Parallel Universes

Posted by Parallel Universes on Feb 16, 2002 at 16:43
(62.59.64.13)

http://arxiv.org/abs/astro-ph/0302131


Authors: Max Tegmark (Penn)
Comments: 18 pages, 8 figs. A less technical adaptation is scheduled for the May 2003 issue of Scientific American. Version with full-resolution figs at this http URL
Journal-ref: In "Science and Ultimate Reality: From Quantum to Cosmos", honoring John Wheeler's 90th birthday. J. D. Barrow, P.C.W. Davies, & C.L. Harper eds. Cambridge University Press (2003)

I survey physics theories involving parallel universes, which form a natural four-level hierarchy of multiverses allowing progressively greater diversity.
Level I: A generic prediction of inflation is an infinite ergodic universe, which contains Hubble volumes realizing all initial conditions - including an identical copy of you about 10^{10^29} meters away.
Level II: In chaotic inflation, other thermalized regions may have different effective physical constants, dimensionality and particle content.
Level III: In unitary quantum mechanics, other branches of the wavefunction add nothing qualitatively new, which is ironic given that this level has historically been the most controversial.
Level IV: Other mathematical structures give different fundamental equations of physics. The key question is not whether parallel universes exist (Level I is the uncontroversial cosmological concordance model), but how many levels there are. I discuss how multiverse models can be falsified and argue that there is a severe "measure problem" that must be solved to make testable predictions at levels II-IV.

Follow Ups:


Post a Followup

Name:
E-Mail:

Subject:
Comments:

[ Forum ] [ New Message ]