Abstract
Thom–Pontrjagin constructions are used to give a computable necessary and sufficient condition for a homomorphism ϕ : H n(L;Z) → H n(M;Z) to be realized by a map f : M → L of degree k for closed (n − 1)-connected 2n-manifolds M and L, n > 1. A corollary is that each (n − 1)-connected 2n-manifold admits selfmaps of degree larger than 1, n > 1.
In the most interesting case of dimension 4, with the additional surgery arguments we give a necessary and sufficient condition for the existence of a degree k map from a closed orientable 4-manifold M to a closed simply connected 4-manifold L in terms of their intersection forms; in particular, there is a map f : M → L of degree 1 if and only if the intersection form of L is isomorphic to a direct summand of that of M.
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Both authors are supported by MSTC, NSFC. The comments of F. Ding, J. Z. Pan, Y. Su and the referee enhance the quality of the paper
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Duan, H.B., Wang, S.C. Non-Zero Degree Maps Between 2n-Manifolds. Acta Math Sinica 20, 1–14 (2004). https://doi.org/10.1007/s10114-003-0307-x
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DOI: https://doi.org/10.1007/s10114-003-0307-x