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The interpretation I prefer: the universal quantum state evolves unitarily at all times, and there are no parallel universes. Problem solved. Parallel univers

The interpretation I prefer: the universal quantum state evolves unitarily at all times, and there are no parallel universes. Problem solved. Parallel universes are — by definition — unfalsifiable, so the best theory then is the simplest one, and that is a theory with one universe. For similar reasoning used in a somewhat different scenario, see also http://plato.stanford.edu/entries/spacetime-holearg/ http://plato.stanford.edu/entries/spacetime-holearg/

hammock 11y ago
>the universal quantum state evolves unitarily at all times What does that mean in layman's terms? Is that basically the Copenhagen interpretation (which has its own issues)
ikeboy 11y ago
It's not so obvious that a single universe is simpler. See http://space.mit.edu/home/tegmark/PDF/multiverse_sciam.pdf http://space.mit.edu/home/tegmark/PDF/multiverse_sciam.pdf and the excerpt quoted in https://en.wikipedia.org/wiki/Multiverse#Occam.27s_Razor https://en.wikipedia.org/wiki/Multiverse#Occam.27s_Razor
pjdorrell 11y ago
In the context of Many Worlds, a "universe" is an approximately classical wave function, where the degree of approximation is limited by the uncertainty principle. Even if you start with an approximately classical wave function, it may evolve into a state where it is no longer approximately classical. However, it might now be equal to the sum of _two_ approximately classical wave functions. Ie, two "universes". So, the universal wave function hasn't split, but the attempt to represent that wave function by approximately classical wave functions _has_ split.
- Xcelerate 11y ago
  > but the attempt to represent that wave function by approximately classical wave functions _has_ split. Exactly. The problem is that people keep trying to view quantum physics through a classical lens. Decoherence is simply the fact that a quantum state evolves to a point where it can no longer be mathematically represented as a tensor product state. I don't lose any sleep over that.

hammock 11y ago

>the universal quantum state evolves unitarily at all times What does that mean in layman's terms? Is that basically the Copenhagen interpretation (which has its own issues)

ikeboy 11y ago

It's not so obvious that a single universe is simpler. See http://space.mit.edu/home/tegmark/PDF/multiverse_sciam.pdf http://space.mit.edu/home/tegmark/PDF/multiverse_sciam.pdf and the excerpt quoted in https://en.wikipedia.org/wiki/Multiverse#Occam.27s_Razor https://en.wikipedia.org/wiki/Multiverse#Occam.27s_Razor

pjdorrell 11y ago

In the context of Many Worlds, a "universe" is an approximately classical wave function, where the degree of approximation is limited by the uncertainty principle. Even if you start with an approximately classical wave function, it may evolve into a state where it is no longer approximately classical. However, it might now be equal to the sum of _two_ approximately classical wave functions. Ie, two "universes". So, the universal wave function hasn't split, but the attempt to represent that wave function by approximately classical wave functions _has_ split.

Xcelerate 11y ago
> but the attempt to represent that wave function by approximately classical wave functions _has_ split. Exactly. The problem is that people keep trying to view quantum physics through a classical lens. Decoherence is simply the fact that a quantum state evolves to a point where it can no longer be mathematically represented as a tensor product state. I don't lose any sleep over that.