Smolin guesses the DNA of physical law

[marcus]

In a new paper, Smolin sketches a mechanism by which the laws of physics can be selected naturally and thus evolve.

He outlines a universal or "meta" law, from which many possible versions of physical law can emerge depending on the start-up----depending on what happens as a new region of space time and matter is initiated (possibly by budding from a prior region.)

The conjectured universal law is general enough that regions with different dimensionality, different spacetime geometry, and differently behaving matter can emerge, depending on initial conditions.


http://arxiv.org/abs/0803.2926
Matrix universality of gauge field and gravitational dynamics
Lee Smolin
21 pages,
(Submitted on 20 Mar 2008)

"A simple cubic matrix model is presented, which has truncations that, it is argued, lead at the classical level to a variety of theories of gauge fields and gravity. These include Yang-Mills theories and background independent theories of connections. The latter includes Chern-Simons theory in d=3, and BF theory and general relativity in d=4. General relativity coupled to Yang-mills theory for any SU(N) may also arise from quantum corrections.
On the basis of these results we conjecture that there are large universality classes of cut-off gauge and gravity theories, connected by transformations that mix up local and spacetime symmetries. 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."

 

[marcus]

Arivero informs us that Lubos Motl attacked this paper shortly after it appeared.

 

[marcus]

"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. Thus it appears that to do physics on the landscape we require a meta-theory that governs how theories evolve in time."

 

[shalayka]

So, a true unified theory should transcend and encompass all changes of all kinds within the universe (ex: the dynamics of dynamics of ... etc)?

I must be missing something, because this sounds like a reiteration of what physics has stood for since its discovery.

 

[MathematicalPhysicist]

Arivero informs us that Lubos Motl attacked this paper shortly after it appeared.

I hope there are no casualties from the attack. (-:

 

[Fra]

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. Thus it appears that to do physics on the landscape we require a meta-theory that governs how theories evolve in time

This sounds fairly sound IMHO, except I don't know what he means with "meta-theory". That sounds a little suspect. But maybe he means that at some point the degree of speculation implied to selecting randomly a meta-theory, is insignificant, and thus the arbitration is not an issue, then I think it sounds plausible.

I like the sound of this but the way I imagine the evolution of laws, even the meta laws governing this evolution would evolve. This is IMO the true spirit of "background independence", becuase it has become clear that there are different degrees of background dependence. Laws fixed as a sort of abstract background (not necessarily a background SPACE), does not comply to my idea of background independence.

The problem seems to be that even if you consider the laws to evolve from a "space of law", if THESE rules of evolution are again fixed be commit the same mistake again. When is this going to end? Here I think that this entire view, is put relative to an observer, the constrains of the observer puts an natural limit to this. Whatever landspace we come up with, it's constrained by the observer. The landspace is only in the microstructure of hte observer. The point is that at some point the questions we ask aren't distinguishable, and hence that becomes the regularisation.

The models we've seen so far always tend to be iterative, and the iteration itself seems to lack physical interpretation. It's seems to be an artifact. Maybe if we could transform our modelling so that hte models expansion = learning, conicindes with the physical time evolution? THIS is what I personally think is a good lead. This will also resolve the issue of the arrow of time and it may explain the relative visibiltiy of the arrow of time in different views.

/Fredrik

 

[Fra]

I don't know what Smolin thinks but since I appreciate the spirit this is some reflections of mine...

So, a true unified theory should transcend and encompass all changes of all kinds within the universe (ex: the dynamics of dynamics of ... etc)?

The way you describe it, one would suspect that a theory can encompasses all possible changes of all kinds, would be a massive super theory -> landscape problems. I think that is smolin's point - it isn't a good idea.

That's also very unphysical since the very theory here must live inside a real observer, or a group of observers. Anything else doesn't describe anything useful IMHO.

Which means that the problems becomes that of optimising the theory and the observer for fitness in a givne unknown environment. The complexity of the theory is bounded. Yes, a complex massive theory can potentiallt be better but it also requires a more complex observer. This might suggest that the laws of nature gets simpler as the observers do, and it also means that all posable questions get bounded.

I think this would be a radical rethinking and takes as yet one level away from realism, more so than ordinary QM did. I wouldn't rule out smolings thinking. I'm curious to see what he comes up with.

