My apologies in advance if this question is poorly worded or doesn't make any sense, however I have just finished reading into this theory and it seems as though Hawkings No Boundary Universe is basically emergent from a Universal Wave Function that is timeless. So no time took place before the big bang.

However to the question-

If the universal wavefunction is static how does a universe(or multiverse if you prefer) emerge at all?

If it is static wouldn't nothing ever change?


That's a very deep question, not easy to answer, and maybe not answerable. However, one way to look at such a question is to consider perspective. From within the universe, it appears that systems evolve over time. The relative states of things change. The "static" nature of the universal wave function implies that its overall properties do not change. This does not mean, however, that from within that system, from a particular perspective, that everything is static. Rather, from vantage points within the universe, various parts of the universe certainly are in relative motion to the other various parts.

The overall wave function will have operators/properties that are conserved (like energy) overall. However, relative to your vantage point you may see things speeding up and slowing down. There is a very big difference in describing things from a localized vantage point, where things behave dynamically, and describing them from an overall perspective, from which certain properties would appear unchanging.

  • $\begingroup$ It's worth reading about the Page-Wooters mechanism $\endgroup$ – lionelbrits Jan 29 '15 at 22:59
  • $\begingroup$ Perhaps I'm not understanding the question correctly. Hybrid is asking whether Hawking's theory describes a truly static wavefunction, right? In the Schroedinger picture? If you have a static function in the Schroedinger picture, all possible measurement operators will have the same expectation values, always, whether they measure some very general property like total energy or some specific property like energy density in a region of space. There's no such thing as local dynamics. This is totally different from saying energy or momentum are conserved. $\endgroup$ – user27118 Nov 18 '15 at 18:10

Yes, you hit the nail right on the head, with respect to the H-H NBP, as well as Vilenkin's related tunnelling mechanism. But, there is a further problem as to why the H-H proposal simply does not work: Conformal modes lead to the Einstein-Hilbert action not being bounded from below, which in turn implies that the sum over all 4-geometries leads to a sum over topologies that cannot be computed.


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