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cos-top@cosmo.torun.pl

January 2007

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2 discussions

1 - sad news (most already know); 2 - equalising of T^3 lengths
by Boud Roukema 29 Jan '07

29 Jan '07

hi cos-top, Probably most of us already know the sad news - Jesper Gundermann is no longer with us - since June 2006. Jeff has submitted an interesting article with Jesper as posthumous co-author: http://arxiv.org/abs/astro-ph/0611640 It's not much of a consolation. Jesper was a nice guy and did good work in cosmic topology. A year ago he (together with Jeff) responded with lightning fast rapidity regarding my attempt to understand the Poincare dodecahedral space, showing (if any more evidence were necessary) that he was someone who thought about the subject deeply: http://cosmo.torun.pl/pipermail/cos-top/2006-February/thread.html My other theme (more pleasant) in this email is that i'm wondering if people have any thoughts on this paper? http://arxiv.org/abs/astro-ph/0602159 In this paper (A&A in press), we show heuristically that contrary to what most of us (well, me anyway) believe(d) and have stated and told to others for many years, topology and dynamics of a nearly FLRW universe are *not* independent of one another. In other words, there is some dependence between them. It's a weak dependence, but there is some link there. And it's related to the difference between an idealised perfectly FLRW (homogeneous) universe and a real one containing perturbations represented statistically in an approximate way by a power spectrum. i was also surprised when we did the calculation and found the result that the effect tends to equalise the three lengths of a T^3 universe, whereas all the papers that used T^3 models assumed this simply because it's simple, without mentioning the fact that it might have a physical justification. For me the obvious question to follow is whether or not the lengths of a PDS universe would also tend to be equalised - by slightly unequal evolution of the scale factor - keeping them to an ideal equilibrium, and avoiding the PDS universe becoming slightly "oblate" or "prolate". Regards boud

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Re: 1 - sad news (most already know); 2 - equalising of T^3 lengths
by weeks＠geometrygames.org 29 Jan '07

29 Jan '07

Your message to Jeff Weeks has *not* been delivered. My old e-mail address (weeks(a)geometrygames.org) was once publicly available on the web, so as a result it gets lots of spam. To shake off the spam, I've stopped using that address. To contact me please go to the page http://www.geometrygames.org/contact.html Thanks, Jeff Weeks

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