Bisection is a mathematical method used to find roots of a continuous function. It is a type of bracketing method, which means it narrows down the search for a root within a certain interval. The key idea behind the bisection method is to divide an interval in half and, based on the signs of the function at the endpoints, determine which half contains the root.

In geometry, a **cross section** refers to the intersection of a solid object with a plane. When a three-dimensional object is cut by a plane, the shape formed by this intersection is known as the cross section. The specific shape of the cross section depends on the orientation and position of the cutting plane relative to the object.

In group theory, the term "component" can refer to various concepts depending on the context. However, one common usage pertains to the component of a group element in a topological or algebraic sense. 1. **Connected Components in Topological Groups**: In the context of topological groups, the component of a group element \( g \) refers to the connected component of the identity element that contains \( g \).

In geometry, a line is a fundamental concept that represents a straight one-dimensional figure that extends infinitely in both directions. It has no thickness, width, or curvature, and is typically defined by at least two points. Lines can be described using a variety of properties: 1. **Definition**: A line is determined by any two distinct points on it.

In geometry, the term "parallel" refers to two or more lines or planes that are the same distance apart at all points and do not meet or intersect, no matter how far they are extended. This property is fundamental in understanding the behavior of lines within Euclidean geometry. ### Key Properties of Parallel Lines: 1. **Equidistant**: Parallel lines maintain a constant distance from each other, meaning the distance between them remains consistent along their entire length.

A spherical shell is a three-dimensional hollow structure that is shaped like a sphere. It is typically defined as the space between two concentric spherical surfaces — an outer surface and an inner surface. The shell has a certain thickness, which is the difference between the radii of the outer and inner surfaces. Key characteristics of a spherical shell include: 1. **Outer Radius (R_outer)**: The radius of the outer surface of the shell.

Bredon cohomology is a type of cohomology theory that is particularly useful in the context of spaces with group actions. It was introduced by Glen Bredon in the 1960s and is designed to study topological spaces with an additional structure of a group action, often leading to insights in equivariant topology.

Witt vector cohomology is a tool in algebraic geometry and number theory that utilizes Witt vectors to study the cohomological properties of schemes in the context of p-adic cohomology theories. Witt vectors are a generalization of the notion of numbers in a ring, particularly for fields of characteristic \( p \), and they allow the construction of an effective cohomology theory that preserves useful algebraic properties. ### Key Concepts 1.

In the context of cohomology, a pullback is a construction that allows you to take a cohomology class on a target space and "pull it back" to a cohomology class on a domain space via a continuous map. This is particularly common in algebraic topology and differential geometry. ### Formal Definition Let \( f: X \to Y \) be a continuous map between two topological spaces \( X \) and \( Y \).

Étale cohomology is a cohomological theory in algebraic geometry that provides a means to study the properties of algebraic varieties over fields, particularly in the context of fields that are not algebraically closed. It was developed in the mid-20th century, notably by Alexander Grothendieck, and is part of the broader framework of schemes in modern algebraic geometry.

In category theory, a preordered set (or preordered set) is a set equipped with a reflexive and transitive binary relation. More formally, a preordered set \( (P, \leq) \) consists of a set \( P \) and a relation \( \leq \) such that: 1. **Reflexivity**: For all \( x \in P \), \( x \leq x \).

In category theory, a Kleisli category is a construction that allows you to work with monads in a categorical setting. A monad, in this context, is a triple \((T, \eta, \mu)\), where \(T\) is a functor and \(\eta\) (the unit) and \(\mu\) (the multiplication) are specific natural transformations satisfying certain coherence conditions.

Samuel Eilenberg (1913-1998) was a renowned Polish-American mathematician known for his significant contributions to the fields of algebra, topology, and category theory. He was particularly influential in the development of algebraic topology and cohomology theories. Eilenberg is perhaps best known for the concept of Eilenberg-Mac Lane spaces, which are important in algebraic topology and homotopy theory.

A **closed monoidal category** is a specific type of category in the field of category theory that combines the notions of a monoidal category and an internal hom-functor. To break it down, let's start with the definitions: 1. **Monoidal category**: A monoidal category \( \mathcal{C} \) consists of: - A category \( \mathcal{C} \).

Differential Galois theory is a branch of mathematics that studies the symmetries of solutions to differential equations in a manner analogous to how classical Galois theory studies the symmetries of algebraic equations. ### Key Concepts: 1. **Differential Equations**: These are equations that involve unknown functions and their derivatives. The solutions to these equations can often be quite complex.

P-derivation, also known as partial derivation, typically refers to the process of finding the derivative of a function with respect to one of its variables while keeping the other variables constant. This concept is commonly used in multivariable calculus, where functions depend on multiple variables. For a function \( f(x, y, z, \ldots) \), the partial derivative with respect to \( x \) is denoted as \( \frac{\partial f}{\partial x} \).

Abelian group theory is a branch of abstract algebra that focuses on the study of Abelian groups (or commutative groups). An **Abelian group** is a set equipped with an operation that satisfies certain properties: 1. **Closure**: For any two elements \( a \) and \( b \) in the group, the result of the operation (usually denoted as \( a + b \) or \( ab \)) is also in the group.