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SUMMARY:Nikolai Bazhenov (Sobolev Institute of Mathematics)
DTSTART:20200609T140000Z
DTEND:20200609T150000Z
DTSTAMP:20260404T131150Z
UID:CTA/8
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/CTA/8
 /">Rogers semilattices in the analytical hierarchy</a>\nby Nikolai Bazheno
 v (Sobolev Institute of Mathematics) as part of Computability theory and a
 pplications\n\n\nAbstract\nFor a countable set S\, a numbering of S is a s
 urjective map from ω onto S. A numbering ν is reducible to a numbering 
 μ if there is a computable function f such that ν(x) = μ f(x) for all i
 ndices x. The notion of reducibility between numberings gives rise to a cl
 ass of upper semilattices\, which are usually called Rogers semilattices. 
 We discuss recent results on Rogers semilattices induced by numberings in 
 the analytical hierarchy. Special attention is given to the first-order pr
 operties of Rogers semilattices. The talk is based on joint works with Man
 at Mustafa\, Sergei Ospichev\, and Mars Yamaleev.\n
LOCATION:https://stable.researchseminars.org/talk/CTA/8/
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