Thursday, July 14, 2005

The next revolution

Most of the talks and discussions at Strings 2005 in Toronto already belong to the history. There have obviously been many talks about interesting calculations of medium importance. And there have been important conceptual discussions about the big questions.

Jacques Distler and Peter Woit have written quite a bit about the talks and especially about the panel discussion called "The Next Superstring Revolution". As expected, I can agree neither with Peter Woit nor with Jacques Distler.

Peter Woit's main profession is to find, extract, and artificially produce poison in string theory and for string theory. If you gave him a bottle of Coke with a label "String Theory", he would extract several atoms of arsen from the bottle and claim that you gave him a bottle of poison.

Jacques Distler argues that the students should not ask where string theory is going because they must think what to work on right now and forget about some "exercises" associated with the medium and long term future of the field. This is what the graduate students - who are deciding whether they should dedicate their lives to a scientific field - are being told. Does this answer describe the actual state of communication we have reached? Should the young physicists join the field with the plan to look around every three months what kind of activity is helpful for their careers because this is the only thing that they should really be interested in? I hope not.

I hope that even among the readers of this blog, there are people with great goals and dreams. Some of these goals and dreams will remain unfulfilled. But the dreams and visions are important nevertheless. One of the primary general goals of string theory is to achieve a deeper and more quantitative understanding of the world of high energy physics and quantum gravity than the Standard Model and General Relativity may offer us. And nothing has changed about the fact that we have very good reasons to think that string theory can do it.

Because July 2005 is definitely not among the most optimistic moments in the history of the field, no one will tell you that we will complete the theory of everything (or calculate the correct masses of the elementary particles around us) in 2005 - even though this is exactly what the leaders of the field thought back in 1985, for example. An exception may be a secretary who is often reading the grant proposals that always look like if the field is living in the most fantastic era right now. Don't ever trust your secretary in these important matters because her or his understanding of the situation is as twisted as the grant proposals. ;-)

If we rely on theoretical considerations, most of us would probably guess that it would take decades before someone will make the "final" steps that will convince everyone that string theory describes reality.

A student who wants to join a scientific field because of some of her scientific dreams simply cannot avoid the question what string theory is going to look like in 5 or 10 years and what is the framework into which the small pieces of the research should fit. Sure, no one knows the answer - much like they did not know in 1992 that the Second Superstring Revolution was behind the corner. But we must still ask this question and try to find the best answer we can because we study string theory - at least I believe so - because of some important things that are emerging and will emerge.

I totally agree that if the string community became a collection of people, neither of whom knows why they're doing what they're doing, the support for this community should decline. And let's hope that this is not the atmosphere we are approaching.

Those who think about joining string theory to build their careers can be assured that string theory won't disappear in the next 5 or 10 years. In the competition between the theories going beyond the language of Quantum Field Theory, string theory has been the winner for 20+ years and it will remain the winner for the years to come. The people who have been saying that the whole field of string theory is a fad that would disappear because there is nothing deep about it have been saying wrong things for 20 years and it has been shown that they have been wrong - and I assure you that the primary statement of their blogs will remain nonsensical in the near future, too.

Despite some increase in the quality of the contributions, Peter Woit's blog will remain a propagandistic web page addressed primarily to the readers who are not terribly demanding - and a web page that gives you wrong answers to many essential questions.

The two previous paragraphs mean that any potential difficulty of string theory is actually a difficulty of the whole theoretical high energy physics; these two things have already been heavily correlated and you can't separate them anymore.

The people who ask whether string theory lives in one of its most optimistic eras should clearly be told that the answer is No. But unlike some other candidate theories, we have not discovered a mathematical consistency in string theory. We have not discovered a serious discrepancy between string theory and the broad features of the real world either. We have learned many things that simply work and will undoubtedly remain a solid piece of mathematical physics and a foundational pillar for future investigations.

Another important question is whether we know what is the most direction where the field is and should be going, and the answer is probably once again No. Of course, the people with their own proposals may disagree because they believe that their proposals should determine the direction.

In the discussion under Jacques' article, Dan noted that it was unexpected that Jacques would work on the fashionable anthropic business. Well, yes, I definitely agree that the anthropic landscape business is fashionable; it is in fact one of the dirtiest fads in the history of theoretical physics. Jacques argues that he never does anything because it's fashionable. Unfortunately it is easy to see that this sentence of Jacques is not true because I still happen to remember Jacques' description of his early days in string theory that he offered when he was blogging from Sidneyfest; it was disappointing enough so that I could not forget about it. Jacques wrote:
  • Sidney Coleman is my hero.
  • That statement requires a little bit of an explanation, as Sidney was my PhD thesis advisor. Truth be told, his direct influence on my thesis was negligible. Midway through my graduate career, string theory swept through high energy physics. As a sensible young man, I dropped everything I’d been doing and rode the wave.

I suppose that someone could argue that "riding the wave" is different from "doing things because they are fashionable". But I would not be terribly impressed by such an argument. This revelation why Jacques became a string theorist was simply a sad thing to learn for me. But not catastrophically sad ;-) because it is pretty clear that "riding the wave" is what a majority of the people are thinking about anyway.

There is no need to say whether I belong to this majority because the readers know it anyway.

Once again. Some graduate students can have a feeling - a very justified feeling - that something is being hidden from their attention. They're not being told the complete truth. But they should know that they are being told the truth about the basic question - namely the question whether string theory will remain the primary direction to attack questions that go beyond the language of quantum field theory. It will and we are aware of no serious problems with string theory. With a help from the LHC (that may generate some fantastic data) and perhaps a next revolution in the theory, we may come closer to God's mind.

