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We define the fundamental group of a Hopf algebra over a field. For this purpose we first consider gradings of Hopf algebras and Galois coverings. The latter are given by linear categories with new additional structure which we call Hopf…

Rings and Algebras · Mathematics 2018-06-12 Claude Cibils , Andrea Solotar

In order to make the fundamental group, one of the most well known invariants in algebraic topology, more useful and powerful some researchers have introduced and studied various topologies on the fundamental group from the beginning of the…

Algebraic Topology · Mathematics 2025-08-28 Naghme Shahami , Behrooz Mashayekhy

For any type of fundamental groupoid scheme, we construct an algebraic cohomology theory for varieties with coefficients in the base field. This is a minor variant of \'etale cohomology, involving neither de Rham complexes nor…

Algebraic Geometry · Mathematics 2026-02-16 Hyuk Jun Kweon

In this paper we define a relative rigid fundamental group, which associates to a section $p$ of a smooth and proper morphism $f:X\rightarrow S$ in characteristic $p$, a Hopf algebra in the ind-category of overconvergent $F$-isocrystals on…

Number Theory · Mathematics 2017-01-25 Christopher Lazda

We exhibit a map f between aspherical spaces X and Y such that f induces an isomorphism on homotopy groups but, with natural topologies, X and Y fail to have homeomorphic fundamental groups. Thus the topological fundamental group has the…

Algebraic Topology · Mathematics 2007-05-23 Paul Fabel

In the setting of homotopy type theory, each type can be interpreted as a space. Moreover, given an element of a type, i.e. a point in the corresponding space, one can define another type which encodes the space of loops based at this…

Logic in Computer Science · Computer Science 2024-05-17 Samuel Mimram , Émile Oleon

In topology, the notions of the fundamental group and the universal cover are closely intertwined. By importing usual notions from topology into the algebraic and arithmetic setting, we construct a fundamental group family from a universal…

Algebraic Geometry · Mathematics 2011-02-08 Ravi Vakil , Kirsten Wickelgren

We prove an equivalence of categories from formal complex structures with formal holomorphic maps to homotopy algebras over a simple operad with its associated homotopy morphisms. We extend this equivalence to complex manifolds. A complex…

Algebraic Topology · Mathematics 2015-01-19 Joan Millès

We develop a homotopical variant of the classic notion of an algebraic theory as a tool for producing deformations of homotopy theories. From this, we extract a framework for constructing and reasoning with obstruction theories and spectral…

Algebraic Topology · Mathematics 2025-08-13 William Balderrama

In this paper, we extend the iterated integrals from smooth manifolds to digraphs and develop the associated algebraic and geometric structures. Iterated integrals on a digraph naturally give rise to the iterated path algebra and the…

Algebraic Topology · Mathematics 2026-03-03 Shing-Tung Yau , Mengmeng Zhang , Yunpeng Zi

This paper is devoted to the study of a natural group topology on the fundamental group which remembers local properties of spaces forgotten by covering space theory and weak homotopy type. It is known that viewing the fundamental group as…

Algebraic Topology · Mathematics 2020-04-14 Jeremy Brazas

We show that the notions of homotopy epimorphism and homological epimorphism in the category of differential graded algebras are equivalent. As an application we obtain a characterization of acyclic maps of topological spaces in terms of…

Algebraic Topology · Mathematics 2021-06-15 Joe Chuang , Andrey Lazarev

A goal in the study of dynamics on the interval is to understand the transition to positive topological entropy. There is a conjecture from the 1980's that the only route to positive topological entropy is through a cascade of period…

Dynamical Systems · Mathematics 2020-07-29 Trevor Clark , Sofía Trejo

One of the prime motivation for topology was Homotopy theory, which captures the general idea of a continuous transformation between two entities, which may be spaces or maps. In later decades, an algebraic formulation of topology was…

Category Theory · Mathematics 2025-11-24 Suddhasattwa Das

Multi-sorted algebraic theories provide a formalism for describing various structures on spaces that are of interest in homotopy theory. The results of Badzioch and Bergner showed that an interesting feature of this formalism is the…

Algebraic Topology · Mathematics 2014-10-07 Bruce R. Corrigan-Salter

Let P be a principal bundle with semisimple compact simply connected structure group G over a compact simply connected four-manifold M. In this note we give explicit formulas for the rational homotopy groups and cohomology algebra of the…

Algebraic Topology · Mathematics 2007-05-23 Svjetlana Terzic

The pro-\'etale fundamental group of a scheme, introduced by Bhatt and Scholze, generalizes formerly known fundamental groups -- the usual \'etale fundamental group $\pi_1^{\mathrm{et}}$ defined in SGA1 and the more general group defined in…

Algebraic Geometry · Mathematics 2024-02-28 Marcin Lara

In this paper we will give a computation of the \'{e}tale fundamental group of an integral arithmetic scheme. For such a scheme, we will prove that the \'{e}tale fundamental group is naturally isomorphic to the Galois group of the maximal…

Algebraic Geometry · Mathematics 2010-09-10 Feng-Wen An

The paper discuss the limit point concept of a subset in a group via ideal of the power set ring. This idea along with anti-ideal give the topological structure in a group. Homomorphic images of both ideal and anti-ideal are played the…

Rings and Algebras · Mathematics 2026-05-04 Monoj Kumar Das , Shyamapada Modak

Using the theory of group action, we first introduce the concept of the automorphism group of an exponential family or a graphical model, thus formalizing the general notion of symmetry of a probabilistic model. This automorphism group…

Artificial Intelligence · Computer Science 2013-09-27 Hung Bui , Tuyen Huynh , Sebastian Riedel