Why is String Theory Considered to be a Scientific Theory?

[atyy]

Let me suggest that when David Gross says we don't know what string theory is, it's not much different from physicists who said we didn't know what renormalization of QED means even after the *successful* work of Schwinger, Feynman, Tomonaga. The understanding of renormalization had to wait till Wilson, following a bunch of clues that went back to Gell-Mann and Low. (And if you read the Clay Institute prize, apparently we still don't even know what QCD is!) But we don't say that Feynman's work did not provide in principle testable hypotheses. In the same way, string theory already does provide in principle testable hypotheses - although unlike Feynman's predictions, those of string theory are not in current practice testable.

An example of string theory prediction near the Planck scale is
http://arxiv.org/abs/hep-th/0601001

There are also only a *finite* number of possibilities for experimentalists to test in string theory.
http://arxiv.org/abs/hep-th/0606212

 

[inflector]

You are posing a challenge. It's clear and makes sense, at least to me. It wouldn't be satisfactory for people to copout by saying "Well nobody else can either!"

For comparison's sake I will give some clue as to LQG falsifiability---it has no extra spatial dimensions and people talk about LHC seeing evidence of extra spatial dimensions. That would falsify LQG.

Here's another indicator of how near to testability LQG is, or how far from testability it is. You have to judge how near or far:
http://arxiv.org/find/grp_physics/1/au:+Barrau_A/0/1/0/all/0/1

marcus, thanks for the specific examples.

This is exactly the kind of thing that I trying to find for string theory. I haven't really dug too deeply but I have been looking and haven't found anything in my hunt so far.

I see how you might be able to "contribute something useful to science". Write a book about the revolutions going on in physics, from a layman's perspective.

...[snip]...

Go visit IceCube the neutrino telescope in Antarctica, and interview somebody. Go visit the MAGIC air cherenkov imaging telescope on San Juan island in the Canaries. Visit that cosmic ray detector spread in Argentina. Visit the ESA (euro space agency) and talk to the people handling the Planck spacecraft mission---mapping the cosmic microwave background. Talk to people at LISA gravity wave detector.

You'd learn a lot and have a successful book and teach other people a lot by seeing frontier science through an intelligent layman eyes.

I certainly hope to write a book about science, or a series of books on science in the future. I really enjoyed the Asimov books (especially the chemistry books) growing up so I have high standards and I feel I have a lot to learn first.

But more important than that, I want to do some actual science myself first. That will make any books all that much better.

 

[atyy]

marcus, thanks for the specific examples.

This is exactly the kind of thing that I trying to find for string theory. I haven't really dug too deeply but I have been looking and haven't found anything in my hunt so far.

Oh, if you want stuff at that level, there's tons of that in string theory.
http://arxiv.org/abs/0807.3333
http://arxiv.org/abs/0908.0409
http://arxiv.org/abs/0904.3547
http://arxiv.org/abs/1001.0577
http://arxiv.org/abs/1008.2379
http://arxiv.org/abs/0806.3905

Observations of these will favour string theory. The problem is that non-observation will not falsify string theory. Just like observing our solar system favours Newtonian gravity, but non-observation of it does not falsify Newtonian gravity, since there are many other configurations consistent with Newtonian gravity. For that, you have to rule out all the finite number of possibilities in the string landscape http://arxiv.org/abs/hep-th/0606212, which will in principle falsify string theory - but in practice the energies needed to eliminate some possibilities of the landscape are too high, and the number of possibilities, though finite, is impracticably large.

 

[inflector]

presumably born around 1965

Yes, I was born in January 1964, one day before Michelle Obama.

I view myself as a post-boomer but not quite gen-X even though by some definitions my year is the cutoff date for being a boomer. I guess I feel we've been slacking off and making excuses while there is still a lot of important work to be done. Too much for someone like me to just go out and make money for myself doing something that won't help out (or make things worse in many cases).

Perhaps that's one of the reasons that I feel the need to join the effort in science. I don't think we'll have a political solution to many of the world's problems in time to avoid very significant worldwide pain unless we get a breakthrough in physics soon. Fusion power would go a long way towards helping with global warming, for example.

