Invitation to the Logic Seminar at the National University of Singapore

Date: Wednesday, 05 October 2016, 17:00 hrs

Room: S17#04-05, Department of Mathematics, NUS

Speaker: Reese Johnston

Title: Computability of isolated paths in uncountable binary trees.

Abstract: Alpha-recursion theory has been a target of study for some time;

a defining feature is the exotic behavior that can occur for general

ordinals alpha. In this talk, we consider the particular, and

better-behaved, case in which alpha is omega-1, and approach a class of

problems well-studied in the classical case: Pi-0-1-classes in Cantor space.

Of particular interest, for reasons that will become apparent, are the

degrees available as isolated paths through computable binary trees

that are restricted to countable width only. In this talk, I will show

that the degrees of these paths can – unlike the classical case – be

noncomputable and may in fact have very high Turing degree.

URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html