Why there is a tensor 4 data for several components pde?

Asked by Qian Han

Several components pde has a general form likes:
(A_{ijkl}*u[k],l),j ..... = ....
I am confused about the tensor 4 data object A:
Einstein notation does not include the index i.
Does this mean, the equation is along the i direction ?
For example, there is a 2d static equilibrium continuum
At axis x, pde is: (A_{xjkl}*u[k],l),j we only sum terms j, k, l.
At axis y, pde looks like pde for x just replace x by y.
Finally, sum the two eqs of x and y in order to get the general pde form as listed in user guide of esys-escript.
Any reply will be grateful!
Thank you!

Best regards,
Qian Han

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Adam Ellery
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Best Adam Ellery (aellery) said :

Hi Qian,

The equation at the top of page 76 of the userguide denotes a system of PDEs in which u is a vector with several components. In this equation the index k denotes the k^th component of the vector and the index i denotes the number of the equation in the system.


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Qian Han (hanqian) said :

Thanks Adam Ellery, that solved my question.