# Comoving integration

From: Evgeny Kurbatov <kurbatov_at_inasan.ru>
Date: Fri, 12 May 2006 13:29:44 +0400

Hi!

1. The drift factor looks as if the internal velocity variables would be
a^2 \dot{x} ,
where x' is the comoving coordinates and a' is the scale factor. But
procedures init' and fill_write_buffer' tell us that internal velocity is
a^{3/2} \dot{x}
(I mean that the `\dot{x}' stores in a snapshots).
2. Why the gravkick factor is
\int da / (a^2 H) ?
3. Why the hydrokick factor differs from the gravkick factor?
4. How in the GADGET-2 the cooling due to cosmological expansion
realizes? Looking into the code I didn't find corresponding term in the
DtEntropy calculation.

Thanks!