Re: [Maxima-discuss] energy-momentum tensor

[Dimiter P. <dim...@gm...>]

Hi Viktor,

Actually, I have in mind a general field lagrangian.
So starting from an input lagrangian to compute the energy-momentum tensor
according to the noether theorem.

best regards,

Dimiter

On Mon, Jan 9, 2017 at 7:39 AM, Viktor T. Toth <vt...@vt...> wrote:

> Dear Dimiter,
>
> No, I do not. The canonical energy-momentum depends on whatever fields we
> are dealing with. I am assuming that you have in mind the electromagnetic
> field and its energy-momentum tensor? In itensor, it would be something like
>
> load(itensor);
> imetric(g);
> igeowedge_flag:true;
> components(F([i,j]),extdiff(A([i],[]),j));
> components(F([i,-k],[]), g([-j,-k])*F([i,j]));
> components(F([-l,-k],[]),g([-i,-l])*F([i,-k]));
> components(T([-m,-n]),F([-m,-a])*F([-n,a])-1/4*g([-m,-n])*
> F([a,b])*F([-a,-b]));
> ishow(T([-m,-n]))$
>
> (Note the use of the negative sign for contravariant indices; this
> notation was implemented specifically to ensure that index ordering is
> preserved when indices are raised/lowered, as in this case.)
>
>
> Viktor
>
>
>
>
>
> > -----Original Message-----
> > From: Dimiter Prodanov [mailto:dim...@gm...]
> > Sent: Friday, January 6, 2017 11:45 AM
> > To: max...@li...
> > Subject: [Maxima-discuss] energy-momentum tensor
> >
> > Dear Viktor,
> >
> > do you have code for compuation of the canonical energy-momentum tensor?
> > I would like to implement it in clifford so I want to compare it with
> reference implementation.
> >
> > best regards,
> >
> > Dimiter
>
>