"CD" == Chris Dams <Chris.Dams@mi.infn.it> writes: CD> Here one CD> clearly sees that neither contractiong g~mu~mu nor g.mu.mu makes CD> any sense.
The mentioned expression indexed(squared_metric, alpha, alpha) did not stand for a contractions, it was simply an abbreviation for pow(e.alpha,4)=pow(g.alpha.alpha,2). However I will rewrite clifford.cpp without this sort of "optimisation". CD> This is why I was wondering in an CD> earlier email whether we should even allow matrices to carry CD> indices with a variance. If g is the metric tensor g with up CD> indices should be the inverse of g with down indices. Why not use the agreement from the second sentence to make sense for the first one? CD> If g is the metric tensor, it automatically obeys g.i~j = CD> delta.i~j. Actually, this simplification is done automatically CD> in GiNaC. It is in the function ex CD> tensmetric::eval_indexed(const basic & i) const. So I only need take care on it if metric is given by a matrix? Best, Vladimir -- Vladimir V. Kisil email: kisilv@maths.leeds.ac.uk -- www: http://maths.leeds.ac.uk/~kisilv/