From 3bd9c730e20c9a70d17c1459ddf78ba71ee84f60 Mon Sep 17 00:00:00 2001 From: Aaron LI Date: Sun, 23 Jul 2017 10:24:00 +0800 Subject: clusters/halo.py: Constrain tau_acc to avoid zero diffusion Zero or negative diffusion coefficient leads to unstable or wrong results due to numerical algorithm/scheme adopted to solve the Fokker-Planck equation. Also add a NOTE to the FokkerPlanckSolver class. Signed-off-by: Aaron LI --- fg21sim/extragalactic/clusters/solver.py | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'fg21sim/extragalactic/clusters/solver.py') diff --git a/fg21sim/extragalactic/clusters/solver.py b/fg21sim/extragalactic/clusters/solver.py index 6c0e653..dea7f3f 100644 --- a/fg21sim/extragalactic/clusters/solver.py +++ b/fg21sim/extragalactic/clusters/solver.py @@ -102,6 +102,13 @@ class FokkerPlanckSolver: by extrapolating an power law to avoid unphysical accumulations. This fix is ignored if this parameter is not specified. + NOTE + ---- + The diffusion coefficients (i.e., calculated by ``f_diffusion()``) + should be *positive* (i.e., C(x) > 0), otherwise unstable or wrong + results may occur, due to the current numerical scheme/algorithm + adopted. + References ---------- [1] Park & Petrosian 1996, ApJS, 103, 255 -- cgit v1.2.2