Supersymmetric world from a conservative viewpoint
Hi Luboš. Let me apologise first for writing something here that has no connection to your "CNN about Witten" posting; I thought it unwise to send you an email since it is something that I would like to comment briefly. I recently listened to a lecture given at some point in time at the Ecole normale supérieure (Paris) by Costas Bachas, who is a physicist and teaches at the 'Ecole polytechnique fédérale de Zurich' (I'm not sure whether he is actually a theorist in stringy physics). The audience listening to his lecture is mainly lay, with a few physicists attending. After delivering his lecture, someone asked him about his thoughts on LQG, and I'm not sure whether it's because of the language differences between English and French, but I had the impression that what he said made more sense than the fanatic (English) statements of some physicists versed in string theory from the US (I don't think you're one of them, to be sincere), which is quite surprising. I have the impression, and this I guess makes sense to some extent, that research in string theory in France does not face a lot of opposition from the other camps or unsided fanatics/crackpots. It's true that the US research program is more mediatised/publicised than that in Europe, and this invites criticism to a larger extent, but then this makes me wonder.. Is the sociological picture of fundamental research very different on the 2 continents (US and France I mean)? Do you think the French care at all, and do you think the intellectual tradition of France (pure mathematics in all its glory) has something to do with this perception?
Dear Nitin,Costas is a smart and nice person, so his particular opinions may reflect his personality rather than the difference between France and the US. But there *are* differences at the national level.As you know, I am still carefully (and in many respects, clearly) closer to the US way of thinking about these things. There are many differences between Europe (represented by France in this case) and America. The US has been focusing on the most advanced directions at the cutting edge, and it led the second string revolution (as well as other revolutions) and other related things; the US tends to focus on the most sexy and attractive subjects.The US physics is - or at least was - much more focused on results as opposed to philosophy. By results, I mean calculating real numbers that can be either compared to experiments or to mathematical "experiments". By this definition, LQG has no results whatsoever. Sorry if it sounds fanatic to you, but it is simply the case. If something sounds more peaceful, it is not necessarily more true - and this statements may apply both to French and American comments about Saddam Hussain as well as Loop Quantum Gravity (sorry for this comparison, Saddam). ;-)France is an example of a country which does a lot of stuff about integrable systems; loop quantum gravity (Rovelli is there right now?); mathematical physics without direct goals to be relevant for the theory of everything. Things that don't change much for decades.Yes, definitely, there are differences between the different nations - and not only in the amount of money. While I am sure that the US system and approach is the most efficient systems to lead the world of science at its best and fastest periods, it is conceivable that the French (or European), more relaxed and less hyped, focused, and excited approach can be better in other contexts.Be sure that America is much more pragmatic; much more competitive; but it also gives fundamental research more freedom.All the bestLuboš
Let me complement Lubos by saying that he is definitely not a string theory fanatics. In challenging Global Warming Theory and in raising many good questions in string theory, I think he showed evidence of independent thinking and so there is evidence of intelligence in him. He is on the wrong track continue working on string theory. But if one is capable of independent thinking, there is hope for salvation.The problem with Witten is he is one of the most intelligent guys but he works on the wrong ideas so that's a waste. Witten might as well work in a restaurant and nothing would have been missed in the world. Actually it would make the world better since less number of smart young people would be following the footstep of Witten, and would instead work on really important, useful, and fruitful ideas. That's how I view Witten: An Einstein that has been wasted.When it comes to fundamental theory of spacetime at microscopic skill, there are two different philosophy beliefs. Lubos belongs to the camp that believes spacetime is inheritantly continuous, which is actually a minority camp. Me and the majority of physicist believe that spacetime is discrete at fundamental level, the majority camp.Now, nobody has a problem with QM, which is well tested experimentally and well established. So both camp agree that all observations are quantum, or discrete, that includes our measurements of spacetime itself.So as far as our observations go, we observe reality as a discrete world, discreteness is all that we can observe. No disagreement, right?So the difference between Lubos's continuous camp, and my discrete camp. Is that he probably believes there is a reality, a "real" reality, that exists behind and beyond the reality that we could possibly observe. So you accept an un-observable reality, beyound the observable one. You accept the reality behind observation, in the same fashion that Newton accepted the existence of an absolute spacetime, behind our own observation.I am having a problem with that. The philosophy developed from Copenhagen Interpretaion accepts observation as the only reality that exists, and we do NOT recognize any absolute hidden reality beyond the reach of our observation. What we see, and can see, is all there is in the reality. We deny the existence of any thing, unless it can at least in principle be observed. And we define physics as purely for the observable only.That's a huge difference!!!Now, if you accept that only the observables are real, you have to accept that spacetime