/Fredrik

 

[Fra]

So, a true unified theory

I think of a "true unified theory" as beeing alive. IE. it's itself a dynamical thing.

I think the idea of a static unified theory, as some kind of objective truth is never going to be found.

/Fredrik

 

[Fra]

Arivero informs us that Lubos Motl attacked this paper shortly after it appeared.

Has Smolin ever written the same type of personal stuff about Lubos, so that this qualifies as defense?

Otherwise I'd think anyone is doing himself a disfavour by these types to writings. Seriously, who is impressed by someone pointing out how stupid someone else is, without showing the slightest sign of doubt in his own position? I thought Smolin is trying to find new ways, and doing so taking a few steps back seems relevant.

Nevertheless, these blogs are entertaining. Maybe the entertainment industry is the future of physics :)

/Fredrik

 

[arivero]

Arivero informs us that Lubos Motl attacked this paper shortly after it appeared.

Well, Perimeter is an early obsesion of Motl

http://groups.google.es/group/sci.physics.research/browse_frm/thread/106a09eeec58c533?tvc=1

but this concrete rant is

http://motls.blogspot.com/2008/03/crackpot-world-matrix-universality.html

 

[CarlB]

I found the Smolin article by reading Lubos's blog. What I liked about the article was the suggestion of using quadratic equations. As it turns out, this fits in well with the density matrix stuff I do.

Let (I,T) be the (weak hypercharge, weak isospin) quantum numbers of the elementary fermions. Actually this works for the rest of the elementary particles as well, but my primary interest is in the fermions. This is a collection of points on the plane:

$$\begin{array}{rccclc} (& I &,& T&)&\\ \hline (& -1&,& 0&)& e_R\\ (&-2/3&,&0&)& \bar{u_L}\\ (&-1/2&,&-1/2&)& e_L\\ (&-1/2&,&+1/2&)& v_L\\ (&-1/3&,&0&)& d_R\\ (&-1/6&,&-1/2&)& \bar{u_R}\\ (&-1/6&,&+1/2&)& \bar{d_R}\\ (& 0&,& 0&)& v_R\\ (& 0&,& 0&)& \bar{v_L}\\ (&1/6&,&-1/2&)& d_L\\ (&1/6&,&+1/2&)& u_L\\ (&1/3&,& 0&)& \bar{d_L}\\ (&1/2&,&-1/2&)& \bar{v_R}\\ (&1/2&,&+1/2&)& \bar{e_R}\\ (&2/3&,& 0&)& u_R\\ (& 1&,& 0&)& \bar{e_L}\end{array}$$

Can these points be described as the solutions of some coupled quadratic equations? That is, can we write quadratic equations in I and T whose solutions are these? (And not a whole lot of other things we don't want.) The answer is yes!

Let J and K be complex numbers that we add to I and T. Then the above set of quantum numbers are the solutions of the following coupled quadratic equations:

$$k\left(\begin{array}{ccc}I&J&K\\K&I&J\\J&K&I\end{array}\right) = \left(\begin{array}{ccc}I&J&K\\K&I&J\\J&K&I\end{array}\right)^2 + \left(\begin{array}{ccc}T&T&T\\T&T&T\\T&T&T\end{array}\right)^2$$

$$k\left(\begin{array}{ccc}T&T&T\\T&T&T\\T&T&T\end{array}\right) = 2\left(\begin{array}{ccc}T&T&T\\T&T&T\\T&T&T\end{array}\right) \left(\begin{array}{ccc}I&J&K\\K&I&J\\J&K&I\end{array}\right)$$

where k=+1 or k=-1, which you might obtain by sticking in an absolute value on the left hand side, but that might get you a few more solutions. I wrote this up more completely (i.e. with derivation) in my blog:
http://carlbrannen.wordpress.com/2008/03/22/cubic-matrix-models-quarks-and-leptons/

And regarding Lubos, I don't care much how insane you are, how brutal you are to yourself or others. So long as you've found one beautiful fact about physics I will paper over those differences I can. And I think that Lubos has found that beautiful fact, in this paper (see the description of "tripled Pauli statistics"):
http://arxiv.org/abs/gr-qc/0212096

 

[marcus]

In a new paper, Smolin sketches a mechanism by which the laws of physics can be selected naturally and thus evolve...

