Latest results from the LHC are casting doubt on the theory of supersymmetry

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Latest results from the LHC are casting doubt on the theory of supersymmetry
http://www.scientificamerican.com/article.cfm?id=beautiful-theory-collides
"I'm wouldn't say I'm concerned," says John Ellis, a theorist at CERN, Europe's particle-physics lab near Geneva, who has worked on supersymmetry for decades. He says that he will wait until the end of 2012--once more runs at high energy have been completed--before abandoning SUSY. Falkowski, a long-time critic of the theory, thinks that the lack of detections already suggest that SUSY is dead.
 

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More discussion from various points of view here
What it your point of view? Do you agree that LHC must find something soon or SUSY be in big trouble?
 
  • #4
marcus
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What is your point of view? ...
I'd be interested to know your point of view, Lievo. I don't know you very well, but I have a vague impression that you would be willing to make a prediction or forecast about this. Some people are good guessers, I judge by their "track record". You might be one of these good guessers regarding particle physics.

From what little I know of you (e.g. the Penrose circles thread) I would be inclined to listen carefully to what you have to say about this SUSY issue.

But as for my point of view? I try to be an objective observer, and usually avoid making predictions (unless it is part of a poll where a bunch of us are predicting.) My viewpoint has a little bit in common with a journalist's.

I like to gather information, provide links, organize and present information.

Also sometimes, by presenting countervailing information, I try to compensate for what I think are fads, commonplace fantasy, hype, and obvious bias. But a lot of the time I don't do that, I just let the fads/fantasies go on peacefully preoccupying the people who like to believe in them. Since it is mostly harmless.

I guess this is a long way of saying that I don't think by now the SUSY issue is so urgent or interesting. I'm not making guesses. I'm more interested in keeping track of other people's opinions on it.

Lievo, let me say what really interests me, rather than questions like at what energy, if ever, Susy might play a part etc etc...

My interest is symbolized by the early June conference at Zurich "Quantum Theory and Gravitation".
A new mathematical model of spacetime that departs from the conventional diff. manif.
and is coming from various directions (GFT, NCG, spinfoam...)
and has the goal of a new QFT that is not based on the diff. manifold.

That is the big news story for me, over a several year horizon. That the continuum is gauge. That it is being replaced by structure that is more combinatorial/algebraic.
That QFT and particle physics can be rebuilt on a new spacetime basis.
That the former cosmo singularity can be replaced by something more interesting that we understand better.
That geometry and matter might be mathematically represented by the same "thing", might be fundamentally the same--just different aspects of it.

These are a bunch of coherent trends I see in the research literature and in the conference/workshop behavior that I observe (from the sidelines).

Stringy math is manifolds within manifolds within manifolds, so it does not go in the direction that I am watching. Instead of getting away from the conventional continuum it plunges into Baroque elaboration of it. I respect it as mathematics but don't see much hope for it as physics.

If you want to get inside my head and see things from my point of view then the simple way is to examine two webpages. The Zako QG school now in progress. And the upcoming Zurich QT&G conference. I will get links to make it easy, if you want

http://www.conferences.itp.phys.ethz.ch/doku.php?id=qg11:start

http://www.fuw.edu.pl/~kostecki/school3/

or just google "3rd quantum gravity" and you will get the Zakopane 3rd quantum gravity school---check out the abstracts of the talks.

and google "quantum theory and gravitation" and you will get the Zurich QT&G conf.

See also this "Beyond" forum thread:
https://www.physicsforums.com/showthread.php?t=477379

This is what is happening AFAICS
 
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  • #5
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From what little I know of you (e.g. the Penrose circles thread) I would be inclined to listen carefully to what you have to say about this SUSY issue.
Well that's very kind and I appreciate the comment very much, but the fact is I really don't have anything to say about this issue. The points I made in the Penrose circles thread were purely because the question was in fact about modelisation and statistics, something I do understand. I don't understand SUSY enough to make any guess.

I try to be an objective observer
That why I thought your opinion would be interesting. :wink: There are many competent folks here, but it's not so easy to read someone both informed and objective on certain topics. For example I'm still trying to make my opinion about the string war... :yuck: ...and I'm afraid it can be such kind of topic.

