On 13 Jul 2013, at 21:06, meekerdb wrote:
On 7/13/2013 1:51 AM, Bruno Marchal wrote:
Irreversibility of first person experience can be recovered from
reversible computation.
That would be statistical irreversibility, i.e. reversal is
improbable but not impossible.
Why? Not necessarily. It can be 100% irreversible from the
machine's point of view.
Indeed some universal machine are reversible (billiard ball,
quantum computer, etc.).
But isn't there a distinction between reversible and irreversible
computations? Doesn't the UD do both of them?
Yes. The main difference is that irreversible computation needs
"energy" (can be virtual), and reversible does not. Erasing memory
is what cost energy in computation, but "erasing memory" can be
simulated by dissociation or discarding information. Quantum
computations are both Turing universal and reversible, like the SWE.
Yes, I know. But since you propose that a world is a kind of bundle
over threads of computations, it seems that having irreversible
computations in that thread would imply the world is irreversible.
Yet all the fundamental physics models are reversible.
That would mean that among the universal dovetailing in arithmetic,
the reversible computations win the "measure competition", or that the
first person plural emerging on that universal dovetailing is governed
by some Turing Universal group. The last case is encouraged by the
material "hypostases", but it is too early to decide. Having
irreversible computations in the base ontology does not necessarily
implies that the physical laws are irreversible, because the physical
itself is an emerging pattern from the first (plural) points of view,
which abstracts itself from the delays in the universal dovetailing.
Bruno
http://iridia.ulb.ac.be/~marchal/
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