is discrete. If you accept discrete spacetime, when you go to a small enough scale, spacetime no longer exist, because there is no longer any thing that differ one spacetime point from another at that small scale.This is why both string theory, and LQG, and most other approaches are all wrong. If you do not even have spacetime to begin with, where do you get your 11 dimentions? And You can't use geometry to describe microscopic world because geometry will need a spacetime background, which you don't even have.Spacetime does NOT exist at fundamental microscopic scale! The only thing exist is quantum information, quantum bits. And you can not push the scale to something even smaller, because there is no longer a spacetime for you to zoom in further!!!So the correct theory must start with no spacetime, and no geometry, and try to construct spacetime using quantum bits of 0s and 1s, and construct the geometry likewise. Currently, my QUITAR theory is the only thing that pursuits along this approach.There is huge indication that this is the right approach, because it leads to the correct G value with the correct magnitude, and only 2% discrepancy, after factor in huge numbers of 10^40 or more. However I do acknowledge that my theory is imcomplete, and it is very hard to find the proper mathematics tool to construct spacetime out of quantum bits. Maybe such math tool hasn't been invented yet.Quantoken
Of course it is important Quanto to realize "this nature" that these camps have been split into, but reality dictated to solid things, is not the only way to look at it.Without, "continuity of expression" what should you do? Discard all the physics processes and embrace only those that might entail such discrete views? Are "gravity and energy" not a quasi-thing? Without understanding, states of fluidity can exist, is there no perfect fluid?:)Since Maldacena's conjecture does not apply to QCD, however, the viscosity of the real quark-gluon plasma cannot be computed via string theory. This makes the RHIC announcement that the viscosity of its plasma is comparable to the values one finds from string-theory calculations even more surprising. If this is true, the quark-gluon plasma created at RHIC could be the most perfect fluid in nature. This in itself is an interesting fact, but it could also indicate that string theory has some relation to real QCD. However, we first need more quantitative evidence from RHIC, such as an upper bound on the viscosity.Of course Lubos is right about such experimental vaidation processes, and none should be surprized, that such validations are at the basis of such theoretical research? To have "new ways" in which to do deal with this reality.Peter Woit:"It quite possibly can provide some sort of dual description of QCD, and that is what much research in string theory these days is aiming forPeter Woit tells us the opportunity is here then for "predictability." How shall it be done? We have to exercise our "mellons," right?:)
nitin - Hmmm. So you don't think Lubos is a fanatic. What did you think of his comparison of Saddam and LQGer's: ...may apply both to French and American comments about Saddam Hussain as well as Loop Quantum Gravity (sorry for this comparison, Saddam). ;-)Lubos - For sure you are right about LQG not producing any experimentally checkable numbers. Maybe you could remind me which priedictions of string theory have been experimentally checked. And how did the numbers compare?
Hello capitalistimperialistpig I don't think Luboš falls into my definition of a 'fanatic'; but then I have to admit I don't know Luboš' thinking and personality enough to pass a reasonable and fitting judgement of the person. His postings about his views on the state and progress of theoretical physics and, despite him, international politics, sometimes surprise me, coming from what one would expect a relatively young cultivated person from Harvard, and it is quite worrying sometimes and a bit sad that these views are posted and defended with fierce blind passion on his blog (but then this is Luboš' reference frame, and only his ;)).I think his comparison of LQG researchers with Saddam Hussain (I don't know to what extent this comparison goes, and I am not at all interested in knowing) is very déplacé. Clearly capitalistimperialistpig, if you think a bit about it, this seeming comparison has no substance, hence this statement of Luboš can be ignored completely (Please learn not to be outraged by Luboš' statements; I would be dropping physics if I took most of what Luboš said at heart). As a young person who is still being trained in physics at the undergraduate level, I am sometimes quite outraged by the very unpleasant and outright disgusting 'dispute' between practising physicists, but then I recognise that I still have to understand my stuff first and let the 'old guys' 'kill'/love each other and be stupid/smart, and then I try to learn from their mistakes/glories. I guess that, given the present state of research in physics, with the US government's (and other less publicised) funding policies, and given the numerous modes of attack deployed and engineered by different groups of physicists to understand how to make a theory from 2, it is hard to know where exactly this is all going. A schism at the level of fundamental research is not very appealing, but then I presume it is how the world functions. What I hope is that, even though the practising physicists are struggling with these big difficulties nowadays, they always recognise and remember this passion for enquiry that brought them into physics in the first place when they ere kids, and not to fool themselves too much.
nitin - Well, if you care about physics, don't let anybody's (especially Lubos's) attitude bother you. Fundamental physics does have a problem right now, though - the theory is too good but not good enough. So good that hardly anything (in particle physics) is unexplained, but so bad that nobody can calculate anything new that can be tested. But you already knew that, and maybe the LHC will give us some new hints - or the high resolution CMBR probes.
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