[Users] Kranc and xAct

[Barry Wardell]

I sent the reply below to Comer earlier, but forgot to cc the list!

Hi Comer,

Yes, it's fine to have xAct loaded when running Kranc. In fact, there is
experimental support in Kranc for using xAct as a backend for all of the
tensor manipulation that Kranc does. For example, you can set
KrancTensor`$KrancTensorNeeds = "xTensorKranc`"; at the start of many of
the examples and it should just work (admittedly, I haven't checked it
still works with the latest version of Kranc).

In principal, this could be made the default in the future, but right now
it is not robust enough. The main problem is that xAct is quite a large,
complicated package and it is somewhat overkill for the requirements of
Kranc. As a result, there are a few hacks and hardcoded values in Kranc's
use of xAct. It may be that the new CTensor features in xCoba would make
this worth revisiting, but I don't think anyone has looked at that yet.


Barry

On Wed, Jul 22, 2015 at 4:26 PM, Ian Hinder <ian.hinder at aei.mpg.de> wrote:

>
> On 22 Jul 2015, at 16:04, Comer Duncan <comer.duncan at gmail.com> wrote:
>
> Do Kranc and xAct play well together?  Just curious since sometimes I do
> things in xAct and then may want to do the same in Kranc and it would be
> nice if I could just say import xAct and the work done in it to a
> developing Kranc script.  Of course, there are several pieces of xAct, so
> maybe my question is not formulated precisely enough, but what do you think?
>
>
> Hi,
>
> There is experimental support in Kranc for using xAct as an input
> language.  However, it is not well-tested, and might be missing important
> functionality.  This was added by Barry Wardell some time ago.  In the
> past, I have converted xAct expressions into the format expected by Kranc
> using some simple replacement rules.  Let me know if you would like an
> example.  Barry might be able to provide more details of the xAct support
> in Kranc; I'm not sure of the current status.
>
> --
> Ian Hinder
> http://members.aei.mpg.de/ianhin
>
>
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