how to do subs for symmetric indexed objects?

Christian Bauer Christian.Bauer at Uni-Mainz.DE
Fri Jun 27 15:52:15 CEST 2003


On Fri, Jun 27, 2003 at 06:06:13PM +0800, Yong Xiao wrote:
> indexed(Y,sy_symm(),i_,m_,n_)*indexed(t,n_,j_)
> ==indexed(Y,sy_symm(),j_,n_,m_)*indexed(t,n_,i_)

This assumes that the first index ('n') of the 't' is equal to the last index
of the 'Y'. However, with sy_symm(), GiNaC will rearrange the indices into
a canonical, but unpredictable, order. So you have to drop the sy_symm()
in the subs() and provide a list of substitutions for all three possible
positions of the common index 'n_' in 'Y'.

You also don't need the subs_algebraic.


  / Physics is an algorithm

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