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.