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Dax discussions of Beyond SM theories/including newcomer questions

by marcus
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Lt_Dax
#37
Nov13-10, 07:58 PM
P: 78
Quote Quote by Kevin_Axion View Post
We have different perspectives and I respect yours, and I do sound harsh, but that is only because people come on this general sub-forum and completely deter String Theory and only focus on one idea falsifiability.
You may find it interesting that I view the falsifiability argument as a meaningless distraction - I care little about it, since an unfalsifiable theory may become falsifiable in the future; this is in my original post. My criticisms of ST are different, it's more to do with how we do science and how we discover real knowledge.
Kevin_Axion
#38
Nov13-10, 08:03 PM
P: 921
Yes, real knowledge precisely what we are lacking. I suppose you are right in that sense. We need real knowledge through experiments, but Theoretical knowledge is just as convincing. I suggest the idea of Bekenstein-Hawking Radiation, an unobserved phenomena but widely accepted. It is because it just seems right, as does SST, that doesn't mean it is though.
JustinLevy
#39
Nov13-10, 08:07 PM
P: 894
Quote Quote by Lt_Dax View Post
These efforts would arguably be minimal if we had proof that a string is the only possible fundamental object.
Come on, are you seriously suggesting people are not searching of a minimal description of quantum gravity?

People would LOVE to find a consistent 4-d field theory version of quantum gravity.

You ask why is string theory considered an advance, it is because this appears to be a possible explanation. This is a huge step forward.

Would you feel more comfortable if we worded it as:
For decades no consistent approach to quantum gravity could be found. People tried to add many different degrees of freedom, or use other mathematical tools, to cancel out divergences. Nothing seemed to work. String theory represents our first data point for finding an upper bound on the minimal amount that needs to be added to find a consistent theory of quantum gravity.

Theorists worked hard to get this data point. The information provided by this data-point should not be dismissed.

It's an awkward way to word it, but as already stated, there is no mathematical nor experimental claim that string theory IS the minimal explanation. I did not claim it was the minimum. I explicitly stated the opposite.
JustinLevy
#40
Nov13-10, 08:10 PM
P: 894
Quote Quote by Kevin_Axion View Post
JustinLevy, I mean there is no experimental evidence for a theory Beyond the Standard Model, I do understand that there is remaining problems and physics beyond as I stated these ideas in my original post.
You seem to be making the same claim that Dax is making, which is confusing me.

How is experimental evidence of gravity, NOT experimental evidence beyond the standard model? Same with dark matter, which is not in the standard model either.

If you claim there isn't evidence beyond the standard model, then all efforts to get theories beyond the standard model DO appear to have no experimental motivation. Which falls right into Dax's complaint.

EDIT:
To make it more clear, I am trying to separate two things:
1) Experimental Evidence showing our current theories are wrong (or at least need adjusting/ something added)
2) Experimental data on gravity at a scale where the quantum corrections become clear over the classical effects

We already have #1. We have yet to get a theory to resolve this. In this sense, experiment has been ahead of theory for close to a century.

We do not have #2. This does not mean we don't have evidence for something "beyond the standard model", or need for figuring out how to get GR as a classical limit of a quantum theory.
Kevin_Axion
#41
Nov13-10, 08:26 PM
P: 921
I am saying that dark matter and dark energy aren't concepts that give us a framework but yes they do suggest something beyond the Standard Model.
bcrowell
#42
Nov13-10, 09:01 PM
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It seems to me that some of the responses to Lt_Dax have involved a lot more hand-wringing and ruffled feathers than was necessary. I think Lt_Dax's original post was spot on. If it hurts people's feelings, then the right response is to calm down, put those feelings aside, and try to write a response that answers intellectual points with intellectual points.

Quote Quote by Kevin_Axion View Post
There is a reason it's called theoretical physics.
What is this supposed to mean? Does it mean that theoretical physics is not supposed to make contact with experiment?

Quote Quote by negru View Post
The answer is easy I don't understand why we always have to revisit the issue.

