Comments on: Multiverses and Super-Turtles http://www.ianhuston.net/2007/05/multiverses-and-super-turtles Compactified Realisations Thu, 02 Apr 2009 07:06:53 +0000 hourly 1 By: The End of Cosmology | Compactified Realisations http://www.ianhuston.net/2007/05/multiverses-and-super-turtles/comment-page-1#comment-7 The End of Cosmology | Compactified Realisations Wed, 06 Jun 2007 12:00:11 +0000 http://www.ianhuston.net/2007/05/multiverses-and-super-turtles/#comment-7 [...] in the same sort of trivial pondering due to lack of evidence. For example any evidences of multiverses or the like which might once have been observable could now be trapped forever beyond even our future [...] [...] in the same sort of trivial pondering due to lack of evidence. For example any evidences of multiverses or the like which might once have been observable could now be trapped forever beyond even our future [...]

]]> By: Ian http://www.ianhuston.net/2007/05/multiverses-and-super-turtles/comment-page-1#comment-5 Ian Tue, 08 May 2007 10:45:44 +0000 http://www.ianhuston.net/2007/05/multiverses-and-super-turtles/#comment-5 Hi Neil, thanks for stopping by. While it certainly would be nice for 3 large dimensions to be in some way natural, the theoretical community currently considers more dimensions to be possible if not probable. There have been some experiments which rule out certain extra dimensional scenarios, including the basic one extra large dimension. The Eot-Wash group in particular has been <a href="http://arxiv.org/abs/hep-ph/0611184" rel="nofollow">improving the constraints</a> on any extra dimensions (<a href="http://cosmicvariance.com/2007/01/13/short-distances-newton-still-the-man/" rel="nofollow">discussion at Cosmic Variance</a>). Maybe N≠3 will someday be ruled out by experiment, and it will be back to the drawing board. Hi Neil, thanks for stopping by.
While it certainly would be nice for 3 large dimensions to be in some way natural, the theoretical community currently considers more dimensions to be possible if not probable.
There have been some experiments which rule out certain extra dimensional scenarios, including the basic one extra large dimension. The Eot-Wash group in particular has been improving the constraints on any extra dimensions (discussion at Cosmic Variance). Maybe N≠3 will someday be ruled out by experiment, and it will be back to the drawing board.

]]> By: Neil Bates http://www.ianhuston.net/2007/05/multiverses-and-super-turtles/comment-page-1#comment-3 Neil Bates Sat, 05 May 2007 20:01:16 +0000 http://www.ianhuston.net/2007/05/multiverses-and-super-turtles/#comment-3 One of the questions associated with string theory/extra dimensions type approaches to universe origination is, why are there three large space dimensions: N =3? Normally, that is thought to derive from some process selection outcome, like Brandenberger and Vafa talking about number of dimensions constraining expansion of dimensions to larger size. Then there are Lisa Randall et al. with large hidden dimensions etc. Well, those approaches assume that spaces of other than three large dimensions are inherently self-consistent/non-contradictory (could exist without violating basic laws like conservation of energy, even if weird about signal transmission, atomic physics, bad for stable orbits and for organisms, etc.) There have been attempts in the past to find actual inconsistencies when N ≠ 3, which apparently aren’t convincing enough as actual prohibitions - however, it is now appreciated that 3-D space is indeed “special” in many ways. However, I have reviewed some apparently novel reasons for there being genuine self-contradiction where N ≠ 3 at linking blog, for anyone interested. If that pans out, then having N = 3 is not ultimately the result of a selection process that at least could have in principle turned out differently (and coincidentally, such processes could also still make N = 3 more likely, but they’d be “moot.”) It would instead be forced by a sort of logical constraint, if we think that the universe somehow tries to keep some basic principles going. BTW, it is a matter of taste as to whether outside explanations of our universe's features are "pleasing" or not. One of the questions associated with string theory/extra dimensions type approaches to universe origination is, why are there three large space dimensions: N =3? Normally, that is thought to derive from some process selection outcome, like Brandenberger and Vafa talking about number of dimensions constraining expansion of dimensions to larger size. Then there are Lisa Randall et al. with large hidden dimensions etc. Well, those approaches assume that spaces of other than three large dimensions are inherently self-consistent/non-contradictory (could exist without violating basic laws like conservation of energy, even if weird about signal transmission, atomic physics, bad for stable orbits and for organisms, etc.) There have been attempts in the past to find actual inconsistencies when N ≠ 3, which apparently aren’t convincing enough as actual prohibitions – however, it is now appreciated that 3-D space is indeed “special” in many ways.

However, I have reviewed some apparently novel reasons for there being genuine self-contradiction where N ≠ 3 at linking blog, for anyone interested. If that pans out, then having N = 3 is not ultimately the result of a selection process that at least could have in principle turned out differently (and coincidentally, such processes could also still make N = 3 more likely, but they’d be “moot.”) It would instead be forced by a sort of logical constraint, if we think that the universe somehow tries to keep some basic principles going.

BTW, it is a matter of taste as to whether outside explanations of our universe’s features are “pleasing” or not.

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