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  1. W

    B Cosmic ray charge

    Yes but that just moves the charges around. The fact remains that there is a large free positive charge in the interstellar medium, which presumably must be balanced by an equal negative charge which is attached to various kinds of matter. Since the volume of interstellar space is far greater...
  2. W

    B Cosmic ray charge

    Indeed I am sure this is the reason. But regardless of reason, the fact is that positive charges are permeating space, while negative charges are not seen. Assuming that charge is overall neutral, where are the corresponding electric charges? That is my question. And it interested me primarily...
  3. W

    B Cosmic ray charge

    Ok, I made at least one error. The cosmic ray density 10^-3 m^-3 is intragalactic, not intergalactic. Most of the rays are trapped in galaxies. So I redo my estimate for a single galaxy, say the milky way, diameter 40 kpc and thickness 0.3 kpc. This volume is less than the previous cluster...
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    B Cosmic ray charge

    A simpler way to look at it is that the mass of a galaxy is about 10^45 g. If the charge is really around 10^64 (negative), as estimated above, then there would be charge of 10^19 per gram, or roughly one Coulomb per gram of mass. This is clearly ridiculous since the electrostatic forces would...
  5. W

    B Cosmic ray charge

    Well, let's estimate it. Cosmic ray density is believed to be basically one per 1000 cubic meters, almost all protons (I read this here: http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/cosmic.html) So charge density is 10^-3/m^3. The Laniakea galaxy supercluster that we are in is approximately...
  6. W

    B Cosmic ray charge

    Are you saying that no charge at all will be built up, or that it doesn't have to be large?
  7. W

    B Cosmic ray charge

    Cosmic rays are overwhelmingly positively charged. Hence, whatever is emitting them must be building up an enormous negative charge. So should we expect to see highly charged Reissner-Nordstrom black holes out there? Perhaps even near extremality?
  8. W

    A Anomaly of self-dual tensor

    I like the spectral-flow viewpoint on chiral anomalies, as described for instance in Peskin & Schroeder, last part of Ch. 19.1 This appears to depend crucially on the concept of fermi sea level, making it specific to fermions. However, bosonic self-dual tensor fields also have an anomaly...
  9. W

    Star groups SU*(N)

    I've run across a Lie group notation that I am unfamiliar with and having trouble googling (since google won't seem to search on * characters literally). Does anyone know the definition of the "star groups" notated e.g. SU*(N), SO*(N) ?? The paper I am reading states for example that SO(5,1)...
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    B Strings 2016 Videos

    Ok, it may be slightly better now, but it still doesn't work. The videos just constantly buffer and are not watchable.
  11. W

    B Strings 2016 Videos

    Here's the first day's worth http://ymsc.tsinghua.edu.cn:8090/strings/?page_id=706
  12. W

    B Strings 2016 Videos

    Is it just me or are the videos at Strings 2016 unwatchable? They start and stop and continually seem to buffer, as if the bandwidth is not sufficient. The organizers did not respond to my email. I don't see a way to download and view offline, and I can't tell anything about the streams, e.g...
  13. W

    I A light wave and a sound wave travelling together

    It's not really a well-defined question since the medium breaks lorentz invariance so that there is a-priori no simple way to compute what observers in different states of motion will see. The observers, and all of their measuring apparatus, are moving through the medium and they will be...
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    Special conformal transformation and inversions

    Question, within the conformal group of say standard euclidean space can the inversion be obtained by exponentiating the standard generators? Presumably it would be with some combination of translation and special conformal transformation in parallel directions but I'm not seeing how it can work...
  15. W

    Quick question - has length contraction actually been experimentally confirmed?

    Length contraction is real. You can compute the length of a moving ruler using E&M and Quantum Mechanics, without ever using Relativity or the Lorentz Transformation. Relativity comes from the physics, not the other way around.
  16. W

    The role of mathematics in physics (and science)

    By "description" I mean of course a description in terms that you can define. One can define an electron, using mathematics, but good luck defining a god or demon. As for "explanation", that is not the role of science. That is the role of fairy tales.
  17. W

    The role of mathematics in physics (and science)

    Can you express this "underlying physics" in some form other than mathematical? I would be interested to see it...and so would the Nobel Prize committee :-)
  18. W

    The role of mathematics in physics (and science)

    The source of these regular behaviors is their underlying mathematical basis. Indeed, it is not even possible to define an atom or a proton on its own (consider all the intermediate states of partially-destroyed atoms and protons). Only the underlying constituents, electrons and quarks and...
  19. W

    The role of mathematics in physics (and science)

    It's difficult for me at least to picture the concept of "no physical laws". For example, is there a space with fixed dimension in which things happen? That is a law... Can truly any event happen, e.g. universe turns into a potato, then Bart Simpson, then War and Peace wrapped on a torus? If...
  20. W

    The role of mathematics in physics (and science)

    Note that you say "rather arbitrary", instead of "arbitrary". There is a big difference between "rather" arbitrary, which implies rules, and completely arbitrary, which is the case with no rules. If you put yourself in the position of the creator of a universe, and attempt to further specify a...
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    The role of mathematics in physics (and science)

    Hi guys, In my blog www.letstalkphysics.com I present an argument (pretty simple) that mathematics must be the foundation of any possible universe (as it certainly seems to be in ours). I wrote it because it seems that so many people, both mathematicians and physicists, not to mention...
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