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4 votes
1 answer
296 views

On the proof of the surgery step in Wall's book

This question regards a part of the proof of the so called surgery step, in Wall's book "surgery on compact manifolds", Theorem 1.1. Setting $M^m$ smooth manifold, $X$ CW complex, $\phi :M\...
13 votes
1 answer
812 views

Roadmap for L-Theory

Background: I spent sometime reading about algebraic K-theory and started reading research papers on the subject with relative facility at least I do understand constructions, statements of the ...
6 votes
1 answer
170 views

Diffeomorphism type of the added sphere in simply connected surgery

A classical result of simply connected surgery theory, is that if two normal maps $f:M_i\rightarrow X$, $i=0,1$ are normally cobordant and if the dimension of the manifolds is odd, there exists a ...
2 votes
0 answers
99 views

Why is the oriented $G$-homotopy type of a $G$-complex uniquely determined by the periodicity generator?

Say we have a periodicity generator $e \in H^k(BG)$. I can show that we then have a $(k-1)$-dimensional $G$-complex $X$ with free $G$-action. It's also not that difficult to see that it has trivial $G$...
3 votes
1 answer
193 views

Sullivan's $H$-space equivalence between $G/PL[1/2]$ and $BO[1/2]$

There is a theorem by Sullivan of the following form: Theorem: There is an equivalence of $H$-spaces $$ G/PL[\tfrac{1}{2}] \simeq BO_{\otimes}[ \tfrac{1}{2} ]\ . $$ It can be found for example ...