// one-loop vacuum polarization in QED
e = dirac_gamma(mu) *
- (dirac_slash(l, dim) + dirac_slash(q, dim) + m * dirac_ONE()) *
+ (dirac_slash(l, dim) + dirac_slash(q, 4) + m * dirac_ONE()) *
dirac_gamma(mu.toggle_variance()) *
(dirac_slash(l, dim) + m * dirac_ONE());
e = dirac_trace(e).simplify_indexed(sp);
result += check_equal(e, 4*((2-dim)*l*l + (2-dim)*ldotq + dim*m*m).expand());
- e = dirac_slash(q, dim) *
- (dirac_slash(l, dim) + dirac_slash(q, dim) + m * dirac_ONE()) *
- dirac_slash(q, dim) *
+ e = dirac_slash(q, 4) *
+ (dirac_slash(l, dim) + dirac_slash(q, 4) + m * dirac_ONE()) *
+ dirac_slash(q, 4) *
(dirac_slash(l, dim) + m * dirac_ONE());
e = dirac_trace(e).simplify_indexed(sp);
result += check_equal(e, 4*(2*ldotq*ldotq + q*q*ldotq - q*q*l*l + q*q*m*m).expand());