[firedrake] Second derivatives

[Andrew McRae]

It's possible to represent second derivatives in a form, such as
assemble(div(grad(f))*dx).  I assume this is true in FEniCS as well as
Firedrake, because this is just UFL/FFC/FIAT functionality.  This would
produce the sum (over cells) of the Laplacian of f on each cell.

However, like FEniCS, none of our function spaces have more than C^0
continuity.  That is, the functions are at most continuous, but won't have
continuous derivatives.  It's likely that you won't want to use second
derivatives of C^0 functions in a practical discretisation (though I'm sure
there are methods that *do* do this).

Andrew

On 17 July 2015 at 01:50, Justin Chang <jychang48 at gmail.com> wrote:

>  Hi everyone,
>
>  Is it possible to do second derivatives? What I mean by that is things
> like div[grad[u]] and grad[grad[u]]. I haven't tried this out yet, but we
> use these discretizations a lot for our research, and FEniC's inability to
> do this made us sad (although our more major qualms had to do with its
> inability to support quads).
>
>  Thanks,
> Justin
>
>
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