# Unexpected behavior of combine()

+3 votes

Hi,

When I apply the command combine() on

$( \Gamma ^ { a } ) { \beta } { } ^ { \gamma } ( \Gamma { c d } ) _ { \gamma }{ }^{ \alpha }$,

I get

$( \Gamma {c d} \Gamma ^ {a} ) ^ { \alpha } { } { \beta }$

while expecting

$( \Gamma ^ {a} \Gamma { c d } ) { \beta }{ } ^ { \alpha }$.

Am i doing something wrong? (In case not rendering tex, i added image )

In addition, Is there any way to tell such structures to Cadabra;

$A {a} B ^ {a} = - A ^ {a} B {a}$.

Since our metric is antisymmetric, the shape of the contraction matters.

Thanks in advance :)

edited

## 1 Answer

0 votes

Thanks for the bug report! The combine() issue has recently been fixed in git. As for the northeast / southwest convention, I would just declare the index positions to be fixed and include explicit metrics. But perhaps Kasper has a better answer.

by (240 points)

I have encountered the same issue. Moreover, Linux version got mentioned the change in combine (still not what I expect!) while Windows 10 has still an old definition. When we can expect new install file for windows?