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Everything posted by BenTheMan

  1. Well... Kind of. Then we would need statistics.
  2. It depends on what you mean by ``wrong''. Personally, I feel that GR is not really a fundamental concept, but emergent. In other words, space-time is only an effective description, that is good classically. I feel that there are good reasons why GR (and all of the things that go along with it) breaks down at short distances, and there is nothing really fundamental about ``geometry''. Martin, I think, will disagree.
  3. I agree, I think. As long as the oscillation time is on order of hbar times a few, right? (So, VERY quickly.)
  4. Well... Try not to lose too much sleep. Think about the numbers involved. Suppose you have, say 10^23 electrons. This is a pretty common number in chemistry---this is like a thimble full of whater. So we have these 10^23 electrons, and we want to do a calculation of something. In order to do the calculation fully, using quantum mechanics, we would have to know instantaneously the state of the 10^23 electrons, spin up or spin down. This means 10^23 bits or 10^14 gigabytes of data all at once. This is roughly five orders of magnitude (10,000 times) more information that the biggest hard drives that I know about. And this is just to know what state the electrons are in---we haven't even done a calculation yet. So it's not that we can't concievably do it, it's that we can't fesably do it. Instead, we use statistical treatment---this is the field of statistical mechanics, which is very useful for people calculating things with lots of electrons. I agree with you. I think string theory is the answer:)
  5. foodchain--- Quantum mechanics can be made consistent with relativity---it is a subject most undergraduates study, Relativistic Quantum Mechanics. QM cannot be made consistent with GENERAL relativity, but this has nothing to do with the problems in this thread. The point that swansont and I made is that there is no conceptual barrier, only a computational one---there aren't enough computers in the world to do even simple problems.
  6. budullewraagh--- you need a position or momentum space representation for psi. Then you can do the integrals at integrals.com. Actually, if you are a physics udergrad, you should own a copy of this book. Seriously. If you go to grad school, you may eventually need this book.
  7. Yeah---(s)he has tacitly assumed that there is a good frame where one can take the photon at rest. But one of the postulates of SR is that there IS NO such frame. So (s)he's using the results of SR (specifically mass-energy relationships) in a frame where SR doesn't hold.
  8. Absolutely not. Two reasons---one, there is no need to, because we can get accurate results from classical computations (as swansont said). Secondly, the numbers are just too big to deal with. One would have to understand how to calculate a system of something like 10^24 particles, and there are fundamental limitations on how much computing power one can have---for example, your computer can do perhaps 10^10 calculations a second. These are basic calculations, no more than true/false comparissons. To analyze a classical system using quantum mechanics, you would have to solve Schroedinger's equation 10^24 times, which is a second order differential equation. If we could measure things 10^23 decimal places, then it may become important. Otherwise, there are better ways to utilize computer time. Unless you have something to prove:)
  9. This represents a breakdown of unitarity, then, because no unitary operator could ever ``lose' information. But you don't seem to have a problem tossing unitarity in WW scattering (i.e. killing the higgs), so I shouldn't be surprised.
  10. Like it or not, the physics involved in calculating the Hawking radiation is not very hard---it is a semi-classical calculation, which any graduate student could do, if given enough time. One just has to understand how a scalar field behaves on a changing gravitational background. We understand quantum field theory very well, and we understand how to make QFT consistent with general relativity (there is a book on it by Paul Davies and Birrell, if I've spelled his name correctly). If you want to do a google search, the actual method is called the Bogolubyov transformation (which I have probably hopelessley misspelled). The point of all of this rambling is that the loss of information in a black hole is very easy to show (I don't remember very many calculations in Hawkings 1972 paper). IF this calculation is wrong (i.e. if you think informaiton is not lost), then you should be prepared to explain why you think it is wrong, and how to fix the derivation from the point of view of quantum field theory on a curved space-time.
  11. Why would you do this? Do you normally go around merging similar threads? The discussion in that other thread has drifted pretty far affield from physics, and this is an attempt by vincent to actually start discussing physics again.
  12. Unless there are macroscopic phenomena based on quantum measurements. Like (perhaps) in the brain. There is simply no way to make a general statement like this---I gave you two examples... In the first case, nuclei past hydrogen cease to exist, which is a pretty radical difference.
  13. touche I think you're right about Nima. Personality-wise, he's absolutely fearless when it comes to making bold claims. For example, in Princeton this summer (in front of the IAS members, of which he is now one), he said (I quote) ``Gauge invariance is a bunch of crap.'' (What he meant was that there is nothing really fundamental about it---it is a tool that we use to build theories. To actually measure something, we have to pick a gauge, which means we have to take the gauge invariance out of the problem, which we inserted in the first place.) And out of all the lecturers I met at Princeton this summer, he was the one who spent the most time with the students. He also has a completely different view of fine tuning, which is something that sets him apart from the older generation of physicsts.
