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    Job opportunties for physicists in the UK?

    Given the current climate for fundamental physics research in the UK right now, you want to avoid it at all costs. Because even if you do get a job as a researcher, you will get no encouragement or support from the government. And the UK scientific community is extremely partisan, political and...
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    How would we find the Higgs if Higgs did not coupe to fermions?

    To be honest, I am surprised this got passed the hep-ph censor, since you have no affiliation. A number of comments: 1. You didn't really explain what the '1's are on your fields, except for "each of the above psi functions has some definite number of indices taking the only value gamma =...
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    Alpha_s calculation

    Think about the Feynman diagrams which make up the processes. At leading order the 2 jet rate is has two quarks in the final state, while the 3 jet rate has 2 quarks and a gluon. The gluon is radiated from a quark line, so there will be an extra factor of alpha_s.
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    Why are Planck quantities so extreme?

    It is unclear to me whether the original poster is asking how we know that the Planck length is so small, or is asking the much harder question of why is it so small. As to the 'how we know', it is simply a reflection of the observable fact that gravity is an extremely weak force compared to...
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    Who has a PhD

    The last time I examined a PhD student, I managed to make her cry. I still passed her though. This one I am reading now looks fine.
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    Who has a PhD

    I have to examine someone for a PhD next week. I just started reading the thesis today.
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    What doyou think about Reactor's Rubbia?

    I think proton driven thorium fission is a really nice idea. No chance of meltdown since it isn't a runaway reaction (it needs to be driven by the proton beam) and waste products with much shorter half-lives. I must admit to initially being put off by it being promoted by Carlo Rubbia, since he...
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    A hot topic : MSSM Higgs

    This was in a talk by John Conway a few weeks ago at Aspen: It is only a 2-sigma excess (actually 2.1 - you can't put the point in an url), so nothing to get exicited about, and (as someone already said) the excess is too...
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    Gluons and combinations

    The symmetry that QCD is based on is basically a symmetry in relabelling the colors red, green and blue. (More exactly, if you consider red green and blue as directions in the color space, QCD is symmetric under rotations.) Now, obviously swapping the colors will change all of your proposed...
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    Is this non-integrable?

    That doesn't really help much because I still don't know how to do \int \sin \left[ 2\pi (x^3+ax^2+bx ) \right] dx or its cosine counterpart.
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    Is this non-integrable?

    Yes, of course e^{-x^2} is integrable. Silly me! Some sort of hypergeometric maybe?
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    Is this non-integrable?

    I am interested in the integral \int e^{2 \pi i \left( x^3+ax^2+bx \right) } dx Since \int e^{-x^2} dx is non-integrable, I suspect this integral may be too, but I am not so sure because of the exponent being imaginary. Does anyone know? If it is integrable, does anyone have any idea how to...
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    What do you eat for a dinner?

    Last night I had sweet and sour chicken with fried rice. The night before, I had friends round so I cooked a proper meal: a starter of scallops, main course was venison steaks with asparagus and croquette potatoes, followed by sticky toffee pudding. Three nights ago I fried some calves liver...
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    The difference of neutrino and anti-neutrino? If Majorana

    Any mass term will flip the helicity - that is what mass terms do. So for a massive particle, helicity is not a good quantum number. Think of it this way: the helicity is the spin in the direction of motion, so all I need to do to change the helicity is go faster than the particle. Then the...
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    Two Neutron Bound State

    I think I have already explained this to you. L&L's analysis assumes non-interacting fermions to simplify the situation for the reader - they are not saying that the fermions must be non-interacting for the PEP to work. I will condeed that the OP's question is ambiguous, and it is feasible...
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    How would we find the Higgs if Higgs did not coupe to fermions?

    When several Higgs fields are considered, they are not talking about the Standard model (which has only one). The most popular theory with multiple Higgs is supersymmetry. If you want to find out about supersymmetry you may find this article helpful:
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    What is a photographic memory?

    Yes, I do that too. But I need to have looked at the book for a long time to get to that stage, so I wouldn't say my memory was photographic (unless you say it has a very long exposure time!). I remember in my finals, I could 'look up' equations in the books in my head - ie. turn to page 65...
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    Two Neutron Bound State

    This makes no odds. L&L make this statement only to simplify the analysis for the reader - one can also apply the Pauli Exclusion principle to interacting particles. Indeed, in the same chapter L&L go on to discuss interacting particles. If one could not apply the Pauli Exclusion Priniple to...
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    Is it true?

    This is called the Feynman-Stuckelberg Interpretation, and is used to get around having negative energy solutions of the wave equations.
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    Two Neutron Bound State

    OK, I went to our library and dug out a copy. I think you are being very disingenuous, and quoting them out of context. The statement in L&L is correct, but is not what you are implying. It is made at the beginning of chapter IX as a prelude to demonstrating that "in a system consisting of...
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    Two Neutron Bound State

    Each field is represented by an operator. For fermions, the operators anticommute, eg. \psi_1 \psi_2 = -\psi_2 \psi_1, and if they are identical, ie. \psi_1 = \psi_2 = \psi, then \psi \psi = - \psi \psi =0 which is not a valid state. Of course, as I said, they have to be identical, which...
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    Two Neutron Bound State

    Then they wouldn't be in an identical state.
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    Two Neutron Bound State

    Yes, it is because they are fermions, so they obey the Pauli Exclusion Principle
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    Americans and their beliefs

    I think this poll exemplifies what I hate about polls made by journalists (who basically don't know their arse from their elbow). The poll is completely rigged to make classifications that they percieve, not to find out what people really think. For the site, thier first question was: I...
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    Americans and their beliefs

    It could also be a sign of being right.
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    How do particles collide?

    Simply put, they have lot and lots of photons in each bunch. Most of them miss (which is actually good because if they all hit it would take a while to clean up the mess).
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    Time for a Poll: Higgs Mass Prediction

    Hmmm... why on Earth would Tilman be giving a talk on Split Susy. I know he thinks its crap. (I will have to tease him about it :D)
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    Photon splitting?

    Once again this is a semantic issue. What does one mean by 'internal structure'? This is the phrasology which is used in the subject, but of course, it does not mean structure actually 'inside' (whatever that means!) a point particle like a photon. The point here is that the particles have...
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    Magnetic field is made of photons?

    Yes, it seems that we are getting confused by semantics. I often think this is one of the biggest sources of confusion in quantum mechanical systems, sinply because our language wasn't built to deal with it. One has to be very careful with what one actually means by phrases like 'made up of'.
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    Time for a Poll: Higgs Mass Prediction

    Sorry, I hadn't realised you were talking about BSM physics. However, I am surprised that your preon setting is Higgs free. In the low energy effective theory where you integrate out the preon degrees of freedom (or rather the boson mediating the preon-preon interaction which holds them...