Vilenkin unconvincing: CNS concerns stellar collapse black holes

[marcus]

On reading Vilenkin's recent paper, I believe he fails to refute the CNS conjecture. This is for a very simple reason. When Smolin has discussed the conjecture he has made it clear that it concerns black holes formed by stellar collapse.

Vilenkin confuses the issue by attempting to switch attention to black holes putatively formed by quantum fluctuations. The abundance of such objects is not what the conjecture is about.

The CNS conjecture is that the fundamental dimensionless constants are at a local max for the production of black holes by stellar collapse. One of the motivations is that the constants are seen to provide for heavier elements such as carbon and oxygen which aid contracting clouds of gas to radiate away heat and promote condensation into stars. Another motivation is that the constants allow supernovae to occur, triggering star-formation.

From the start, in the earliest CNS papers back around 1994, the focus has been on optimality for star-formation and (stellar) gravitational collapse-to-hole. The conjecture is not about formation of holes by quantum fluctuation.

So the conjecture still stands, and is not affected by Vilenkin's paper. Either we are at a local max for black holes formed by stellar collapse, or we are not. The challenge, issued around 1994, is to show that we are not at a local max by pointing out a direction in which varying the constants would cause MORE BLACK HOLES TO FORM BY STELLAR COLLAPSE.

Villenkin's paper is quite orthogonal to this. Still, it raises some issues that might be fun to think about, so I will take some posts to do this and hope for some discussion---in case otherse are interested.

 

[marcus]

we do not yet have a tested quantum theory of spacetime geometry.
Several proposed theories in the general area of Loop/Spinfoam Quantum Gravity have begun to make contact with matter and with the low-energy Newtonian limit. And some tests are approaching in the near term. So one can expect some testable background independent non-string QG theories before very long. However!

Without an accepted background independent theory of QG, without a quantum geometry able to deal with highly curved dynamic geometry, talking about "quantum fluctuation black holes" seems very speculative.
There may be contraints on their occurrence which we don't know about.
It may simply not be worthwhile to talk about such things.

===================

the implied context of Smolin's CNS conjecture, as I understand it, is that the Universe is finite (spatially closed) as it WOULD BE if it arose from a black hole bounce.

That is consistent with the recent WMAP3 data, which suggest a nearly flat universe with possibly some positive curvature.

Such a universe could expand indefinitely but would contain finite matter and would produce, in its possibly infinite lifetime, only FINITELY MANY black holes by stellar or other material gravitational collapse.

Black hole (from collapse) abundance is already an intutive idea that one can work with, but eventually we may need some explicit definition. Total lifetime production, because we can assume it finite, is one way of defining a measure of (collapsed) black hole abundance.

I have some more to say, but perhaps others would like a word

 

[selfAdjoint]

Thanks for that pertinent analysis Marcus. You read Vilenkin so we don't have to!

 

[marcus]

Oh no! Everybody should read Vilenkin. It is only 4 pages!

actually it is very tricky and slippery.
he seems to engulf Smolin with infinities of quantum fluctuation black holes
so that whatever be the abundance of the USUAL kind, it doesn't matter, because of the infinite number of
those formed by quantum hiccup.

the fecundity of quantum fluctuations (according to Vilenkin) depends only on the cosmological constant Lamda.
The larger Lambda, the more quantum fluctuation holes!
Thus there is no control of other parameters of the standard model, no payoff for adjusting alpha, no reward for having a rich periodic table of elements. The only desideratum is to have a large Lambda.

The Smolin conjecture would appear to be wiped out. But one has to be careful: for one thing, Smolin is only interested in a local max. The conjecture is not about the set of all universes. the conjecture is not about whether we are mediocre or not
That kind of talk is for MOTIVATION----explaining why the conjecture might be interesting.

One could say that Vilenkin's paper is an (only partially effective) attack on the MOTIVATION for the conjecture, not on the conjecture itself.

there is a lot to say. I would welcome very much if anyone could think about the paper some and help out.

 

[marcus]

there is one key unsustantiated statement, which it would be great if someone wants to comment on. I find it completely unconvincing but maybe someone else can provide a different take.

===quote Vilenkin===

Even if one insists that universes can be created only in black holes resulting from stellar collapse, suitable stars will pop out as quantum fluctuations in de Sitter space at a nonzero rate (assuming that the radius of the star is much smaller than the de Sitter horizon). Quantum fluctuations generally get stronger when Lambda is increased (since the effective de Sitter temperature gets higher). Thus, black hole production should increase with increase of Lambda. For the observed value of Lambda, the nucleation rate (3) is extremely small. And yet this process dominates over any black holes that have been or will be produced by stellar collapse, since the number of nucleated black holes is infinite. A slight increase in Lambda would enhance the nucleation rate, thus falsifying Smolin’s conjecture.
==endquote==

in the end Vilenkin's argument seems to depend on an infinite number of stars popping out of nothing.

I am skeptical that we understand quantum mechanics well enough to attach a quantitative meaning to this idea.

His argument seems to depend on stars popping into existence from nothing and remaining in existence unannihilated long enough to form a black hole and foster a daughter universe. And depend as well on this happening throughout the infinite life of the universe with sufficient regularity to produce a infinitude of ersatz stellar-collapse black holes.

I'm skeptical that we really know enough to support such an idea.
Rather, I think an argument can be made that this does NOT happen.
(try to sketch this in next post)

 

[Chronos]

Agreed, it looks like 100 pills to me, marcus

 

[Ontoplankton]

Is there any reason to think stellar collapse black holes spawn new universes, but other black holes do not? To judge CNS, we have to judge the claims logically implied by the theory, not the claims made by the person Lee Smolin. The theory implies the parameters of the universe are optimized for spawning more universes.

 

[selfAdjoint]

Don't post the same text on two different threads. To answer you, yes, there is reason to think there's a difference. Not because it's Smolin saying it, but because the model was specified in a particular way, and Vilenkin's proposed refutation addresses a different model he made up. The classical straw man strategy.

 

[Ontoplankton]

Don't post the same text on two different threads.

Not sure if it's me you're addressing, but I did no such thing.

To answer you, yes, there is reason to think there's a difference.

Well, what is it? What's the relevant difference between stellar and quantum-fluctuation black holes that should cause us to believe that quantum-fluctuation black holes do not spawn random universes even if stellar black holes do? I'm not saying there isn't such a reason -- I'd just like to know.