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snapvratio - compute various global virials (clausius, newton)
snapvratio computes the global
virial of a snapshot. It works best if the snapshot has potentials as well
as forces are present. They are normally created by the N-body integrator,
but see also e.g. hackforce(1NEMO)
Currently a table is produced with the
time, -2T/W, T+W, T, W, W_1, W_2, Mass
where W is the potential energy (which one depends on the selected wmode).
wmode=phi is the potential as obtained from appropriately summing the product
of masses and potentials in the snapshot, wmode=acc gets the Clausius
Wacc = sum_(m r.f)
(sum over all masses (m), position (r) and forces (f)), and wmode=exact
the Newtonian (m/r) potential.
W_1 and W_2 in the table are the other two
potentials not selected as the prime potential, the original order of the
potentials is acc, phi, exact. The choosen one comes first, the others ones
follow in the order left from this array.
The following parameters
are recognized in any order if the keyword is also given:
file name (snapshot). No default.
- Times to select snapshot.
- Mode how to compute the prime potential: choice
is between acc (forces from the snapshot, hence Clausius virial), phi (potentials
from the snapshot), and exact (computed exact newtonian potential m/r [expensive!]).
The remaining unchoosen ones are listed as W_1 resp. W_2 in the output table.
- Do an N^2 newtonian calculation too? If true,
an N^2 algorithm will be used and [Default: f]
- Standard gravitational
softening for mode=exact. [Default: 0.05]
Marmo, C.; Secco, L. Clausius’ virial vs. total potential
energy in the dynamics of a two-component system (2003NewA....8..629M)
05-nov-91 V0.0 Created SMF
27-Mar-92 V0.1 added clausius - changed columns and names PJT
3-apr-92 V0.2 added wmode= keyword PJT
13-mar-97 V0.4 added total mass to the output PJT
30-jul-97 V0.5 added eps= PJT
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