On Tue, Aug 01, 2006 at 04:01:09PM -0400, Alejandro Limache wrote:
according to Ginac-mini FAQ:
The indexed class (and most derived classes) is intended for tensor manipulation without referring to a particular basis. Thus, the indexed class is well suited for calculations involving (formally defined) tensor algebra of "non-integer-dimensional space". .... In that framework, unrolling ai*ai to a1^2+a2^2+a3^2+... is not possible, since the dimension >is not integer!
I am physicist (not a relativist one though).. but, is there something more useful than tensors representations (i.e tensor components) defined for integer indexes?!!!.
That depends. For calculations in perturbative quantum field theory withing the dimensional regularisation tensor compontents are useless (and in fact, ill-defined).
It is because that I always want to get the components of tensors (which can be arranged as multidimensional arrays/matrices) is that I want to be able to unroll indexed objects. I don't think GiNaC is a proper tool for that. Something like blitz++[1], tvmet[2], ublas[3] might be more useful for you.
[1] http://www.oonumerics.org/blitz/ [2] http://tvmet.sourceforge.net [3] http://www.boost.org/libs/numeric/ublas/doc/index.htm Best regards, Alexei. -- All science is either physics or stamp collecting.