I guess this is a long way of saying that I don't think by now the SUSY issue is so urgent or interesting. I'm not making guesses. I'm more interested in keeping track of other people's opinions on it.
From the track you keep, would you agree that the most common opinion is that not finding SUSY at LHC would not discard SUSY proper, but would discard the idea that SUSY can solve the hierarchy problem?

What is really unclear to me (and in fact that's my first question reworded) is whether SUSY is likely to be found soon, if SUSY applies to reality. Ellis seems to think it's a clear yes, and http://blogs.discovermagazine.com/cosmicvariance/2008/08/04/what-will-the-lhc-find/" [Broken] may be interpreted in the same way (he bets 60% to see SUSY, which means a high conditional probability to find SUSY at LHC if it exists in the first place). But I really don't know whether this is representative of what most phycisits believe.
Any cue from anyone wellcome. :smile:

Lievo, let me say what really interests me
Thanks, I'll took a close look (although a layman's one -I may ask a couple questions later ;-) ).
 
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  • #6
marcus
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What is really unclear to me (and in fact that's my first question reworded) is whether SUSY is likely to be found soon, if SUSY applies to reality. Ellis seems to think it's a clear yes, and http://blogs.discovermagazine.com/cosmicvariance/2008/08/04/what-will-the-lhc-find/" [Broken] may be interpreted in the same way (he bets 60% to see SUSY, which means a high conditional probability to find SUSY at LHC if it exists in the first place). But I really don't know whether this is representative of what most phycisits believe.
...
It's always hard to make pronouncements about "what most physicists believe" but my impression is that what you say is right:

If SUSY applies to reality, to understanding real experiments, then (many seem to be saying) it is likely to emerge from the data soon.

Just my impression---if it doesn't show up within 2 or 3 years many people seem ready to forget about it and address particle questions in ways that don't depend on it.

...
Any cue from anyone wellcome. :smile:
...
Absolutely! Any clue that anyone else can give would be welcome from my standpoint too!
 
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  • #7
PAllen
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SUSY has no reliable physical motive. It has arisen from desire to expand a class of renormalizable models of canonical QFT.
That may be its origin, but one can add a post-facto physical motivator. It happens to predict particles well suited to explain dark matter, and this prediction was made before most other candidates were excluded (to the best of my recollection).
 
  • #8
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I think this article may shed much light on the topic:
http://arxiv.org/abs/arXiv:1102.4585" [Broken]
The CMS and ATLAS Collaborations have recently published the results of initial direct LHC searches for supersymmetry analyzing ~ 35/pb of data taken at 7 TeV in the centre of mass. We incorporate these results into a frequentist analysis of the probable ranges of parameters of simple versions of the minimal supersymmetric extension of the Standard Model (MSSM), namely the constrained MSSM (CMSSM), a model with common non-universal Higgs masses (NUHM1), the very constrained MSSM (VCMSSM) and minimal supergravity (mSUGRA). We present updated predictions for the gluino mass, m_gl, the light Higgs boson mass, M_h, BR(B_s to mu mu) and the spin-independent dark matter scattering cross section, sigma_SI. The CMS and ATLAS data make inroads into the CMSSM, NUHM1 and VCMSSM (but not mSUGRA) parameter spaces, thereby strengthening previous lower limits on sparticle masses and upper limits on sigma_SI in the CMSSM and VCMSSM. The favoured ranges of BR(B_s to mu mu) in the CMSSM, VCMSSM and mSUGRA are close to the Standard Model, but considerably larger values of BR(B_s to mu mu) are possible in the NUHM1. Applying the CMS and ATLAS constraints improves the consistency of the model predictions for M_h with the LEP exclusion limits.
It greatly limits MSSM and some other SUSY models. However, very little of the mSUGRA parameter space has been ruled out, which would still suggest viability.

On the other hand, perhaps SO(10) or other more non-SUSY GUT's will see a resurgence? Another thing that is exciting though not directly related to the LHC are the MiniBOONE and MINOS results which strongly suggest either CPT violation (and therefore Lorentz violation) or far more likely the existence of sterile neutrinos.
 