1.we have experimental data: we use it

2.we don't have experimental data:
a. we do what we can
b. we do nothing

Choose between a and b.
Well, my opinion is that the answer should be 2b, in the sense that pursuits like LQG and string theory should get zero institutional support. (And this is not the same as saying that nobody will ever do any work on them. Once someone has tenure at a university, you can't stop him/her from working on something s/he finds compelling.)
Kevin_Axion
#43
Nov13-10, 09:24 PM
P: 921
Yes it is supposed to make contact with experiment but you don't need experiments to research theoretical physics, it's a purely logical subject based on reason and deduction. Others would differ as the OP has and I absolutely accept that viewpoint I was just expressing my own.
negru
#44
Nov13-10, 09:27 PM
P: 308
Quote Quote by bcrowell View Post
Well, my opinion is that the answer should be 2b, in the sense that pursuits like LQG and string theory should get zero institutional support. (And this is not the same as saying that nobody will ever do any work on them. Once someone has tenure at a university, you can't stop him/her from working on something s/he finds compelling.)
Well you see this is the issue. If the problem with "dubious" research is the funding, I'd have to agree with you. However, I also find "research" in literature, or humanities in general to be pretty worthless. Does that mean we should cut funding?

And why should tenured people be allowed to work on whatever they want? What's so special about them? Pretty much all universities receive federal funding whether they're private or not, so it's still tax money funding tenured profs.
MTd2
#45
Nov13-10, 10:20 PM
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Quote Quote by negru View Post
Well you see this is the issue. If the problem with "dubious" research is the funding, I'd have to agree with you. However, I also find "research" in literature, or humanities in general to be pretty worthless. Does that mean we should cut funding?
Humanities can arguably be in touch with reality. But some areas of it, like paranormal research, still get funding from governments. I think QG and paranormal are in the same zone of priority according to bcrowell.
Lt_Dax
#46
Nov14-10, 09:03 AM
P: 78
@Justin Levy

To make it more clear, I am trying to separate two things:
1) Experimental Evidence showing our current theories are wrong (or at least need adjusting/ something added)
2) Experimental data on gravity at a scale where the quantum corrections become clear over the classical effects

We already have #1. We have yet to get a theory to resolve this. In this sense, experiment has been ahead of theory for close to a century.

We do not have #2. This does not mean we don't have evidence for something "beyond the standard model", or need for figuring out how to get GR as a classical limit of a quantum theory.
This is the key. I think some have mistakenly thought that I don't believe there is evidence that our current theories need revising. On the contrary, one thing I have emphasized repeatedly is that not only do we have such evidence, but we probably have a lot more than we think (the "long list of unsolved problems" concept).

The main cause of confusion is that some people are saying that such evidence justifies developing entire 'frameworks' aside from experiment. This is bizarre because the actual point shows that we are not devoid of data or experimental oddities (I think this is a pernicious myth). The trend towards massive model building such as string theory is a separate issue, and seems motivated more by grandiose desires to build a theory of everything, not a lack of unsolved observational problems to work on.

My view, which could be overly simplistic, is that we should do theoretical physics by examining experimental problems. The [tex]g-2[/tex] may be a good example, and there are other examples (which people have mentioned) of where we need to extend or revise the standard model. The development of ST seems to be a separate exercise. I'm sorry to say, I find the concept of doing 'theoretical research' alone somewhat strange. The [tex]g-2[/tex] people, for example, do their research in concert with experimentalists. The other two main divisions of theoretical physics (Lattice Gauge Theory, Particle Phenomenology) fit the "old", proper definition of what theory is. The meaning of the word "theory" really does matter. If it didn't matter, then we can basically just do anything we want, no matter how wild. If "theoretical" physics is no longer a part of physics (an experimental science by definition), then that would probably result in a huge mountain of 'theory' papers which say a lot but explain very little.

