General Information
This is the website of the research seminar of the Computational Logic Group at the
Institute of Discrete Mathematics and
Geometry of TU Wien. The seminar
usually takes places on Wednesdays from 10:00 to 11:00 in the
Zeichensaal 1, 8th floor, green area.
The seminar is organised by
J. Aguilera,
E. Fokina and
S. Hetzl.
If you want to receive talk announcements by e-mail, please subscribe to the
mailing list of this seminar on its
administration page.
Preliminary Programme
- October 7, 2026
-
Johannes Weiser (TU Wien)
title: t.b.a.
- October 14, 2026
-
Franziskus Wiesnet (TU Wien)
title: On the Limits of Recursive Characterizations in the Refined A-Translation
abstract:
The refined A-translation, due to Berger, Buchholz, and Schwichtenberg, is based on recursively defined classes of formulas in minimal arithmetic, in particular the classes of definite and goal formulas. Schwichtenberg and Wainer observed that one of the key proof-theoretic properties of definite formulas also holds for formulas outside the original class and asked whether all formulas satisfying this property admit a useful characterization.
In this talk, I show that this is not possible. More precisely, none of the four proof-theoretic properties associated with the formula classes in the refined A-translation admits a recursive characterization. We will also show how the original framework can nevertheless be extended, and present an extended formulation of the refined A-translation including conjunction.
- October 28, 2026
-
Antonio Nakid Cordero (TU Wien)
title: t.b.a.
- November 4, 2026
-
Logan McDonald (TU Wien)
title: t.b.a.
- November 11, 2026
-
Elijah Schulzki (TU Wien)
title: t.b.a.
Archive
- September 23, 2026
-
Anders Lundstedt (Stockholm University)
title: Finitely non-standard models of Robinson arithmetic
abstract:
To the best of my knowledge, there is no systematic study of *finitely
non-standard* models of Robinson arithmetic - that is, there is no systematic
study of those models of Robinson arithmetic that have a non-empty finite set
of non-standard numbers. I will present a modest attempt at such a systematic
study. With addition and multiplication both defined recursively in the second
argument, the main conclusions are roughly: (1) addition and multiplication
with a non-standard first argument is "well-behaved"; and (2) addition and
multiplication with a non-standard second argument is "wild".
- September 16, 2026
-
Heer Tern Koh (University of Electronic Science and Technology of China)
title: (Non-)density of punctual degrees
abstract:
A punctual structure is a countable structure with domain omega whose functions
and relations are uniformly primitive recursive. Since the inverse of a
bijective primitive recursive function is not necessarily primitive recursive,
the relation "being primitive recursively isomorphic" is a preorder rather than
an equivalence relation. This gives rise to a degree structure which we call
the punctual degrees. Intuitively, this is an algorithmic invariant which
measures the different primitive recursive speeds of enumerations of a given
(punctual) structure. In this talk, we provide a survey of results and
techniques concerning density and non-density of the punctual degrees of
various structures.
Last Change: 2026-09-28, Stefan Hetzl.