Higher category theory | Algebraic topology

Fundamental groupoid

In algebraic topology, the fundamental groupoid is a certain topological invariant of a topological space. It can be viewed as an extension of the more widely-known fundamental group; as such, it captures information about the homotopy type of a topological space. In terms of category theory, the fundamental groupoid is a certain functor from the category of topological spaces to the category of groupoids. [...] people still obstinately persist, when calculating with fundamental groups, in fixing a single base point, instead of cleverly choosing a whole packet of points which is invariant under the symmetries of the situation, which thus get lost on the way. In certain situations (such as descent theorems for fundamental groups à la Van Kampen) it is much more elegant, even indispensable for understanding something, to work with fundamental groupoids with respect to a suitable packet of base points, [,,,] — Alexander Grothendieck, Esquisse d'un Programme (Section 2, English translation) (Wikipedia).

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Definition of a group Lesson 24

In this video we take our first look at the definition of a group. It is basically a set of elements and the operation defined on them. If this set of elements and the operation defined on them obey the properties of closure and associativity, and if one of the elements is the identity el

From playlist Abstract algebra

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301.2 Definition of a Group

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From playlist Modern Algebra - Chapter 15 (groups)

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What is a Group? | Abstract Algebra

Welcome to group theory! In today's lesson we'll be going over the definition of a group. We'll see the four group axioms in action with some examples, and some non-examples as well which violate the axioms and are thus not groups. In a fundamental way, groups are structures built from s

From playlist Abstract Algebra

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Centralizer of a set in a group

A centralizer consider a subset of the set that constitutes a group and included all the elements in the group that commute with the elements in the subset. That's a mouthful, but in reality, it is actually an easy concept. In this video I also prove that the centralizer of a set in a gr

From playlist Abstract algebra

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GT1. Definition of Group

Abstract Algebra: We introduce the notion of a group and describe basic properties. Examples given include familiar abelian groups and the symmetric groups. U.Reddit course materials available at http://ureddit.com/class/23794/intro-to-group-theory Master list at http://mathdoctorbob.o

From playlist Abstract Algebra

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Algebraic topology: Calculating the fundamental group

This lecture is part of an online course on algebraic topology. We calculate the fundamental group of several spaces, such as a ficure 8, or the complement of a circle in R^3, or the group GL3(R). For the other lectures in the course see https://www.youtube.com/playlist?list=PL8yHsr3EF

From playlist Algebraic topology

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Please Subscribe here, thank you!!! https://goo.gl/JQ8Nys Group Theory: The Center of a Group G is a Subgroup of G Proof

From playlist Abstract Algebra

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From playlist Summer School 2020: Motivic, Equivariant and Non-commutative Homotopy Theory

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Groups and subgroups

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From playlist Basics: Group Theory

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Volodymyr Nekrashevych: Contracting self-similar groups and conformal dimension

HYBRID EVENT Recorded during the meeting "Advancing Bridges in Complex Dynamics" the September 20, 2021 by the Centre International de Rencontres Mathématiques (Marseille, France) Filmmaker: Guillaume Hennenfent Find this video and other talks given by worldwide mathematicians on CIRM'

From playlist Dynamical Systems and Ordinary Differential Equations

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Constructive Type Theory and Homotopy - Steve Awodey

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From playlist Mathematics

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Egbert Rijke: Daily applications of the univalence axiom - lecture 1

HYBRID EVENT Recorded during the meeting "Logic and Interactions" the February 21, 2022 by the Centre International de Rencontres Mathématiques (Marseille, France) Filmmaker: Guillaume Hennenfent Find this video and other talks given by worldwide mathematicians on CIRM's Audiovisual M

From playlist Combinatorics

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Charles Rezk - 4/4 Higher Topos Theory

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From playlist Toposes online

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GT2. Definition of Subgroup

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From playlist Abstract Algebra

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PROGRAM DUALITIES IN TOPOLOGY AND ALGEBRA (ONLINE) ORGANIZERS: Samik Basu (ISI Kolkata, India), Anita Naolekar (ISI Bangalore, India) and Rekha Santhanam (IIT Mumbai, India) DATE & TIME: 01 February 2021 to 13 February 2021 VENUE: Online Duality phenomena are ubiquitous in mathematics

From playlist Dualities in Topology and Algebra (Online)

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Vincent Guirardel - Measure equivalence rigidity for Out(Fn) and dynamical decomposition

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From playlist Geometry in non-positive curvature and Kähler groups

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Erik van Erp: Lie groupoids in index theory 1

The lecture was held within the framework of the Hausdorff Trimester Program Non-commutative Geometry and its Applications. 9.9.2014

From playlist HIM Lectures: Trimester Program "Non-commutative Geometry and its Applications"

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From playlist Abstract Algebra

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5 - Kick-off afternoon : Vladimir Voevodsky, Univalent Foundations

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From playlist T2-2014 : Semantics of proofs and certified mathematics

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Topological space | Homotopy | Groupoid | Conjecture | Alexander Grothendieck | Up to | Edwin Spanier | Algebraic topology | Additive group | Skeleton (category theory) | Path (topology) | Differentiable manifold | Locally constant sheaf | Homology (mathematics) | Connected space | Integer | Equivalence of categories | ∞-groupoid | Singleton (mathematics) | Category theory | Local system | Topological property | Functor | Fundamental group | Group homomorphism | Esquisse d'un Programme | Lie groupoid | Homotopy hypothesis | Circle