Exterior derivative and complex-valued forms

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g.lomo...@gmail.com

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Jul 25, 2017, 9:58:21 AM7/25/17
to xAct Tensor Computer Algebra
Hello,

I'm working with complex valued forms and sometimes I need to take exterior derivatives of complex conjugate of some expression; however, in this case the result the mathematica gives is:

Diff[ Conjugate[a] ]= Diff[ a ]*Conjugate'[ a ]

where Conjugate' should be the derivative of conjugate with respect to its argument. However, I would like to obtain something like:

Diff[Conjugate[ a] ]    or   Conjugate[Diff[ a ]] 

In the same way, Exterior derivative and Real (or Imaginary) part don't commute; In fact in some expression like:

Re(Diff[ a ])

It doesn't enter the real part in the exterior derivative, getting

Diff[Re(a)]

Someone knows how to solve this kind of problems? thank to everybody,

Gabriele

Leo Stein

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Jul 25, 2017, 10:03:58 AM7/25/17
to g.lomo...@gmail.com, xAct Tensor Computer Algebra
Hi Gabriele,

I hope you have seen the option 'Dagger' which can be used when defining a tensor or differential form. By default it's Dagger->Real, but if you specify Dagger->Complex, then you will get a pair of complex-valued tensors or forms. Then, within the xAct suite, we use Dagger[] instead of Conjugate[] to perform complex conjugation. Thus you can write something like
  Dagger[ Diff[ w[] ] ]
and it will automatically get turned into
  Diff[ w†[] ].

Best
Leo

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