[Users] output from WeylScal

[Erik Schnetter]

Jose

I think that comparing waveforms is one of the best ways of doing so
-- comparing the metric or horizon data or any strong field properties
doesn't make much sense.

I believe it was pointed out that converting Psi4 to strain is a
complex task. The other way around (converting strain to Psi4) should
be straightforward.

Several readers on this list have extensive experience in handling and
converting ET waveforms. Maybe someone is interested in a
collaboration?

-erik

On Mon, Feb 6, 2012 at 9:19 PM, Jose Fiestas Iquira <jafiestas at lbl.gov> wrote:
> Thanks. I checked the literature, and looked at the irreducible mass, given
> by AHFinderDirect, which is growing in time, with respect to the initial
> mass (ADM mass). By substracting I obtain an estimate (upper limit I guess)
> ob the radiated energy during coalescence.
>
> As mentioned I am seeking for a method to test/validate ETK tools together
> with N-body using Post Newtonian approximations. I am using binary
> coalescence.
>
> My N-body code (up to 3.5 PN terms), can calculate strain amplitudes vs.
> frequency, My first idea was to validate this results by creating the same
> plot using ETK. Would you recommend a more direct way to do such a
> comparison?
>
> Thanks,
> Jose
>
>
>
>
> On Wed, Feb 1, 2012 at 3:02 AM, Eloisa Bentivegna <bentivegna at cct.lsu.edu>
> wrote:
>>
>> On Feb 1, 2012, at 3:12 AM, Jose Fiestas Iquira wrote:
>>
>> > Dear all,
>> > I am using WeylScal for BH binary coalescence, and I am obtaining
>> > 'weylscal4::psi4r...' and 'weylscal4::psi4i ...' files, with which I could
>> > plot the wave against distance/time.
>> > Could somebody advise me how to get the energy emission due to grav.
>> > waves from the WeylScal output? I would like to construct a plot: GW Energy
>> > vs. distance/time.
>>
>> Hi Jose,
>>
>> there's a couple of things to keep in mind:
>>
>> 1) In broad terms, there is no notion of gravitational-wave energy
>> density; one can at best associate a mass with the whole spatial
>> hypersurface, but not state how much of this is in gravitational waves or
>> where it is localized;
>> 2) Under reasonable assumptions, the radiated power at infinity can be
>> expressed in terms of the Weyl scalars. You'd probably best start learning
>> about this is in one of the numerical-relativity textbooks: either section
>> 8.9 of
>> <http://books.google.de/books?id=4hDvRvVJeEIC&dq=alcubierre&hl=de&sa=X&ei=GBopT--LC87ItAbI-b3FAQ&ved=0CDIQ6AEwAA>
>> or section 9.4 of
>> <http://books.google.de/books?id=dxU1OEinvRUC&dq=baumgarte&hl=de&source=gbs_navlinks_s>
>> (notice that this is still a function of time only -- no localization);
>> 3) If you're just interested in how much energy leaves the system during
>> the merger, you may be better off subtracting the final horizon mass (given
>> by AHFinderDirect) from the ADM mass (given by TwoPunctures).
>>
>> Let me know if this isn't clear enough!
>> Eloisa
>>
>
>
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-- 
Erik Schnetter <schnetter at cct.lsu.edu>   http://www.cct.lsu.edu/~eschnett/