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Consider the following expressions, which are identical except that in ex2, the last Gamma matrix has "t" instead of "e". But, the combine for the second expression is giving some strange output.

ex:=(\Gamma_r)_{\alpha\beta} (\Gamma_{r t u} \Gamma_{e v h})_{\beta\gamma}; 
ex1:=(\Gamma_r)_{\alpha\beta} (\Gamma_{r t u} \Gamma_{t v h})_{\beta\gamma}; 
combine(ex);
combine(ex1);

I think part of the problem in the second case is illustrated by

ex3:= (\Gamma_{r t u} \Gamma_{t v h})_{\beta\gamma};

which tries to combine the t and t contraction?

in General questions by (560 points)

1 Answer

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combine is in a bit of a weird state right now, it will need a bit of work to make it do the right thing in all cases. Will keep you posted.

by (66.3k points)
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