" 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.
..

...
I must be missing something, because this sounds like a reiteration of what physics has stood for since its discovery.

There is something profoundly new here. It is aimed at injecting a DARWINIAN insight into physics.

To understand this you have not only to look at the recent paper but also see the earlier papers of Smolin that he refers to.
===========================================

What Smolin attempts to sketch out in this paper is a GENETIC CODE for physical law. 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.

 

[marcus]

The significance of the paper turns on the key issue of verifiability/falsifiability.

Smolin is saying that if we can come up with a UNIQUE unified theory of space time and matter with no vast landscape of different possibilities then FINE!

But if the only theoretical framework we can discover has millions of possibilities with no apparent explanation of why the laws/constants we see should be those particular ones, then we are back in Darwin's situation-----

he saw all these complex elegant lifeforms, species, that looked like they were designed nearly perfectly to fill their niches

-----and he came up with a mechanism for generating complex patterns that look like they were designed, but weren't.

Basically the mechanism was natural selection by reproductive success. Smolin is setting things up so he can apply the same idea to explain space time matter and natural law.

 

[Chronos]

I think a unique, building block version of reality is implausible.

 

[marcus]

I think a unique, building block version of reality is implausible.

but what is the relevance to Smolin's paper? In this approach he has no set building block
and he is allowing for complete non-uniqueness.

Ah! I see, you are agreeing with Smolin's approach! You must be declaring that alternatives to it are implausible. Or? Perhaps you could be more explicit?

 

[Fra]

I tend to see this as two issues

The first issue regards the general plausability of what I see as Smolin's sentiment Marcus refers to.

Basically the mechanism was natural selection by reproductive success. Smolin is setting things up so he can apply the same idea to explain space time matter and natural law.

If you think this is insane there is no second issue. But I can imagine that either you like it or you simply don't see how this can possibly be of any use to physics.

Personally I like it, and I can definitely see the beauty and the potential in this. If Smolin is way off chart with this, then so am I because I like his reasoning and I see similarities with my personal views.

So if you like it, the second issue is the next step - wether Smolins more specific suggestion is the right realisation of this? Here I am not sure I follow him. But I get the impression that he is "experimenting" with *possible* realisations of his basic idea? In this sense I can't anything but like it, even if I don't understand, or disagree on the second point. I suspect he is searching or maybe thinking out loud, motivated by a basic instinct in which general direction to go.

How many here sort of like his sentiment, granted that it's open for interpretation? Regardless of the realisation he tries to make is right? I'm curious.

/Fredrik

 

[marcus]

I like it, Fra.
And I predict this paper will be important.
See the prediction poll thread here
https://www.physicsforums.com/showthread.php?t=223644
and view the results---we have four forecasts so far.

You make a good observation. This kind of seeking is in a right direction, even if
one particular reproductive/evolutionary mechanism might be wrongly conjectured.

 

[shalayka]

Stephen Baxter has already posited that the universe evolves (in regard to the fine-tuning problem). Throwing in a formula or two is not a lot more rigorous.

Creationists believe that evolution is false. Evolutionists believe otherwise, obviously. Extrapolating this contrast from just carbon-based systems to all systems (including the all-encompassing one known as the universe) is not really a far stretch, intellectually anyway, especially when it's been done before. In fact, it would be somewhat unscientific to deny that the extrapolation beyond just organic chemistry is a necessity.

However, I'll assume that I am still missing the main point.

 

[Fra]

I'm not aware of Stephen Baxter and on first reading I don't follow Smolins logic that lead him to come up with the cubic action. But OTOH I'm not sure there is a profound one beyond the "pick a simple model and see what it gives", but that may be a way to create yourself some references. That's fine with me.

My personal expectation of realisation in line with Smolin's supposed sentiment is that the dynamics of the configuration is not separable from the dynamics of the degrees of freedom. IE. I expect a more elementary origin of "action" itself, that can be traced to the point where the concept of action becomes trivial. I suspect that the process that has selected the degrees of freedom also has with it an action measure. In a certain sense I'm not sure the "action formulation" is the cleanest way.

