d + 1-dimensional manifold, whose is a union of d-dimensional boundary
disjoint v manifolds and d, a linear: -+ The manifold -Zod V(Md+l)
V(Zod) V(Zld). ma- is with the orientation. The axiom in that z0g, Zod
opposite gluing [Ati88] requires if we two such d + 1-manifolds a
common d-subma- glue together along (closed) fold of in their the linear
for the has to be the boundaries, composite compo- map tion of the
linear of the individual d + 1-manifolds. maps the of and as in we can
state categories functors, [Mac88], Using language axioms as follows:
concisely Atiyah's very Definition 0.1.1 A in dimension d is a
([Ati88]). topological quantumfield theory between monoidal functor
symmetric categories [Mac881 asfollows: V: --] k-vect. Cobd+1 finite
Here k-vect denotes the whose are dimensional v- category, objects for
field tor over a field k, which we assume to be instance, a perfect,
spaces The of of characteristic 0. set between two vector is morphisms,
simply spaces the set of linear with the usual The has as composition.
category Cobd+1 maps manifolds. such closed oriented d-dimensional A
between two objects morphism. Zd d oriented d 1-- d-manifolds and is a +
1-cobordism, an + Zod meaning gMd+l = Zd is the d- mensional manifold,
Md+l, whose Lj boundary _ZOd of the d-manifolds. consider union two we
as joint (Strictly speaking morphisms cobordisms modulo relative Given
another or homeomorphisms diffeomorphisms).