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Rafael Porto: the new paper with Gambini and Pullin

  1. Apr 27, 2006 #1


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    Rafael Porto is a young QG researcher who visited us at this forum and posted some in late 2004. He posted a mere 7 posts, but more recently, even when not posting, he has occasionally shown up to read.
    Porto is now at Carnegie-Mellon.

    Porto publishes with the team of Gambini and Pullin. They recently posted a beautiful paper on arxiv. It is intended to be understandable by non-specialists and to give a clear intuitive expostion of results from a couple of their more technical papers.

    This paper of Gambini Porto and Pullin disposes of the "black hole information paradox" (about which much fuss has been made) in the case of ordinary size black holes. Indeed it does so in a clever and rather elegant way.

    In effect they find a way out of the apparent contradiction at least for stellar mass holes, and, in my view, say what Steven Hawking SHOULD have said about the puzzle but did not.

    Here is from GPP page 6:
    " ...we have argued that due to the lack of perfectly classical clocks, quantum mechanics really implies that pure states do evolve into mixed states. The question is: could the effect be fast enough to render the black hole information paradox effectively unobservable?...

    ...For astrophysical sized black holes, where MBH is of the order of the mass of the Sun, this indicates that the off diagonal elements are suppressed by the time of evaporation by 10-28, rendering the information puzzle effectively unobservable. What happens for smaller black holes? The effect is smaller. So can one claim that there still is an information puzzle for smaller black holes? This is debatable. After all, we do expect decoherence from other environmental effects to be considerably larger than the one we are considering here. If one makes the holes too small, then none of these calculations apply, and in fact the traditional Hawking evaporation is not an adequate description, since one has to take into account full quantum gravity effects. So we can say that the paradox is effectively eliminated for large black holes and we cannot say for sure for smaller ones using this simplified analysis. ..."

    Fundamental decoherence from quantum gravity: a pedagogical review
    Rodolfo Gambini, Rafael Porto, Jorge Pullin
    9 pages, dedicated to Octavio Obregon on his 60th birthday
    "We present a discussion of the fundamental loss of unitarity that appears in quantum mechanics due to the use of a physical apparatus to measure time. This induces a decoherence effect that is independent of any interaction with the environment and appears in addition to any usual environmental decoherence. The discussion is framed self consistently and aimed to general physicists. We derive the modified Schroedinger equation that arises in quantum mechanics with real clocks and discuss the theoretical and potential experimental implications of this process of decoherence."

    Last edited: Apr 27, 2006
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