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A measurable relation algebra is a relation algebra in which the identity element is a sum of atoms that can be measured in the sense that the "size" of each such atom can be defined in an intuitive and reasonable way (within the framework…

Logic · Mathematics 2026-03-19 H. Andréka , S. Givant

A relation algebra is measurable if the identity element is a sum of atoms, and the square x;1;x of each subidentity atom x is a sum of non-zero functional elements. These functional elements form a group Gx. We prove that a measurable…

Logic · Mathematics 2025-02-12 Hajnal Andréka , Steven Givant

Generalizing results of J\'onsson and Tarski, Maddux introduced the notion of a pair-dense relation algebra and proved that every pair-dense relation algebra is representable. The notion of a pair below the identity element is readily…

Logic · Mathematics 2023-03-27 Steven Givant

A coset relation algebra is one embeddable into some full coset relation algebra, the latter is an algebra constructed from a system of groups, a coordinated system of isomorphisms between quotients of these groups, and a system of cosets…

Logic · Mathematics 2025-02-12 Steven Givant , Hajnal Andréka

We define an easily verifiable notion of an atomic formula having uniformly bounded arrays in a structure $M$. We prove that if $T$ is a complete $L$-theory, then $T$ is mutually algebraic if and only if there is some model $M$ of $T$ for…

Logic · Mathematics 2020-11-11 Michael C. Laskowski , Caroline A. Terry

In this paper we give an alternative construction using Monk like algebras that are binary generated to show that the class of strongly representable atom structures is not elementary. The atom structures of such algebras are cylindric…

Logic · Mathematics 2013-07-17 Tarek Sayed Ahmed , Mohammed Khaled

A series of nonrepresentable relation algebras is constructed from groups. We use them to prove that there are continuum many subvarieties between the variety of representable relation algebras and the variety of coset relation algebras. We…

Logic · Mathematics 2025-02-12 H. Andréka , S. Givant , I. Németi

We show that every finite semilattice can be represented as an atomized semilattice, an algebraic structure with additional elements (atoms) that extend the semilattice's partial order. Each atom maps to one subdirectly irreducible…

Rings and Algebras · Mathematics 2021-02-17 Fernando Martin-Maroto , Gonzalo G. de Polavieja

Orbit-finite models of computation generalise the standard models of computation, to allow computation over infinite objects that are finite up to symmetries on atoms, denoted by $\mathbb{A}$. Set theory with atoms is used to reason about…

Logic · Mathematics 2025-12-03 Jake Masters

We introduce a class of monotone $\sigma$-complete effect algebras, called representable, which are $\sigma$-homomorphic images of a class of monotone $\sigma$-complete effect algebras of functions taking values in the interval $[0,1]$ and…

Mathematical Physics · Physics 2015-06-17 Anatolij Dvurečenskij

The structures $\langle M,\subseteq^M\rangle$ arising as the inclusion relation of a countable model of sufficient set theory $\langle M,\in^M\rangle$, whether well-founded or not, are all isomorphic. These structures $\langle…

Logic · Mathematics 2017-04-17 Joel David Hamkins , Makoto Kikuchi

In physics, Lie groups represent the algebraic structure that describes symmetry transformations of a given system. Then, the descending Lie algebra of those groups are necessarily real. In most cases, the complexification of those Lie…

Mathematical Physics · Physics 2026-03-20 Tanguy Marsault , Laurent Schoeffel

We prove two results intended to streamline proofs about cellularity that pass through mutual algebraicity. First, we show that a countable structure $M$ is cellular if and only if $M$ is $\omega$-categorical and mutually algebraic. Second,…

Logic · Mathematics 2022-08-11 Samuel Braunfeld , Michael C. Laskowski

For representation by partial functions in the signature with intersection, composition and antidomain, we show that a representation is meet complete if and only if it is join complete. We show that a representation is complete if and only…

Rings and Algebras · Mathematics 2017-08-01 Brett McLean

We show that the class of representable substitution algebras is characterized by a set of universal first order sentences. In addition, it is shown that a necessary and sufficient condition for a substitution algebra to be representable is…

Logic · Mathematics 2015-03-05 Norman Feldman

We prove the result in the title. We infer, that unlike cylindric algebras, there is a first order axiomatization of the class of completely representable polyadic algebras of infinite dimension, though the one we obtain is infinite; in…

Logic · Mathematics 2013-06-07 Tarek Sayed Ahmed

Representable implication algebras are known to be axiomatised by a finite number of equations (making the representation and finite representation problems decidable here). We show that this also holds in the context of unary (and binary)…

Logic · Mathematics 2023-01-09 Andrew Lewis-Smith Jaš Šemrl

An amorphic association scheme has the property that any of its fusion is also an association scheme. In this paper we generalize the property to be amorphic to an arbitrary C-algebra and prove that any amorphic C-algebra is determined up…

Combinatorics · Mathematics 2007-05-23 Ilia Ponomarenko , A. Rahnamai Barghi

We propose that observables in quantum theory are properly understood as representatives of symmetry-invariant quantities relating one system to another, the latter to be called a reference system. We provide a rigorous mathematical…

Quantum Physics · Physics 2018-03-14 Leon Loveridge , Takayuki Miyadera , Paul Busch

An association scheme is called amorphic if every possible fusion of relations gives rise to a fusion scheme. We call a pair of relations fusing if fusing that pair gives rise to a fusion scheme. We define the fusing-relations graph on the…

Combinatorics · Mathematics 2025-03-07 Edwin R. van Dam , Jack H. Koolen , Yanzhen Xiong
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