From: Anders Sandberg <asa@nada.kth.se>

Date: Sat Jan 17 1998 - 02:25:34 PST

Date: Sat Jan 17 1998 - 02:25:34 PST

Forwarded from Mitch (isn't he on this list? If not, then I think we

should invite him).

From: Mitchell Porter <mitch@thehub.com.au>

Subject: baby universes and open universe

To: asa@nada.kth.se

Date: Sat, 17 Jan 1998 15:45:56 +1000 (EST)

I wonder if the concept of baby universes is cast into doubt by

evidence for a spatially infinite universe?

It's hard to see how a spatially infinite universe can be

produced by the straightforward version of "baby universe"

reproduction - i.e. a collapsing finite region pinches off and

becomes an expanding finite hypersphere - since a spatially

infinite universe has to start infinite in extent.

In a "minisuperspace" quantum cosmology model you could

probably describe tunneling from a closed finite space

to an infinite open one, but only by adopting a finite-dimensional

simplification. In practice, an infinite space has infinitely

many degrees of freedom, unlike a compact space (assuming

something like the Bekenstein bound). I can't think of a

physical way to model a transition from finite to infinite

complexity.

On the other hand, perhaps the universe is only "locally"

(on a scale of >10 billion light-years) hyperbolic. Think

of a saddle-point on a mountain range, which is a region

on the (finite) surface of the Earth which is locally

hyperbolic.

Incidentally, if space really were Euclidean-in-the-large, it

could still be finite, by having a torus (T^3) topology.

I'd be interested to hear polymath's thoughts on all this;

feel free to forward this message there.

-mitch

http://www.thehub.com.au/~mitch

-- ----------------------------------------------------------------------- Anders Sandberg Towards Ascension! asa@nada.kth.se http://www.nada.kth.se/~asa/ GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !yReceived on Sat Jan 17 10:27:14 1998

*
This archive was generated by hypermail 2.1.8
: Tue Mar 07 2006 - 14:45:29 PST
*