Is string theory dead?

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Is string theory dead?

Postby Louis_B on September 27th, 2010, 5:47 pm 

A few years ago string theory came about via quantum physics. Nobody knew they existed for sure but they were hoped to be the building blocks of matter. Then, we heard about super-strings..The hopeful wrung thier hands in anticipation. but then, like cold-fusion, it just kinda fizzled out. Now it just seems to be a plaything of mathematicians. As matter would seem intuatively to have a basic matter-energy relationship at the quantum level, are strings now just another dead-end or is there anything still to be learned from them?
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Re: Is string theory dead?

Postby Lincoln on September 27th, 2010, 5:52 pm 

Marshall will give you a different view.

I don't think strings are dead. They're a neat idea. I personally like them, although I have precisely zero confidence that they are real.

The real issue is that after a couple of decades of attack by very smart people, there are no predictions. Indeed, the best they've been able to do is to make approximate solutions of approximate equations. Because of this, people are taking a breath, backing off, and thinking about alternatives. It is, after all, frustrating to work for so long and make only minimal progress.

So, I wouldn't call them dead. They're just no longer the darling of the theoretical world that they once were.
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Re: Is string theory dead?

Postby Louis_B on September 27th, 2010, 8:25 pm 

Hi Lincoln;

I personally like the idea of strings. I like the idea there is a fundamental building-block that all matter can be whittled down to..it makes sense. I was a bit disappointed when people started saying that they were not the gateway to the fundamental principals of matter we hoped they would be. They seemed to be the crossover between matter and energy, the missing link.
I try to dig deeper and all I get is incomprehensible math, nothing solid; nothing physical. I still hold out hope, even quarks and measons and electrons are made of yet smaller bits and pieces aren't they? If there is one fundamental law of matter it has to be simple enough that everything can follow it, that's just common sense. So the parent particle must be a simple beast, whatever it is. So the horse may have bolted, but it's still in the paddock...Well I hope so anyway. Maybe its's a Schrodinger horse, everywhere and nowhere. I wonder if he ever got his cat back!
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Re: Is string theory dead?

Postby Marshall on September 27th, 2010, 8:29 pm 

Marshall won;t give you a different viewpoint, unfortunately :-D
Lincoln wrote:...

I don't think strings are dead. They're a neat idea. I personally like them, although I have precisely zero confidence that they are real.

The real issue is that after a couple of decades of attack by very smart people, there are no predictions. Indeed, the best they've been able to do is to make approximate solutions of approximate equations. Because of this, people are taking a breath, backing off, and thinking about alternatives. It is, after all, frustrating to work for so long and make only minimal progress.

So, I wouldn't call them dead. They're just no longer the darling of the theoretical world that they once were.


That seems like a fair assessment.As an inside perspective. I can't think of anything to change.

The outside, on the other hand, the publicity, hype, and popularization is another business. Stephen Hawking raising unfounded expectations about "M-theory" (which is a string outgrowth.) A lot of that was misleading/excessive. Maybe the hype will gradually die down
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Re: Is string theory dead?

Postby Lincoln on September 27th, 2010, 9:21 pm 

Well I gather from the body of your posts that you were not very fond of strings. I could dig up the many posts where you said that the best and the brightest were going elsewhere. Plus a thread or two with enthusiastic interest with some of the newer quantum gravity efforts. I didn't think I was going out on a limb here....
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Re: Is string theory dead?

Postby Marshall on September 28th, 2010, 1:42 am 

Lincoln wrote:... I could dig up the many posts where you said that the best and the brightest were going elsewhere. ....


I think that's true. Just in the past 2 or 3 years some of the top people have found ways out of string.
And Witten was already doing other stuff in 2006--recently at some string conferences he either doesn't attend, or he doesn't give a technical paper, just a public lecture for laymen (which in Rome was not about string), or he gives a technical paper in conference but it is not about string----it's about 3D gravity.

But this is not a criticism of string. I think your statement was fair. You said it had lost favor. It has. It has lost interest among top researchers, for reasons you gave..
Simply as mathematics, it is nice and it has applications to doing approximate calculations (not as a fundamental theory of everything but as a toolkit or bag of tricks) as you indicated.

