[LORENE] strange GRV2/3 behaviour (Newtonian)

[Reinhard Prix]

Hi,

that's great, I've just updated the code and now grv2 and grv3 are
indeed excellent even for Newtonian static configurations, thanks!

Cheers,
Reinhard

* Eric Gourgoulhon <eric.gourgoulhon at obspm.fr> [2003-11-19 23:13]:
> Dear Reinhard,
> 
> Many thanks for having pointed this out. We haven't
> noticed this yet (actually we haven't much practice
> with Newtonian configurations...).
> 
> The strange behaviour that you have noticed was due
> to the conjunction of two facts:
> 
> 1/ the relaxation of logn and dzeta in Etoile_rot::equilibrium
>    (parameter relax in the file parrot.d)
> 2/ the very fast convergence of static Newtonian configuration
> 
> Indeed, because of the relaxation, the gravitational potential
> logn keeps some memory of its initial (very crude !) stage
> and this spoils the final GRV2 and GRV3 if the number of steps
> is very small, as in static Newtonian case.
> You can recover a very good GRV2 and GRV3 by setting relax=1
> (i.e. no relaxation), or by forcing the code to run for
> a large number of steps (setting mer_max=100 and precis=1.e-20
> in parrot.d).
> 
> In order to correct this behaviour, without setting manualy
> relax=1 or running for a large number of steps,
> I've modified the functions
> 
> Etoile_rot::equilibrium
> Et_rot_bifluid::equilibrium_bi
> Et_rot_diff::equilibrium
> Et_rot_mag::equilibrium_mag
> 
> so that the relaxation is started only at the 10th step.
> Therefore, if you perform a cvs update, the problem you have
> mentioned should have disappeared.
> 
> Best wishes,
> 
>     Eric.
> 
> 
> Reinhard Prix wrote:
> 
> >Hi,
> >
> >I've just noticed a funny feature of the codes Rotstar and Sfluide in
> >the Newtonian case:
> >we had noticed a while ago that for very low rotation rates or static
> >cases the virials in the Newtonian case become quite "bad", i.e. of
> >the order of 1e-5 for a precision of 1e-10, while in the relativistic
> >case one consistently gets GRV <= 1e-9. 
> >
> >However, if you set freq_ini_si=100 for example, even if freq_si=0,
> >then you seem to get a solution that has GRV~1e-9...! 
> >
> >Cheers,
> >Reinhard
> >
> 
> 
> -- 
> Eric Gourgoulhon
> Laboratoire de l'Univers et de ses THeories (LUTH)
> UMR 8102 du CNRS / Observatoire de Paris, F-92195 Meudon Cedex, France
> tel: +33 1.45.07.74.33 (secretariat : +33 1.45.07.75.10)
> e-mail: Eric.Gourgoulhon at obspm.fr    WWW: http://www.luth.obspm.fr/
> 
> 
> 

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