Sunday, April 25, 2004

I really like this picture of a forest dragon that Allison took in Australia.

So, getting back to the Lee Smolin visit. OK, he builds on the idea that collapsing black holes could have Bojowald bounces through the singularity, thus seeding baby universe big bangs, furthermore if the fundamental constants change slightly at each bounce, then those universes that have conditions best suited to produce more black holes will dominate the counting, and you would expect to find yourself in a universe with physical constants at least close to a local maximum for producing as many black holes as possible. Indeed it appears we do - one indicater is the masses of neutron stars - the lower the upper bound the better, and all observed so far do have the low value of 1.4 solar masses. Also the nuclear chemistry in stars leads to heavy element production in large stars, which is good for both life and black hole production...

That said, Lee didn't really push his theory very hard - because the fine details aren't there yet at all. For instance, in string theory the physics is determined by the geometry of the compactification of the higher dimensions. This geometry would melt at each bounce, so it's not clear in what manner it recrystallizes afterwards, and whether it would likely be similar to the previous compactification (good for evolutionary cosmology), or completely random (bad - and seems more likely...).

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