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Abramsky, Dawar, and Wang (2017) introduced the pebbling comonad for k-variable counting logic and thereby initiated a line of work that imports category theoretic machinery to finite model theory. Such game comonads have been developed for…

Logic in Computer Science · Computer Science 2023-09-14 Moritz Lichter , Benedikt Pago , Tim Seppelt

We give several examples of pairs of non-isomorphic cubic fourfolds whose Fano varieties of lines are birationally equivalent (and in one example isomorphic). Two of our examples, which are special families of conjecturally irrational…

Algebraic Geometry · Mathematics 2024-12-20 Corey Brooke , Sarah Frei , Lisa Marquand

We provide a new criterion for embedding $\mathbb{E}_{0}$, and apply it to equivalence relations in model theory. This generalize the results of the authors and Pierre Simon on the Borel cardinality of Lascar strong types equality, and…

Logic · Mathematics 2013-08-27 Itay Kaplan , Benjamin D. Miller

We introduce the notion of a `pure` Abstract Elementary Class to block trivial counterexamples. We study classes of models of bipartite graphs and show: Main Theorem (cf. Theorem 3.5.2 and Corollary 3.5.6): If $(\lambda_i : i \le…

Logic · Mathematics 2015-02-20 John T. Baldwin , Martin Koerwien , Ioannis Souldatos

We exhibit two relation algebra atom structures such that they are elementarily equivalent but their term algebras are not. This answers Problem 14.19 in the book Hirsch, R. and Hodkinson, I., "Relation Algebras by Games", North-Holland,…

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

Game comonads offer a categorical view of a number of model-comparison games central to model theory, such as pebble and Ehrenfeucht-Fra\"iss\'e games. Remarkably, the categories of coalgebras for these comonads capture preservation of…

Logic in Computer Science · Computer Science 2024-07-02 Samson Abramsky , Luca Reggio

For a congruence subgroup $\Gamma$, we define the notion of $\Gamma$-equivalence on binary quadratic forms which is the same as proper equivalence if $\Gamma = \mathrm{SL}_2(\mathbb Z)$. We develop a theory on $\Gamma$-equivalence such as…

Number Theory · Mathematics 2017-11-02 Bumkyu Cho

We introduce and study a unital version of shift equivalence for finite square matrices over the nonnegative integers. In contrast to the classical case, we show that unital shift equivalence does not coincide with one-sided eventual…

Dynamical Systems · Mathematics 2025-04-15 Kevin Aguyar Brix , Efren Ruiz

We construct infinitely many smooth oriented 4-manifolds containing pairs of homotopic, smoothly embedded 2-spheres that are not topologically isotopic, but that are equivalent by an ambient diffeomorphism inducing the identity on homology.…

Geometric Topology · Mathematics 2019-08-07 Hannah R. Schwartz

It is shown that the fundamental group of the Griffiths double cone space is isomorphic to that of the triple cone. More generally if $\kappa$ is a cardinal such that $2 \leq \kappa \leq 2^{\aleph_0}$ then the $\kappa$-fold cone has the…

Group Theory · Mathematics 2024-03-13 Samuel M. Corson

Self-similar models are important in general relativity and other fundamental theories. In this paper we shall discuss the ``similarity hypothesis'', which asserts that under a variety of physical circumstances solutions of these theories…

General Relativity and Quantum Cosmology · Physics 2009-11-11 B. J. Carr , A. A. Coley

Using the simulation paradigm in information theory, we define notions of quantum hypergraph homomorphisms and quantum hypergraph isomorphisms, and show that they constitute partial orders and equivalence relations, respectively.…

Operator Algebras · Mathematics 2022-11-10 Gage Hoefer , Ivan G. Todorov

We give two results on guessing unbounded subsets of lambda^+. The first is a positive result and applies to the situation of lambda regular and at least equal to aleph_3, while the second is a negative consistency result which applies to…

Logic · Mathematics 2007-05-23 Mirna Džamonja , Saharon Shelah

We develop methods to formally describe and compare games, in order to probe questions of game structure and design, and as a stepping stone to predicting player behavior from design patterns. We define a grammar-like formalism to describe…

Logic in Computer Science · Computer Science 2021-01-05 Paul Riggins , David McPherson

We give an example for the Kuznetsov-Shinder conjecture, with infinitely many non-isomorphic D-equivalent and L-equivalent varieties.

Algebraic Geometry · Mathematics 2024-01-02 Tanya Kaushal Srivastava

The "Modularity Conjecture" is the assertion that the join of two nonmodular varieties is nonmodular. We establish the veracity of this conjecture for the case of linear idempotent varieties. We also establish analogous results concerning…

Rings and Algebras · Mathematics 2012-12-24 Wolfram Bentz , Luis Sequeira

The Church-Turing Thesis confuses numerical computations with symbolic computations. In particular, any model of computability in which equality is not definable, such as the lambda-models underpinning higher-order programming languages, is…

Logic in Computer Science · Computer Science 2014-11-07 Barry Jay , Jose Vergara

The authors show, by means of a finitary version square^{fin}_{lambda,D} of the combinatorial principle square^{b^*}_{lambda}, the consistency of the failure, relative to the consistency of supercompact cardinals, of the following: for all…

Logic · Mathematics 2007-05-23 Juliette Kennedy , Saharon Shelah

A seminal result by Whitney describes when two graphs have the same cycles. We consider the analogous problem for even cycle matroids. A representation of an even cycle matroid is a pair formed by a graph together with a special set of…

Combinatorics · Mathematics 2011-09-15 Bertrand Guenin , Irene Pivotto , Paul Wollan

We prove the existence of lattice isomorphic line arrangements having $\pi_1$-equivalent or homotopy-equivalent complements and non homeomorphic embeddings in the complex projective plane. We also provide two explicit examples, one is…

Geometric Topology · Mathematics 2018-01-10 Benoît Guerville-Ballé
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