Smolin: Anthropery is not science

[sol2]

Hi Sol, tho often perceptive you may have a misconception here. If you could get Witten and Motl and Smolin to sit down just to talk about the effect on String theory research
of Susskind invoking multiple universes and resorting to athropery

(not to quarrel about other issues or discuss the merits of Loop or anything else, but just to assess whether AP has had a good effect)

what do you think? I don't want to put words in their mouths, but I think you should realize that they might agree in condemning Susskind's line and the AP, or deploring it's taking String theory in an unscientific direction.

Witten has expressed disapproval of resorting to AP
Motl (who may tend to follow Witten's lead in some matters) has
strongly condemned AP
Incidentally Jeff (who may tend to follow Motl's lead on key issues, or have come to similar positions independently) is here in solidarity with Witten and Motl.
Incidentally BTW (tho small fry outsider to string) I am in agreement with these people----Susskind's noisy invocation of AP, which has damaged the perceived integrity of String research, is causing distraction and a waste of intellectual resources.
Smolin would agree I believe.

Your post seems to suggest (if I read your symbolic and ornamented language correctly---which can be both a challenge and a pleasure)
that you expect disagreement and see a possibility for debate.

Of course I can't speak definitely for Jeff or any of those others but I strongly suspect that if you could get Witten, Motl and Smolin to discuss just that one issue they would be in hearty agreement-----contrary to what you seem to expect.

Let's not manufacture disagreement where there is none, sol

Marcus,

I like to create some humour as well and it should be taken in that context.

Do you really think I think any of these guys as tuff? I am challenging the group(flower children) per say that it has all been said and done. Do you really think they could sit down and agree? I know what they choose to believe

I also am speaking to Lubos on his position with Penrose. Imagine those math minds:)

 

[Ontoplankton]

If you could get Witten and Motl and Smolin to sit down just to talk about the effect on String theory research
of Susskind invoking multiple universes and resorting to athropery

I don't think physicists should be going down the path of "you must not think or talk about that, because it would be harmful to our cause". I prefer if they just tell me what they think are the most likely possibilities for what reality is like, rather than worry about taboos. If people like Gross and Witten and Smolin think no anthropic explanation will be needed, that's great. If people like Susskind think string theory leads to an anthropic scenario, that's also great.

 

[jeff]

What started this whole thing was the astonishing discovery that, contrary to all previous thinking, our universe is undergoing accelerated expansion.

This can be considered in the framework of GR as indicating something like a de sitter cosmology. However, the moduli space of string vacua don't include spatially compact cosmologies (consistent with the basic holographic nature of any correct theory of quantum gravity, the only true observable is the S-matrix whose inputs and outputs lie at spatial infinity and there's no such thing in spatially compact cosmologies). There are then two ways to look at this.

One is that we have to somehow find a way of bringing de sitter into strings and it was this attitude that led to the current debate. Specifically, they looked for metastable (that is stable for long periods of time) de sitter spacetime among all vacua, not just string vacua, with the very justifiable belief that string theory would still have relevance in such situations. Unfortunately, they found many such vacua but with no closed mathematical-physical principle to choose among them. Hence the invocation of the anthropic principle. Of course, it's possible that there is a way to sneak de sitter into string theory, but we just don't yet know how.

The other way to look at it is that the accelerating expansion is due to something that we don't yet understand and doesn't require de sitter.

The question is then whether we understand strings well enough to settle for the anthropic principle, and the answer is clearly no. From this standpoint, it's premature to be worrying too much about the anthropic principle. More generally, our understanding of strings is so primitive that we can't honestly conclude that any of it's current problems are fatal. Striking oil often requires we drill mighty deep holes and we've got a whole lot more drilling to do before we can give up on what has proven to be such a rich and self-consistent well-spring of deep ideas that is still our only known genuine quantum theory of gravity.

 

[selfAdjoint]

This was a very informative contribution. Thanks Jeff. I had wondered why the multiple solutions probloem, which I remember being discussed several years ago, had suddenly become such a hot topic.

