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Good intro to "cyclash" universe by Steinhardt
There are a lot of cyclic theories of the universe----different ways a bounce could occur, or something like a bigbang occur repeatedly. Penrose just came up with a new one, as if there weren't enough already. Now Steinhardt is an outstanding scientist and an exceptionally good writer, but it is a misleading and pretentious of him to call his model THE Cyclic Theory of the Universe, or on other occasions call it THE Cyclic Universe. What about all the other cyclic models?
That said, we should still know about his (and Turok's) model and Steinhardt has a really good essay for beginners on it that presents both the stringy and the more recent NONstringy version, and which MOTIVATES the model and also strongly criticizes the fashionable scenarios of inflation. His model doesn't need inflation, and takes care of the same cosmic puzzles.
An earlier version of it was called "ekpyrotic". The gist is that two 3D manifolds repeatedly BUMP each other. And then they rebound off again, and while they are rebounding they each SPREAD OUT some. In a 3D sense as in usual expanding universe pictures. So after about a trillion years they have each expanded so much they look blank and empty and they fall together and BUMP again.
Even in the nonstringy version he calls the flexible clashing 3D continuums "branes" short for membranes. There is only one extra dimension to make the surround 4D so the 3D things can clash and rebound in it.
Well the essay is really good and what's interesting to me is the motivation and the strong criticism of inflation scenarios.
I found it at Paul Steinhardt's Princeton website.
http://wwwphy.princeton.edu/~steinh/
The URL tag for this particular essay is VAASREV.pdf
It is not on arxiv and seems only available in PDF here at his site
http://wwwphy.princeton.edu/~steinh/vaasrev.pdf
"Vaasrev.pdf" does sound a bit like Vaas, the science writer/editor, suggesting it's a review article written for Vaas book.
It's too pretentious to call this particular clash-type cyclic model "THE Cylic Universe" so I am privately calling it the CYCLASH universe.
It could be that both Inflation and Cyclash are wrong and that there are still other ways of solving to those puzzles (flatness, uniformity of temperature, absence of mag monopoles...)
I don't advocate Steinhardt's clash-type cosmology----even if it doesn't need string theory and only takes 4D space I still find it dubious. But I think as many of us as possible should read it because he's a bright creative scientist who writes well (and I think has a strong commitment to empiricism).
There are a lot of cyclic theories of the universe----different ways a bounce could occur, or something like a bigbang occur repeatedly. Penrose just came up with a new one, as if there weren't enough already. Now Steinhardt is an outstanding scientist and an exceptionally good writer, but it is a misleading and pretentious of him to call his model THE Cyclic Theory of the Universe, or on other occasions call it THE Cyclic Universe. What about all the other cyclic models?
That said, we should still know about his (and Turok's) model and Steinhardt has a really good essay for beginners on it that presents both the stringy and the more recent NONstringy version, and which MOTIVATES the model and also strongly criticizes the fashionable scenarios of inflation. His model doesn't need inflation, and takes care of the same cosmic puzzles.
An earlier version of it was called "ekpyrotic". The gist is that two 3D manifolds repeatedly BUMP each other. And then they rebound off again, and while they are rebounding they each SPREAD OUT some. In a 3D sense as in usual expanding universe pictures. So after about a trillion years they have each expanded so much they look blank and empty and they fall together and BUMP again.
Even in the nonstringy version he calls the flexible clashing 3D continuums "branes" short for membranes. There is only one extra dimension to make the surround 4D so the 3D things can clash and rebound in it.
Well the essay is really good and what's interesting to me is the motivation and the strong criticism of inflation scenarios.
I found it at Paul Steinhardt's Princeton website.
http://wwwphy.princeton.edu/~steinh/
The URL tag for this particular essay is VAASREV.pdf
It is not on arxiv and seems only available in PDF here at his site
http://wwwphy.princeton.edu/~steinh/vaasrev.pdf
"Vaasrev.pdf" does sound a bit like Vaas, the science writer/editor, suggesting it's a review article written for Vaas book.
It's too pretentious to call this particular clash-type cyclic model "THE Cylic Universe" so I am privately calling it the CYCLASH universe.
It could be that both Inflation and Cyclash are wrong and that there are still other ways of solving to those puzzles (flatness, uniformity of temperature, absence of mag monopoles...)
I don't advocate Steinhardt's clash-type cosmology----even if it doesn't need string theory and only takes 4D space I still find it dubious. But I think as many of us as possible should read it because he's a bright creative scientist who writes well (and I think has a strong commitment to empiricism).
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