On the realisation problem for mapping degree sets
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arXiv
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| Main Authors: | , , , , |
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| Format: | Preprint |
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2023
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| _version_ | 1866915444865105920 |
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| author | Neofytidis, Christoforos Sun, Hongbin Tian, Ye Wang, Shicheng Wang, Zhongzi |
| author_facet | Neofytidis, Christoforos Sun, Hongbin Tian, Ye Wang, Shicheng Wang, Zhongzi |
| contents | The set of degrees of maps $D(M,N)$, where $M,N$ are closed oriented $n$-manifolds, always contains $0$ and the set of degrees of self-maps $D(M)$ always contains $0$ and $1$. Also, if $a,b\in D(M)$, then $ab\in D(M)$; a set $A\subseteq\mathbb Z$ so that $ab\in A$ for each $a,b\in A$ is called multiplicative. On the one hand, not every infinite set of integers (containing $0$) is a mapping degree set [NWW] and, on the other hand, every finite set of integers (containing $0$) is the mapping degree set of some $3$-manifolds [CMV]. We show the following:
(i) Not every multiplicative set $A$ containing $0,1$ is a self-mapping degree set.
(ii) For each $n\in\mathbb N$ and $k\geq3$, every $D(M,N)$ for $n$-manifolds $M$ and $N$ is $D(P,Q)$ for some $(n+k)$-manifolds $P$ and $Q$.
As a consequence of (ii) and [CMV], every finite set of integers (containing $0$) is the mapping degree set of some $n$-manifolds for all $n\neq 1,2,4,5$. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2303_11922 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | On the realisation problem for mapping degree sets Neofytidis, Christoforos Sun, Hongbin Tian, Ye Wang, Shicheng Wang, Zhongzi Geometric Topology Algebraic Topology Number Theory The set of degrees of maps $D(M,N)$, where $M,N$ are closed oriented $n$-manifolds, always contains $0$ and the set of degrees of self-maps $D(M)$ always contains $0$ and $1$. Also, if $a,b\in D(M)$, then $ab\in D(M)$; a set $A\subseteq\mathbb Z$ so that $ab\in A$ for each $a,b\in A$ is called multiplicative. On the one hand, not every infinite set of integers (containing $0$) is a mapping degree set [NWW] and, on the other hand, every finite set of integers (containing $0$) is the mapping degree set of some $3$-manifolds [CMV]. We show the following: (i) Not every multiplicative set $A$ containing $0,1$ is a self-mapping degree set. (ii) For each $n\in\mathbb N$ and $k\geq3$, every $D(M,N)$ for $n$-manifolds $M$ and $N$ is $D(P,Q)$ for some $(n+k)$-manifolds $P$ and $Q$. As a consequence of (ii) and [CMV], every finite set of integers (containing $0$) is the mapping degree set of some $n$-manifolds for all $n\neq 1,2,4,5$. |
| title | On the realisation problem for mapping degree sets |
| topic | Geometric Topology Algebraic Topology Number Theory |
| url | https://arxiv.org/abs/2303.11922 |