Balance with Unbounded Complexes (1108.1100v1)

Abstract: Given a double complex $X$ there are spectral sequences with the $E_2$ terms being either H$I$ (H${II}(X))$ or H${II}($H$_I (X))$. But if $H_I(X)=H{II}(X)=0$ both spectral sequences have all their terms 0. This can happen even though there is nonzero (co)homology of interest associated with $X$. This is frequently the case when dealing with Tate (co)homology. So in this situation the spectral sequences may not give any information about the (co)homology of interest. In this article we give a different way of constructing homology groups of $X$ when H$I(X)=$H${II}(X)=0$. With this result we give a new and elementary proof of balance of Tate homology and cohomology.