Plus, I was a little kid when Apollo 11 landed on the moon. I remember the Apollo 13 mission and the drama of that. I guess I grew up assuming we'd have clean energy and would be traveling to the stars by now. I'm not ready to give up on that dream while I'm still alive.

 

[MTd2]

The only input that string theory takes are special relativity and quantum mechanics.

That is not quite true because branes are fundamental objects of the theory but they must be put in the theory for consistency. So, what you write is more of a starting point.

Also, there are a lot of non fundamental inputs to realize realistic compactifications, which requires most of the expertize needed to model possible experiments to test it. And that goes way beyond any textbook available. So, either one studies those or do something else or is called an armchair critic.

 

[inflector]

Thanks atyy, that helps a lot. I figured that the theorists must be trying to find evidence, so there should be some hints that things are going the string way before we get to the Planck scale. It is good to see the specific papers/reviews you listed.

The problem is that non-observation will not falsify string theory. Just like observing our solar system favours Newtonian gravity, but non-observation of it does not falsify Newtonian gravity, since there are many other configurations consistent with Newtonian gravity. For that, you have to rule out all the finite number of possibilities in the string landscape http://arxiv.org/abs/hep-th/0606212, which will in principle falsify string theory - but in practice the energies needed to eliminate some possibilities of the landscape are too high, and the number of possibilities, though finite, is impracticably large.

Yes, this is certainly a problem that won't be easily surmounted. It's a weakness but if reality is stringy it's one we'll have to live with.

 

[MTd2]

Yes, I was born in January 1964, one day before Michelle Obama.

I cannot help but thinking that you, and mainly marcus, are around 19-21 years old...

 

[inflector]

And that goes way beyond any textbook available. So, either one studies those or do something else or is called an armchair critic.

This goes along with my general impression that for me to make an impact in string theory would probably require 3 to 6 years of work (and perhaps as much as 10) first, just to get to the point where I can evaluate the papers and have an intelligent discussion at the professional level about the latest aspects of the theory.

That's probably reason enough for me to work in some other area.

 

[inflector]

I cannot help but thinking that you, and mainly marcus, are around 19-21 years old...

Why is that?

 

[Fra]

I just want to add what I think the immediate question is.

One can evaluate a research program from any perspective one wants. One does not need to be an experienced reputed "string theorist" in order to be allowed to have an opinon on string theory.

On the contrary, it's up to those that feed on public funding to explain to the public what they get back. The public want benefit for society and makind, not feed mental masturbation of minorities. To think that the public should fund any crazy ideas of everyone that wanted to do research is unreasonable. I think it would be wrong.

It's not a question of answering to wether it is ultimately "correct" or not, because not even string theorists know that. NOone is then "qualified". Maybe in another 100 years mankind can look back and answer this, to see wherther we were heroes or fools to invest 140 years in this.

The question is IMHO: given what we think we konw now, and given the quest we face, to expand knowledge, to what extent is it RATIONAL to INVEST money and manhours into string theory reasearch?

This is a question everyone will answer on it's own. Individual researcher ask themselves this, do I feel the best use of my time is to research ST? Also the society that does funding should ask to what extent it's rational to fund this or that?

I judge research programs in it's starting points, methodology and logic of reasoning, and of course state of progress. I have an opinon of string, but I'm certainly no string expert, but that does not invalidate my opinon, because my opinion is important just for my own actions.

So what is the option to ST funding? Well there are OTHER ideas than string theory, also from the point of view of funders, there are OTHER scientific work to fund.

The point is that the decision we all have to ask ourselves is decision based on incomplete information, and it's a bet. We are all our own qualifiers of where to place the bets. If the experts dismiss critique as armchar criticts, that's a failure of the experts to communicate (still after 40 years) the benefits of what they do.

So I don't personally accept the armchair rejection of all critique. Although it's probably fair to say that SOME critique aren't that well thought out, it's silly to think that the only ones that are allowed to critque the program is the experts themselves. It should be the other way around.

