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We introduce the notion of local fibration, a generalization of the notion of fibration which takes into account the presence of Grothendieck topologies on the two categories, and show that the classical results about fibrations lift to…

Category Theory · Mathematics 2025-07-22 Léo Bartoli , Olivia Caramello

We develop the theory of topoi internal to an arbitrary $\infty$-topos $\mathcal B$. We provide several characterisations of these, including an internal analogue of Lurie's characterisation of $\infty$-topoi, but also a description in…

Category Theory · Mathematics 2025-03-19 Louis Martini , Sebastian Wolf

In this note we define fibrations of topological stacks and establish their main properties. We prove various standard results about fibrations (fiber homotopy exact sequence, Leray-Serre and Eilenberg-Moore spectral sequences, etc.). We…

Algebraic Topology · Mathematics 2010-10-11 Behrang Noohi

In this paper we develop the theory of topological categories over a base category, that is, a theory of topological functors. Our notion of topological functor is similar to (but not the same) the existing notions in the literature (see…

Category Theory · Mathematics 2007-05-23 Eduardo J. Dubuc , Luis Español

We characterise proper morphisms of $\infty$-topoi in terms of a relativised notion of compactness: we show that a geometric morphism of $\infty$-topoi is proper if and only if it commutes with colimits indexed by filtered internal…

Category Theory · Mathematics 2025-03-18 Louis Martini , Sebastian Wolf

In the context of relative topos theory via stacks, we introduce the notion of existential fibred site and of existential topos of such a site. These notions allow us to develop relative topos theory in a way which naturally generalizes the…

Algebraic Geometry · Mathematics 2022-12-23 Olivia Caramello

We gather conditions on a class H of continuous maps of topological spaces that allow a reasonable theory of fibrations up to an equivalence (a map from this class) which we call H-fibrations. The weak homotopy equivalences recover…

Algebraic Topology · Mathematics 2010-01-14 Lukáš Vokřínek

In 2002, Biss investigated on a kind of fibration which is called rigid covering fibration (we rename it by rigid fibration) with properties similar to covering spaces. In this paper, we obtain a relation between arbitrary topological…

Algebraic Topology · Mathematics 2017-11-28 Tayyebe Nasri , Behrooz Mashayekhy

Homotopy type theory is a formal language for doing abstract homotopy theory -- the study of identifications. But in unmodified homotopy type theory, there is no way to say that these identifications come from identifying the path-connected…

Category Theory · Mathematics 2022-04-06 David Jaz Myers

The classical fiber product in algebraic geometry provides a powerful tool for studying loci where two morphisms to a base scheme, $\phi: X \to S$ and $\psi: Y \to S$, coincide exactly. This condition of strict equality, however, is…

Algebraic Geometry · Mathematics 2025-11-03 Dongfang Zhao

In this survey, we remind some fibrations structure theorems (also called Milnor's fibrations) recently proved in the real and complex case, in the local and global settings. We give several Poincar\'e-Hopf type formulae which relates the…

Algebraic Geometry · Mathematics 2014-09-18 Nicolas Dutertre , Raimundo N. Araújo Dos Santos , Ying Chen , Antonio Andrade

This article introduces and studies the tight approximation property, a property of algebraic varieties defined over the function field of a complex or real curve that refines the weak approximation property (and the known cohomological…

Algebraic Geometry · Mathematics 2024-06-18 Olivier Benoist , Olivier Wittenberg

We realize higher-form symmetries in F-theory compactifications on non-compact elliptically fibered Calabi-Yau manifolds. Central to this endeavour is the topology of the boundary of the non-compact elliptic fibration, as well as the…

High Energy Physics - Theory · Physics 2022-08-24 Max Hubner , David R. Morrison , Sakura Schafer-Nameki , Yi-Nan Wang

The goal of this article is to develop the theory of presentable categories and topoi internal to an arbitrary $\infty$-topos $\mathcal{B}$. Our main results are internal analogues of Lurie's and Lurie-Simpson's characterisations of…

Category Theory · Mathematics 2025-03-25 Louis Martini , Sebastian Wolf

In this paper we present new results about the topology of the Milnor fibrations of analytic function-germs with a special attention to the topology of the fibers. In particular, we provide a short review on the existence of the Milnor…

Algebraic Geometry · Mathematics 2022-12-08 Taciana O. Souza , Cesar A. Ipanaque Zapata

We study Hurewicz fibrations between finite T$_0$--spaces from a combinatorial viewpoint and give strong conditions that a continuous map between finite T$_0$--spaces must satisfy in order to be a Hurewicz fibration. We also show that there…

Algebraic Topology · Mathematics 2019-07-10 Nicolás Cianci , Miguel Ottina

\textit{Harmonic amoebas} are generalisations of amoebas of algebraic curves immersed in complex tori. Introduced in \cite{Kri}, the consideration of such objects suggests to enlarge the scope of tropical geometry. In the present paper, we…

Algebraic Geometry · Mathematics 2020-02-25 Lionel Lang

The paper is devoted to the problem when a map from some closed connected manifold to an aspherical closed manifold approximately fibers, i.e., is homotopic to Manifold Approximate Fibration. We define obstructions in algebraic K-theory.…

Algebraic Topology · Mathematics 2018-07-06 Tom Farrell , Wolfgang Lueck , Wolfgang Steimle

We introduce the notion of a higher covering diagram in a base $\infty$-category $\mathcal{C}$. The theory of higher covering diagrams in $\mathcal{C}$ will be shown to recover various descent conditions known from the $\infty$-categorical…

Category Theory · Mathematics 2024-06-04 Raffael Stenzel

We study fibred spaces with fibres in a structure category $\V$ and we show that cellular approximation, Blakers--Massey theorem, Whitehead theorems, obstruction theory, Hurewicz homomorphism, Wall finiteness obstruction, and Whitehead…

Algebraic Topology · Mathematics 2007-05-23 Hans-Joachim Baues , Davide L. Ferrario
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