dirac_slash(0) Does'nt work !!!
I'm trying to write an expression wich uses a Dirac " gamma 0 " for calculations on spin polarization projector, the line looks like: ex XAA=dirac_slash(0)* dirac_slash(k,4)*proj1* dirac_slash(E,4)* (dirac_slash(p,4)+ m * dirac_ONE()) * dirac_slash(E,4) * dirac_slash(k,4)*proj1* dirac_slash(E1,4) * (dirac_slash(p1,4)+m * dirac_ONE()); i'm not surethis is right, but I can't find other way to put a "gamma 0" in the expression... For instance I get the error: /usr/local/include/ginac/clifford.h: In function ‘int main()’: /usr/local/include/ginac/clifford.h:231: error: too few arguments to function ‘GiNaC::ex GiNaC::dirac_slash(const GiNaC::ex&, const GiNaC::ex&, unsigned char)’ QED_slasshes.cc:80: error: at this point in file what is wrong ? How I have to do it? Thanks. Jorge. -- View this message in context: http://www.nabble.com/dirac_slash%280%29-Does%27nt-work-%21%21%21-tf4167675.... Sent from the Ginac - General mailing list archive at Nabble.com.
Hello! On Fri, Aug 03, 2007 at 11:22:56AM -0700, J. gallardo wrote:
I'm trying to write an expression wich uses a Dirac " gamma 0 " for calculations on spin polarization projector, the line looks like:
ex XAA=dirac_slash(0)* dirac_slash(k,4)*proj1* dirac_slash(E,4)* (dirac_slash(p,4)+ m * dirac_ONE()) * dirac_slash(E,4) * dirac_slash(k,4)*proj1* dirac_slash(E1,4) * (dirac_slash(p1,4)+m * dirac_ONE());
Write your expression in Lorentz-invariant way: ex XAA=dirac_slash(P0, 4)*dirac_slash(k,4)*proj1* dirac_slash(E,4)* (dirac_slash(p,4)+ m*dirac_ONE())*dirac_slash(E,4)* dirac_slash(k,4)*proj1*dirac_slash(E1,4)*(dirac_slash(p1,4)+m*dirac_ONE()); ex result = dirac_trace(XAA).expand(expand_options::expand_indexed); // or whatever And calculate invariant combinations in whatever reference frame: scalar_products sp; symbol k0("k0"), E10("E10), p10("p10"), E0("E0"); sp.add(P0, k, k0); sp.add(P0, p, p0); sp.add(P0, E1, E10); sp.add(P0, E, E0); // add something for p*k and so on... result = result.simplify_indexed(sp); Another possible variant is (I don't recommend it): varidx mu(symbol(mu), 4); ex XAA=dirac_gamma(mu)*dirac_slash(k,4)*proj1* dirac_slash(E,4)* (dirac_slash(p,4)+ m*dirac_ONE())*dirac_slash(E,4)* dirac_slash(k,4)*proj1*dirac_slash(E1,4)*(dirac_slash(p1,4)+m*dirac_ONE()); XAA = XAA.subs(mu==0); Best regards, Alexei -- All science is either physics or stamp collecting.
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J. gallardo
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varg＠theor.jinr.ru