Edit: ie. you need to convince your opponents that you are right, you need to present for them, objective and undeniable progress. Usually this is in the form of corroboration after falsification attempts. Now if that still hasn't been done after 40 years, we need to find new ways to describe our work. Perhaps like trying ot measure progress, and then hypothesis could be that "this research program or algorithm" will perform better than the compoeting programs, in terms of reducing the number of "options" etc, then this could be tested in terms of effiencty of algortihms if you see the research as such. But here the landscape problem of ST seems to have diverged rather than converged, this is a problem as I see it. So one may ask where the progress is, when the set of possibilities just seems to expand, rather than shrink? There seems to be an imbalance between generation of new possibilities and selection from them. To me this looks like a flawed algorithm.

/Fredrik

 

[Micha]

I am currently an advanced amateur, I'd say.

If you are serious to become a good physicist, I think you should read this:

http://www.phys.uu.nl/~thooft/theorist.html

 

[inflector]

Thats very interesting inflector.

Well, I'm no expert in string theory, but here's a brief outline of its starting point.

Thanks dx, that was a helpful outline.

 

[inflector]

If you are serious to become a good physicist, I think you should read this:

http://www.phys.uu.nl/~thooft/theorist.html

An excellent and valuable reference. I'm shocked that this was the first I've seen that reference since I've been reading and looking for a long time.

Thank you.

 

[arivero]

This thread is advancing to a topic of more general interests that plain "Beyond Standard Model". The question is now, it seems, how to be trained as physicist at a late age (beyond 30, say). I think that the internet is providing enough resources, from pirated books to open lecture notes from the main campuses. The great problems is how to provide the discipline (if needed) to keep going, the feedback (to correct errors) and the local human contact (to be encouraged generally, and to reinforce both discipline and feedback).
Of course, it is not even a question of theoretical physics, we could think about math or about other disciplines where some advance can be done without access to a laboratory.

 

[atyy]

This thread is advancing to a topic of more general interests that plain "Beyond Standard Model". The question is now, it seems, how to be trained as physicist at a late age (beyond 30, say). I think that the internet is providing enough resources, from pirated books to open lecture notes from the main campuses. The great problems is how to provide the discipline (if needed) to keep going, the feedback (to correct errors) and the local human contact (to be encouraged generally, and to reinforce both discipline and feedback).
Of course, it is not even a question of theoretical physics, we could think about math or about other disciplines where some advance can be done without access to a laboratory.

I'm an experimental biologist, so I have no idea how theorists work (if you can't think, just measure - unfortunately, that's sometimes expensive - I mean scotch tape was just the first step, wasn't it)? Anyway, I read an interesting story of what a good non-genius (ie. not Ramanujan) amateur can achieve in http://books.google.com/books?id=shuJFCWWql4C&dq=king+of+infinite+space&source=gbs_navlinks_s. Douglas Hofstadter had discovered for himself some beautiful geometry theorem. To find out whether his discovery was unknown to anyone else, he wrote to Donald Coxeter, who didn't know, but pointed him to some books. It turns out that after some searching, his discovery was already known. Nonetheless, he did have lots of fun in the process.

 

[Fra]

if you can't think, just measure - unfortunately, that's sometimes expensive

If one doesn't know, for whatever reason (which one usually does not; at least not with infinite confidence) one have to based ones actions upon an educated guess anyway. Sometimes it's expensive to be wrong. But also, sometimes guessing is the only way, as resisting to guess can be sometimes more "expensive", if one is constantly challanged. It's also what happens when you have a certain time to make a decision, usually the quality of decisions are worse, but a "better decisions" that is late, may be lethal.

to act based on an educated guess and then observing feedback = to measure

In that sense all measurements have a "cost", it's like placing a bet, but the rational player bets only when and where the estimated gain is higher than the cost of the bet.

Acting upon incomplete information and educated guesses, beeing wrong is OK, it's possible even the way nature work. So each rational action is a tradeoff, between cost and estimated gain.

