On Friday, January 10, 2014 10:56:03 PM UTC+1, Comer wrote: > > Today I have been looking at the sympy tensor package. I have attached a > script in which I am trying to end of defining the Einstein tensor: R_{a b} > - 1/2 *g_{a b} * R. But the script does not succeed on the last step of > evaluating the above expression and hence fails to agree to create the > Einstein tensor. I am wondering what I am doing incorrectly? > > Thanks for advice. > > Comer >
This is a bug, d0 and -d0 have not been recognized as dummy indices and are not contracted. I think I'll have a look tomorrow. In the meantime, you can use this workaround, replace it into your last line: gR = tensor_mul(Rational(1,2)*g(-a,-b) * R) gR = TensMul(*gR.args) Ric(a,-b) - gR This basically forces reconstruction of the tensor, and the dummy index gets recognized this time. -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sympy+unsubscr...@googlegroups.com. To post to this group, send email to sympy@googlegroups.com. Visit this group at http://groups.google.com/group/sympy. For more options, visit https://groups.google.com/groups/opt_out.