Should either make the checks solid so that joins never work with mixed indices, or make it always do the same thing consistently.
{a,b}::Indices(flat, position=fixed).
{\mu, \nu}::Indices(curved, position=fixed).
\gamma{#}::GammaMatrix(metric=\eta);
and I would like to signal the following behavior of join_gamma.
Calling join_gamma on the following expression does nothing
ex:=\gamma_{a} \gamma_{\mu};
join_gamma(_);
while join_gamma works fine on expressions containing only one type of
indices. This implies that it is hard to manipulate these terms since
sort_spinors does not work if previously the gamma has not been joined.
Furthermore acting on a term like
ex2:=\gamma_{a}\gamma_{\mu}\gamma_{\nu}\gamma_{b};
it produces
(\gamma_{a \mu}+\eta_{a \mu})\gamma_{\nu}\gamma_{b};
Should either make the checks solid so that joins never work with mixed indices, or make it always do the same thing consistently.