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Self-full ceers and the uniform join operator
Journal of Logic and Computation ( IF 0.7 ) Pub Date : 2020-04-22 , DOI: 10.1093/logcom/exaa023
Uri Andrews 1 , Noah Schweber 1 , Andrea Sorbi 2
Affiliation  

A computably enumerable equivalence relation (ceer) |$X$| is called self-full if whenever |$f$| is a reduction of |$X$| to |$X$|⁠, then the range of |$f$| intersects all |$X$|-equivalence classes. It is known that the infinite self-full ceers properly contain the dark ceers, i.e. the infinite ceers which do not admit an infinite computably enumerable transversal. Unlike the collection of dark ceers, which are closed under the operation of uniform join, we answer a question from [ 4] by showing that there are self-full ceers |$X$| and |$Y$| so that their uniform join |$X\oplus Y$| is non-self-full. We then define and examine the hereditarily self-full ceers, which are the self-full ceers |$X$| so that for any self-full |$Y$|⁠, |$X\oplus Y$| is also self-full: we show that they are closed under uniform join and that every non-universal degree in |${\operatorname{\textbf{Ceers}}}_{\operatorname{{\mathcal{I}}}}$| have infinitely many incomparable hereditarily self-full strong minimal covers. In particular, every non-universal ceer is bounded by a hereditarily self-full ceer. Thus, the hereditarily self-full ceers form a properly intermediate class in between the dark ceers and the infinite self-full ceers, which is closed under |$\oplus $|⁠.

中文翻译:

自足的伙伴和统一的加入运营商

可计算的等价关系(ceer)| $ X $ | 如果| $ f $ |被称为自满 减少了| $ X $ | | $ X $ |⁠,然后| $ f $ |的范围 与所有| $ X $ |相交 等价类。众所周知,无限的自我充实的顶点适当地包含了深色的顶点,即不容许无限的可计算的横向的无限的顶点。与在统一连接操作下关闭的深色ceer集合不同,我们通过显示[ $ X $ |是自满的ceers]来回答[4]中的问题| $ Y $ | 使他们的制服加入| $ X \ oplus Y $ |不自满。然后,我们定义并检查遗传自足的子代,即自足子代|| $ X $ |。这样,对于任何自满| $ Y $ |⁠| $ X \ oplus Y $ | 也是自满的:我们证明它们在统一联接下是封闭的,并且| $ {\ operatorname {\ textbf {Ceers}}} _ {\ operatorname {{\ mathcal {I}}}}中的每个非通用学位$ | 具有无数无与伦比的遗传自足强壮的极小的掩护。特别是,每个非通用Ceer都以遗传自足的Ceer为边界。因此,遗传自足的子代在黑暗的子代和无限的自我子代的子代之间形成适当的中间类,它们在| $ \ oplus $ |⁠下封闭
更新日期:2020-04-22
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