Subject: Re: The Life of the Cosmos - Lee Smolin From: baez@math.ucr.edu (john baez) Date: 1998/03/28 Message-ID: <6fkldm$874@charity.ucr.edu> Newsgroups: sci.physics,rec.arts.sf.science,sci.astro In article <6f4pep$58n@camel20.mindspring.com>, Riboflavin wrote: >OK, this Smolin thread has been going on for a while now, but one thing I've >missed: why does he have this thing about maximizing black hole production? >It just seems very out of place, and gives the theory a feeling of having >been "buzzword enhanced" to me. So, why the black hole maximization bit? Perhaps you missed my summary of his theory, which explained why he expects black hole production to be maximized. Here it is again: Smolin's theory is based on 2 hypotheses. A. The formation of a black hole creates "baby universe," the final singularity of the black hole tunnelling right on through to the initial "big bang" singularity of the new universe thanks to quantum effects. While this must undoubtedly seem outre to anyone unfamiliar with the sort of thing theoretical physicists amuse themselves with these days, in a recent review article by John Preskill on the information loss paradox for black holes, he reluctantly concluded that this was the *most conservative* solution of that famous problem! Recall the problem: if a black hole evaporates its mass away via Hawking radiation, and that radiation is pure blackbody radiation, hence carries none of the information about the matter that originally formed the black hole, one does not have conservation of information, or more technically speaking, the time evolution is not unitary, since a pure state is evolving into a mixed state. Hawking's original solution to this problem was to bite the bullet and accept the nonunitarity, even though it goes against the basic principles of quantum theory. This appears in: 2) S. W. Hawking, Phys. Rev. D13, 191 (1976). The "baby universe" solution simply says that the matter seeds a baby universe and the information goes *there*. Many other solutions have been proposed; two recent review articles are 3) Do Black Holes Destroy Information? by J. Preskill, Caltech report CALT-68-1819, available as hep-th/9209058, Sept. 1992. 4) Black hole information, by Don Page, review lecture to be published in Proceedings of the 5th Canadian Conference on General Relativity and Relativistic Astrophysics, University of Waterloo, 13--15 May, 1993}, edited by R. B. Mann and R. G. McLenaghan (World Scientific, Singapore, 1994), now available in LaTeX form as hep-th/9305040. Personally, I am a complete agnostic about this problem, since it rests upon so many phenomena that are hypothesized but not yet observed, and since any solution would require a theory of quantum gravity. I am merely reporting the ideas of respected physicists! In any event, the second hypothesis is: B. Certain parameters of the baby universe are close to but different than those of the parent universe. The notion that certain physical facts that appear as "laws" are actually part of the state of the univese has in fact been rather respectable since the application of spontaneous symmetry breaking to the Weinberg-Salam model of electroweak interactions, part of the standard model. (Again, being my usual cautious self, I must note that a crucial piece of evidence for this model, the Higgs boson, has not yet been seen.) The notion of spontaneous symmetry breaking has become quite popular in particle physics and is a key component of all current theories, such as GUTs or string theory, that attempt to model the messy heap of observed particles and interactions by some pristinely symmetrical Lagrangian. The spontaneous symmetry breaking would be expected to have occured shortly after the big bang, when it got cool enough, much as a hot piece of iron will randomly settle upon some direction of magnetization as its temperature fall below the Curie temperature. One application of this notion to cosmology is already widely popular, namely, inflation. In fact, pursuing the analogy with magnetic domains, i.e. small regions with different directions of magnetization, cosmologists have spend a fair amount of energy thinking about "domain walls," "cosmic strings," monopoles and other defects that might occur as residues of this cooling-down process. So again, while the idea must seem wild to anyone who has not encountered it before, physicists these days are fairly comfortable with the idea that certain "fundamental constants" could have been other than they were. As for the constants of a baby universe being close to, but different than, those of the parent universe, there is as far as I know no suggested mechanism for this. This is perhaps the weakest link in Smolin's argument (though I haven't seen his book yet). But it is at least conceivable. Now, given these hypotheses a marvelous consequence ensues: Darwinian evolution! Those universes whose parameters are such that many black holes are formed will have many progeny, so the constants of physics can be expected to be "tuned" for the formation of many black holes. As Smolin emphasizes, while the hypotheses A and B may seem impossible to test directly at present, we do at least have a hope of testing this consequence. He has studied the marvelously intricate process of star formation in the galaxy and attempted to see whether altering the constants of physics appear "tuned" for maximizing black hole production, and he argues in his book that they do appear so tuned.