[Developers] CactusEinstein/2052: Patch: Add time derivatives of lapse and shift as new variables

Erik Schnetter schnetter at cct.lsu.edu
Thu Sep 7 09:32:50 CDT 2006


On Sep 7, 2006, at 09:29:59, schnetter at cct.lsu.edu wrote:

>> Number:         2052
>> Notify-List:    developers at cactuscode.org
>> Category:       CactusEinstein
>> Synopsis:       Patch: Add time derivatives of lapse and shift as  
>> new variables
>> Confidential:   no
>> Severity:       serious
>> Priority:       medium
>> Responsible:    rideout
>> State:          open
>> Class:          feature-request
>> Submitter-Id:   user
>> Arrival-Date:   Thu Sep 07 09:29:59 -0500 2006
>> Originator:     Erik Schnetter
>> Release:        Cactus 4.0.b16
>> Organization:
>> Environment:
>> Description:
> I suggest to add the time derivatives of lapse and shift as  
> additional variables to ADMBase.  Together with the extrinsic  
> curvature, this allows constructing the time derivative of the four- 
> metric.  This "completes" the set of variables; since the Einstein  
> equations are second order in time, initial data for them have to  
> set both the four-metric and its time derivative.
>
> This is necessary to provide complete initial data to some  
> formulations of Einstein's equations which are not based on lapse  
> and shift.  It also allows using exact solutions with such  
> formulations.
>
> The new variables have no storage by default.  Their storage is  
> handled in the same way as for the shift, i.e., via parameters and  
> a run time state variable.
>
> Later, other thorns (such as AEIThorns/Exact) would be modified to  
> set these variables as well when they have storage.
>> How-To-Repeat:
>> Fix:
> Unknown
>> Unformatted:

It seems these emails to the developers' list are now sent  
automatically.  Could that be changed to exclude the ill-formatted un- 
readable base64-encoded attachments?  I thought we wanted to forward  
these emails manually, so that people can strip off the  debris and/ 
or attach the attachment in clear text?

-erik

-- 
Erik Schnetter <schnetter at cct.lsu.edu>

My email is as private as my paper mail.  I therefore support encrypting
and signing email messages.  Get my PGP key from www.keyserver.net.



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