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  • #9
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Stringy math is manifolds within manifolds within manifolds, so it does not go in the direction that I am watching. Instead of getting away from the conventional continuum it plunges into Baroque elaboration of it.
I'm sorry Marcus but this comment of yours is complete BS. Nothing in string theory tells you that the worldsheet scalar degrees of freedom that correspond to the string embedding must have a geometric interpretation. The fundamental description of the theory is always in terms of the 2-d CFT as long as it has the correct central charge. Have you ever heard about non-geometric compactifications, the Gepner model, for example? Apart from that, in many "geometric" cases one must consider singular varieties where near the singularities the full stringy quantum geometry replaces the classical geometric description and where new massless degrees of freedom emerge and give rise to non-Abelian gauge fields and charged chiral matter fields.
 
  • #10
Haelfix
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It has been explained a number of times on this board already, but it will take at least two years of uninterupted data taking before we start to worry about the lack of a detection signal, so say rendevous december 2013 for a more definitive update. Even then, you can easily hide SuSY in regions of the parameter space such that the LHC wouldn't be able to detect it even in principle, requiring perhaps a linear collider or many years worth of data taking, although I think nature would be really perverse if it chose that route..

This same story happened with the search for the top quark, where it escaped detection for something like 17 years. Many 'topless' models were invented in the interim to explain the nondetection thereof.

Anyway, my impression is that the belief in weak scale SuSY is on the order of 1 out of 3 (at least that's roughly my Bayesian prior), which is probably an order of magnitude greater than the belief in any other competing model, like say technicolor extensions. And for good reason, the MssM fixes problems with the standard model that simply won't go away, and really requires new physics to explain.

The biggest problem with the nondetection story is that if SuSy isn't detected, it also *probably* means that no new physics will be detected, since a lot of potential new physics signals mimics the experimental SuSy signal. Indeed, the much more likely LHC scenario is that we mistake something else for SuSY and will take many years before we can say one way or the other.

The nondetection story is of course rather bad for predictivity and fundamental physics in general and yes that logically implies that a lot of people will jump into more anthropic explanations of the universe, which tends to reintroduce SuSY at GUT or Planck scales anyway.
 
  • #11
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it will take at least two years of uninterupted data taking before we start to worry about the lack of a detection signal, so say rendevous december 2013 for a more definitive update.
If a definitive update is december 2013, I guess many will become either very excited or very worried by mi 2012. BTW, 2014 is tomorow morning in my mind. :wink:

Anyway, my impression is that the belief in weak scale SuSY is on the order of 1 out of 3 (at least that's roughly my Bayesian prior)
Would you think that your prior is higher, lower or median comparing to most of your colleagues?

The biggest problem with the nondetection story is that if SuSy isn't detected, it also *probably* means that no new physics will be detected, since a lot of potential new physics signals mimics the experimental SuSy signal. Indeed, the much more likely LHC scenario is that we mistake something else for SuSY and will take many years before we can say one way or the other.
Thx for this insight.

a lot of people will jump into more anthropic explanations of the universe
Then let's place our faith in Feyerabend. :cry:
 
  • #12
marcus
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Then let's place our faith in Feyerabend. :cry:
Where better to place our faith than in Feyerabend, but why cry about it?

I don't imagine that the scientific spirit will die just because some people give up on the quest.

Others will continue to struggle towards understanding "why it is this way and not that" based on empirical data. And there always was an element of anarchy and intellectual combat.

BTW I liked this bit from the Wikipedia article on Feyerabend:
==quote==
The decline of the physicist-philosopher

Feyerabend was critical of the lack of knowledge of philosophy shown by the generation of physicists that emerged after World War II:

The withdrawal of philosophy into a "professional" shell of its own has had disastrous consequences. The younger generation of physicists, the Feynmans, the Schwingers, etc., may be very bright; they may be more intelligent than their predecessors, than Bohr, Einstein, Schrödinger, Boltzmann, Mach and so on. But they are uncivilized savages, they lack in philosophical depth – and this is the fault of the very same idea of professionalism which you are now defending.[6]​
==endquote==
 
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  • #13
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Where better to place our faith than in Feyerabend
In Kuhn I trust.