I'm trying to see the common denominators of rovelli, penrose and perhaps smolin. IMO they all at least partially share something, although on the surface it may differ. But I see no reason what these ideas shouldn't be able to converge.

/Fredrik

 

[Coin]

So, I have noticed Smolin proposing this "evolving universes" idea in several of his writings. Every time I have noticed Smolin mentioning this, he does not seem terribly enthusiastic about it-- his tone usually seems to be "this is an idea I keep thinking is interesting, and I don't really take it very seriously, but by the way I wish people would mention I had this idea in 1995 when they talk about the history of anthropic/multiverse reasoning" :)

But, what I am trying to figure out is whether this research is really in the same line as his previous "evolving universes" idea? Your OP makes the new paper here sound a lot like the old "evolving universes" stuff, with the difference being that he gives a specific way in which a universe could be "described" and that this would act like DNA. (I assume this to be the state space of the cubic "meta-theory" he proposes.) However reading the paper, although I don't think I'm qualified to understand all of it, it seems like his paper entirely talks about this cubic matrix model "meta-theory" and doesn't discuss the evolutionary idea at all. May I assume that the reason why you talk about this paper using the evolutionary language in your OP is because there is a connection you see between this "meta-theory" stuff and Smolin's older evolutionary-universe stuff?

Here's what I understand of where Smolin was up until now: Smolin's previous "evolution of the universe" idea involved proposing a theory where universes could spawn other universes, with each spawn creating a universe whose laws and constants were similar to, though somehow slightly different from, the parent universe. Smolin proposed this in part to explain how certain settings of fundamental constants are picked out given a random starting point-- since even if the "universal ancestor" universe had random physical laws, if you consider the totality of the tree of universes it will naturally be dominated by that branch of universes that happens to stumble upon that that general family of laws+constants which maximizes the number of child universes per parent. (For example if the way in which universes spawn other universes is that bubble universes occur within black holes, then we would expect our universe's laws to be somewhere close to a maxima for the probability of creating lots of individual black holes over the universe's lifetime.) This principle would allow one to identify some set of the phase space for possible universes as preferred, while retaining maybe slightly more productivity than one would be given by concepts like the "principle of mediocrity". Does that sound about right?

This new paper however seems to be describing a slightly different type of thing. This is the part of Smolin's new paper which seems to describe the idea most succinctly:

Third, there have been a number of suggestions that physical processes are computations[12].
However, the central result in computer science is the universality of computation, that
all computers are equivalent to a universal computer, a Turing machine. Any computer
can be simulated on any other computer, by writing an appropriate program. Might it be
that there is also a universality class of dynamical theories, any solution of one may be
represented by a solution of another by a precise choice of initial conditions?

...so, since I am a CS person this of course is the part that sticks out to me :) (And I find this a very interesting question to ask because I've seen a couple of visible attempts [say, Tegmark] to suggest computational models are sufficient to produce the laws of physics, but very few people doing this in a way that seriously asks the question of which computational model is most appropriate-- i.e., are vanilla turing machines enough?) But, this also seems to be asking a different question from his previous evolutionary-universe ideas. In fact he appears to allude to his evolutionary ideas at the top of page 3 (mentioning a multiverse with "a meta-theory that evolves in time") and then suggest this paper is trying to talk about something different.

In this paper, Smolin appears to be suggesting that is slightly confused to take some theory (say, the laws of our universe) and then ask "what is the meta-theory from which these laws emerged?". His argument instead is that it is reasonable to suggest that any dynamical theory of a certain expressive power qualifies as such a meta-theory, in the sense that properly formed initial conditions can cause that theory to "truncate" (I'm not entirely sure what this means) to the action of one of the other theories in the class. So for example maybe there is some set of initial conditions for string theory which, if you run string theory, the resulting dynamics are a perfect simulation of Twistor theory, and likewise there is some set of initial conditions for Twistor theory from which emerges the behavior of string theory (I picked these two randomly and I don't know if either would be in Smolin's universality class). Smolin then proposes a specific model, a "cubic matrix" model, to act as the examplar for theories in this universality class-- like a turing machine, in the sense that if you show some theory has initial conditions which produce the behavior of the cubic matrix model you have also shown that your theory can produce the behavior of any other theory in the universality class. Does that sound about accurate?

