Time travel-->fast algorithms-->Singularity??

From: Cole Kitchen (kitchenc@mindspring.com)
Date: Sun Oct 27 2002 - 23:49:34 MST

Computers with closed timelike curves can solve hard problems
Authors: Todd A. Brun (Institute for Advanced Study)
(nine-page paper)

"A computer which has access to a closed timelike curve, and can thereby
send the results of calculations into its own past, can exploit this to
solve difficult computational problems efficiently. I give a specific
demonstration of this for the problem of factoring large numbers, and argue
that a similar approach can solve NP-complete and PSPACE-complete problems.
I discuss the potential impact of quantum effects on this result."


(It might occur to the reader of the early part of the paper that the time
needed to solve a large factoring problem could exceed the lifetime of the
computer [or the universe!], so that the result would never be sent back.
Brun addresses this objection by devising a recursive algorithm that breaks
the problem into short chunks.)

P.S. For another take on the importance of fast algorithms to the
Singularity, see Charles Stross's story "Antibodies," available in his

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