Recent content by earth2

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    Question on Tachyon Correlator (Green Schwarz Witten)

    Thanks fzero! Since both - Trimok and you - suggested to look at Polchinksi I will do so :) To the Library...!
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    Question on Tachyon Correlator (Green Schwarz Witten)

    Thanks Trimok for clearing that up :) As mentioned on phys stackexchange, I would like to understand this, since GSW say in the appendix that getting 7.A.17 is possible from 7.A.12 and 7.A.22... :)
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    Question on Tachyon Correlator (Green Schwarz Witten)

    Hi fzero, Thanks for your answer but I'm not sure I understand it in the context of the equations above. Would you be so could to make it more precise w.r.t. the formulae I used above. That would be very nice since i'm banging my head against this for a while now. Moreover, this point is...
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    Question on Tachyon Correlator (Green Schwarz Witten)

    I'm reading through chapter 7 of Green-Schwarz-Witten and I have a problem with the derivation of the M-tachyon correlation function. Basically I'm trying to get 7.A.17 from 7.A.12 and eq 7.A.22 in the appendix of the first volume. Basically I want to prove...
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    Amplitudes in CFT vanish. Why does N=4 have them?

    Hi guys, one question in this growing amplitude business that i don't understand. Usually one says that conformal field theories do not have any non-trivial scattering amplitudes because one cannot define asymptotic states. But say we consider now N=4 Super Yang Mills and moreover treelevel...
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    Mathematica Streamlining Replace in Mathematica 8

    Hi and thanks for your answer. Ok, i just realize i have been too vague. Acutally my expressions are of the type MP[X,a_1]...MP[X,a_{2n}] where MP is the Minkowski scalar product. Some of the a_n might be the some. This can be replaced in my case (under an integral over X) by...
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    Mathematica Streamlining Replace in Mathematica 8

    Hi guys, i have expressions of the type (X*a)(X*b). I want replace this by X^2(a*b). So i tried building a block which does nothing but %//.(X*a_)(X*b_)->X^2(a*b). However, this works only if a is distinct from b. If a and b are equal if HAVE to use the replacement command...
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    Loop Integration in Spinor Language

    Ah, thanks for the explanation. One more question about this: So coming back to the numerator, i could rewrite is in terms of a four-vector product as: \langle a |L|b]^2 = (2q\cdot L )^2 where q is a four-vector build from the spinors \langle a| and |b]. Under the integral sign i could...
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    Loop Integration in Spinor Language

    Hi and thanks for your reply. Look for instance at hep-th/0612007. They never do the integrals (they reduce them to scalar integrals using PV) but i was wondering how to do them without reducing them. Look for instance at eq (3.9). If one is given such a type of integral but has no idea about...
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    Loop Integration in Spinor Language

    Hi! Thanks for your reply! I understand how to treat these integrals if the numerator of the integrand is expressed in terms of four-vectors. But how do I proceed if the numerator is written in the spinor bra-ket language above? I don't really know how to handle these expressions if the loop...
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    Loop Integration in Spinor Language

    Hi guys, i'm looking at one-loop calculations in terms of helicity spinor (basically a paper by Brandhuber, Travglini and others) language but i have no idea how to integrate them :) For instance \int FeynParam\int d^D L \frac{\langle a|L|b]^2}{(L^2-\Delta^2)^3} How would I do...
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    Self-Dual Field Strength in complex coordinates

    Ah cool, i didn't know that i could just plug in numbers back :) Nice, thank you!
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    Self-Dual Field Strength in complex coordinates

    Hi guys, I have to brush up my knowledge about self-dual Yang Mills and I'm reading an ancient paper by Yang about it...and of course I'm stuck...although Yang writes 'it is easy to see that'... Ok, so the self-duality condition of the YM field strength tensor is defined as...
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    2Point Correlator in CFTs

    Yupp, thank you for your answer!
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    2Point Correlator in CFTs

    Thank you for your answer! That is a nice way to understand this! From the book however I have the impression that the conclusion is much simpler to get and follows 'for free' from the invariance statements. But thanks a lot anyways! earth2 P.s. you were right, the \sim should be an...
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