So if this is Smolin's point, then it seems like when he talks about one theory "evolving" from another within this framework he doesn't mean "evolve" in the Darwinian sense, he means "evolve" in the everyday-language sense of one thing turning into another. Twistor theory could "evolve" from string theory (or whatever) in the sense that twistor theory could emerge from some set of initial conditions in string theory.

Is the connection you are trying to draw in the OP that once we have defined an appropriate "universality class" theory, we can immediately turn around and also use that as a meta-theory for evolution of universes (since it may not be the theory of everything, but it can probably emulate it)? Do you have reason to believe Smolin intends to do this or are you just highlighting this as a possible application?

Or am I missing something altogether...?

Just trying to understand, thanks :)

One more thing, I think Smolin misspelled "Mendel" on page 3. Is there some way to inform him of this? :|

 

[Coin]

That aside:

Stephen Baxter has already posited that the universe evolves (in regard to the fine-tuning problem). Throwing in a formula or two is not a lot more rigorous.

It seems like adding formulas would be the definition of "more rigorous" :) Isn't Stephen Baxter a science-fiction author?

In fact, it would be somewhat unscientific to deny that the extrapolation beyond just organic chemistry is a necessity.

So... hm. It depends on what you mean by this. Evolution has already been "extrapolated" beyond organic chemistry, if you count computer science. Evolutionary algorithms are a subject of active study, and they work.

But this does not necessarily mean that evolution should be applied to any and all structures in nature. Evolution would seem to require a couple of things be at least approximately conceptually present (off the top of my head I'd say: items which reproduce, a way of encoding each item as information; a rule by which that encoding may change between "generations"; at least one selection rule) in order for something like evolution to happen. If you have or can define those things, it seems one might as well say that evolution-like processes are inevitable. If you don't have those required things, though, how can you have evolution?

As far as being "scientific" or "unscientific" goes (and assuming I understand the sense in which we are talking about "universes evolving" at all!), the primary problem I see with thinking about the "evolution" of universes is the same problem any multiverse theory has: there's only one. There is only one universe we know of, can observe, or have any evidence of. Biological evolution's first and strongest scientific justification is that we can see it, that evolution's outlines are blatantly clear in the fossil timeline of species and the geographic distribution of characteristics. Evolution was justified on those grounds (observation) for eighty years before we discovered the "DNA" of biology; Darwin didn't even have the insights of Mendel, his theory sprung just from going around on a boat looking at things and noting patterns between the different species he saw. Going the other way around and saying well, we can describe our universe in some kind of DNA-like sense and we can postulate an evolution-like chain of universes that would have produced this one; therefore we postulate those other universes in the postulated chain are actually real... perhaps the theory itself can be viewed as an "extrapolation" of the biological evolutionary theory, but it definitely isn't coming from the same kind of reasoning which lead us to embrace biological evolution.

(And of course I don't think we can fairly use the word "evolution" if we're just talking about a multiverse where different initial conditions produce different apparent laws of physics-- the "evolution" only really starts to come in if the universes engage in the "budding" marcus mentioned, and even then I might have some question as to whether this is really like biological evolution except in a metaphorical kind of sense.)

 

[marcus]

I'm not aware of Stephen Baxter ...

Stephen Baxter is a SciFi novelist. I doubt there's any real connection between Stephen Baxter and what we are talking about.

Oh, I see Coin already responded! Yeah. He is British and there is a Wikipedia article about him and his novels.

 

[marcus]

- the "evolution" only really starts to come in if the universes engage in the "budding" marcus mentioned, and even then I might have some question as to whether this is really like biological evolution except in a metaphorical kind of sense.)

Smolin's first published this idea in 1992, and from the start he made the point that it is empirically testable. (for example by measuring the masses of neutron stars).

I would not say that this kind of evolution is "really like" biological evolution.

But it is a kind of evolution. Those spacetimematter tracts which are good at reproducing will come to predominate. Natural selection by reproductive success, favoring certain characteristics. Even if those characteristics seem highly fine-tuned to us.

I think you say this, Coin, and indicate a complete understanding. So I am just repeating.
===================

I think the current paper is in some sense GENERAL PURPOSE. It proposes a line of investigation which could result in something that is useful in various different contexts.
I think it was probably motivated by the evolutionary conjecture.

