The concept of universal wavefunction was introduced by Hugh Everett in his 1956 PhD thesis draft The Theory of the Universal Wave Function.[8] It later received investigation from James Hartle and Stephen Hawking[9] who derived the Hartle–Hawking solution to the Wheeler–deWitt equation to explain the initial conditions of the Big Bang cosmology.
Hugh Everett's universal wavefunction supports the idea that observed and observer are all mixed together:
Eugene Wigner and John Archibald Wheeler take issue with this stance. Wigner wrote:
Wheeler wrote: