[GiNaC-list] Differentiation of a function with respect to a tensor

[Bernardo Rocha]

Dear Vladimir,

first of all thanks for your reply.

Well, defining the function as a GiNaC expression is part of my doubt, since
I do not know how to represent the second-order
tensor E in GiNaC, and consequently, how to differentiate Psi with respect
to it.

I've seen some classes for special tensors, like clifford, delta, etc, but
it is not clear for me how to represent a second order tensor. I was guess I
should use matrix and idx....but how? and how do I use diff afterwards?

Many thanks in advance.

Best regards,
Bernardo M. Rocha


2011/2/10 Vladimir V. Kisil <kisilv at maths.leeds.ac.uk>

>                Dear Bernardo,
>
> >>>>> On Wed, 9 Feb 2011 10:07:51 -0200, Bernardo Rocha <
> bernardosk at gmail.com> said:
>    BMR> the strain energy function for the St. Venant-Kirchhoff
>    BMR> material
>    BMR> \Psi(E) = 0.5 * \lambda * (tr E)^2 + \mu E:E
>
>        To start with, can you write this functions as a GiNaC expression?
>
>        Best wishes,
>        Vladimir
> --
> Vladimir V. Kisil     email: kisilv at maths.leeds.ac.uk
> --                      www: http://www.maths.leeds.ac.uk/~kisilv/
>
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