Are congenial constants also holey ?

[marcus]

Are congenial constants also "holey"?

Crowell pointed to two very interesting papers by Jaffe et al and by Jenkins (MIT)

This is the long one, with a lot of interesting detail:
http://arxiv.org/abs/0809.1647
Quark Masses: an Environmental Impact Statement
This other one is more of a quick summary:
http://arxiv.org/abs/0906.0029
(A workshop paper Jenkins gave at Zakopane, Poland about the results.)

The general impression one gets is that Standard Model parameters are not, after all, very fine-tuned for conscious life to exist. A lot of variation (at least in quark masses, for instance) would still allow "us".

The question remains, are the parameters tuned to produce a lot of astrophysical black holes? Around 1993 Smolin pointed out that IF tracts of spacetime reproduce by black hole bounce during which slight variations in the SM constants can occur, THEN the population of tracts would be dominated by those whose SM constants are "holey" or conducive to reproduction. The typical array of SM constants would be at or near a local maximum for reproductive success. So that one would predict that no "small" change in the parameters would result in more abundance of holes.

But this is the sort of detailed analysis that Jaffe and Jenkins do in the 2008 paper! They study the effect of slight variations in SM parameters (namely quark masses.)
However the criterion they watch is whether the parameters are "congenial". They use "congenial" to mean conducive to complex life. They find that the quark masses we have are not especially congenial. A fine-tuner would have been able to play around quite a bit.

I wonder how the Jaffe Jenkins analysis would have gone if the criterion they were varying for had been "holey"---apparently so far Smolin's hypothesis has not been disproven. No one has yet been able to exhibit a small change in any SM parameter which would have resulted in more astrophysical black holes. So the conjecture stands. The most recent status report on this is here:
http://arxiv.org/abs/hep-th/0612185
The status of cosmological natural selection

It seems to me that with a little work someone might be able to falsify (disprove the CNS hypothesis). One of the main predictions derived from it so far is about the strange quark mass as reflected in the maximum mass a neutron star can have without collapsing to hole. The prediction is that one will never find a neutron star of mass > 1.6 solar, because that would mean the top quark mass was not finetuned to promote collapse. The whole thing is a bit IFFY, and it seems in need of some solid analytical work. (Stable elements like C, N, O help gas clouds radiate heat and thus facilitate collapse to form stars---many things we think of as anthrogenic are also simply star-genic or hole-genic. We aren't the only things that benefit from supernova explosions. Star-formation in general benefits. And so on. You can see that issues here need to be sorted out.

 

[marcus]

"The Status of CNS" paper mentions predictions (and already attempted refutations) on page 8.

I will omit one of the predictions because it depends on a form of the hypothesis that goes beyond astrophysical to include "primordial" black holes--too speculative for my taste, anyone interested can look it up

Two of the predictions discussed there, in case someone is interested, are as follows:

== quote page 8 http://arxiv.org/abs/hep-th/0612185 ==
...
...
3.2 Predictions

Three predictions have been published about cosmological natural selection[8, 9, 10, 2].
To my knowledge all of these so far hold up.

CNS implies a prediction that neutron stars are Kaon-condensate stars and that the upper mass limit for neutron stars is M_uml ≈ 1.6 M_solar [15]. This comes about because the strange quark mass can be varied to raise and lower M_uml without strongly affecting the processes that lead to massive star formation and supernovas. [8]

So far all the well measured neutron stars have masses between 1.3 and 1.45 solar masses. There is one dangerous case of a neutron star in which imprecise estimates give a range of masses which exceeds the prediction, but at less than one sigma[18].

...
...

Little early star formation. The explanation of the special tuning observation given by CNS could be wrong is if there are channels for massive star formation other than those presently observed, which do not require carbon chemistry[8]. But if this were the case they might operate at high z when the abundances of carbon and oxygen are much lower. In that case it might be possible to observe many more supernovas at high z. These so far have not been observed[19].
==endquote==

A key part of the argument about CNS predictions is the a point that someone here may be able to challenge. This is that carbon compounds play an important role in facilitating the condensation of gas clouds to form stars. When carbon is scarce it is hard for stars to form, and in particular it is hard for large stars to form (which may eventually go supernova and seed the surrounding cloud with heavier elements like carbon, in a feedback process.)

