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Computability of Products of Chainable Continua
Theory of Computing Systems ( IF 0.6 ) Pub Date : 2020-11-13 , DOI: 10.1007/s00224-020-10017-6
Matea Čelar , Zvonko Iljazović

We examine conditions under which a semicomputable set in a computable topological space is computable. In particular, we examine topological pairs (A, B) with the following property: if X is a computable topological space and \(f:A\rightarrow X\) is an embedding such that f(A) and f(B) are semicomputable sets in X, then f(A) is a computable set in X. Such pairs (A, B) are said to have computable type. It is known that \((\mathcal {K},\{a,b\})\) has computable type if \(\mathcal {K}\) is a Hausdorff continuum chainable from a to b. It is also known that (In, In) has computable type, where In is the n-dimensional unit cube and In is its boundary in \(\mathbb {R}^{n} \). We generalize these results by proving the following: if \(\mathcal {K}_{i} \) is a nontrivial Hausdorff continuum chainable from ai to bi for \(i\in \{1,{\dots } ,n\}\), then \(({\prod }_{i=1}^{n} \mathcal {K}_{i} ,B)\) has computable type, where B is the set of all \((x_{1} ,{\dots } ,x_{n})\in {\prod }_{i=1}^{n} \mathcal {K}_{i}\) such that xi ∈{ai, bi} for some \(i\in \{1,{\dots } ,n\}\).



中文翻译:

可链接连续体乘积的可计算性

我们研究了可计算拓扑空间中的半计算集可计算的条件。特别是,我们检查具有以下属性的拓扑对(AB):如果X是可计算的拓扑空间,并且\(f:A \ rightarrow X \)是一个嵌入,使得fA)和fB)为X中的半可计算集合,则fA)是X中的可计算集合。此类对(AB)具有可计算类型。已知\((\ mathcal {K},\ {a,b \})\)如果\(\ mathcal {K} \)是可从a链接b的Hausdorff连续体,则具有可计算的类型。还已知的是(ÑÑ)具有可计算的类型,其中ÑÑ维单位立方体和Ñ是其边界在\(\ mathbb {R} ^ {N} \) 。我们通过证明以下概括这些结果:如果\(\ mathcal {K} _ {I} \)是一个非平凡的Hausdorff连续环连接从一个b\(I \在\ {1,{\点}, n \} \),则\(({{prod} _ {i = 1} ^ {n} \ mathcal {K} _ {i},B)\)具有可计算类型,其中B是所有\((x_ {1 },{\点},X_ {N})\在{\ PROD} _ {i = 1} ^ {N} \ mathcal {K} _ {I} \),使得X∈{一个b}表示\(i \ in \ {1,{\ dots},n \} \)

更新日期:2020-11-13
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