The "calculus of functors" is a concept from category theory, a branch of mathematics that deals with abstract structures and the relationships between them. In more detail, it refers to methods and techniques for manipulating functors, which are mappings between categories that preserve the structures of those categories. ### Key Concepts: 1. **Categories**: A category consists of objects and morphisms (arrows) between those objects that satisfy certain properties (e.g., composition and identity).
A CW complex (pronounced "C-W complex") is a type of topological space that is particularly useful in algebraic topology. The term "CW" stands for "cellular" and "weak," referring to the construction method used to create such complexes. A CW complex is constructed using "cells," which are basic building blocks, typically in the shape of disks of different dimensions.
The Bockstein homomorphism is a tool in algebraic topology, specifically in the study of cohomology theories and exact sequences of coefficients. It often appears in the context of Singular Cohomology and Cohomology with local coefficients. To understand the Bockstein homomorphism, it helps to start with the following concepts: 1. **Exact Sequence**: The Bockstein homomorphism is most commonly associated with a short exact sequence of abelian groups (or modules).
The Bloch group is a mathematical construct in the field of algebraic K-theory and number theory. It is named after the mathematician Spencer Bloch. The main idea behind the Bloch group is to provide a way to study the properties of values of certain functions, particularly the behavior of rational numbers and algebraic numbers within the context of abelian varieties and algebraic cycles.
Aspherical space is a term used in topology, a branch of mathematics that studies the properties of space that are preserved under continuous transformations. Specifically, an aspherical space is a manifold (or more generally, a topological space) whose universal covering space is contractible. This means that the universal cover does not have any "holes"; it can be continuously shrunk to a point without leaving the space.
Approximate fibration is a concept in algebraic topology and related fields that generalizes the notion of a fibration. In topology, a fibration is a specific type of mapping between spaces that has certain lifting properties, often characterized by a homotopy lifting property. The concept of approximate fibration arises when one relaxes some of these strict conditions.
Algebraic cobordism is a cohomology theory in algebraic geometry that emerges from the study of algebraic cycles and their intersections. It provides a space to study algebraic varieties in a manner similar to how bordism theories function in topology. The notion of cobordism in algebraic geometry can be understood as a way to classify algebraic varieties (or schemes) through the idea of "cobordism classes" that respect certain algebraic operations and relations.
Alexander duality is a fundamental theorem in algebraic topology, specifically in the study of topological spaces and their homological properties. Named after mathematician James W. Alexander, the duality provides a relationship between the topology of a space and the topology of its complement. In its most basic form, Alexander duality applies to a locally finite CW complex, particularly when considering a subcomplex (or a subset) of a sphere.
Adams' Resolution is a concept from Jewish law (Halakha) that refers to a decision made by a Jewish court (Bet Din) or an authority regarding a specific question of law or practice. It is particularly associated with the role of a rabbi or authority in the community and serves as a means to address complex legal issues or disputes within the framework of Jewish tradition.
An **acyclic space** can refer to several concepts depending on the context, but it is most commonly associated with graph theory and algebraic topology. 1. **In Graph Theory**: An acyclic graph (or directed acyclic graph, DAG) is a graph with no cycles, meaning there is no way to start at any vertex and follow a sequence of edges to return to that same vertex.
An **Abelian 2-group** is a specific type of group in the field of abstract algebra. Let’s break down the main characteristics: 1. **Group**: A set equipped with a binary operation that satisfies four fundamental properties: closure, associativity, the existence of an identity element, and the existence of inverses.
A 4-polytope, also known as a 4-dimensional polytope or a polychoron, is a four-dimensional geometric object that is the generalization of polygons (2-dimensional) and polyhedra (3-dimensional). In more simple terms: 1. **Polygon**: A 2-dimensional shape with straight sides (e.g., triangle, square). 2. **Polyhedron**: A 3-dimensional shape with flat polygonal faces (e.g.
Topology of Lie groups refers to the study of the topological structures and properties of Lie groups, which are groups that are also differentiable manifolds. The intersection of group theory and differential geometry, this area is essential for understanding how the algebraic and geometric aspects of Lie groups interact.
Topological methods in algebraic geometry refer to the application of topological concepts and techniques to study problems and objects that arise in algebraic geometry. This interdisciplinary area combines elements from both topology (the study of properties of space that are preserved under continuous transformations) and algebraic geometry (the study of geometric objects defined by polynomial equations).
Topological graph theory is a branch of mathematics that studies the interplay between graph theory and topology. It focuses primarily on the properties of graphs that are invariant under continuous transformations, such as stretching or bending, but not tearing or gluing. The key aspects of topological graph theory include: 1. **Graph Embeddings**: Understanding how a graph can be drawn in various surfaces (like a plane, sphere, or torus) without edges crossing.
Surgery theory is a branch of geometric topology, which focuses on the study of manifolds and their properties by performing a kind of operation called surgery. The central idea of surgery theory is to manipulate manifold structures in a controlled way to produce new manifolds from existing ones. This can involve various operations, such as adding or removing handles, which change the topology of manifolds in a systematic manner.
Knot theory is a branch of mathematics that studies mathematical knots, which are loops in three-dimensional space that do not intersect themselves. It is a part of the field of topology, specifically dealing with the properties of these loops that remain unchanged through continuous deformations, such as stretching, twisting, and bending, but not cutting or gluing. In knot theory, a "knot" is defined as an embedded circle in three-dimensional Euclidean space \( \mathbb{R}^3 \).
K-theory is a branch of mathematics that studies vector bundles and more generally, topological spaces and their associated algebraic invariants. It has applications in various fields, including algebraic geometry, operator theory, and mathematical physics. The core idea in K-theory involves the classification of vector bundles over a topological space. Specifically, there are two main types of K-theory: 1. **Topological K-theory**: This version studies topological spaces and their vector bundles.
Homotopy theory is a branch of algebraic topology that studies the properties of topological spaces through the concept of homotopy, which is a mathematical equivalence relation on continuous functions. The main focus of homotopy theory is to understand the ways in which spaces can be transformed into each other through continuous deformation.