Smolin guesses the DNA of physical law

[Fra]

I associate "the equivalence" of all the different theories as the equivalance of observers. Choosing the theory means choosing a real inside observe, and the evolution of law seems to then conicinde with the evolution of observers. The observers(structures) that come to populate the world, has with them a "theory" and thus there is almost one-2-one mapping with population biology and theories.

What I do not agree with though, but I am not sure if smolin thinks this or not ?? is that say I can find a transformation to transform between all observers. I don't think that's possible because that transformation would then be part of my microstructure.

This is the point where I am not sure what smolin thinks. Does anyone else understand this?

/Fredrik

 

[ccdantas]

I think that what Smolin argues is that there is not an absolute, final theory of everything, as much as in analogy with relativistic theories, in which there is not an absolute space or time. There would be a landscape of intrinsically equivalent theories, and the "invariant element" of those theories would be fixed by initial conditions in cosmology.

Smolin is trying to relativise the concept of "theory of everything", IMO. I'd say that this is a strong version of relativism applied to the physical laws themselves; I see here influence from the philosophy of Leibniz, Paul Feyerabend, and ideas from Mangabeira Unger on the problem of time.

 

[ccdantas]

For those who may not know Unger,

http://en.wikipedia.org/wiki/Roberto_Unger

He is extremely well-known in Brazil, and I should say that he's considered a highly controversial public figure here. Smolin and Unger have been collaborating in recent years in philosophical matters on the problem of time, and Smolin acknowledges him in his recent paper.

 

[MTd2]

I interpret that he argues that to any landscape of choices, there must be a selection dynamical principle, but then how is the selection principle selected from the landscape of "selection principles"? We are just moving from one "landscape" to another. And a clever selection principle makes the effective landscape smaller.

That´s what I thought until I read th3 paragraph closely, and remembering what he said in the introduction about several dualities in string theories and the likes, and also citing the universality of Turing Machines. I am not really sure he proposed a conjecture, it's too vague. It sounds more like a general program to find and prove dualities among wide classes of theories.

Smolin proposed a matrix model, as he did once, with a kind of compactification, in which several equivalent theories would be recovered in some kind of aproximation. String Theory for example. That's not much different in terms of what M-Theory tries to accomplish. Now, Lubos Motl worked a lot in a Matrix version of M-Theory, and Smolin, this time, not even tried to cited one of his works, or of his direct colaborators as he did in previous articles...

PS.: CCDantas, that´s a nice way to put it.

 

[Fra]

I think that what Smolin argues is that there is not an absolute, final theory of everything, as much as in analogy with relativistic theories, in which there is not an absolute space or time. There would be a landscape of intrinsically equivalent theories, and the "invariant element" of those theories would be fixed by initial conditions in cosmology.

Then a reformulation of my question would be, does smolin really think that there exists a universally invariant element - in the measureable sense so that all observers would measure this to be the same? And same here means the comparasion process would not revise anything. Or is this some hidden variable idea where we assume that there exists an objective invariant element, it's just that we don't know it?

or

is he simply noting a from his point of view plausible equivalence between questions?

This is like in GR, no frame of reference is more right than any other - it's relative. The choice of frame is arbitrary. What is not arbitrary is the transformation between any two frames. This is assumed objective (observer invariant).

Paradoxally, since GR is supposedly a "theory of relativity", the transformations between the frames are not relative. I find this to be a inconsistency at the level of reasoning because it distinguish between information and information. I personally fail to see the physical basis of this distinction. Why is some information relative, and some isn't.

I was hoping that Smoling was trying to find a solution of this, to thus find TRULY background independent theory. (because in the light of this reflection, classical GR isn't quite background indepedent in this generalised sense). The task would be howto retain some stability, when everything gets principally relaxed.

This is what I thought he meant, but wasn't sure. His matrix actions confuses me and
makes me wonder if he does what I think he does.

Comments?

/Fredrik

 

[Fra]

Paradoxally, since GR is supposedly a "theory of relativity", the transformations between the frames are not relative. I find this to be a inconsistency at the level of reasoning because it distinguish between information and information. I personally fail to see the physical basis of this distinction. Why is some information relative, and some isn't.

I mentioned this to illustrate the point, not to pick on GR. I don't think of classical GR as a information theory anyway, so it's not too surprising and nothing to waste time on. But I'd expect this issue to be taken care of in the full information theory (QG).

/Fredrik

 

[marcus]

Marcus, I read the paper, and it is not about finding the DNA of physical law...

He means that all theories that can model correctly the initial conditions, and forwards, for our universe are "gauge equivalent"(crudely speaking), or related in a way similar that a turing machine can emulate any other theory.

To put in other way, he is not quite making a falsifiable theory, rather that all falsifialbe theories are necesseraly related by a equivalence relation at mathematical level.

I am glad you read the paper! I think you give an excellent concise summary of the paper here, especially what I highlighted.

What I am talking about in this thread is how the ideas in this paper FIT IN to the context of the empirically testable conjecture indicated in the INTRODUCTION SECTION of the paper with its references [1], [5], and [6].

There Smolin motivates this particular paper and puts it in context of his other work.
It is a new piece of the puzzle which he has not introduced before. That's how I see it.

I think you correctly describe the paper, in isolation. And give a very perceptive summary. What interests me is how it fits in (to a program which is, as he says in the introduction, empirically testable and falsifiable.)