Thus one can argue that any small change in SM parameters that caused elements like carbon to be unstable and decay, or to not form by fusion at all, would have diminished the abundance of stars and consequently of black holes.

 

[MTd2]

So, the favored universes are those with as many black holes with the smallest masses as possible.

 

[marcus]

What are favored are arrays of SM parameters.

I prefer the form of the conjecture where it is astrophysical black holes. I suppose details of how many of what masses, on what schedule could largely be governed by chance, or by cosmological parameters/initial conditions.

All I can remember being conjectured as passed on from parent to child is SM parameters, so it's how those affect matter, other things being equal(?) random(?).

The main thing is can you think of a small change in some SM constant that would have made black holes incrementally more abundant?

That is pretty clear. The universe looks almost like it does today, but something is slightly different, and black holes slightly more abundant. How does that seem to you? Understandable? No big changes, because we are talking about a local max.

More does not necessarily mean they have to be less massive.

 

[bcrowell]

I'd be more interested in Smolin's ideas if I were aware of some theoretical reason, however flimsy, to believe that the formation of a black-hole singularity would lead to the creation of a baby universe.

 

[marcus]

Plenty of that---"however flimsy" as you say. John Archibald Wheeler (Feynman's thesis advisor at Princeton) respected. Wheeler introduced the idea, 1980s I think. Or earlier.

Various people have studied it analytically. Dah-wei Chiou, Kevin Vandersloot, Leonardo Modesto.

It goes along with the bounce cosmology idea, which is better-established. People run LQG models of cosmological collapse all the time and they mostly bounce.

It is easier to model a whole universe collapse, and the bounce result is rather robust.

This leads people, postdocs/junior faculty like Chiou, Vandersloot, Modesto to want to model a local (astrophysical) collapse. It is harder and they use various approximations and sometimes patch stuff together. Sometimes they get a good bounce 3D --> 3D. But in one paper I saw the black hole collapse gave something lame----Nariai I think. They were trying a non-isotropic black hole collapse model.

We have no reason to suppose that black hole collapse DOES re-expand "elsewhere", in the LQG context.
But any LQG bounce does initiate at least a brief inflation, and I guess as Alan Guth said the total energy of U might be zero, his "free lunch" comment. So it is just barely possible (within Lqg context). And if all you are asking for is FLIM, then sure!

The work in progress, I think, has to follow Rovelli 1003:3483 which is just beginning to apply the full theory (with spinfoam dynamics) to cosmology----they have to show bounce with the full degrees of freedom, the full LQG theory (not symmetry reduced or
minisuperspace). That effort basically began in March this year.

Or else it will have to follow Lewandowski http://arxiv.org/abs/1009.2445 which is also aiming at cosmology with the full theory, in a conservative canonical version of LQG, unlike Rovelli's.
Thread on the Lewandowski paper: https://www.physicsforums.com/showthread.php?t=429023

Naturally they will first try to see if they get the usual cosmological big bounce. And then they will try to re-do the work of Modesto Chiou, Vandersloot but with the full theory, maybe they will also get the same kind of thing.

My guess is at least 2 years before we know really what happens in the LQG context, at collapse singularities. And then that is still not knowing anything because tests have to be devised for LQG itself.

Maybe I can find some links, to augment what I can remember off the top of my head.

 

[bcrowell]

Very interesting -- thanks, Marcus!

One thing that bugs me about the baby universe stuff is that it's not clear to me what its empirical status would be. Say LQG becomes a highly successful theory that makes cool predictions that are verified by experiment, and LQG also predicts that b.h. singularities spawn baby universes. Furthermore, let's say we buy Smolin's argument that cosmological natural selection is a falsifiable theory, and we try our best to falsify it, but we fail. I'm still not really convinced that such claims about baby universes would have any solid empirical status. It's not enough that a theory risk falsification and survive unscathed. We also want an accumulation of positive evidence in favor of the theory's predictions -- and that just can't happen in the case of baby universes.