It certainly would fill in a missing piece of the evolutionary model.

He presents it in broader generality, so it's applicability is not limited to the 1992 idea.

But in the introduction he maps out the context of the current proposal by giving some references to earlier work.
For instance:

[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]

Coin this is a nice concise summary of Smolin's evolutionary cosmology idea!

Here's what I understand of where Smolin was up until now: Smolin's previous "evolution of the universe" idea involved proposing a theory where universes could spawn other universes, with each spawn creating a universe whose laws and constants were similar to, though somehow slightly different from, the parent universe. Smolin proposed this in part to explain how certain settings of fundamental constants are picked out given a random starting point-- since even if the "universal ancestor" universe had random physical laws, if you consider the totality of the tree of universes it will naturally be dominated by that branch of universes that happens to stumble upon that that general family of laws+constants which maximizes the number of child universes per parent. (For example if the way in which universes spawn other universes is that bubble universes occur within black holes, then we would expect our universe's laws to be somewhere close to a maxima for the probability of creating lots of individual black holes over the universe's lifetime.) This principle would allow one to identify some set of the phase space for possible universes as preferred, while retaining maybe slightly more productivity than one would be given by concepts like the "principle of mediocrity". Does that sound about right?

Yes. It sounds perfectly right! The idea is highly vulnerable to falsification because all you have to do is think of a slight modification in the proportions of the standard model which you can argue would result in greater abundance of astrophysical black holes.

People have tried to do this and have so far failed. We seem to be at a local maximum, which is rather odd unless it has something to do with reproduction.

I was also delighted by the TURING MACHINE aspect of the paper, as you were.

This seems like just the right concept----or metaphor if you prefer.

The whole of particle physics should somehow be implicit and intrinsic to every point of spacetime----well Einstein pointed out that points of spacetime have no physical existence but you know what I mean----built into the fabric everywhere.

Getting back to the evolutionary reproductive idea, there has to be something that gets thru the black hole and contains the seeds of physics. It is the DNA, or better still it is the Turing machine instructions.

 

[MTd2]

This idea is not falsifiable at all. It´s the same as with landscape, you can't analyze other universes to see if it works like that. It's a statistics of 1, it won´t work. Apply all the criticism that Peter Woit on landscape to this case, and that's what I mean.

 

[marcus]

This idea is not falsifiable at all...

You don't understand what we are talking about. The whole point is that Smolin's conjecture as he stated it is highly vulnerable to falsification. If you don't understand this, and have not read his statement of the conjecture, then it probably is impossible to explain it to you.
============================

this has been discussed in several PF threads already. In case someone is just dropping in fresh to the discussion, the best way to catch up is to read stuff from references [5] and [6] of the present paper, like the article "A Scientific Alternative to the Anthropic Principle" (what he means is a falsifiable alternative to the Anthropic Principle).

Just very briefly, Smolin's conjecture, or challenge if you like, is that you can't think of a small change in the parameters of the standard models of matter and cosmology which would increase the abundance of astrophysical black holes.

If you or anybody can find a change that would, that falsifies the conjecture that the parameters are at an approximate local maximum for black hole abundance. People have tried and so far failed to think of any change that would refute the conjecture.

This is the conjecture that Smolin has repeatedly and explicitly stated in the stuff he has published. A related challenge is to find a neutron star with greater than 1.6 solar mass, because this would show that a specific one of the standard model parameters could be adjusted in such a way so as to make black holes more abundant.

By parameters what is meant is dimensionless parameters-----ratios and proportions between quantities---not basic dimensionful quantities like the speed of light.

Smolin's conjecture has been standing unrefuted for about 15 years. If one accepts the conjectured local optimality then one has a very curious coincidence to explain----which is a whole other issue.

 

[MTd2]

If that was an absolute maximum, I'd agree, but merely a local, that means the same situation of string landscape.

And, if you find a higher mass of a neutron star, that would just mean that the theory doesn't fit well. You don´t have other universes to analyze.

 

[Fra]

When I read your comments I think I may associate this "evolution" from a different angle but I'm not sure, that makes it more interesting.

