[Users] SimulationTools Frequency

[Gwyneth Allwright]

Awesome. Thanks Ian!


On Sat, May 6, 2017 at 10:03 AM, Ian Hinder <ian.hinder at aei.mpg.de> wrote:

>
> On 6 May 2017, at 08:49, Gwyneth Allwright <allgwy001 at myuct.ac.za> wrote:
>
> Hi Ian,
>
> I've been finding SimulationTools very useful for looking at the results
> of my Cactus simulations. I just have a question about the function called
> "Frequency", which is used in the context of gravitational waveforms. How
> is this frequency defined? Is it an angular frequency? I don't know how to
> interpret the negative values I'm getting.
>
>
> Hi Gwyneth,
>
> There is actually some documentation for SimulationTools.  You can get the
> brief usage message for Frequency by typing
>
> ?Frequency
>
> in the notebook.  This tells you:
>
> Frequency[d] returns the first derivative of the complex phase of d.
>
> That's maybe not as detailed as it could be.
>
> So, if d is a DataTable of complex numbers (i.e. representing a list of
> {t, f(t)} pairs), Frequency[d] is the time derivative of arg f(t).
>
> So yes, it is an angular frequency.  The reason it is negative is probably
> because the orbital angular velocity is positive, and the dominant GW
> emission is proportional to Exp[-2 I omOrb t].  So omGW = - 2 omOrb.
> Usually I plot - Frequency[h].
>
> --
> Ian Hinder
> http://members.aei.mpg.de/ianhin
>
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