Monday, September 28, 2009

Collisions of universes

The arxiv blog took notice of an article about the possible existence ofo experimental evidence of the collision of universes. You can read it here.

For those people who has read the conventional cosmological sceneries, that is, a FRW type cosmology, slightly corrected by a very tiny cosmological constant and an early period of inflation the idea of many universes could sound to them very speculative. and probably the could immediately think that it is based on that "evil string theorists" inventions.

In these last dates my readings in theoretical physics have been mainly related to cosmology. I have learned that the most extended idea of the multiple universes is rooted in the "eternal inflation" and also by the alternative idea of "chaotic inflation". Those are inventions of cosmologists and not of string theorists, although the last ones have got the idea, merged it with ideas of Weinberg and the Bethe-Theitleboin mechanism and implemented it in stirng theory leading to the bousso-Polchinsky proposal, the KKLT realization of it and in last instance the whole odea of the landscape.

But, basically the idea of eternal inflation is independent of string theory. If one takes seriously the problem of the vacuum energy in QFT one is faced with the problem that this is of the order of the supersymmetry breaking (if one doesn't belive in supersymmetry one would have the planck energy). That energy would led to a very fast expansion of the universe when part of it is released by transition to a level with less energy. The whole thing is that that transition would not be simultaneous on all points. Then one would have an expanding universes coexisting with an stationary one. The expanding universes could, agian, suffer another phase transition to a less energetic vacuum, resulting in new expanding universe. and so on, in a nested proccess. This is, roughly speaking, the idea of "bubble nucleation" that I have mentioned sometimes in this blog without too many explanations.

Ideally that universes would be disconnected and couldn't collide. That paper on arxiv investigate the opposite possibility.

One consequence of eternal inflation is the possibility that there would be an infinite number of universes. Taking account of the fact that here are a limited number of configurations that results in the need that every event , and it's variants would happen an infinite of times. It is a variant, for practical purposes, of the Everet's "many worlds" interpretation of quantum mechanics.

Well, if in some way one could us that infinite worlds variants amazing things could happen. In fact some people propose seriously that quantum computers make basically that. They would be many copies of the same computer, but in different universes, every one doing an independent calculation. Some people even try to relate the quantum and the eternal inflation into a single mechanism.

All this is very CF like. I remember the film "the unique" by the martial arts star Jet Li. There the protagonist kills his copies in the other universes and recipes it's strength and knowledges.

If insome wya I could use that many worlds doubles I could read in detaillthis paper about a new proposal of unified theories, somewhat in the line of the everybody favourite surfer physicist. A superficial reading seems to suggest that the proposal is most satisfactory but I am skeptic about it.

Also I could read some other interesting papers in arxiv today, and advance with my own ideas faster. And I could write the article, in Spanish, about F-theory. In fact I am reading some further papers about F-theory and I'll wait a little bit before writing that entry.

Besides reading physics/maths I could dedicate more time to touch piano, to make some amateur composition of electronic music, to practice more hours in the week martial arts, and make also other sport activities. And I still would have time to read more CF books, go cinema, and etc, etc. But lacking that technology a most likely possibility would be to win some random game (euromillion or similar) and in that way I wouldn't have to waste time in "economic activities" (althought fortunately sometimes this overlap with my research/academic activities).

But even in the worst of cases I guess that I am going to have more time to dedicate to the blogs and think that there are a good bunch of interesting themes to write about.

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