Homological algebra | Group theory | Cohomology theories | Algebraic number theory
In mathematics (more specifically, in homological algebra), group cohomology is a set of mathematical tools used to study groups using cohomology theory, a technique from algebraic topology. Analogous to group representations, group cohomology looks at the group actions of a group G in an associated G-module M to elucidate the properties of the group. By treating the G-module as a kind of topological space with elements of representing n-simplices, topological properties of the space may be computed, such as the set of cohomology groups . The cohomology groups in turn provide insight into the structure of the group G and G-module M themselves. Group cohomology plays a role in the investigation of fixed points of a group action in a module or space and the quotient module or space with respect to a group action. Group cohomology is used in the fields of abstract algebra, homological algebra, algebraic topology and algebraic number theory, as well as in applications to group theory proper. As in algebraic topology, there is a dual theory called . The techniques of group cohomology can also be extended to the case that instead of a G-module, G acts on a nonabelian G-group; in effect, a generalization of a module to non-Abelian coefficients. These algebraic ideas are closely related to topological ideas. The group cohomology of a discrete group G is the singular cohomology of a suitable space having G as its fundamental group, namely the corresponding Eilenberg–MacLane space. Thus, the group cohomology of can be thought of as the singular cohomology of the circle S1, and similarly for and A great deal is known about the cohomology of groups, including interpretations of low-dimensional cohomology, functoriality, and how to change groups. The subject of group cohomology began in the 1920s, matured in the late 1940s, and continues as an area of active research today. (Wikipedia).
Paul GUNNELLS - Cohomology of arithmetic groups and number theory: geometric, ... 2
In this lecture series, the first part will be dedicated to cohomology of arithmetic groups of lower ranks (e.g., Bianchi groups), their associated geometric models (mainly from hyperbolic geometry) and connexion to number theory. The second part will deal with higher rank groups, mainly
From playlist École d'Été 2022 - Cohomology Geometry and Explicit Number Theory
Aurel PAGE - Cohomology of arithmetic groups and number theory: geometric, ... 2
In this lecture series, the first part will be dedicated to cohomology of arithmetic groups of lower ranks (e.g., Bianchi groups), their associated geometric models (mainly from hyperbolic geometry) and connexion to number theory. The second part will deal with higher rank groups, mainly
From playlist École d'Été 2022 - Cohomology Geometry and Explicit Number Theory
The idea of a quotient group follows easily from cosets and Lagrange's theorem. In this video, we start with a normal subgroup and develop the idea of a quotient group, by viewing each coset (together with the normal subgroup) as individual mathematical objects in a set. This set, under
From playlist Abstract algebra
Paul GUNNELLS - Cohomology of arithmetic groups and number theory: geometric, ... 1
In this lecture series, the first part will be dedicated to cohomology of arithmetic groups of lower ranks (e.g., Bianchi groups), their associated geometric models (mainly from hyperbolic geometry) and connexion to number theory. The second part will deal with higher rank groups, mainly
From playlist École d'Été 2022 - Cohomology Geometry and Explicit Number Theory
This video contains the origins of group theory, the formal definition, and theoretical and real-world examples for those beginning in group theory or wanting a refresher :)
From playlist Summer of Math Exposition Youtube Videos
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
Aurel PAGE - Cohomology of arithmetic groups and number theory: geometric, ... 1
In this lecture series, the first part will be dedicated to cohomology of arithmetic groups of lower ranks (e.g., Bianchi groups), their associated geometric models (mainly from hyperbolic geometry) and connexion to number theory. The second part will deal with higher rank groups, mainly
From playlist École d'Été 2022 - Cohomology Geometry and Explicit Number Theory
Group theory 2: Cayley's theorem
This is lecture 2 of an online mathematics course on group theory. It describes Cayley's theorem that every abstract group is the group of symmetries of something, and as examples shows the Cayley graphs of the Klein 4-group and the symmetric group on 3 points.