Before it happens, people will probably have to get rid of many incorrect ideas and prejudices - the anthropic craziness is almost definitely one of them. And things will be a lot of fun. And one more thing for the students: there is a lot of stuff for a student to learn - stuff that will remain a part of theoretical physics forever. It actually takes some time before one learns enough to be able to judge whether the stock price of a field is increasing or decreasing and whether a particular project is gonna be a breakthrough that will amaze everyone else. And before you learn all these things, the trend can be completely different and you don't want to miss the next explosion of stimulating ideas.

And don't forget: you are not expected to follow someone else throughout your life. All of string theorists can be doing something silly, and you will be the first one to point it out. But if you want to be serious about these things, you must first learn a lot of material and work on some serious things. Good luck to all of us.


  1. Dear Prof. Motl
    I would greatly appreciate your response.

    Please what is interrelation mutually fractal attractor of the black hole condensation, Bott spectrum of the homotopy groups
    and moduli space of the nonassociative geometry?

    Please what is the topological quantum foam structure like which is generated by base of the U-dual manifold (octonionic tree)?

    Thank you very much obliged.
    With great respect
    Marcel Steiner

  2. Lubos:
    Let's discuss some of your beliefs a little bit deeper and see what they are.
    You believe, and made numerous claim that string theory is the clear winner in the past 20+ years. I think you have used a strange keyword. I wish you had used a more appropriate word, which I will give below later.
    Winner/Loser is a competitive term. Who is a winner or loser is purely decided by the comparison between competitors' physical, mental, intelligence capability. Winning or losing, in this case, however, has nothing to do with the truth of the nature, but has everything to do with the skills of participants of competition.
    When it comes to describing the truth of the nature, there really is no competition and so there is really no winner or loser. All we can say is one theory either correctly describe the nature, or it does n't correctly describe the nature. Your theory is either a succeeder, or a failer, but not a winner or loser.

    Whether your theory, SST succeed or fail, is purely a thing between your theory and the nature, and it has nothing to do with how the other camp, LQG, is doing. If you are right, you are right regardless what is LQG, if you are wrong, you are wrong, regardless of the state of LQG. So there is no competition. There is really no winner or loser if this is not a matter of competition.

    So I hope you would have used the word successer or failer to describe your favorite theory, instead of winner/loser.

    Now my question is, regardless of what other theories are doing, are you willing to call SST a successer, or a failer, when it comes to describing nature? Are you even willing to answer this question?

    Isn't the claim of "winner" an invain attempt to hide your reluctance to even discuss whether SST is a successer or a failer? Sure you are a winner, you win in fundings, you win in researcher head counts. But you are not a successer, so far you are a failer theory. You have not describe a single thing in nature successfully.


  3. "If you are right, you are right regardless what is LQG"

    Sure, but if he's right LQG is not what it purports to be. That's the point.

  4. Your psyco said: "Sure, but if he's right LQG is not what it purports to be. That's the point."

    The reverse of logic does NOT work. If SST is right, then LQG is probably wrong unless it can be shown to be an equivalence of SST. But if LQG is wrong, you can not reverse the logic and say it proves SST right. It doesn't work that way.

    Whether SST is right or wrong is based purely on its own merit. Attacking LQG or other theories does NOT make SST more correct or less correct. It seems to me that SSTers are spending much more energy in attacking others, rather than showing us what SST can do. That's because you really do not have much to show in SST.

  5. Dear quantoken,

    I completely disagree with your last two statements. In discussing the present status of quantum gravity etc. - or whatever we should correctly call it (only future will tell) - SSTers are not using much energy on attacking LQG or any other rival theories. Just take a look at Spires; how many papers by string theorists on QG/SST are actually comparing SST with LQG, and saying that the latter one is wrong for these and these reasons..., and how many people, who favour LQG, are saying that SST must be wrong for these and these reasons? And concerning your last statement, I would recommend a further quantitative study of the bulk of papers @ Spires comparing the number of predictions proposed by SST compared with the number of predictions by LQG per paper, of course.

    Best regards,
    Kasper Olsen

  6. Perhaps I am a rarity, or maybe simply insane, but when I decided to be a String Theorist (my senior year in high school), I did so BECAUSE the subject was so mysterious, was so little understood. Questions like "What is M-theory?" and "How do we describe 4-d physics from a 10/11 dimensional theory?" (both popular at the time, circa 1996) were what interested me. Indeed, had these questions been answered (or at least, not simply transformed into different questions as they have been) by the time I entered graduate school, I would not have decided to enter the field. It was not hope to describe reality, or a sense that this was a way of getting a job/grant, but was an intellectual challenge that still drives me today. What my adviser tells me, what I experienced at Strings 2005 (I was there), they all simply increase the mystery, and therefore increase my desire to work in this field further.

    But then again, I may be a rarity.

  7. Dear Sam,

    you're not alone. The thing that always attracted me to the field has also been the mystery from the beginning and there are many of us.

    But I am afraid that that we disagree whether the mystery grows or not. In my opinion, the mystery of M-theory in the narrow 11D sense (for example) has largely diminished. We have found its definition, we're pretty sure that we know all of its stable objects and other phenomena, we know a great deal about its compactifications etc.

    We don't know everything yet, but given this fact, we have just learned too much, in a sense, especially compared to the almost completely missing relevant experiments.

    The mystery of the overarching M-theory in the broad sense remains, but too many attempts to uncover it have failed recently.

    I think that much of the very recent attempts to go forward do not enhance the mystery but rather confusion which is a slightly different thing. A confusion occurs when we cease to agree what is a mystery and what is not, and whether we have solved it or not. And this situation should go away.

    All the best