And it could of course turn out 20 years from now to be a correct fundamental theory---we don't know the future.

So I thought the way you put it was precise and balanced.

I don't object to the fancy string mathematics. math is math. you never know what uses it may have.
I object to the arrogance and the hype. Information I assemble about the shift in interest away from string mainly just objectively correlelates with what you say based on your own experience in expert circles.

Plus, since the field has pretty much stalled, I'd like to see less string hype in the popularization market. It is bad for physics to mislead people, raise expectations, and then have it turn out to be a phony bubble.
Popularizers should stick to more solid empirical stuff, less gaga speculation. Longterm it undermines respect for the field. This is not about string *per se*. It is about hype and speculation in pop sci TV series and books.
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Re: Is string theory dead?

Postby Lincoln on September 28th, 2010, 8:03 am 

Well good luck on that. Popularizers sell books if they are breathy and passionate. No heaving bosom, no extensive sales. (Trust me on that one...and I so wanted that Jag....) Plus, the public buys what it already knows something about. Something truly new....no sales.

I write popular science in a pragmatic and empirical way. But you probably wouldn't have heard about my books except through SCF. Maybe I need a cool robot voice synthesizer....
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Re: Is string theory dead?

Postby Forest_Dump on September 28th, 2010, 11:16 am 

Well, Lincoln, if it is any consolation, I bought a copy of your book in a book store in the Great White North. But, true, on the other side of the coin, I doubt very much I would have if I didn't know you from here. Unfortunately, that book ended up in a box before I could read it and I have no idea where it is now. But you have your royalty from me by now. BTW, don't feel so bad about the Jag. Don't the cheaper ones just use Ford engines now?
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Re: Is string theory dead?

Postby Lincoln on September 28th, 2010, 11:55 am 

You didn't buy >>both<< books? See, it's guys like you who keep me from aspiring for that Diablo and making due with a piddly little British car. At least it's no longer owned by Ford. On the other hand, I'm not sure that Tata motors is much better.
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Re: Is string theory dead?

Postby Louis_B on September 28th, 2010, 7:50 pm 

Hi Lincoln.

It's pretty much as I thought then. It's not dead, its just kinda lying there with its legs in the air, twitching occasionally. Not so much strings as mathematical noodles. I still can't help thinking there must be some kind of phase barrier between matter and energy. Some kind of quantum DNA that codes for matter. I was hoping string theory was going to be it, but had noticed a deep cooling of the subject in the popular mags. Quantum gravity seems to have taken its column inches now. 3d gravity- Doh! was it ever anything else? Smashed anything good lately?
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Re: Is string theory dead?

Postby Lincoln on September 28th, 2010, 8:38 pm 

I don't think string theory is dead, nor on its back. It is simply that the boost in the popular literature from Brian's book made people think it was farther along than it was. Theorists always write in such a way that it is difficult for the general public to distinguish between an idea and a substantiated fact. Very sad. It's a lot like politicians....
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Re: Is string theory dead?

Postby pradeepsharma on September 30th, 2010, 1:44 pm 

If the predictions of any theory cannot be verified through experiments it automatically becomes suspect.Sometimes the existing technology may be insufficient to verify the predictions ,if there are any at all.I remember long time back Prof Richard Feynman had said that people kept on asking him about new theories but never about something which he knew very well and was well established.We are all fascinated by unknown.
I have read in some books that to verify string theory acceleraters as big as pluto's orbit in circumference (?) will be required as the size of strings is so small that very high energy is involved to look into this small range.So the string theory is safe as long as it cannot be proved wrong or right.
Infact Prof Martinus Veltman was very critical about string theory in his book he says 'it is not even wrong'.I must also add that Mr Lincoln did not agree very much with Prof Veltman's views in his very well written book 'Understanding the Universe'.
Even Prof Frank Wilczek is not so sure of string theory, this is evident through his interviews.
So the field is wide open.But the ultimate truth will be revealed by experiments only.
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Re: Is string theory dead?

