## Surgery in codimension 3 and the Browder--Livesay invariants

##### Authors
Hegenbarth, Friedrich
Muranov, Yurij V.
Repovš, Dušan
##### Description
The inertia subgroup $I_n(\pi)$ of a surgery obstruction group $L_n(\pi)$ is generated by elements which act trivially on the set of homotopy triangulations $\Cal S(X)$ for some closed topological manifold $X^{n-1}$ with $\pi_1(X)=\pi$. This group is a subgroup of the group $C_n(\pi)$ which consists of the elements which can be realized by normal maps of closed manifolds. In all known cases these groups coincide and the computation of them is one of the basic problems of surgery theory. The computation of the group $C_n(\pi)$ is equivalent to the computation the image of the assembly map $A:H_{n}(B\pi, \bold L_{\bullet})\to L_{n}(\pi)$. Every Browder-Livesay filtration of the manifold $X$ provides a collection of Browder-Livesay invariants which are the forbidden invariants in the closed manifold surgery problem. In the present paper we describe all possible forbidden invariants which can give a Browder-Livesay filtration for computing the inertia subgroup. Our approach is a natural generalization of the approach of Hambleton and Kharshiladze. More precisely, we prove that a Browder-Livesay filtration of a given manifold can give the following forbidden invariants for an element $x\in L_n(\pi_1(X))$ to belong to the subgroup $I_n(\pi)$: the nontrivial Browder-Livesay invariants in codimensions 0, 1, 2 and a nontrivial class of obstructions of a restriction of a normal map to a submanifold in codimension 3.
##### Keywords
Mathematics - Geometric Topology, Mathematics - Algebraic Topology, 57R67, 19J25, 55T99, 58A35, 18F25