Name: Aliaksandr Dubrouski Date: 04/09/15-12:32:54 PM Z
2 Stanislav
Look at the input form of the \[Epsilon]^(K2*P1*P2*K1),
because what you
see is just a format used to display the contraction of LeviCivita
tensor
with four 4-momenta.
Substitution rules work for the InputForm expressions. This is
basically
not a FeynCalc question but a Mathematica programming question. You
can
specify the custom tensor with Tensorfunction as follows
>>> Tensorfunction[t, mu, nu, …]
See http://www.feyncalc.org/FeynCalcBook/Tensorfunction/index.html
for
details.
Additionally I would suggest substituting the contractions of your
tensor
with four-vectors after the FeynCalc will contract the lorentz indices
for
you with the vector components.
I.e. you do not need to specify the tensor in components as you
mentioned
phi_mu_nu = diag{0,1,1,0} but specify it as a substitution rules for
tensor
contracted with two arbitrary 4-vectors and its trace.
2015-04-09 0:30 GMT+03:00 Stanislav <[noreply_at_HIDDEN-E-MAIL]>:
> Okay, several questions have arised…
>
> 1. Is there a way to specify my own tensor? Metric and LeviCivita
are not
> enough for me. For example, i’d like this one with lower indices to
be
> specified: phi_mu_nu = diag{0,1,1,0}
>
> Does FeynCalc contract this kind of predefined tensors?
>
> 2. When contracting 4 vectors with LeviCivita symbol i get an object
like
> \[Epsilon]^(K2*P1*P2*K1)
>
> I would like either to make this contraction explicit or to replace
it
> with already known expression.
>
> But things like
> >>> M = M /. \[Epsilon]^(K2*P1*P2*K1) ->
my_expression
> do not work. What’s going on?
>
>
--
Regards,
Aliaksandr Dubrouski