, but why cry about it?
Because Feyerabend is a fertiliser, and science an orchid. You don't want to much fertiliser on your orchids.

I don't imagine that the scientific spirit will die just because some people give up on the quest.
In Kuhn you trust.

Feyerabend was critical of the lack of knowledge of philosophy shown by the generation of physicists that emerged after World War II: (...) The younger generation of physicists (...) are uncivilized savages, they lack in philosophical depth
I tend to agree, except I've never got why he was thinking that was specific to this generation. I suspect the reason is that they were young when he was old. But physicists have always been uncivilized savages... they lack respects for the philosophical corpus built far before they grown up. Maybe that's why they succeed in the first place. At least according to Kuhn. :wink:
 
  • #14
marcus
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Surely philosophical depth does not always favor traditionalism. Not always, but periodically, physics may need serious analysis of concepts in order to advance. Philosophical analysis can lead to NEW ways of thinking, and eventually may motivate new mathematical entities.

Sometimes in history it is good to shut up and calculate with the given mathematical formulation that one has and the conventional concepts. Sometimes that kind of progress gets stalled---then a rigorous critical examination of concepts may help.

For instance I think today one of the issues is the differential manifold. How, with only finite measurements, can we verify that spacetime is a smooth manifold? We can't. How can we determine that it is a smooth manifold down to really small scale, or at really high densities? We can't. Why should we assume that it is, then? Why should we assume that spacetime has a fixed prior geometry?

Why should we assume there even is a spacetime continuum? Isn't that like imagining that a moving particle has a definite classical trajectory? Spacetime is like a trajectory through a region of possible geometries. Maybe there is no trajectory, only transition amplitudes and sampling along the way. Maybe geometry takes all possible routes from here to there. How then should we mathematically represent spacetime?

Those are my two cents---the questions that come to mind. Perhaps not the most perceptive questions. But I want to exhibit that there is scope for conceptual analysis.
And I think we could use people like that earlier generation of philosopher-physicists that Feyerabend mentioned in the quote. They did not just shut up and calculate, or mindlessly keep repeating what had worked in the past (it is the superstitious who are the real savages. Those who do not consider what they are doing, who keep repeating something that has worked in the past because it has worked in the past. The essence of superstition.)
 
  • #15
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Surely philosophical depth does not always favor traditionalism.
Sure. I just think that the one statement you quote (from Feyerabend) was more traditionalism than deep philosophy. In other words, I don't think the Feynmans, the Schwingers, etc. did just shut up and calculate, or mindlessly keep repeating what had worked in the past. And I don't think that's your belief either.

Philosophical analysis can lead to NEW ways of thinking, and eventually may motivate new mathematical entities.
Sure. What is the best example you have in mind?
 
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  • #16
marcus
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Sure. I just think that the one statement you quote (from Feyerabend) was more traditionalism than deep philosophy. In other words, I don't think the Feynmans, the Schwingers, etc. did just shut up and calculate, or mindlessly keep repeating what had worked in the past. And I don't think that's your belief either.

Philosophical analysis can lead to NEW ways of thinking, and eventually may motivate new mathematical entities.
Sure. What is the best example you have in mind?
I agree about the shortcomings of the Feyerabend quote---especially with the examples. I'm not expert in history but I recognize Feynman as philosophically sophisticated, he thought critically and creatively about people's concepts and procedures. He was smarter about science than many or most philosophers of science, he just didn't express his insight their way. His philosophy did not sound like philosophy.

Philosophical insight can express itself as irony and mockery (if it really gets to the heart of something, not just for its own sake.)

Philosophical insight is in part about being able to break out of mental habits and get a fresh grip on the concepts.

these are just my opinions and they are in part cliché

In any case you are right that I don't think of those people as exclusively "shut up and calculate"

(nor do you).

You asked for an example. Correct me if I am wrong: wouldn't Einstein be a good example?
His strength seems to have been as a philosopher, analyzing the concepts, taking them seriously, following through with the thoughts----more than his strength in mathematics.
He took other people's mathematics and realized the consequences.

