[FoRK] Djinni vs. White Rabbit (for Turpin)

[Jeff Bone]

At some point in the past Turpin and I (and others) argued about 
whether the simulation argument and / or the multiple worlds 
interpretation of quantum mechanics implies an "every possible world" 
(EPW) interpretation, i.e. one in which highly improbable events, laws 
of physics, etc. obtain.

Stumbled across an interesting if tangential paper that has something 
to say about this.  First some terminology:  let's call events that are 
highly improbable "white rabbits" and universes in which such events 
happen frequently (or universes with entirely inscrutable laws of 
physics) "white rabbit worlds."  (This nomenclature is standard 
practice among some of the folks that think a lot about these things.)

Let's further adopt the term "djinni" or (to follow Gott's 
nomenclature) "jinni" to refer to closed time-like (causally cyclic) 
curves, and "jinn worlds" as worlds (n-dimensional "spacetime" slices 
of the higher-order spacetime, or rather n-m dimensional phase-space 
volumes where n is the total dimensionality of the phase space) that 
contain such causal cycles.  In order to explain what this means:  
these are causally consistent chains of events in which there is no 
ultimate cause, but rather a closed causal chain that traverses both 
forward and backward along the time dimension.  A peculiarity of this 
idea is that, in such a world, information "appears" without cause.  
For example a computer employing a closed time-like curve as a register 
can compute "hard" problems, but when one examines the execution 
history of the computer through time one finds that it never actually 
executes the computation!  Cf.:

	http://arxiv.org/pdf/gr-qc/0209061

Anyway, "jinni" are these little closed curves of causality in the 
presence of time travel that are consistent but defy common sense.

David G. Boulware of the University of Washington published this paper 
in PRD:

	http://arxiv.org/abs/hep-th/9207054

...in which he studies the behavior of quantum fields in spaces with 
closed time-like curves.  What he finds is that probabilities are not 
"conserved", i.e. not unitary, in such spaces.  That is, the Feynman 
sum-over-histories approach always yields precisely 1 --- except when 
space contains one or more jinn.  In such cases, there are quantum 
events that simply cannot occur.

So:  jinn defeat white rabbits.  If any world-line through the phase 
space is cyclic / allowed to self-intersect, the overall phase-space is 
constrained, presumably to those set of configurations which are of 
higher probability.  The very existence of such causal cycles may 
indeed be --- meta-paradoxically ;-) --- essential in stabilizing the 
overall structure of the phase space.  It would seem that these cycles 
act as a kind of strange attractor around which probable configurations 
(universes) coalesce.

Speculation:  it may be that through studying the impact of such closed 
time-like curves in various spacetimes that we ultimately reconcile 
Cramer's transactional interpretation (retarded waves moving forward in 
time, advance waves reaching back to "handshake" on each quantum event, 
producing a kind of causal contract) of QM with MWI --- and ultimately 
COMP.  Indeed, each retarded wave-advance wave pair *is* a jinni.  
Cramer doesn't just embrace jinn in his interpretation --- he bases the 
whole idea on their existence!  The implication ala Boulware is that if 
this is a real physical effect, then this provides a kind of 
probabilistic censorship that makes the world the predictable place 
that it is!  And --- connectionism --- it's rather ironic that Cramer's 
transactional hypothesis is based in part on some of Feynman's own 
speculation.  Feynman probably didn't realize the essential seemingly 
paradoxical consequences of pairing the histories approach with cyclic 
causality.

So that's all well and good for physics, but what about the more 
algorithmic cosmologies?  One school of thought regarding the COMP 
hypothesis is that it is easier to simulate all possible worlds than it 
is to simulate any subset of them.  (Cf. previously-discussed 
Champernowne machine / "everything" algorithm.)  But what if the 
dynamics of the simulation are such that these jinni exist as a priori 
structural parameters, "roots" if you will of the computation.  In such 
an environment, "every computable universe" is NOT every possible 
universe.

Curiouser and curiouser,

jb