We investigate the complexity of various combinatorial theorems about linear and partial orders, from the points of view of computability theory and reverse mathematics. We focus ...
We give four examples of theories in which Kreisel’s Conjecture is false: (1) the theory PA(-) obtained by adding a function symbol minus, ‘−’, to the language of PA, and t...
In this paper we answer the following well-known open question in computable model theory. Does there exist a computable not ℵ0-categorical saturated structure with a unique com...
Bakhadyr Khoussainov, Pavel Semukhin, Frank Stepha...
The paper studies how the localic notion of sublocale transfers to formal topology. For any formal topology (not necessarily with positivity predicate) we define a sublocale to b...
We observe that the W∗ -hierarchy, a variant (introduced by Downey, Fellows, and Taylor [8]) of the better known W-hierarchy, coincides with the W-hierarchy, though not level wi...