LANL preprint: "Parallel Universes" by Tegmark

From: Amara Graps (amara@amara.com)
Date: Mon Feb 10 2003 - 03:22:23 MST

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    Astrophysics, abstract
    astro-ph/0302131

    http://it.arXiv.org/abs/astro-ph/0302131

    From: Max Tegmark <max@hep.upenn.edu>
    Date: Fri, 7 Feb 2003 01:39:52 GMT (614kb)

    Parallel Universes

    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.

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