# how can i tell cadabra that the partial derivatives commute upto linear order while calculating Riemann Tensor

+1 vote

i was trying to tell it like the following -

c1:= \partial_{\alpha}{\partial_{\beta}{h_{\mu \nu}} =
\partial_{\beta}{\partial_{\alpha}{h_{\mu \nu}};


its showing error " free index is not matching" something like that

That one had me puzzled for a minute... The solution is to match your brackets: both terms should have an additional } to close the argument of the outmost derivative. So
\partial{#}::PartialDerivative;

And to answer the question in the subject: you can then make these terms equal with a call to canonicalise(c1).