Higher order Nielsen numbers
Peter Saveliev
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Suppose $X,Y$ are smooth manifolds, $f,g:X\rightarrow Y$ are maps. Then the
Coincidence Problem studies the coincidence set $C=\{x:f(x)=g(x)\}$ and $%
m=\dim X-\dim Y$ is called the codimension of the problem. For a map $%
f:X\rightarrow Z$ and a submanifold $Y$ of $Z,$ the Preimage Problem studies
the preimage set $C=\{x:f(x)\in Y\},$ $m=\dim X+\dim Y-\dim Z.$ In case of
codimension $0$, the Nielsen number is the lower estimate of the number of
points in $C$ changing under homotopies of $f,g,$ and for an arbitrary
codimension, of the number of components of $C$. In this talk I will
consider an approach to the calculation of other topological characteristics
of $C.$ The goal will be to estimate the bordism groups $\Omega _{\ast }(C).$
In comparison to the classical theory the Nielsen equivalence of the points
of $C$ is replaced with an equivalence of singular submanifolds of $C$. We
consider topologically and algebraically essential classes and define higher
order Nielsen numbers.
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