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Computable reducibility is a well-established notion that allows to compare the complexity of various equivalence relations over the natural numbers. We generalize computable reducibility by introducing degree spectra of reducibility and…

Logic · Mathematics 2018-10-09 Ekaterina Fokina , Dino Rossegger , Luca San Mauro

The structure of covariant instruments is studied and a general structure theorem is derived. A detailed characterization is given to covariant instruments in the case of an irreducible representation of a locally compact group.

Mathematical Physics · Physics 2009-10-16 Claudio Carmeli , Teiko Heinosaari , Alessandro Toigo

In this paper, we study properties of asymptotic resemblance relations induced by compatible coarse structures on groups. We generalize the notion of asymptotic dimensiongrad for groups with compatible coarse structures and show this notion…

Geometric Topology · Mathematics 2021-11-12 Sh. Kalantari

We review some definitions and basic notions relating to generalised spin structures and introduce the notion of reducibility. We discuss connections on these structures, define a covariant Lie derivative for associated bundles and develop…

Differential Geometry · Mathematics 2025-11-06 Andrew D. K. Beckett

We study reductions well suited to compare structures and classes of structures with respect to properties based on enumeration reducibility. We introduce the notion of a positive enumerable functor and study the relationship with…

Logic · Mathematics 2021-02-10 Barbara Csima , Dino Rossegger , Zhi Ying "Daniel" Yu

This paper investigates some issues arising in categorical models of reversible logic and computation. Our claim is that the structural (coherence) isomorphisms of these categorical models, although generally overlooked, have decidedly…

Category Theory · Mathematics 2013-04-29 Peter Hines

We study the degrees of selector functions related to the degrees in which a rigid computable structure is relatively computably categorical. It is proved that for some structures such degrees can be represented as the unions of upper cones…

Logic · Mathematics 2023-05-31 I. Sh. Kalimullin

Adapting a result of Bazhenov, Kalimullin, and Yamaleev, we show that if a Turing degree $\textbf{d}$ is the degree of categoricity of a computable structure $\mathcal{M}$ and is not the strong degree of categoricity of any computable…

Logic · Mathematics 2026-01-19 Joey Lakerdas-Gayle

We compare three notions of genericity of separable metric structures. Our analysis provides a general model theoretic technique of showing that structures are generic in descriptive set theoretic (topological) sense and in measure…

Logic · Mathematics 2008-02-04 Alexander Usvyatsov

We study links between first-order formulas and arbitrary properties for families of theories, classes of structures and their isomorphism types. Possibilities for ranks and degrees for formulas and theories with respect to given properties…

Logic · Mathematics 2021-04-02 Sergey V. Sudoplatov

A general theme of computable structure theory is to investigate when structures have copies of a given complexity $\Gamma$. We discuss such problem for the case of equivalence structures and preorders. We show that there is a $\Pi^0_1$…

Logic · Mathematics 2020-01-23 Nikolay Bazhenov , Luca San Mauro

Interconnected dynamic systems are a pervasive component of our modern infrastructures. The complexity of such systems can be staggering, which motivates simplified representations for their manipulation and analysis. This work introduces…

Systems and Control · Computer Science 2015-03-19 E. Yeung , J. Goncalves , H. Sandberg , S. Warnick

Similarity notions between vertices in a graph, such as structural and regular equivalence, are one of the main ingredients in clustering tools in complex network science. We generalise structural and regular equivalences for undirected…

Combinatorics · Mathematics 2026-01-01 Marzieh Eidi , Nina Otter

In this work we advance a generalization of quantum computational logics capable of dealing with some important examples of quantum algorithms. We outline an algebraic axiomatization of these structures.

Quantum Physics · Physics 2019-01-21 Federico Holik , Giuseppe Sergioli , Hector Freytes , Angelo Plastino

We show that the theory of the partial order of computably enumerable equivalence relations (ceers) under computable reduction is 1-equivalent to true arithmetic. We show the same result for the structure comprised of the dark ceers and the…

Logic · Mathematics 2020-02-25 Uri Andrews , Noah Schweber , Andrea Sorbi

Symmetries and isomorphisms play similar conceptual roles when we consider how models represent physical situations, but they are formally distinct, as two models related by symmetries are not typically isomorphic. I offer a rigorous…

History and Philosophy of Physics · Physics 2024-07-22 Lu Chen

We present a concept of uniform encodability of theories and develop tools related to this concept. As an application we obtain general undecidability results which are uniform for large families of structures. In the way, we define…

Logic · Mathematics 2010-12-07 Hector Pasten , Thanases Pheidas , Xavier Vidaux

We develop a novel formal theory of finite structures, based on a view of finite structures as a fundamental artifact of computing and programming, forming a common platform for computing both within particular finite structures, and in the…

Logic in Computer Science · Computer Science 2018-08-16 Daniel Leivant

Generic computability has been studied in group theory and we now study it in the context of classical computability theory. A set A of natural numbers is generically computable if there is a partial computable function f whose domain has…

Group Theory · Mathematics 2014-02-26 Carl G. Jockusch , Paul E. Schupp

In this work, we will introduce the notion of generalized topological groups using generalized topological structure and generalized continuity defined by ?A. Cs?asz?ar [2]. We will discuss some basic properties of this kind of structures…

General Topology · Mathematics 2016-11-11 Murad Hussain , Moiz Ud Din Khan , Cenap Özel