Postby Lincoln on September 30th, 2010, 3:04 pm 

I don't recall taking a very positive direction in Understanding the Universe regarding string theory. I described what it was and pointed to some of its merits. However, I've long been a string skeptic.

One other thing. The accelerator size is dependent on many things and so the "Pluto's orbit" is contingent on technology choices.

It is more likely that string theory will be supported by something like successfully predicting the hierarchy of masses in the quarks and leptons. This doesn't require any additional accelerator. It requires smarter theorists.

In short, string theory is a neato-keen idea. It's even a scientific idea. But nobody should take it seriously until it makes a prediction not possible by other means.
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Re: Is string theory dead?

Postby Louis_B on September 30th, 2010, 6:41 pm 

I'm glad that there is still hope for strings yet. I had begun to think it had been all but abandoned as a serious reality and was now just a plaything of math-heads. To me it makes intuative sense that there is a parent particle/energy "thing", whatever strings may eventually turn out to be. Is the LHC going to be able to shine any more light on the subject do you think?
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Re: Is string theory dead?

Postby Lincoln on September 30th, 2010, 6:48 pm 

Louis_B wrote:Is the LHC going to be able to shine any more light on the subject do you think?

Nope.

The theorists need to be able to calculate something we can measure. The LHC is the biggest machine for the next 20 years. We won't build a bigger one in that time. So the weight lies entirely on the shoulders of the smarty-pants theorists.

This may be like "interpretations of quantum mechanics" which has buried many a smart young lad or lass. The physicists may just run out of steam and go somewhere else. Eventually there will be the "enlightening thought" that breaks the whole thing wide open. But that could be years, decades or even centuries.

Time will tell.

In the meantime, don't hold your breath over strings.
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Re: Is string theory dead?

Postby Louis_B on September 30th, 2010, 7:06 pm 

Aww That's a pity. If there is a unified theory of everything its gotta be so simple that every particle can follow it. It seems, like you say, that it's gonna be an inspirational thing. Look how simple E=MC2 turned out to be, yet so elusive. Maybe the math guys are looking too hard. Oh well, when it comes I reckon a lot of folks are really gonna kick themselves!
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Re: Is string theory dead?

Postby Nick on October 1st, 2010, 3:08 am 

While the LHC will not say anything definitive about string theories it will definitely have implications for them. For example whether or not we discover any SUSY candidates could have important ramifications.

I wouldn't hold out much hope that any ToE that arrives will be simple enough for me to understand without much effort.
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Re: Is string theory dead?

Postby pradeepsharma on October 1st, 2010, 4:01 am 

This reply is for Mr Lincoln, I did not mean that you are a great believer of string theory, I just meant that you were less critical of string theory than Prof Veltman.(pg 443 last paragraph of your book).
I must add that all of those among my UG students who read your book have developed deep a interest in particle physics.My elder son is doing physics major(1st year) and he liked your book a lot and my younger son a 9th standard student in school is currently reading it and is loving it.
Now back to string theory,I believe in particle physics a sort of stagnation has set in.We really need some new ideas either from theoretical side or some new exciting events from experimental side.
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Re: Is string theory dead?

Postby Lincoln on October 1st, 2010, 8:57 am 

I agree with Nick that observation of supersymmetry at the LHC would lend support to superstring theory. On the other hand, just because SUSY isn't observed at LHC energies doesn't mean that the SUSY principle doesn't hold at higher energies. (Mind you, if this turns out to be the case, then theorists will like SUSY less. After all, if SUSY applies at higher energies only, it cannot be used to solve such issues as the hierarchy problem.) But these are questions of aesthetics and not fact.

Pradeepsharma,

I didn't write much about the validity of string theory. I wrote about what string theory was. It's just because I chose a different topic. Personally I find the work done thus far to be not so interesting. But even that's not so correct. You have to take baby steps before you can do the final thing. The problem is that it has taken decades to just do the baby steps. Without some breakthrough, there is no way to know if these calculations are an accurate description of the world, or just for fun.

