Hubble cst as absolute error for integration

From: Johan Maes <Johan.Maes_at_UGent.be>
Date: Fri, 20 Mar 2009 11:49:35 +0100

Hi all,

This may be a minor thing, well this is a minor thing, but still, I'm
wondering why in init_drift_table (in driftfac.c), the Hubble constant
is used as absolute error for the integrations. Here's a description of
adaptive gsl integration taken from
http://linux.math.tifr.res.in/manuals/html/gsl-ref-html/gsl-ref_16.html#SEC246

/This function applies an integration rule adaptively until an estimate
of the integral of f over (a,b) is achieved within the desired absolute
and relative error limits, epsabs and epsrel
/
In the code it says the absolute error is just used as a dummy, so I
guess the goal is to make it as big as possible (compared to the result)
so the above is always ok. But since the results have dimension of time,
I would rather expect some fraction of the Hubble time then...what am I
missing here? I'm doing something similar now to convert a to t, using
the integration in Gadget as an example, that's why I noticed.

Thx & cheers,

Johan

-- 
En toen zei de kikker: "Voor mij ne kleine me stoverij, alstublieft."
Received on 2009-03-20 12:11:34

This archive was generated by hypermail 2.3.0 : 2022-09-01 14:03:42 CEST