 

[setAI]

more lenny vs lee action!


http://www.edge.org/3rd_culture/smolin_susskind04/smolin_susskind.html

 

[marcus]

more lenny vs lee action!


http://www.edge.org/3rd_culture/smolin_susskind04/smolin_susskind.html

setAI thanks for posting this!
a big reason I (and I would guess others) come to PF is to
get links to new really interesting stuff.

Smolin said something new in the final letter section, that caught my attention.
He referred to what I think is an important paper of Gambini Porto Pullin
about how using a realistic clock (instead of a nonexistent ideal clock)
can resolve the black hole information paradox.
(information decoheres by itself before the hole evaporates)

the two final letters start 2/5 of the way down the page, printed side by side in parallel columns.

If you go down to the 2/3 mark of the page----a ways down in the
final letters----and look in Smolin's column you will see this paragraph:

---quote---
"A second point is that there is good reason to believe that in quantum gravity information accessible to local observers decoheres in any case, because of the lack of an ideal clock. In particle physics time is treated in an ideal manner and the clock is assumed to be outside of the quantum system studied. But when we apply quantum physics to the universe as a whole we cannot assume this: the clock must be part of the system studied. As pointed out independently by Milburn [e] and by Gambini, Porto and Pullin [f], this has consequences for the issue of loss of information. The reason is that quantum mechanical uncertainties come into the reading of the clock — so we cannot know exactly how much physical time is associated with the motion of the clock's hands. So if we ask what the quantum state is when the clock reads a certain time, there will be additional statistical uncertainties which grow with time. (In spite of this, energy and probability are both conserved.) But, as shown by Gambini, Porto and Pullin, even using the best possible clock, these uncertainties will dominate over any loss of information trapped in a black hole. This means that even if information is lost in black hole evaporation, no one could do an experiment with a real physical clock that could show it."
---endquote---

where you see footnote reference [f] that is to this neat paper.
It came out in June before the big fuss over Hawking GR17 talk in July.
In my view it probably made the hooraw about Hawking superfluous.
I am glad Smolin is recognizing and citing this work. Jorge Pullin
occasionally visits here at PF and also puts out Matters of Gravity newsletter. I should get a link or two

 

[sol2]

I read this first thing this morning when reading in sci.physics the link (Should of read Peter Woits, Not Even Wrong Blog. Sorry Peter.

What I took with me from that article is the perception that is embedded in the debate about black holes.

That raises the question of what exactly is a black hole? One of the deepest lessons that we have learned over the past decade is that there is no fundamental difference between elementary particles and black holes. As repeatedly emphasized by 't Hooft [10][11][12], black holes are the natural extension of the elementary particle spectrum. This is especially clear in string theory where black holes are simply highly excited string states. Does that mean that we should count every particle as a black hole?

Smolin's theory requires not only that black hole singularities bounce but that the parameters such as the cosmological constant suffer only very small changes at the bounce. This I find not credible for a number of reasons. The discretuum of string theory does indeed allow a very dense spectrum of cosmological constants but neighboring vacua on the landscape do not generally have close values of the vacuum energy. A valley is typically surrounded by high mountains, and neighboring valleys are not expected to have similar energies.

http://www.edge.org/3rd_culture/smolin_susskind04/smolin_susskind.html

The word Susskind uses as discretuum(in bold) in regards to strings is most troubling. Maybe someone can speak to that?


Can Consciousness be truly expressed in the geometrical design( this has yet to be discerned), although I have been working on it as you can tell in liminocentric structures.


This might be found different from Smolins, based on their diffrent views and the different in the choice of geometry? The SRian approach and revisions?

You cannot speak about the background dependence unless you are immersed in it? And of course this requires a different frame? See http://wc0.worldcrossing.com/WebX?14@84.f0BIcWLAyal.19@.1ddf4a5f/99 for consideration about those frames?

 

[Ontoplankton]

Now http://www.edge.org/discourse/anthropic.html#myhrvold weighs in with yet another confused piece on the anthropic principle. His definitions of the "weak anthropic principle" and "strong anthropic principle" are around the tenth completely different variant that I've seen.

