Usage:
<cohomology1 i M j H
Computes the cohomology module
H = \sum_{n >= 0} H^i(M(n))
of the module M , regarded as
a coherent sheaf on projective space.
The low degree parts of the module computed may
or may not mean much (see below).
Parameters:
i>0 the index of the cohomology group
M
j>0 a sufficiently large integer (see below.)
Output values:
H = Ext^i(J, M),
where J is the ideal
generated by the jth powers of the variables in the
base ring of M.
The answer coincides with the cohomology (at least)
in degrees >= d - numvars + 1 - j,
where d is the maximum degree of a generator of a syzygy module of M,
and numvars is the number of variables in the ring.