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We prove a constructive existence theorem for abelian envelopes of non-abelian monoidal categories. This establishes a new tool for the construction of tensor categories. As an example we obtain new proofs for the existence of several…

Category Theory · Mathematics 2023-06-22 Kevin Coulembier

Using toric geometry we prove a B\'ezout type theorem for weighted projective spaces.

Algebraic Geometry · Mathematics 2016-04-11 Bernt Ivar Utstøl Nødland

We build a purely inseparable Galois theory using non-derived commutative algebra. Our theory works on fields and on normal varieties. It says that a purely inseparable morphism corresponds to a finite (saturated) subalgebra of differential…

Algebraic Geometry · Mathematics 2025-10-08 Przemysław Grabowski

In this expository note, we present a transparent proof of Toponogov's theorem for Alexandrov spaces in the general case, not assuming local compactness of the underlying metric space. More precisely, we show that if M is a complete…

Metric Geometry · Mathematics 2012-07-26 Urs Lang , Viktor Schroeder

The main results in this note concern the characterization of the length of continua 1 (Theorems 2.5) and the parametrization of continua with finite length (Theorem 4.4). Using these results we give two independent and relatively…

Classical Analysis and ODEs · Mathematics 2017-10-06 Giovanni Alberti , Martino Ottolini

It is shown the construction of a module structure [2] with universe over a set of a particular kind of mathematical proofs, the base ring of this module will be built on a maximal consistent extension of a set of propositions, this…

Logic · Mathematics 2013-07-25 Kevin Davila Castellar , Ismael Gutierrez Garcia

We construct an example announced in the title. It answers in a strong way a well-known open problem in topological dynamics. In fact our construction is an existence theorem. It is based on a Borsuk-Ulam type theorem whose proof heavily…

Dynamical Systems · Mathematics 2025-09-23 Alexander Dranishnikov , Michael Levin

The famous \v{S}varc-Milnor Lemma says that a group $G$ acting properly and cocompactly via isometries on a length space $X$ is finitely generated and induces a quasi-isometry equivalence $g\to g\cdot x_0$ for any $x_0\in X$. We redefine…

Geometric Topology · Mathematics 2008-02-27 N. Brodskiy , J. Dydak , A. Mitra

In this paper we consider Kakutani's extension of the Brouwer fixed point theorem within the framework of Bishop's constructive mathematics. Kakutani's fixed point theorem is classically equivalent to Brouwer's fixed point theorem. The…

Logic · Mathematics 2016-11-09 Matthew Hendtlass

We prove analogues of the Craig interpolation theorem for the continuous model theory of metric structures.

Logic · Mathematics 2025-01-17 H. Jerome Keisler

We present a constructive proof of Tychonoff's fixed point theorem in a locally convex space for sequentially locally non-constant functions, As a corollary to this theorem we also present Schauder's fixed point theorem in a Banach space…

Logic · Mathematics 2011-05-19 Yasuhito Tanaka

In the study of the real projective plane, harmonic conjugates have an essential role, with applications to projectivities, involutions, and polarity. The construction of a harmonic conjugate requires the selection of auxiliary elements; it…

History and Overview · Mathematics 2018-05-11 Mark Mandelkern

We introduce a notion of equivalence on tilings which is formulated in terms of their local structure. We compare it with the known concept of locally deriving one tiling from another and show that two tilings of finite type are…

Condensed Matter · Physics 2009-10-28 Johannes Kellendonk

This article is concerned with a general scheme on how to obtain constructive proofs for combinatorial theorems that have topological proofs so far. To this end the combinatorial concept of Tucker-property of a finite group $G$ is…

Combinatorics · Mathematics 2007-05-23 Mark de Longueville , Rade T. Zivaljevic

A proof of the continuous martingale convergence theorem is provided. It relies on a classical martingale inequality and the almost sure convergence of a uniformly bounded non-negative super-martingale, after a truncation argument.

Probability · Mathematics 2021-11-25 Joe Ghafari

We define an equivalence relation on propositions and a proof system where equivalent propositions have the same proofs. The system obtained this way resembles several known non-deterministic and algebraic lambda-calculi.

Logic in Computer Science · Computer Science 2013-04-01 Alejandro Díaz-Caro , Gilles Dowek

In this paper, we prove the Evans-Krylov theorem for nonlocal parabolic fully nonlinear equations.

Classical Analysis and ODEs · Mathematics 2017-01-03 Yong-Cheol Kim , Ki-Ahm Lee

We prove a new version of Hall's Harem Theorem, where the final matching is realized by a unary function with additional conditions on behavior of cycles. The present paper can be considered as a helpful companion of the paper of the…

Combinatorics · Mathematics 2026-05-19 Karol Duda

When a proposition has no proof in an inference system, it is sometimes useful to build a counter-proof explaining, step by step, the reason of this non-provability. In general, this counter-proof is a (possibly) infinite co-inductive proof…

Logic in Computer Science · Computer Science 2023-04-12 Gilles Dowek , Ying Jiang

In this paper we establish a new equivalence relation on the spaces of almost periodic functions which allows us to prove a result like Bohr's equivalence theorem extended to the case of all these functions.

Complex Variables · Mathematics 2018-01-29 J. M. Sepulcre , T. Vidal