Zobrazeno 1 - 10
of 298
pro vyhledávání: '"Nies, André"'
Autor:
Paolini, Gianluca, Nies, Andre
It is an open question whether topological isomorphism of oligomorphic groups is smooth in the sense of Borel reducibility. We show smoothness for two Borel classes of oligomorphic groups: groups with no algebraicity, and groups with finitely many {\
Externí odkaz:
http://arxiv.org/abs/2410.02248
Autor:
Melnikov, Alexander G., Nies, Andre
Given a computably locally compact Polish space $M$, we show that its 1-point compactification $M^*$ is computably compact. Then, for a computably locally compact group $G$, we show that the Chabauty space $\mathcal S(G)$ of closed subgroups of $G$ h
Externí odkaz:
http://arxiv.org/abs/2407.19440
Autor:
Nies, Andre, Stephan, Frank
We consider word automaticity for groups that are nilpotent of class $2$ and have exponent a prime $p$. We show that the infinitely generated free group in this variety is not word automatic. In contrast, the infinite extra-special $p$-group $E_p$ is
Externí odkaz:
http://arxiv.org/abs/2302.12446
Autor:
Nies, Andre
The 2022 logic blog has concentrated on the connections of group theory and logic. It discusses Gardam's 2021 refutation of the Higman/ Kaplansky unit conjecture, and its connections to logic and to computation. The rest is about topological groups o
Externí odkaz:
http://arxiv.org/abs/2302.11853
Autor:
Melnikov, Alexander, Nies, Andre
We study totally disconnected, locally compact (t.d.l.c.) groups from an algorithmic perspective. We give various approaches to defining computable presentations of t.d.l.c.\ groups, and show their equivalence. In the process, we obtain an algorithmi
Externí odkaz:
http://arxiv.org/abs/2204.09878
Autor:
Nies, Andre
The blog has several entries on group theory interacting with computability and wider logic, several open questions, and an entry on undecidability in physics.
Externí odkaz:
http://arxiv.org/abs/2202.13643
Publikováno v:
The Journal of Symbolic Logic. 2023;88(3):1170-1190
The tower number $\mathfrak t$ and the ultrafilter number $\mathfrak u$ are cardinal characteristics from set theory. They are based on combinatorial properties of classes of subsets of~$\omega$ and the almost inclusion relation $\subseteq^*$ between
Externí odkaz:
http://arxiv.org/abs/2106.00312
We study the algorithmic content of Pontryagin - van Kampen duality. We prove that the dualization is computable in the important cases of compact and locally compact totally disconnected Polish abelian groups. The applications of our main results in
Externí odkaz:
http://arxiv.org/abs/2105.12897
Autor:
Nies, Andre
This year's blog has focused on the connections of group theory with logic and algorithms. The first post is on automata presentable groups. Then there are several posts related to topological groups, for instance Ivanov and Majcher showing that extr
Externí odkaz:
http://arxiv.org/abs/2101.09508