/Fredrik

 

[arivero]

... a good non-genius (ie. not Ramanujan) amateur can achieve in http://books.google.com/books?id=shuJFCWWql4C&dq=king+of+infinite+space&source=gbs_navlinks_s. Douglas Hofstadter ...

Hmm, D.H. was physics PhD with a good training on mathematics in 1992, when he wrote to Coxeter. It could be said to be a case similar to the OP, inflector, in the sense that he is addressing another field out of his current experience, but it is a very different case. Not to say that to be the son of a Nobel Prize on experimental physics is not the average experience.

 

[atyy]

Hmm, D.H. was physics PhD with a good training on mathematics in 1992, when he wrote to Coxeter. It could be said to be a case similar to the OP, inflector, in the sense that he is addressing another field out of his current experience, but it is a very different case. Not to say that to be the son of a Nobel Prize on experimental physics is not the average experience.

Also, he probably didn't misspell "Feynman".

 

[inflector]

Yeah, that was pretty bad huh. Must have been a Freudian slip. I didn't catch that despite proofing it three times. I must have been hoping that somehow Einstein was coauthor. Especially funny since I melded two of my favorites.

 

[inflector]

Hmm, D.H. was physics PhD with a good training on mathematics in 1992, when he wrote to Coxeter. It could be said to be a case similar to the OP, inflector, in the sense that he is addressing another field out of his current experience, but it is a very different case. Not to say that to be the son of a Nobel Prize on experimental physics is not the average experience.

One very significant example of an amateur physicist is http://en.wikipedia.org/wiki/Alfred_Lee_Loomis" .

Interestingly, he only had an undergraduate degree in math and science at Yale, and a law degree at Harvard. He started his career after a very brief stint as a lawyer by making a fortune on Wall Street as a trader/financier. He got bored as his true passion was experimental physics. So he retired from finance and started his own laboratory. Most of the famous scientists of the 20s and 30s came to his Tuxedo Park lab.

He came up with the idea for LORAN, did a lot to help his good friend Ernest Lawrence get funding to build his larger cyclotrons, ran the government lab which developed practical radar for airborne use, i.e small antennas and transmitters, among many other things.

 

[arivero]

OT, and now that you mention finance: I read, here and there, that Gauss did some money as trader, but I am not sure if it is myth of if there are actually some recording of the transactions he managed, and/or his strategy.

 

[Fra]

Hey inflector, FWIW, when you guys discuss trading it strikes me that if you have developed a good intuition about how the market behaves, perhaps it can be used to your advantage as an odd experience.

Now of course I would have to agree that wether you go for string theory or anything else, there is probably no way around trying to acquire the basic prerequisites, so one understands the basic history of physics and what the we currently know, and what the current problems are.

But if I may throw in a speculative, but still IMHO interesting possibility that may be more interesting to you than others, is an idea I have, and that is also related to several information theoretic inference approaches to physics.

Namely the idea that the actions of a physical systems interacting with each environment follows something analogous to the rational expectations theory in macroeconomics. You have been a trader, and you konw how you act in a given situation, then you can ask, what would you have done if you where a proton? :)

The conceptual idea is that the physical action of a physical system, when properly abstracted in terms of information theory, and how the system processes input and releases output, can be understood as "rational", and that his behaviour has been selected for since it's the best way for any player to "stay in business" and not be outcompeted. It's not a certain path to victory, but it's the most rational way to place the best.

The point is, that while this is speculative, it's something I personally think is very interesting and it's a highly underdeveloped direction of physics. So I see plenty of room for anyone that maybe has some skills/experience from decision theory, learning models to make a cross-field applications here with physics.

Recently many interesting cross-discipline stuff emerges. Another extremely interesting area is molcular biology and population dynamics crossing with computer science. It's been found that problems that was impossible to solve be reductionist ideas like "simulating the chemistry from molecular level" due to the overwhealming complexity, rounding errors, computation time etc are now possible to solve with clever algorithms that mimic the feedback mechanism of the overall organisms, suchs as optimizing growth rates etc.

So may try to see the laws of physics, and the interaction rules between physical systems from the point of view of a trader? :) It could be interesting.