I have the feeling that you expected me to give Einstein as an example. Again it is a cliché, but who else can you think of that would be better? You asked for the "best example".

Philosophical depth leading to new ways of thinking: (what is time, what is space, how do we actually measure a speed, a length, how do we actually determine the simultaneity of two events.)

But I think that the central European universities of that period may have encouraged this. We shouldn't give him all the credit.
 
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  • #17
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Well, I may be more a first degree mind than what you think, but I had no particular expectation. In my field I would have mentionned Donald Hebb, who on first principles predicted a law that turn out to be amazingly true; the associationnists that I think can be seen as a precursor of connectionnism; Alfred Korzybski and his aphorism (the map is not the territory) which seems simple and self-evident but have all of a value when you try to interpret the existence of a map of the vegetative functions within what almost every body think as the primary visual cortex; and maybe Chomsky for the idea that human have inborn abilities toward langage -something which is now almost proven since the appearance of the nicaraguan sign language.

So I was wondering which exemples you had in mind in physics. I would think that needs for philosophy is there lower than for human sciences, something which may explain why the progression have been easier, but yes maybe Einstein is good example -although is hard to tell apart what may have been reinterpretation from what have been the true path of the discovery. Can you think of an example with some gap between the philosophical ideas and the scientific discovery?

(forum is a nightmare tonight, see you tomorow)
 
  • #18
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More biggest problem in the case when sparticles really exist, but contemporary SUSYQFT models does not work only owing to using _renormalizability principle_.
Would you mind to develop the idea a bit?
 
  • #19
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I am saying this based mostly only on blog comment sections and interviews in news articles, but one thing that is interesting to me is that people seem to be much more willing to abandon the Higgs Boson than Supersymmetry. People are cheerfully, openly saying that if the LHC does not find the Higgs then we will have to take serious looks at little higgs, technicolor, stranger and more exotic things even. But if the LHC does not find supersymmetry, even though this push the mass of the lightest supersymmetric particle up into the range where it would knock out major motivating factors for supersymmetry, I am hearing things like "well of course supersymmetry will survive, it's just too beautiful of an idea, we'll just look for supersymmetry at higher energies".

Now maybe my comparison is unfair because maybe replacing the traditional Higgs Boson with one of the alternate "Higgs Mechanism" type hypotheses I mentioned would really just be a change analogous to replacing the MSSM with a high-energy supersymmetry theory? But the contrast is still interesting to me, in the science textbooks it is the Higgs that is treated as essential but culturally it is supersymmetry that physics seems maybe less able to let go of.

EDIT: Wait, I mention Little Higgs as an alternative if LHC does not find the normal Higgs but it may be Little Higgs is a TeV scale theory also. Would Little Higgs be excluded if it is not found at the LHC?
 
  • #20
Haelfix
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Would you think that your prior is higher, lower or median comparing to most of your colleagues?
1 out of 3, 1 out of 4 something like that depending on which group of physicists you talk too (theorists or phenomenologists, or say condensed matter physicists) but yea it is easily the most dominant idea for stabilizing the electroweak sector and for beyond the standard model collider physics.

I mean the real worry among physicists, is not that SuSy isn't observed, its that we don't see ANY physics that properly explains why the electroweak sector is stabilized. That would be highly discouraging!
 
  • #21
Haelfix
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I am saying this based mostly only on blog comment sections and interviews in news articles, but one thing that is interesting to me is that people seem to be much more willing to abandon the Higgs Boson than Supersymmetry. People are cheerfully, openly saying that if the LHC does not find the Higgs then we will have to take serious looks at little higgs, technicolor, stranger and more exotic things even. But if the LHC does not find supersymmetry, even though this push the mass of the lightest supersymmetric particle up into the range where it would knock out major motivating factors for supersymmetry, I am hearing things like "well of course supersymmetry will survive, it's just too beautiful of an idea, we'll just look for supersymmetry at higher energies".
Yea that is kind of correct. The reason is that as an idea, supersymmetry naturally does things for phenomenology that will always make it a primary candidate for being a physical idea. As an idea it is most beautiful at LHC energies, but it still has many benefits at higher energy scales. People will thus always make SuSy models, just like they would make See-Saw models if that particular mechanism is falsified in neutrino physics! You get too much for free so to speak!