So I don't question that there is physics beyond the standard model, I think there is evidence for that already, I want to make that clear. My main question is about why string theorists use such incredible language to describe what they are doing. Is it really justified to say we have had a "revolution" (or two, no less) even though it hasn't been confirmed experimentally? The two real revolutions of the early 20th century were tightly linked to experiment, front and back.* The Standard Model in the 60s and 70s is a brilliant example of a highly predictive theory which was developed and verified at famous particle accelerators in the USA and CERN in cooperation with theorists, but even with this level of success, they never ever made unwarranted claims about the importance of the theory. They knew that they could only be sure it was right up to a certain energy scale. Wilsonian renormalization taught us that beautifully.

Again regarding language, why do we describe the development of string theory as discovery? This is not a question regarding its usefulness in pure mathematics, or how interesting it is, it is a question about whether we can discover a real fact about the universe by writing down a new equation. In the Standard Model, didn't we write down equations to explain new observations (e.g. the QCD lagrangian wasn't written down before we had experimental knowledge of the features of the strong force). String theory doesn't just claim to explain what we already know, it is so unconstrained that it results in a unified theory (which may or may not be the case) and even branes and multiverses (which may or may not exist). Is this discovery? I'm still certain we've never done anything like this in the past, and surely it is false that we don't have any new data to work with?

* Not only that, but the judgment of whether something is a revolution is not made by the practitioners of the subject at that precise moment. It is typically made in the future, and it is typically made by others. So what makes Green, Witten et. al. so comfortable using these words?
Lt_Dax
#47
Nov14-10, 09:31 AM
P: 78
By the way I'm still not purely making assertions - my questions are not all rhetorical. If any cool heads can explain why pure model building can be real discovery even without experiment, then I welcome it.

One thing I may anticipate is the "argument from beauty" - i.e. Dirac did it, so that's what we're doing. Well, I think there are essential differences (Dirac didn't develop the theory with exotic objects and dimensions, only new matrices), but apart from anything else, to use an old quark physics pun, truth comes before beauty. (This may be why Dirac was nervous about calculating [tex]g[/tex] from his equation and left it til the next day, assuming he was nervous).
suprised
#48
Nov14-10, 09:51 AM
P: 407
What is routinely neglected in these discussions, is that there are, as a matter of fact, extremely non-trivial computational results! For example, state counting in black holes. This is a theoretical arena where the two pillars of modern physics, GR and QM, seem to clash and strings provide a way to reconcile these. It is very non-trivial that this, and many other things, do work at all! This is what has been "discovered" and the reason for excitement.

It is simply not so that string theory is an unmotivated "belief" and people just say: well let's postulate that we have those little strings and see what comes out. If it doesn't work, we "believe" instead in membranes, or yellow octopi, for that matter.

On the contrary, strings are a framework, or machine, that seems to "work" and make sense as a physical model, whenever one checks something, so many people view this as very meaningful and not as a random idea. This is a very important point and sets it apart from countless other attempts that have been tried in the past. Whether it directly or indirectly applies to nature is a different question. It is in principle testable, so qualifies as a scientific theory despite certain people want to deny this.
Lt_Dax
#49
Nov14-10, 10:05 AM
P: 78
@suprised, you make some interesting points, but I'm not convinced that what makes a scientific theory is falsifiability - as I've said before, I think this is given greater importance than it deserves. An unfalsifiable idea may become falsifiable as technology advances, so it's irrelevant. All ideas are falsifiable in principle. Something only achieves theory status when it has been experimentally confirmed (and repeatedly!). We say this to creationists all the time when they claim that evolution is only a theory. Is it one rule for creationists, another for us?

It is very clear that string theory is not just a random idea. From what I know of it, it is a remarkable construction, but I think you can see that the implications of string theory go way beyond just state counting in black holes. It opens up a whole new can of worms, a vast array of new predictions. The demands upon String Model to make it String Theory are very big. (I might not be expressing this viewpoint very clearly so i apologize if that's the case.)