/Fredrik

 

[sachinism]

If you are serious to become a good physicist, I think you should read this:

http://www.phys.uu.nl/~thooft/theorist.html

it does not work anymore :(

 

[marcus]

it does not work anymore :(

I'm not sure whether you are serious or joking. The link to the 't Hooft advice essay works. But the essay has been reformatted. Last time I looked at it, maybe 5 years ago, it was black and white---or anyway not in color. Now it is in many colors: purple, green, pink, brown, and laid out in blocks of text, with blocks of useful resource links.

Basically the features of HTML have been used to present the information in a more mind-catching way, so as to make a stronger impression on the young reader.

So the link ( http://www.phys.uu.nl/~thooft/theorist.html ) works just fine. Maybe I am just dense and not getting your joke, or your meaning. What "does not work anymore"?

 

[MTd2]

Maybe it is not a joke and his provider blocked the site for some unrelated random reason. BTW, I really would like you Marcus, to open a thread on the paper I sent you by PM.

 

[marcus]

Maybe it is not a joke and his provider blocked the site for some unrelated random reason. BTW, I really would like you Marcus, to open a thread on the paper I sent you by PM.

I did open a thread several days ago, as you requested. The paper was about the octonions, a math topic.
https://www.physicsforums.com/showthread.php?t=438585

Crowell noticed the thread the same day I posted it, and kindly replied with some additional information.

 

[MTd2]

Really? Where?

 

[inflector]

Really? Where?

Try the link in post #131.

 

[MTd2]

Oh, yes. I answered too soon! :) Marcus edited. :)

 

[arivero]

a cross-field applications here with physics.

...

So may try to see the laws of physics, and the interaction rules between physical systems from the point of view of a trader? :) It could be interesting.

The big thing about econophysics is that in economy we are pretty sure that there are no quantum effects, any probability is just classical probability, albeit it can be very complicated.

 

[sachinism]

@marcus :

yep it works properly

sadly my campus proxy settings won't allow me to access it , but yes i got it confirmed from my friends that itw orks and got a pdf of it by mail

i wasnt joking there :|

thanx anywyas

 

[Fra]

The big thing about econophysics is that in economy we are pretty sure that there are no quantum effects, any probability is just classical probability, albeit it can be very complicated.

That's obviously right in the sense that it's more than reasonable to consider the players in the economy to be "classical systems", but the analogy and mechanis I have in mind is in fact much more subtle and clever than that.

In the sense I mean, there ARE most probably effects "analogous" to quantum effects also in economy. I already declared that it is speculative but "Quantum effects" as per my VISION (don't ask me for proof; I don't have it yet) can be understood in a more general sense, namely that the action of a system does not obey a normal classical probability distribution: which would mean that the action is as if it chooses one simple possibilities at random. But that's not how a rational player would act, the rational action accounts for ALL possibilities at once. But the key to the "quantum logic" as opposed to the classical logic, is that each rational player, has FINITE memory, and FINITE processing power; this means that in order to survive non-commutative structures are preferred. IE. a player that implements non-commutative sub-sets in his memory structure, rather than just a big classical microstructure can be more FIT. And this is the key to the "quantum logic".

So the notion of "rational action" can be generalized to non-commutative structures (ie. the observers knowledge is composed of non-commutative sub-structures that are defined and ordered in the flwo of information processing) and this is the orginal of quantum logic.

I'm not suggesting that current economic models solve the problem, I'm just noting that there are similar problems in macoreconomy, such as defining fundamental values etc. Not to unlike defining fundamental degrees of freedom.

But maybe intuition acquired from that field, may provide new light to some physics problems. They I personally "understand" quantum mehcnaics, is exactly in terms of these things. And the key is to understand that quantum logic is related to non-commutative information structures; and to understand WHY non-commutative structures are in fact more FIT than just one classical microstructure.

Sorry for the long response, we shouldnt' discuss that in this thread but I just want to insiste that I meant something much deeper with the analogy. Economic theory, as well as social theory are just fields where there exists similar problems, and experience from other fields may be a nice source of inspiration and may help ask good questions.

/Fredrik