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 \( Y \).

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.

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 mathematics, particularly in the field of abstract algebra and category theory, a **category of groups** is a concept that arises from the framework of category theory, which is a branch of mathematics that deals with objects and morphisms (arrows) between them. ### Basic Definitions 1. **Category**: A category consists of: - A collection of objects. - A collection of morphisms (arrows) between those objects, which can be thought of as structure-preserving functions.

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 \( x \in P \), \( x \leq x \).

Emily Riehl is a mathematician known for her contributions to category theory, homotopy theory, and algebraic topology. She is an associate professor at Johns Hopkins University and has published several research papers in her areas of expertise. Riehl has also been involved in mathematical education, producing resources aimed at improving the teaching and understanding of mathematics, particularly in higher education. She is recognized for her work in making advanced mathematical concepts more accessible.

In mathematics, particularly in the field of algebraic geometry and homological algebra, a **derived category** is a concept that allows one to work with complexes of objects (such as sheaves, abelian groups, or modules) in a way that takes into account their morphisms up to homotopy. Derived categories provide a framework for studying how complex objects relate to one another and for performing calculations in a more flexible manner than is possible in the traditional context of abelian categories.

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.

Michael Shulman is a mathematician known for his work in the fields of algebra, category theory, and type theory. He has made contributions to the study of homotopy theory, higher categories, and the connections between mathematics and computer science, particularly in the context of programming languages and formal systems. Shulman has also been involved in research that bridges the gap between abstract mathematical theory and practical computational applications.

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.

Valeria de Paiva is a Brazilian mathematician known for her work in the field of type theory, particularly in the context of computer science and programming languages. She has made significant contributions to the development of mathematical frameworks that inform type systems in software, which are critical for ensuring code correctness and safety. Additionally, Valeria de Paiva has been involved in research related to category theory and its applications in functional programming. She is also noted for her engagement in teaching and collaboration within the academic community.

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 \( \frac{\partial f}{\partial x} \).

The Pincherle derivative is a concept from the field of functional analysis, particularly in the study of linear operators and spaces of functions. It is a type of derivative that generalizes the traditional notion of differentiation for certain classes of functions, especially those that can be represented as power series or polynomials in some functional spaces.

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.

In group theory, a branch of abstract algebra, an essential subgroup is a specific type of subgroup that has particular relevance in the context of group actions and the structure of groups. A subgroup \( H \) of a group \( G \) is said to be essential in \( G \) if it intersects every nontrivial subgroup of \( G \).

A primary cyclic group is a specific type of cyclic group in the field of group theory, a branch of abstract algebra. A cyclic group is one that can be generated by a single element, meaning that every element of the group can be expressed as a power (or multiple) of this generator.

A Prüfer group, also known as a Prüfer \(p\)-group, is a type of abelian group that can be defined for a prime number \(p\).

In mathematics, "E7" typically refers to one of the exceptional Lie groups, which are important in various fields, including algebra, geometry, and theoretical physics. Specifically, E7 is a complex, simple Lie group of rank 7 that can be understood in terms of its root system and algebraic structure.