The Higgs physics meanwhile is essentially observed, we've already seen 3 out of 4 components of the Higgs field, which is why we can say with great confidence that we will see something to explain the 4th component at the LHC. Further, we basically know a lot about the physics of such a simple solution. Now it would be exciting if it was something exotic, b/c that has the capacity to perhaps elucidate more about the world than just a simple scalar could.
 
  • #22
Haelfix
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Would Little Higgs be excluded if it is not found at the LHC?
That depends what else is found, but morally speaking yes, b/c it loses its explanatory power as an idea.

In particle physics you can always write down new particle types or posit new substructure with arbitrary characteristics, and if you make them heavy enough and decouple them from other physics, for the most part they just sit there and do nothing. However, those sorts of ideas violate Occams razor, unless they are part of a larger structure that perhaps explains something that we didn't already know.
 
  • #23
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The comments of Haelfix IMO illustrates a deeper sense of what a theory is, that is often ignored, I'd like to take the opportunity to note it.
it will take at least two years of uninterupted data taking before we start to worry about the lack of a detection signal
When do we have sufficient confidence (or evidence) to say that we are certain? ie. to make a choice?
Even then, you can easily hide SuSY in regions of the parameter space such that the LHC wouldn't be able to detect it even in principle
How do we interpret deviating data? There is often more than one possible inference to be made. Again there is a choice to be made here.
This same story happened with the search for the top quark, where it escaped detection for something like 17 years. Many 'topless' models were invented in the interim to explain the nondetection thereof.
At any instant we have some choices, to change route, or to keep looking for more and more unlikely possibilities to make sense out of an observation. There is a choice to be made.

This illustrates a deeper aspect of the nature of theories. How do we see a theory? What IS a theory?

What this illustrates is the lack of a distinction betwee a theory as a purely descriptive - ie to DESCRIBE NATURE; or as an interaction tool - ie to aid our interaction learning and inference of nature in the context of a decision problem.

The descriptive nature of theory, is the form which is the conventional view of a theory. It makes sense only to the extent that we can acquired and represent sufficient statistics and repetability to arrive at a stable description - refer to what Smolin refered to as the "newtonian scheme" in this talk (although I think I take the meaning of this farther than Smolins really means).
http://pirsa.org/08100049

The view of a theory as an interaction inferface is the view that is the preferred one if you take the inferencial perspective. Here the description doesn't refer to nature in an realist sense, but to the acquired and constantly evolving image of nature the observer has.

This is why I think the strategy and discussion above does contain choices. It's not just a matter of "seeking the correct description of nature". That is an idealisation of the scientific process to the point there it's useless. That's my opinion at least.

One may wonder what this has to do with any of this, but I claim it has. This is one of the points behind the inferential perspective of theory, and this connects in a deeper sense to the entire RG and inside observer perspective and the context of general theory duality.

/Fredrik
 
  • #24
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Haelfix thanks for the responses.
 
  • #25
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What this illustrates is the lack of a distinction betwee a theory as a purely descriptive - ie to DESCRIBE NATURE; or as an interaction tool - ie to aid our interaction learning and inference of nature in the context of a decision problem.

The descriptive nature of theory, is the form which is the conventional view of a theory. It makes sense only to the extent that we can acquired and represent sufficient statistics and repetability to arrive at a stable description -
...

The view of a theory as an interaction inferface is the view that is the preferred one if you take the inferencial perspective. Here the description doesn't refer to nature in an realist sense, but to the acquired and constantly evolving image of nature the observer has.
Fredrik, are you trying to make the distinction between model and meaning, where a mathematical model helps us make predictions but does not necessarily give any understanding as to why that model works, as opposed to a theory which tells us why things are as they are? Isn't this the same as the ontological vs. epistemological perspectives? If so, I would be more comfortable if you would use that language. And I think you'd have to put it in one of the philosophy forums.
 

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