4 papers
Categoricity without Power
Jun Le Goh, Chieu-Minh Tran
We prove an analogue of Morley's categoricity theorem where cardinality is replaced by the recursion-theoretic notion of arithmetic degree. We say that a complete arithmetically de…
Finite combinatorics and computability theory
Damir D. Dzhafarov, Jun le Goh
We prove that the existence of finite combinatorial objects such as affine planes, mutually orthogonal Latin squares, and resolvable balanced incomplete block designs can be reform…
The weakness of finding descending sequences in ill-founded linear orders
Jun Le Goh, Arno Pauly, Manlio Valenti
We explore the Weihrauch degree of the problems ``find a bad sequence in a non-well quasi order'' () and ``find a descending sequence in an ill-founded linear order''…
Open Problems in Computability Theory and Descriptive Set Theory
George Barmpalias, Nikolay Bazhenov, Chi Tat Chong +11
These open problems were presented in the Problem Sessions held during the Tianyuan Workshop on Computability Theory and Descriptive Set Theory, June 16-20, 2025. The problems are…