Post-2004 work on cosmological natural selection?

[bcrowell]

I'm going to do a little popular-level talk for undergraduates (not necessarily science majors) on baby universes, cosmological natural selection, and Penrose's cyclical universe. The most recent substantive paper I have on CNS is this:

Smolin, "Cosmological natural selection as the explanation for the complexity of the universe," Physica A: Statistical Mechanics and its Applications Volume 340, Issue 4, 15 September 2004, Pages 705-713

Citations of this paper don't show any really new work: http://arxiv.org/cits/hep-th/0612185

Does anyone know of anything more recent that I should be reading?

Thanks in advance!

-Ben

[EDIT] Oops, the paper I'd meant to refer to was this one: Smolin, "The status of cosmological natural selection," 2006, http://arxiv.org/abs/hep-th/0612185

 

[marcus]

Smolin has a 2006 Status of CNS. Oh! I see you already found that one using "cits".

http://arxiv.org/abs/hep-th/0612185
The status of cosmological natural selection
Lee Smolin
25 pages
(Submitted on 18 Dec 2006)
"The problem of making predictions from theories that have landscapes of possible low energy parameters is reviewed. Conditions for such a theory to yield falsifiable predictions for doable experiments are given. It is shown that the hypothesis of cosmological natural selection satisfies these conditions, thus showing that it is possible to continue to do physics on a landscape without invoking the anthropic principle. In particular, this is true whether or not the ensemble of universes generated by black holes bouncing is a sub-ensemble of a larger ensemble that might be generated by a random process such as eternal inflation.
A recent criticism of cosmological natural selection made by Vilenkin in hep-th/0610051 is discussed. It is shown to rely on assumptions about both the infrared and ultraviolet behavior of quantum gravity that are very unlikely to be true."

I can't think of anything more recent. Maybe something will occur to me later.

 

[bcrowell]

Thanks, Marcus! I actually had meant to ask for anything more recent than the 2006 paper, but I cited the wrong one in my post.

 

[Chronos]

If there is anything new on CNS, it is well hidden on arxiv. I queried Smolin about CNS a couple years ago. Unsurprisingly, he was preoccupied with other projects and had not given much further thought to CNS at that time.

 

[bcrowell]

Having looked into the theory a little this evening, what really impresses me is that although it is clearly falsifiable in principle, it appears to be extremely difficult to falsify in practice. Finding a two-solar-mass neutron star would definitely do it. Other than that, everything seems to be mired in the horrible complexity and uncertainty of the mechanisms of star formation, which we basically know nothing about.

 

[Chronos]

EXO 0748-676 was a potential CNS buster at 1.8-2.1 solar masses. More recent measurements by Ozel constrain it to 1.55 +- .12 solar masses - http://arxiv.org/abs/1007.0647. Still a challenge to CNS but not quite as convincing. It's all about the EOS ...

 

[marcus]

Having looked into the theory a little this evening, what really impresses me is that although it is clearly falsifiable in principle, it appears to be extremely difficult to falsify in practice. Finding a two-solar-mass neutron star would definitely do it. Other than that, everything seems to be mired in the horrible complexity and uncertainty of the mechanisms of star formation, which we basically know nothing about.

Crowell, I like this summary very much! It is fair.

There may be ways of testing CNS that haven't been thought of yet. As more is learned about the mechanisms of star formation, and more early universe star formation is observed, ways of falsifying CNS may turn up. But at the present time there are only the 3 tests mentioned in the paper (one of which is the neutron star test Chronos is considering here.) This is not enough--I hope people will keep trying to find ways to falsify the conjecture.

Despite the scant testability, I like CNS for two reasons. It provides at least a partial answer to questions about why nature provides a rich periodic table of stable elements with e.g. carbon chemistry. Also to questions about why physical constants allow stars, including supernovae, to exist. We can't claim that CNS is right, but it can give some alternative to challenge the claims of necessity for "designer" and "give up it's just luck" multiple existence hypotheses.

1. "designer" idea: some people argue the necessity of physical constants having been consciously adjusted to make the world congenial to life, say because of carbon chemistry. CNS gives a tentative rebuttal: carbon compounds seem to facilitate star formation. (And a prediction that we will see lower rates of star formation in the early universe before the first generation of short-lived stars spread such heavier elements around.)

2. "dumb luck" idea: some people argue we must necessarily abandon the search for selective causes. They presume that all different worlds exist and our world just happens to be one where conditions are suitable for us. This means giving up looking for reasons that favor the physics we see. CNS provides a challenging counterexample to this: showing that we don't HAVE to give up. We can still use intellect to propose testable reasons why the constants of physics are what they are.

From my perspective the CNS conjecture can benefit us as a rebuttal and counterexample even if it is eventually falsified. It helps sustain the discipline of the empirical tradition, by challenging us to propose other testable reasons for how the world is, rather than putting it all on Luck or a Designer. If CNS were to be falsified, I would hope that some other selective cause idea would be proposed to take its place. We should have several!

EXO 0748-676 was a potential CNS buster at 1.8-2.1 solar masses. More recent measurements by Ozel constrain it to 1.55 +- .12 solar masses - http://arxiv.org/abs/1007.0647. Still a challenge to CNS but not quite as convincing. It's all about the EOS ...

I'm impressed that you spotted that, Chronos. Thanks. I'm curious how you keep track, did you do a search with keyword "EXO 0748-676" or what?