 

[marcus]

I found the paper where Vandersloot got a bad result. The black hole produced a NARIAI cripple universe out the back door!
Things don't always work. Really early stages.
http://arxiv.org/abs/0807.3042

EDIT: I found a paper where Dah-wei Chiou again got a bad result.
http://arxiv.org/abs/0807.0665
He found that the "baby universe" from the BH has less mass than the parent!
Cripes we can't have that. Very bad for the Smolin conjecture!

These people are not using the full LQG theory, but some radically reduced form. I consider it preliminary. Let's see what Leonardo Modesto says.

EDIT:
Modesto http://arxiv.org/abs/0811.2196
==quote page 5 around equation (26) ==
We now want underline the similarity between the equation of motion for p_c (t) and the Friedmann equation of loop quantum cosmology. We can write the differential equation for p_c(t) in the following form ...
... (equation 26)
From this equation is manifest that p_c bounces on the value a₀/4π. This is quite similar to the loop quantum cosmology bounce [16].
==endquote==

But still this is unsatisfactory, not robust, involving a simplified model. And it conflicts with what the others got, where things went awry! The others got baby universes with birth defects.

I need to look for more recent papers, hopefully with more senior co-author. It has been a while since i checked into this.

 

[marcus]

Very interesting -- thanks, Marcus!

One thing that bugs me about the baby universe stuff is that it's not clear to me what its empirical status would be. Say LQG becomes a highly successful theory that makes cool predictions that are verified by experiment, and LQG also predicts that b.h. singularities spawn baby universes. Furthermore, let's say we buy Smolin's argument that cosmological natural selection is a falsifiable theory, and we try our best to falsify it, but we fail. I'm still not really convinced that such claims about baby universes would have any solid empirical status. It's not enough that a theory risk falsification and survive unscathed. We also want an accumulation of positive evidence in favor of the theory's predictions -- and that just can't happen in the case of baby universes.

I am indebted to you for questioning and discussing. What I suspect is that Smolin's conjecture is out there on the table partly to offer a challenge.

"I dare you to find a small change in the SM parameters that would have made BH more abundant". It is just asking to be falsified by someone good in particle physics and stellar astrophysics.

It is also a challenge to the "Anthropic Landscape Multiverse" guys----"I challenge you to make your multiverse scenarios have some directly falsifiable prediction. Look it's possible, here's an example!"

The conjecture has an intellectual function, in other words. It fills a need.

Somebody should consider the possibility that the SM parameter are at a local maximum for SOME imaginable reproductive mechanism (natural selection = reproductive success) and maybe BH is not the right mechanism. So?

You look ahead and see a possible quandary, a terrible dilemma, but it might never happen. Let's cross that bridge when we get there. If we ever do.

I understand feeling queasy misgivings looking ahead if it ever came to that. You are perfectly right that it would be very very weird if:

A. LQG passed some tests by predicting features of the CMB, gained moderate cred.
B. Some Rovelli postdoc proves full LQG theory BH bounce (which might never happen)
C. Ten more years go by and people try and fail to show SM parameters are NOT at local max for BH abundance.

Yes I'm with you. that would be stressful. It would be very weird. Hee hee.

 

[marcus]

To sum up:
I did a kind of quick literature search in response to request for evidence of BH bounce "however flimsy" in the LQG theoretical context. It was in general unsatisfactory, with some papers circa 2008 where they got "bad" results. Something went wrong with the bounce. The universe that came out did not have the right number of dimensions, or enough mass, or enough ability to grow.
Or alternatively "good but weak" results--not general or robust enough to inspire confidence.

So my conclusion is that at least for now the BH bounce idea is languishing. But I don't want to draw snap conclusions. They still have to apply the full LQG theory to BH collapse. And applying full Lqg to cosmology is only just getting started http://arxiv.org/abs/1003.3483