He questions "what value there is in not being surprised", but isn't the whole point to have theories under which our observations are unsurprising -- isn't that what an explanation is?

 

[marcus]

another word for it

Tom Banks has just posted 0408260
the first lines of the introduction go:


"Introduction
The hypothesis of Cosmological SUSY Breaking[1] (CSB) correlates the gravitino mass, m_3/2 with the cosmological constant, according to the formula

$$F_G \sim m_{3/2}M_P \sim \Lambda^{1/4}M_P$$ . (1.1)

Lambda is viewed as a discrete, tunable parameter (perhaps determined in the real world by galactothropic considerations), and the limiting model with vanishing Lambda is assumed to preserve exact N = 1, d = 4 super-Poincare invariance and..."

then again on page 3 he goes:

"...This gives rise to a gravitino mass of order 10^-3 eV. The formula for the mass scales with the power of Lambda predicted in [2]. The value of w(0), which is a number of order 1, must be fine tuned to an accuracy
$$\inline{\frac{\Lambda^{1/2}}{M_P^2}}$$ in order to produce the correct value, Lambda, for the value of the effective potential at its minimum. Lambda is a fundamental input parameter in CSB, rather than a calculable low energy effective parameter, so this fine tuning is philosophically unexceptional. If one wishes, one can determine the correct value of this parameter in the real world, by applying the galactothropic principle of Weinberg[5], rather than simply fitting more recent cosmological data..."

Lot of stuff going down around Lambda these days. For Smolin it seems to be a kind of pre-stressed curvature in space and a fundamental constant that applies to LQG, mond, etc.
for Banks it seems to be the "gravitino" mass
Banks does seem to respect Smolin's point that what Weinberg did was NOT
an application of the anthopic principle because it derives constraints on the value of Lambda by theorizing about galaxy-formation.
Nothing said about multiple universes or conscious life or all that jazz.
Just that whatever it is Lambda couldn't be too big or it would blow galaxies apart before they could form. So you could estimate an upper bound on it, from existence of galaxies.
Smolin made that point in "Scientific Alternatives to the Anthropic Principle"
the paper that yanked Leonard Susskind's chain to a considerable degree.
So now, for whatever reason, Tom Banks has the consideration to
call Weinberg's reasoning galactothropic rather than anthropic.
Clearly an idea whose time has come

 

[Ontoplankton]

This is why people distinguish between the "weak anthropic principle" and the "strong anthropic principle". The weak anthropic principle says that since we exist (or: since galaxies exist), we should predict the value of the cosmological constant isn't too far from zero. Whether we should call this "anthropic" at all is a question of terminology; maybe we shouldn't, because we're reasoning from the existence of galaxies, not from the existence of humans.

So far, so good. But there also exists a strong anthropic principle. The strong anthropic principle says that the fact that a sufficiently low cosmological constant is necessary for the existence of observers explains that our universe is that way, e.g. because there is an ensemble of universes over which the cosmological constant varies, and the ones where it's too high don't contain any people. So if it's about explanations of the cosmological constant, you do have to talk about observers instead of galaxies; it makes no sense to say that we (a priori) have to observe a small cosmological constant because we have to observe galaxies, unless it's because galaxies are necessary to have observers. The existence of galaxies doesn't explain why we observe a small cosmological constant, just because we live in a universe with galaxies; saying this would be like saying that the existence of cows explains why there is gravity, because we observe cows, and for there to be cows, there has to be gravity.

It's very easy to get confused about these things, and I think it's happened to many people.

Also, in the debate at Edge, I see Susskind saying this:

In particular Weinberg's prediction that if the anthropic principle is true, then the cosmological constant should not be exactly zero, is very similar to the example I just invented.

So, as I understand it (though I haven't looked at what exactly Weinberg did), Weinberg didn't just predict the cosmological constant to be within certain bounds; he predicted it to be nonzero, and not extremely close to zero.