From playlist Group theory
The Completed Cohomology of Arithmetic Groups - Frank Calegari
Frank Calegari Northwestern University; Member, School of Mathematics October 13, 2010 The cohomology of arithmetic groups (with real coefficients) is usually understood in terms of automorphic forms. Such methods, however, fail (at least naively) to capture information about torsion clas
From playlist Mathematics
Cohomological Field Theories from GLSMs (Lecture 2) by David Favero
PROGRAM: VORTEX MODULI ORGANIZERS: Nuno Romão (University of Augsburg, Germany) and Sushmita Venugopalan (IMSc, India) DATE & TIME: 06 February 2023 to 17 February 2023 VENUE: Ramanujan Lecture Hall, ICTS Bengaluru For a long time, the vortex equations and their associated self-dual fie
From playlist Vortex Moduli - 2023
Cup Products in Automorphic Cohomology - Matthew Kerr
Matthew Kerr Washington University in St. Louis March 30, 2012 In three very interesting and suggestive papers, H. Carayol introduced new aspects of complex geometry and Hodge theory into the study of non-classical automorphic representations -- in particular, those involving the totally d
From playlist Mathematics
Motivic action on coherent cohomology of Hilbert modular varieties - Aleksander Horawa
Joint IAS/Princeton University Number Theory Seminar Topic: Motivic action on coherent cohomology of Hilbert modular varieties Speaker: Aleksander Horawa Affiliation: University of Michigan Date: February 03, 2022 A surprising property of the cohomology of locally symmetric spaces is tha
From playlist Mathematics
Weil conjectures 6: etale cohomology of a curve
We give an overview of how to calculate the etale cohomology of a nonsinguar projective curve over an algebraically closed field with coefficients Z/nZ with n invertible. We simply assume a lot of properties of etale cohomology without proving (or even defining) them.
From playlist Algebraic geometry: extra topics
Vladimir Berkovich: de Rham theorem in non-Archimedean analytic geometry
Abstract: In my work in progress on complex analytic vanishing cycles for formal schemes, I have defined integral "etale" cohomology groups of a compact strictly analytic space over the field of Laurent power series with complex coefficients. These are finitely generated abelian groups pro
From playlist Algebraic and Complex Geometry
Galilean group cohomology in classical mechanics
In this video we discuss how the second group cohomology relates to classical mechanics. We discuss Galilean invariance in the Lagrangian formalism and its quantum mechanics analog. You find the used text and all the links mentioned here: https://gist.github.com/Nikolaj-K/deb54c9127b6f0f3f
From playlist Algebra
Cohomological decomposition of the diagonal in small dimension (Lecture - 05) by Claire Voisin
Infosys-ICTS Ramanujan Lectures Some new results on rationality Speaker: Claire Voisin (College de France) Date: 01 October 2018, 16:00 Venue: Madhava Lecture Hall, ICTS campus Resources Lecture 1: Some new results on rationality Date & Time: Monday, 1 October 2018, 04:00 PM Abstra
From playlist Infosys-ICTS Ramanujan Lectures
Jacek Brodzki (6/30/17) Bedlewo: The Geometry of Synchronization Problems and Learning Group Act
We develop a geometric framework that characterizes the synchronization problem — the problem of consistently registering or aligning a collection of objects. We formulate a theory that characterizes the cohomological nature of synchronization based on the classical theory of fibre bundles
From playlist Applied Topology in Będlewo 2017
Lars Hesselholt: Around topological Hochschild homology (Lecture 8)
The lecture was held within the framework of the (Junior) Hausdorff Trimester Program Topology: "Workshop: Hermitian K-theory and trace methods" Introduced by Bökstedt in the late eighties, topological Hochschild homology is a manifestation of the dual visions of Connes and Waldhausen to
From playlist HIM Lectures: Junior Trimester Program "Topology"
Cong Xue - 2/2 Cohomology Sheaves of Stacks of Shtukas
Cohomology sheaves and cohomology groups of stacks of shtukas are used in the Langlands program for function fields. We will explain (1) how the Eichler-Shimura relations imply the finiteness property of the cohomology groups, (2) how the finiteness and Drinfeld's lemma imply the action of
From playlist 2022 Summer School on the Langlands program
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