People often talk about the large stuff. Different "cosmological level" models, black holes creating new universes, wavefunctions of the universe etc. Marcus uses wordings like "there has to be something that gets thru the black hole and contains the seeds of physics". And how can the laws of the universe yield viable dynamics, like the one we see?

I like to see how those who think like that reason and what they come up with. It's interesting becaues it seems like different to my preferred view.

I tend to think of these evolutionary models relative to a abstract inside observer. This is the small stuff and the local stuff. Ie. the evolution regards the observable(distinguisable) parts of the universe only. In this way, I see the evolution of the laws of physics to be described by the same logic than ordinary dynamics within a "stabilised universe". And the evolution of universes is thus indistinguishable from evolution of observers? And it also really almost make the transition from selection of physical laws to biological evolution unbroken. There should be no "missing link" or switch of logic.

Evolution would seem to require a couple of things be at least approximately conceptually present (off the top of my head I'd say: items which reproduce, a way of encoding each item as information; a rule by which that encoding may change between "generations"; at least one selection rule) in order for something like evolution to happen. If you have or can define those things, it seems one might as well say that evolution-like processes are inevitable.

I personally think the ultimate generalisation of "biological reproduction" in this context is to not make any distinction between ordinary dynamics and evolution. I don't think we need any sexual or asexual reproduction "cycles". I rather think of the selection as ongoing in parallell with normal dynamics.

It just seems like there may be a artifical decomposition between evolution of our references; laws of physics; spacetime; and dynamics on top of spacetime. An observer, unable to distinguish/resolve the dynamics of laws and spacetime will probably only distinguish the ordinary dynamics - this is most ordinary physics.

So in a way STABILITY is reproduction too, "reproduce into the future" or something like that. That sounds silly but this connects to what stability is? and what intertia is? So whatever isn't stable, will fall apart.

And time is perhaps the fact that everything keeps falling bkac and forth all the time and perhaps reproduction = survival in the sense of making sure you fall into the future without beeing ripped apart and survival is maintained by adjusting the internal state (adaption). The arrow of time is simply the estimated direction where you're falling/moving.

I don't know if this is related to smolins idea, but I think the problem of time, problem of choosing observables and this evolution/dynamics is different faces of the same problem. I can't separate this things myself. I think the solution to one, might help solve them all. The difficulty in defining a state, and the uncertainty associated with it is I think the same uncertainty that causes a drift, and this drift may be indistinguishable from local time evolution.

IMHO We might as well just take away the word time and just call it "local evolution".

Still, I can't see that smolin addresses this, at least not directly here. But I think all elaboration could provide hints.

/Fredrik

 

[Fra]

It just seems like there may be a artifical decomposition between evolution of our references; laws of physics; spacetime; and dynamics on top of spacetime. An observer, unable to distinguish/resolve the dynamics of laws and spacetime will probably only distinguish the ordinary dynamics - this is most ordinary physics.

IMHO We might as well just take away the word time and just call it "local evolution".

Shouldn't we this way, be able to assign an intertia even to spacetime itself (well we do already), but also to the laws of physics? The assumption that the laws of physics are fixed, corresponds to an estimated infinite inertia. Similarly the assumption of fixed spacetime geometry corresponds to an infinite intertia relative to the system under question. This is what one does when considering a light testparticle moving in a curved but fixed background.

The physical problem one can see here, regardless of previous discussions, is that no finite observer can realize an infinite inertia as far as I see. So there is a self-imposed constraint on the total confidence. When ignoring this we get the typical convergence problems and the renormalisation mess.

I didn't see this in smolins paper. Maybe I didn't see it, or it's not there? This seems to be the similar objection i had to rovellis relational QM. There still something missing there.

/Fredrik

 

[marcus]

If that was an absolute maximum, I'd agree,

If what were an absolute maximum? You would agree to what?

but merely a local, that means the same situation of string landscape.

how so?

And, if you find a higher mass of a neutron star, that would just mean that the theory doesn't fit well. You don´t have other universes to analyze.

So what? The conjecture does not involve "other universes". Please try to pay careful attention and get the basic message, MTd2. The conjecture which is falsifiable involves only the particles and fields of matter that we see, and only the region of spacetime that we occupy. This conjecture is empirically testable with available means, and is being tested as we speak. It is highly vulnerable to falsification. The conjecture is also important. It would be surprising and consequential if it were true. (More precisely, if it continues to pass observational tests.)