I think string theory is science. It's just an early part of the process. Essentially it's stuck in the "generate hypothesis" stage. The reason people leave is because they want to see it proceed to the "test" phase. After decades of work, it is becoming clear that progress is hard. And, given that there is no real reason to believe that string theory is true, people are looking around to see if there are ways to make faster progress.

I think you will find that Veltman et al. have a similar opinion. They don't think much of the fact that string theory was elevated to a prominent position without any positive tests. (Me too.) But none of us are opposed to the string idea, nor the work that has gone so far.
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Re: Is string theory dead?

Postby Tomyhoi on October 2nd, 2010, 12:48 am 

What are the leading rivals to String Theory? Loop Quantum Gravity? I know little of it.
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Re: Is string theory dead?

Postby Lincoln on October 2nd, 2010, 7:32 am 

Plus Navel-Gazing.

Since Marshall is particularly interested in this topic, perhaps he will want to expand on the various principals.

In general, these are topics of quantum gravity. Superstrings are (among other things) also a quantum gravity theory. There are several schools, all with different approaches, none of which are very far along.

I guess the answer you receive will just depend on how far down this rabbit hole you want to go.
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Re: Is string theory dead?

Postby xris on October 2nd, 2010, 8:15 am 

Not really understanding the science, I find the questioning of these theories the same questions that philosophy asks. What is reality? is it just a song of creation that vibrates the universe into existence and when the song ends, we disappear, till the next song begins.
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Re: Is string theory dead?

Postby Lincoln on October 2nd, 2010, 9:47 am 

Yeah, but the difference is that science provides answers with substance. Regarding questions of this nature, philosophy's time has past. Philosophy has its place for other things, but it is the alchemy of questions of reality.
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Re: Is string theory dead?

Postby xris on October 2nd, 2010, 12:42 pm 

Lincoln wrote:Yeah, but the difference is that science provides answers with substance. Regarding questions of this nature, philosophy's time has past. Philosophy has its place for other things, but it is the alchemy of questions of reality.

I dont think science has all the answers, it still requires philosophical debate. There are no certainties only valued judgements. I do appreciate science and its amazing discoveries, I admire the scientific mind and its devotion but I dont worship it.
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Re: Is string theory dead?

Postby Lincoln on October 2nd, 2010, 3:56 pm 

I don't think science has all the answers either. Nor do I think that all questions even >>have<< answers.

However, within the topic of this thread...string theory and how it relates to describing reality...I'm quite confident that philosophy doesn't have >>any<< useful answer.
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Re: Is string theory dead?

Postby xris on October 2nd, 2010, 4:42 pm 

Lincoln wrote:I don't think science has all the answers either. Nor do I think that all questions even >>have<< answers.

However, within the topic of this thread...string theory and how it relates to describing reality...I'm quite confident that philosophy doesn't have >>any<< useful answer.

So if we accept science and admit energy is matter and matter is energy what are strings, matter or energy. This it aint a trick question, its my ignorance.
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Re: Is string theory dead?

Postby Louis_B on October 2nd, 2010, 5:48 pm 

If strings are what I hope they are, they are a phase barrier artifact between matter and energy.
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Re: Is string theory dead?

Postby Nick on October 2nd, 2010, 6:01 pm 

Energy is not matter and matter is not energy. Mass is a form of energy (as is momentum). Particles may have mass, energy or momentum but they are not just these things as they also have other properties, similarly for strings (I guess).
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Re: Is string theory dead?

Postby Lincoln on October 2nd, 2010, 7:23 pm 

Matter is certainly a concentrated form of energy.

Time is short right now, but the mass of matter turns out to be at least 98% hidden energy. I can say more later.

I think that if superstrings are true (and I don't claim they are,) then they are energy.
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Re: Is string theory dead?

Postby Nick on October 3rd, 2010, 4:38 am 

My point was that people usually confuse matter and mass. Mass is a concentrated form of energy. Matter is a (somewhat poorly defined) class of particles. The matter particles have mass, energy, spin, charges, etc. You should not say that an electron is energy just as you wouldn't say a car is a steering wheel. Similarly strings have energy, but asking whether or not a string is energy probably means you are misunderstanding something (or you've read too many pop sci books that refer to photons as "pure energy").
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