 

[marcus]

That´s what I thought until I read th3 paragraph closely, and remembering what he said in the introduction about several dualities in string theories and the likes, and also citing the universality of Turing Machines. I am not really sure he proposed a conjecture, it's too vague. It sounds more like a general program to find and prove dualities among wide classes of theories.
...

The way to understand it in context is to read the introduction carefully and look at the key references he gives in the introduction [1], [5], and [6]. Since people seem likely to overlook this, I guess I should copy them in.References
[1] L. Smolin, Life of the Cosmos Oxford University Press, New York and Weidenfeld
and Nicolson, London, 1997.
...

[5] L. Smolin, Did The Universe Evolve?, Class.Quant.Grav.9:173-192,1992;

The fate of black hole singularities and the parameters of the standard models of particle physics and cosmology, arXiv:gr-qc/9404011;

Using neutron stars and primordial black holes to test theories of quantum gravity, arXiv:astro-ph/9712189;

Cosmology as a Problem in Critical Phenomena, arXiv:gr-qc/9505022;

Experimental Signatures of Quantum Gravity, arXiv:gr-qc/9503027.

[6] L. Smolin, The status of cosmological natural selection , arXiv:hep-th/0612185;

Scientific alternatives to the anthropic principle, arXiv:hep-th/0407213, Contribution to ”Universe or Multiverse”, ed. by Bernard Carr et. al., ... published by Cambridge University

 

[marcus]

I was just watching a video lecture Smolin gave not too long after this paper was posted.
It was at a conference/workshop of observational astrophysicists whose observation programs are aimed at testing the constancy of physical constants. He got a lot of aggressive questioning, a sign the astrophysicists were excited. Pretty good video, fun to watch.

The video lecture is currently the third from the top on this list
http://pirsa.org/index.php?p=speaker&name=Lee_Smolin
This let's you choose from several video formats---and also if you prefer just looking at the slides and listening to audio (but then you miss some blackboard work.)

The title of the lecture is How to test multiverse theories.

I guess the overall idea, in generality, is that what you mean by a multiverse theory (MVT) is basically regional variation in the parameters of physical law.

And although the term multiverse has acquired a bad odor, it is all right to study MVTs if they are truly testable. Then what you are doing is not mere Anthropery, it's science in the classic Baconian sense.

 

[marcus]

To review what we've been talking about, initial conditions are what get thru from one region to the next, and determine physics in the offshoot region. Figuratively, the initial conditions for a new tract of space are the DNA of its physics.

http://arxiv.org/abs/0803.2926
Matrix universality of gauge field and gravitational dynamics
Lee Smolin
" If our universe is described by one of these theories then the question of the choice of the laws of physics is to a large extent subsumed in the problem of the choice of initial conditions in cosmology."

Here's a quote from Smolin's 0803 paper providing a contextual overview:

"It used to be widely believed that the search for the unification of the known interactions and particles within quantum theory would lead to a unique theory, knowledge of which would lead to explanations for the gauge and symmetry groups, representations and parameters of the standard model and predictions for future experiments. Instead, string theory, the most developed approach to such a unification, appears to lead to a vast landscape of equally consistent theories[1, 2], at least perturbatively, while non-perturbative approaches to quantum gravity also show few constraints on matter coupling[3].

There are roughly speaking two factors that may go into an explanation of why particular laws are selected from a landscape of possible laws: statistical considerations such as the Anthropic principle[4] and dynamical principles such as proposed in cosmological natural selection[5, 1]. There are several arguments, given in detail in [6], that lead to the conclusion that statistical considerations alone cannot yield predictions that are verifiable or falsifiable. The many recent attempts to achieve predictions from some version of statistical or anthropic considerations on the landscape have not contradicted this. This means that any approach to a landscape of theories that leads to verifiable or falsifiable predictions must be based on a dynamical mechanism for selection of the laws that apply to our universe.

Thus, a list of possible theories is not enough, there must be processes that allow the choice of laws to evolve as the universe does..."

Here is the paraphrase I gave earlier. Let me know in what way, if you think it is unfaithful to the ideas in the paper.

...When a baby universe (or region) buds off from a mother region and begins expanding, in what form does it inherit physical laws and its constitution of space time and matter? Wherein gradual random mutations occur as well. This is what Smolin means by initial conditions.

If the act of budding corresponds to the formation of a certain type of black hole in the mother region, then those versions of the law will dominate which are optimized for the production of that kind of black hole.

There is some helpful clarification of this line of thinking in the lecture referred to here:

I was just watching a video lecture Smolin gave not too long after this paper was posted. It was at a conference/workshop of observational astrophysicists...

The video lecture is currently the third from the top on this list
http://pirsa.org/index.php?p=speaker&name=Lee_Smolin
...

The title of the lecture is How to test multiverse theories.
...

 

[Fra]

I like a lot of Smolins way of phrasing the problems and his focuses and some of his remarks are well in line with my personal thinkings. In my perception his choice of focus is fairly suitable for treating the two problems of origin of the universe, and the origin of matter on the same footing. It all sounds very interesting and I'm curious to hear what he comes up with in the future.

I have difficulty in getting time to watch videos (reading papers is easier for me) but I'll try to watch that video and see if he says is somewhat in line with my own ideas of how the ponderings of evolving laws in "different universes" can be tested.

The most obvious entangled key question I would raise (that I don't yet know if Smolin have an answer to? all that seems clear is that he has poses the question) in this context is if Smolin thinks the distinction between what constitutes law, and what constitutes state (subject to change, as per the law) is constructible in an unambigous way, or if the answer depends on the choice of observer?

/Fredrik