Homotopy theory | Knot theory | Algebraic topology
In algebraic topology, a peripheral subgroup for a space-subspace pair X ⊃ Y is a certain subgroup of the fundamental group of the complementary space, π1(X − Y). Its conjugacy class is an invariant of the pair (X,Y). That is, any homeomorphism (X, Y) → (X′, Y′) induces an isomorphism π1(X − Y) → π1(X′ − Y′) taking peripheral subgroups to peripheral subgroups. A peripheral subgroup consists of loops in X − Y which are peripheral to Y, that is, which stay "close to" Y (except when passing to and from the basepoint). When an ordered set of generators for a peripheral subgroup is specified, the subgroup and generators are collectively called a peripheral system for the pair (X, Y). Peripheral systems are used in knot theory as a complete algebraic invariant of knots. There is a systematic way to choose generators for a peripheral subgroup of a knot in 3-space, such that distinct knot types always have algebraically distinct peripheral systems. The generators in this situation are called a longitude and a meridian of the knot complement. (Wikipedia).
In this tutorial we define a subgroup and prove two theorem that help us identify a subgroup. These proofs are simple to understand. There are also two examples of subgroups.
From playlist Abstract algebra
Abstract Algebra | Normal Subgroups
We give the definition of a normal subgroup and give some examples. http://www.michael-penn.net http://www.randolphcollege.edu/mathematics/
From playlist Abstract Algebra
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
From playlist Rates of Change
Center of a group in abstract algebra
After the previous video where we saw that two of the elements in the dihedral group in six elements commute with all the elements in the group, we finally get to define the center of a group. The center of a group is a subgroup and in this video we also go through the proof to show this.
From playlist Abstract algebra
Bena Tshishiku: Groups with Bowditch boundary a 2-sphere
Abstract: Bestvina-Mess showed that the duality properties of a group G are encoded in any boundary that gives a Z-compactification of G. For example, a hyperbolic group with Gromov boundary an n-sphere is a PD(n+1) group. For relatively hyperbolic pairs (G,P), the natural boundary - the B
From playlist Topology
Ashani Dasgupta: Local Connectedness of Boundaries for Relatively Hyperbolic Groups
Ashani Dasgupta, University of Wisconsin-Milwaukee Title: Local Connectedness of Boundaries for Relatively Hyperbolic Groups Let $(\Gamma,\mathbb{P})$ be a relatively hyperbolic group pair that is relatively one ended. Then the Bowditch boundary of $(\Gamma,\mathbb{P})$ is locally connect
From playlist 39th Annual Geometric Topology Workshop (Online), June 6-8, 2022
Denis Osin: Acylindrically hyperbolic groups (part 3)
The lecture was held within the framework of Follow-up Workshop TP Rigidity. 1.5.2015
From playlist HIM Lectures 2015
Abstract Algebra | Cyclic Subgroups
We define the notion of a cyclic subgroup and give a few examples. http://www.michael-penn.net http://www.randolphcollege.edu/mathematics/
From playlist Abstract Algebra
Louis Funar : Automorphisms of curve and pants complexes in profinite content
Pants complexes of large surfaces were proved to be vigid by Margalit. We will consider convergence completions of curve and pants complexes and show that some weak four of rigidity holds for the latter. Some key tools come from the geometry of Deligne Mumford compactification of moduli sp
From playlist Topology
Denis Osin: Acylindrically hyperbolic groups (part 2)
The lecture was held within the framework of Follow-up Workshop TP Rigidity. 30.4.2015
From playlist HIM Lectures 2015
Before we carry on with our coset journey, we need to discover when the left- and right cosets are equal to each other. The obvious situation is when our group is Abelian. The other situation is when the subgroup is a normal subgroup. In this video I show you what a normal subgroup is a
From playlist Abstract algebra
David Rosenthal - Finitely F-amenable actions and decomposition complexity of groups
38th Annual Geometric Topology Workshop (Online), June 15-17, 2021 David Rosenthal, St. John's University Title: Finitely F-amenable actions and decomposition complexity of groups Abstract: In their groundbreaking work on the Farrell-Jones Conjecture for Gromov hyperbolic groups, Bartels
From playlist 38th Annual Geometric Topology Workshop (Online), June 15-17, 2021
Abstract Algebra - 3.3 Examples of Subgroups: The Cyclic Subgroup and the Center
Now that we know how to determine if a subset is a subgroup, let's take a look at two subgroups we should become familiar with. The first is the cyclic subgroup. We will devote our next chapter to cyclic groups, but you'll find we have already discussed generators and cyclic groups when di
From playlist Abstract Algebra - Entire Course
Abstract Algebra: We define the notion of a subgroup and provide various examples. We also consider cyclic subgroups and subgroups generated by subsets in a given group G. Example include A4 and D8. U.Reddit course materials available at http://ureddit.com/class/23794/intro-to-group-
From playlist Abstract Algebra
Convex real projective structures on closed surfaces (Lecture 01) by Tengren Zhang
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From playlist Surface group representations and Projective Structures (2018)
Stephan Tillmann: On the space of properly convex projective structures
SMRI Seminar: Stephan Tillmann (University of Sydney) This talk will be in two parts. I will outline joint work with Daryl Cooper concerning the space of holonomies of properly convex real projective structures on manifolds whose fundamental group satisfies a few natural properties. This
From playlist SMRI Seminars
Group Definition (expanded) - Abstract Algebra
The group is the most fundamental object you will study in abstract algebra. Groups generalize a wide variety of mathematical sets: the integers, symmetries of shapes, modular arithmetic, NxM matrices, and much more. After learning about groups in detail, you will then be ready to contin
From playlist Abstract Algebra
Knot contact homology and partially wrapped Floer homology - Lenhard Ng
Workshop on Homological Mirror Symmetry: Methods and Structures Speaker:Lenhard Ng Title: Knot contact homology and partially wrapped Floer homology Affilation: Duke Date: November 7, 2016 For more vide, visit http://video.ias.edu
From playlist Workshop on Homological Mirror Symmetry: Methods and Structures