On representations as an infinite series of isols
On resemblance and recursive isomorphism types of bounded partial recursive functions.
On resemblance and recursive isomorphism types of partial recursive functions.
On Some Classes Of Unrecognizable Properties Of Groups
On some classes of unrecognizable properties of groups.
On some properties of -maximal sets and -reducibility.
On the complexity of computable real sequences
On the complexity of events recognizable in real time
On the complexity of the word problem for finitely presented commutative semigroups.
On the Conjugacy Problem for Knot Groups.
On the continuity set of an Omega rational function
In this paper, we study the continuity of rational functions realized by Büchi finite state transducers. It has been shown by Prieur that it can be decided whether such a function is continuous. We prove here that surprisingly, it cannot be decided whether such a function f has at least one point of continuity and that its continuity set C(f) cannot be computed. In the case of a synchronous rational function, we show that its continuity set is rational and that it can be computed. Furthermore...
On the definition of a Lachlan semilattice.
On the Degrees of Universal Regressive Isols.
On the Difficulty of Triangulating Three-Dimensional Nonconvex Polyhedra.
On the Ershov upper semilattice .
On the form of countable admissible ordinals
On the form of functions which preserve regressive isols
On the Goldbach conjecture and the consistency of general recursive arithemetic.
On the hierarchies of Δ20-real numbers
A real number x is called Δ20 if its binary expansion corresponds to a Δ20-set of natural numbers. Such reals are just the limits of computable sequences of rational numbers and hence also called computably approximable. Depending on how fast the sequences converge, Δ20-reals have different levels of effectiveness. This leads to various hierarchies of Δ20 reals. In this survey paper we summarize several recent developments related to such kind of hierarchies shown by the author and his collaborators. ...
On the index sets of -subsets of the real numbers.