 

[MTd2]

You would agree to what?

I´d agree that it would falsifiable. That there would be millions of equivalent theories, so that whenever one theory would be proven wrong, you´d just find another one that would fit the parameters.

 

[marcus]

I´d agree that it would falsifiable. .

that's just it. WHAT would be falsifiable? What statement, what conjecture? Make an explicit statement that you think would be falsifiable and let us see if you have some clue as to what we are talking about.

That there would be millions of equivalent theories, so that whenever one theory would be proven wrong, you´d just find another one that would fit the parameters.

You sound as if you don't understand the basic proposition, MTd2. Smolin's primary conjecture does not involve "millions of theories". The falsifiable conjecture just involves one or two well-established theories----General Relativity and the Standard Particle Model.

The conjecture is that the parameters are optimal in the sense that you can't make a small change that would significantly increase black hole production.

This is the scientific hypothesis that has to be refuted or confirmed by evidence. The rest of it is working out possible explanations JUST IN CASE it turns out to be right. I think it is a good idea to be conceptually prepared for that, don't you.

I hope you are understanding better now. If you totally don't get what we are talking about, maybe you should just move on to another thread. But you could give it another try. If you do, please use plenty of words and say explicitly what propositions you are talking about. Please don't just say "it" and keep us guessing

 

[MTd2]

Marcus, I read the paper, and it is not about finding the DNA of physical law. It is rather arguing that you may find a landscape of equivalent theories, and which the right one depends on your point of view, whatever you ask. You can see 24 dimensions, 11 dimensions, 3, 4, string theory, quantum gravity,or whatever, depending on how you ask the question relevant or what physical circunstance you consider.

"If true, this hypothesis imply that the question of why particular laws and degrees of
freedomare observed in our universe is just part of the question of what chooses the initialconditions in cosmology. A universality of dynamics such as conjectured here would
mean that the question of what is the ”ultimate theory” may play as minor a role in
physics as the choice of physical computer plays in computer science."

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.

 

[Fra]

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.

On first impression one can argue that any selection principle is possible.

But I don't think each selection principle is equally probable, or equally fit. But again that "probability" is estimated by an inside observer. And if all players so to speak, ask themselves similar questions, there are chance that there will be emergent a common local reference.

I think to a given observer, wether there is a small landscape with a random selection, or a huge landscape with a clever narrowed down selection principle may be indistinguishable. I think it's just two views of the same thing.

So what I personally think is interesting is not if we can find he objective landscape, or the objective selection principle (because I don't think they exists) it's more how any given lanscape and selection principle are responding to feedback (interaction). And then understand how effective landscapes and selection principeles emerge locally. What more can we ask for?

/Fredrik

 

[Fra]

I particularly like the idea of transformations mixing internal and external symmetries and how this possibly can explain QM statistics, and emergent locality.

"Finally, we may remark that there are four independent lines of argument that matrix
models may underlie quantum mechanics as their ordinary statistical mechanics appears
to naturally describe give a non-local hidden variables theory which approximates quantum
mechanics"

I think there is something to this, although I wouldn't think of it as "hidden variables".

I think a better description is the relational view. To say that the relative views, are hidden from other views is IMO a misnomer because it suggest that the mictrostructure is known, but it's state is unknown. That's what doesn't make sense to me. I think that not even the microstructure is known, because I don't see how you can distinguish a structure that is totally random. Something isn't right.

I still don't get where his matrix model comes from. I would expect something that is basically a combinatorical model. Where you would get the action along, related to the discrete inverse probability. This way the action could simply be replaced by the subjective probability as dictated by local information, of change. And I think the trick that will give non-trivial dynamics as opposed to diffusion type stuff is the mixing of internal and external degrees of freedom. This makese sense if you think that all the local observer has is an IMAGE of the external degrees. So the mixing really isn't non-local. It's non-local in the sense of classical spacetime, but local in terms of information.

I think the new locality principle refers to local information, not localisation in spacetime.

This is why I tend to read out and like Smolins sentiment, but I am doubtufl that his realisation is right. But maybe I just don't understand it, which is effectively the same thing.

/Fredrik