Niel Cornish and the 78 billion lightyears

[Martin]

Niel Cornish is an Australian who has a monkey for a pet

 

http://www.physics.montana.edu/faculty/cornish/

 

and he studied at Cambridge with StephenHawking and at Princeton

and is now in the physics department at Montana State U.

 

and he and co-authors have a paper in Phys Rev. Lett. 21 May 2004

saying that

whereas cosmologists generally allow the U might be infinite because it looks spatially flat

nevertheless there is enough uncertainty about the curvature that it might be just slightly positive

in which case the U would be finite but very very large

 

Cornish et al have determined that it could be no smaller than 78 billion LY (halfway round as I understand them)

 

they do this with a statistical measure they invented, applied to the bumps in the CMB that are seen by WMAP, that thing orbiting the sun at a lagrange point a million miles or so out from earth. WMAP is mapping the CMB with exquisite precision and so it is not too incredible that people like Cornish (ozzies with monkeys) can derive estimates for the smallest possible size of the universe.

 

Since this is a tourdeforce we should get the original article and look at it.

 

Here it is in arxiv

http://arxiv.org/abs/astro-ph/0310233

And it looks like the hardcopy version in PhysRevLett has been scanned and posted at Niel Cornish website (presumably by the monkey)

 

Here is the abstract:

"The first year data from the Wilkinson Microwave Anisotropy Probe are used to place stringent constraints on the topology of the Universe. We search for pairs of circles on the sky with similar temperature patterns along each circle. We restrict the search to back-to-back circle pairs, and to nearly back-to-back circle pairs, as this covers the majority of the topologies that one might hope to detect in a nearly flat universe. We do not find any matched circles with radius greater than 25 degrees. For a wide class of models, the non-detection rules out the possibility that we live in a universe with topology scale smaller than 24 Gpc."