2
1.THE LERAY-SERRE SPECTRAL SEQUENCE
In fact, one has not to go to infinity in this situation. Since E ^ = 0 for i 0 or
j 0, the arrows dr starting or ending at (z, j) are trivial maps for r large enough
(e.g. r max{i, j}). Thus, the modules
E^J
become stationary after some time.
However, there is one big problem: in general, no information is given about the
arrows c?2, fife,...! Thus, it seems to be impossible to determine E^'-7, E4"7,.... Here,
the multiplicative structure of the cohomology becomes important. The arrows dr
act as derivations, and this makes it (often) feasible to determine all terms in the
spectral sequence.
The material of this chapter can be found in McCleary [69], Borel [9, 12],
Spanier [90], Whitehead [113], and Fomenko-Fuchs-Gutenmacher [35].
Throughout this chapter, R is a principal ideal domain.
l.A. Additive structure
1.1. GRADED AND BIGRADED MODULES
A graded R-module is a direct sum
zGZ
of i?-modules M% indexed by the integers. Similarly, a bigraded R-module is a
direct sum
M = M" = 0
M^J
tj'GZ
of i?-modules M
2 J
, indexed by pairs of integers. The elements of
M2
or
M2'-7
are
called homogeneous of degree i or bidegree (i, j), respectively. A graded or bigraded
module is of finite type if the
Ml
or M
M
are finitely generated. A submodule
N C M
#
is graded if JV = 0 -
G Z
N\ where
Nl
= N n M \
1.2. TOTAL GRADINGS AND TENSOR PRODUCTS
Associated to a bigraded module M** is the graded module M* = Tot(M) which
is graded by the total degree,
Tot(M)*= 0
M3'k.
j-\-k=i
A typical example for a bigraded module is a tensor product of graded modules.
Put
(MS)NfJ =Ml®Nj.
Then the corresponding graded module is
(M®Ny= 0
(Mj®Nk).
j-\-k=i
Another example is obtained from nitrations.
1.3. FlLTRATIONS AND ASSOCIATED GRADINGS
A filtration of a module M is a collection of submodules
C F 2 M C F ' _ 1 M C ¥Z~2M C F 2 _ 3 M C
The filtration is bounded if F°M = M, and convergent if p | ^ o
F
' ^
=
°-
I f
M = M* is graded, then one requires that the submodules in the filtration are
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