[Carpet] Tracking the puncture with Carpet

[Yosef Zlochower]

Christian David Ott wrote:
> Hi Yosef,
> 
> On Thu, 20 Jul 2006, Yosef Zlochower wrote:
> 
> 
>>  I want to evolve d Y^a / dt =  - beta^a (Y) to track the location
>>of the punctures. With a unigrid code I simply added this as an
>>evolved array to MoL.
> 
> 
> So what you want is dY^a / dt = - beta^a(Y) only at the puncture
> location and zero everywhere else? I don't do these puncture runs
> and am a bit ignorant about what you are trying to do here with
> beta^a (the shift?).

Beta is the shift. Y^a is not a GF its just a 3 single values.

> 
> 
>>However, it seems that this is not simply
>>done with mesh refinement. Is there some way of knowing if the current
>>level and component is the finest available resolution for the point
>>Y^a.
>>If there is, then I suppose that I could set d Y^a = 0 for all
>>levels and all components but the right one. I can think of another
> 
> 
> 
> Yes, there is. Doing what you want to do would be an ugly hack but
> would probably work.
> 
> In Fortran:
> 
> reflevel = aint(log10(dble(cctk_levfac(1)))/log10(2.0d0))
> 
> You of course need to know what the maximum number of active
> levels is. That you have to get via a parameter.
> 

The problem that I see is that I will have different components at the
same refinement level. So I'll also need to know if the correct 
component is active as well.

> 
>>If there is, then I suppose that I could set d Y^a = 0 for all
>>levels and all components but the right one. I can think of another
>>method where I interpolate beta at y^a after the timestep is complete.
>>Will the interpolator give me beta at the highest refinement level
>>at point y^a, and if so, how do I get the appropriate dt for this
>>refinement level?
> 
> 
> Yes. The interpolator will always use the highest available resolution.
> The appropriate dt on each level is given in CCTK_DELTA_TIME.
> 
> Are you running an AH finder? If so, why don't you use the AH centroids to
> get the puncture locations?
>

That is an alternative posibility.

> - Christian
> 
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