about the softening length in comoving integration

From: Yves Revaz <yves.revaz_at_obspm.fr>
Date: Fri, 13 Apr 2007 11:06:08 +0200

Dear Gadget list,

In Gadget-2 (as well as in Gadget-1) the user has the possibility
to fix the softening length at high z, in comoving units (SofteningGas)
and below a certain redshift, to fix it in the physical units
(decreasing in comoving units).

As the integration is done in comoving units, I do not really understand
the interest of fixing it in physical units, except that the particle
is strongly increasing. But choosing a small softening (fixed in
comoving units),
according to the final state should not affect the integration a high z.

In the literature, some peoples use this option (with different redshift
while some other do not. In the Millennium run, no information is given
about fixing
the softening length in physical units and then I assume that the
softening length stays
fixed in comoving units during all the simulation.

What is the best solution to use ?
How choosing the redshift transition ?

I haven't found any reference to this problem in the literature...

Thanks in advance.


                                                (o o)
  Yves Revaz
  Lerma Batiment A           Tel : ++ 33 (0) 1 40 51 20 79
  Observatoire de Paris      Fax : ++ 33 (0) 1 40 51 20 02 
  77 av Denfert-Rochereau    e-mail : yves.revaz_at_obspm.fr
  F-75014 Paris              Web : http://obswww.unige.ch/~revaz/
Received on 2007-04-13 11:06:09

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