Re: Is the universe computable?

From: Wei Dai <weidai.domain.name.hidden>
Date: Mon, 12 Jan 2004 20:50:24 -0500

On Tue, Jan 06, 2004 at 05:32:05PM +0100, Georges Quenot wrote:
> Many other way of simulating the universe could be considered like
> for instance a 4D mesh (if we simplify by considering only general
> relativity; there is no reason for the approach not being possible in
> an even more general way) representing a universe taken as a whole
> in its spatio-temporal aspect. The mesh would be refined at each
> iteration. The relation between the time in the computer and the time
> in the universe would not be a synchrony but a refinement of the
> resolution of the time (and space) in the simulated universe as the
> time in the computer increases.
>
> Alternatively (though both views are not necessarily exclusive), one
> could use a variational formulation instead of a partial derivative
> formulation in order to describe/build the universe leading again to
> a construction in which the time in the computer is not related at
> all to the time in the simulated universe.

Do you have references for these two ideas? I'm wondering, suppose the
universe you're trying to simulate contains a computer that is running a
factoring algorithm on a large number, in order to cryptanalyze somebody's
RSA public key. How could you possibly simulate this universe without
starting from the beginning and working forward in time? Whatever
simulation method you use, if somebody was watching the simulation run,
they'd see the input to the factoring algorithm appear before the output,
right?
Received on Mon Jan 12 2004 - 20:52:57 PST