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This paper introduces effectful toposes as an extension of the effective topos and investigates their structure relative to Lawvere-Tierney topologies. First, we formulate effectful toposes by lifting the evidenced frame, which is a…

Logic in Computer Science · Computer Science 2026-02-27 Rinta Yamada

We define a class of skeletons on Berkovich analytic spaces, which we call "accessible", which contains the standard skeleton of the n-dimensional torus for every n and is preserved by G-glueing, by taking the inverse image along a morphism…

Algebraic Geometry · Mathematics 2025-01-28 Antoine Ducros , Amaury Thuillier

The (pseudo-)Riemann-metrizability and Ricci-flatness of Finsler spaces with $m$-Kropina metric $F = \alpha^{1+m}\beta^{-m}$ of Berwald type are investigated. We prove that the affine connection on $F$ can locally be understood as the…

Differential Geometry · Mathematics 2024-12-18 Sjors Heefer

Let M be a connected generic real-analytic CR-submanifold of a finite-dimensional complex vector space E. Suppose that for every point a in M the Lie algebra hol(M,a) of germs of all infinitesimal real-analytic CR-automorphisms of M at a is…

Complex Variables · Mathematics 2009-06-18 A. Isaev. , W. Kaup

We prove that, assuming Vop\venka's principle, every small projectivity class in a locally presentable category is accessible.

Category Theory · Mathematics 2024-09-05 Sean Cox , Jiří Rosický

In this note we show that every definably connected, definably compact abelian definable group in an o-minimal expansion of a real closed field of dimension not 4 is definably homeomorphic to a torus of the same dimension. Moreover, in the…

Logic · Mathematics 2014-02-26 Elias Baro , Alessandro Berarducci

This paper investigates topological reconstruction, related to the reconstruction conjecture in graph theory. We ask whether the homeomorphism types of subspaces of a space $X$ which are obtained by deleting singletons determine $X$…

General Topology · Mathematics 2013-12-02 Max F. Pitz , Rolf Suabedissen

We prove that any singular K\"ahler--Ricci shrinker $X$ arising as a noncollapsed limit of K\"ahler--Ricci flows admits a natural structure of a locally algebraic complex-analytic variety with log terminal singularities. We then derive…

Differential Geometry · Mathematics 2026-05-26 Max Hallgren , Junsheng Zhang

An abstract topological graph (briefly an AT-graph) is a pair $A=(G,\mathcal{X})$ where $G=(V,E)$ is a graph and $\mathcal{X}\subseteq {E \choose 2}$ is a set of pairs of its edges. The AT-graph $A$ is simply realizable if $G$ can be drawn…

Combinatorics · Mathematics 2020-06-16 Jan Kynčl

In this work one proves that, around each point of a dense open set (regular points), a real analytic or holomorphic bihamiltonian structure decomposes into a product of a Kronecker bihamiltonian structure and a symplectic one if a…

Symplectic Geometry · Mathematics 2011-07-13 Francisco-Javier Turiel

We introduce the notion of a contractible subshift. This is a strengthening of the notion of strong irreducibility, where we require that the gluings are given by a block map. We show that a subshift is a retract of a full shift if and only…

Dynamical Systems · Mathematics 2026-04-24 Leo Poirier , Ville Salo

Firstly we show a generalization of the (1,1)-Lefschetz theorem for projective toric orbifolds and secondly we prove that on 2k-dimensional quasi-smooth hypersurfaces coming from quasi-smooth intersection surfaces, under the Cayley trick,…

Algebraic Geometry · Mathematics 2023-02-09 William D. Montoya

We construct a continuum of non-homeomorphic compact subspaces of the real line R without singleton components. Thus from the purely topological point of view the real line contains not only more closed sets than open sets but also more…

General Topology · Mathematics 2020-04-24 Gerald Kuba

A locally connected topos is a Galois topos if the Galois objects generate the topos. We show that the full subcategory of Galois objects in any connected locally connected topos is an inversely 2-filtered 2-category, and as an application…

Category Theory · Mathematics 2008-01-03 Eduardo J. Dubuc

We show that any complex (respectively real) representation of finite group naturally generates a open-closed (respectively Klein) topological field theory over complex numbers. We relate the 1-point correlator for the projective plane in…

Representation Theory · Mathematics 2011-07-19 Sergey A. Loktev , Sergey M. Natanzon

We classify and investigate locally conformally K\"ahler structures on four-dimensional solvable Lie algebras up to linear equivalence. As an application we can produce many examples in higher dimension, here including lcK structures on…

Differential Geometry · Mathematics 2019-12-23 Daniele Angella , Marcos Origlia

We present a uniform theory of constructible sheaves on arbitrary schemes with coefficients in topological or even condensed rings. This is accomplished by defining lisse sheaves to be the dualizable objects in the derived infinity-category…

Algebraic Geometry · Mathematics 2023-05-30 Tamir Hemo , Timo Richarz , Jakob Scholbach

We construct a topos in which the Dedekind reals are countable. The topos arises from a new kind of realizability, which we call parameterized realizability, based on partial combinatory algebras whose application depends on a parameter.…

Logic · Mathematics 2026-04-02 Andrej Bauer , James E. Hanson

This note characterizes a universal Kripke frame for the variable-free fragment of the reflection calculus with conservativity operators RC$^\nabla$. The frame here is obtained from the set of all filters on the Ignatiev RC$^\nabla$-algebra…

Logic · Mathematics 2018-04-10 Lev D. Beklemishev

We call a polytope P of dimension 3 admissible if it has the following two properties: (1) for each vertex of P the set of its first-neighbours is coplanar; (2) all planes determined by the first-neighbours are distinct. It is shown that…

Combinatorics · Mathematics 2012-07-31 Gábor Gévay , Tomaž Pisanski