  14. sinc is an elliptic function, right? When you analyze the diffraction in one dimension, called Fraunhofer Single Slit Diffraction, you get a sine squared functions. Because sines and cosines are the one dimensional analogue of the elliptic functions, one would probably get the behavior you are talking about in two dimensions. It happens because light is a wave, and the pattern that you see is interference at the screen between light that takes different paths to the same point. See the link that I posted, it has some nice physics there.
  15. What do you consider a ``little effect''? It is possible that we live in a metastable vacuum, for example. This means that our universe is sitting on the edge of a canyon. There is a finite chance that we could tunnel to another vacuum at any instant, which means that there are universes where this happens, and there are universes that are VASTLY different from ours---i.e. we no longer exist. Because it is unlikely, the number of universes that tunnel to another vacuum are few. But this is a quantum event, so I don't know how you can claim that there will be little effects at large scales. Another (canonical) example is Schroedinger's cat: half of the universes find it dead. So in half of the cases, the cat has ceased to be (did anyone catch the monty python ref?)---this is a pretty radical difference if you're the cat.
  16. Lee Smolin has very little influence over the physics community. As does Hawking, actually. Hawking hasn't contributed much to physics in a long time. For high energy theory, it's probably Witten. Judging by citations, though, it could be Maldacena, who discovered the AdS/CFT correspondence. If it's based on book sales, then definitely Brian Greene, who's book has won many prizes, and still outsells other pop science books after eight years in print.
  17. Ummm... I AM a physicist? Take a poll of physicists and ask them if they believe in a higgs or in technicolor, and then ask them why. The two answers are both possible, as we haven't observed the higgs sector yet. The consequences of the two theories are the same for the low energy data. But only a handful of people in the world think that technicolor is right, because the higgs is much simpler. lucaspa---I think perhaps you are coming from a different world. Aparently you're a biologist of some ilk. Maybe what you say is true in your field, but I can say, without a doubt, that in MY field (physics), simplicity is the deciding factor when it comes to two different descriptions of nature. There is a simpler way to do quantum field theory calculations than Feynman path integrals??? Please show me. They are a bitch to do. Oh, wait. Have you ever calculated a cross section using Feynman's path integrals? Radiative corrections to electron-positron scattering? The anomalous magnetic moment of the electron? Muon decays? Proton decays? You can save your lectures---I am writing a PhD on curled up dimensions. lucaspa---You and I are of the same opinion of intelligent design, this much is clear. But you are not right about the way we select theories, at least in physics. I think you are outside your area of expertise, I think. ``I think that when a physicist talks about things that aren't physics, he's just as dumb as the next guy.'' ---Feynman
  18. I think that you're making difficulties Consider this---in THIS universe, some people obey the law and some people do not. Does the fact that people exhibit a range of compliance with the law mean that the law is unjust? I don't want to have to read fifty pages in the other thread to get caught up, but there is simply no way to know this without knowing the details of how the brain works.
  19. Whatever man. I am not under the impression that citations don't matter. And if you really want my honest opinion, there hasn't been a field changing paper in the past ten years or so. The one paper that has come out recently that will probably spawn a huge cite count is Intrilligator, Seiberg and some other guy whose name begins with S, about metastable supersymmetric vacua. There are a thousand reasons why your index doesn't prove anything---perhaps the biggest reason is that the community is bigger now. Why don't you apply the same index to condensed matter, or biophysics? Or even (gasp) non-stringy quantum gravity approaches.
  20. It's only a concern to people with nothing else to concern themselves about. Besides, it's all a bunch of bullshit like these sales numbers---they don't MEAN anything, except to people like you and Peter Woit. Look at how many people cite Maldacena's AdS/CFT paper. Or Witten's String Theory Dynamics in Various dimensions. These papers outlined HUGE new areas of research, neither of which could be filled out in five years.
  21. Pseudoscience is in this year. But seriously... The point is to show how ridiculous this all is. You may think that this is ``great fun'', but it seems that martin takes it awfully serious---to the point of spending his time scouring amazon.com sales records. Showing that Lee Smolin's book is selling better than some string books is kind of a goofy thing to do. Personally, I am more impressed that Elegant Universe is the top selling string book after almost ten years in press.
  22. Ahh. No. We are always quite frank about the numbers. And we actually do phsyics, instead of sociology. But whatever.
  23. Wait, is this the claim that evolution is not consistent with the second law of thermodynamics? Edit: lucaspa has succesfully rebutted this argument already.
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