The real test of a 'theory of everything' is that it can explain everything, old experimental results and new experimental results. Isn't that a tall order?
suprised
#50
Nov14-10, 12:01 PM
P: 407
Well what one calls theory is semantics, there is eg in mathematics also the theory of modular forms and countless other "theories", so the string phyisicists just don't care how their field of research is called and go on. It is the self-declared critics who are obsessed with this kind of questions, in particular with falsifiability.

The string physicists are more interested in positive questions, like what can be learned from the results and how to make further progress. This is right now mainly conceptual, ie about understanding how things works. An example is holography in quantum gravity, which is a spin-off of string theory and seems to be a central point of quantum gravity. Many see this as one of the most important insight in theoretical physics in the last decades; if the naysayers would have had their will, this kind of research would have been stopped since long, and an enormous damage would have resulted. Fortunately, and for good reasons, the naysayers don't matter! Most of them are not even scientists.

Of course ultimatively the goal is to make contact with experiment, but this goal is far away (if it ever can be reached), so people content themselves with more modest goals for the time being. They are difficult enough.
Kevin_Axion
#51
Nov14-10, 12:07 PM
P: 921
That's exactly the points I was trying to address, surprised, you're a string theorist, correct?
Lt_Dax
#52
Nov14-10, 12:19 PM
P: 78
Well what one calls theory is semantics, there is eg in mathematics also the theory of modular forms and countless other "theories", so the string phyisicists just don't care how their field of research is called and go on. It is the self-declared critics who are obsessed with this kind of questions, in particular with falsifiability.
Semantics (meaning) really does matter! It's unfair of you to call me a self-declared and obsessed critic because of that. The meaning of things really does matter, because if words can mean anything, then the discussion becomes meaningless. (And as I've said, I don't care about falsifiability because all ideas are "in principle" falsifiable).

Your comment about parts of mathematics which are called "theories" illustrates the point. I'm not talking about those parts of mathematics which can be called "formal theories" - where the word formal is used because we adhere to mathematical standards of proof. I am talking about "empirical theories" - which is what we mean when we call something a scientific theory. "Proof" in what scientists call a theory means something different.

Maybe the problem is that many string theorists trained as mathematicians, so they think that the only thing that matters is proof in mathematical sense?

The string physicists are more interested in positive questions, like what can be learned from the results and how to make further progress.
Again, your semantics are unclear to me. What do you mean by "results"? Part of the whole problem seems to be that people involved with speculative models feel comfortable with building upon results which haven't been rubber stamped by experiment yet. In the past, you could only build such a house of cards if you know that the foundations are correct.

In real science, contact with experiment is not a "goal", it is part of the enterprise. Right up until the 1980s it was always very close by.

Here's the problem: even for very high energy physics which might require something like a string theory, the cry of being devoid of experiments is false. Cosmological or even some condensed matter physics results may be capable of showing things which we can't do in a super accelerator (again some of these reports have been prominent lately). The point is that you develop a theory from these results, not in anticipation of them. This is what the creationism cartoon was mocking.

(And I believe there is a lot to be learned about how science works from the evolution/creation debate).

By the way, I'm beginning to wonder if string theorists often find no further recourse than a personal attack of some form. I realize that some of what I say is uncomfortable, but I'd prefer a crystal clear answer to some of my questions than accusations about personal character.
negru
#53
Nov14-10, 12:25 PM
P: 308
Quote Quote by Lt_Dax View Post
@suprised, you make some interesting points, but I'm not convinced that what makes a scientific theory is falsifiability - as I've said before, I think this is given greater importance than it deserves.
So who exactly gives it greater importance than it deserves? The people who work on it? It's their business what they're interested in. The people who fund it? See my post above.
Lt_Dax
#54
Nov14-10, 12:29 PM
P: 78
Quote Quote by negru View Post
So who exactly gives it greater importance than it deserves? The people who work on it?
No, the usual low-quality critics of string theory who haven't really thought about it. The problem is that string theorists then spend too much time trying to claim that string theory is in principle falsifiable, even though it is irrelevant either way.

And I have to say, if someone's career is publicly funded, then the public has a say in what they work on. It's our job to explain to people how we're advancing physics. If they're self funded, then that's different.


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