Areas of mathematics
From Cosmopedia
Here is a list of all areas of modern mathematics, with a brief explanation of their scope and links to other parts of this encyclopedia, set out in a systematic way.
The way researchlevel mathematics is internally organised is mostly determined by practitioners, and changes over time; this contrasts with the apparently timeless syllabus divisions used in mathematics education, where calculus can seem to be much the same over a time scale of a century. Calculus itself does not appear as a major heading — most of the traditional material would be divided amongst topics under analysis. This example illustrates, in part, the difficulty of communicating the principles of any largescale organization. The research on most calculus topics was carried out in the eighteenth century, and has long been assimilated. The story of why fields exist as specialties involves, in most cases, quite a long intellectual (and sometimes institutional) history.
The American Mathematical Society's Mathematics Subject Classification (2000 edition) (MSC) has been used as a starting point to ensure all areas are covered, and related areas are close together. However, the MSC aims to classify mathematical papers, not mathematics itself, so additional categories have been used. Further, the headings used here mean that the order does not always follow the MSC number See also the list of mathematics lists.
Contents
Foundations / general
 General (MSC 00)
 This is the pigeonhole for everything that doesn't fit anywhere else.
 Recreational mathematics (MSC 00)
 From magic squares to the Mandelbrot set, numbers have been a source of amusement and delight for millions of people throughout the ages. Many important branches of "serious" mathematics have their roots in what was once a mere puzzle or game.
 History and biography (MSC 01)
 The history of mathematics is inextricably interwined with the subject itself. This is perfectly natural: mathematics has an internal organic structure, deriving new theorems from those which have come before. As each new generation of mathematicians builds upon the achievements of our ancestors, the subject itself expands and grows new layers, like an onion.
 Mathematical logic and foundations, including set theory (MSC 03)
 Mathematicians have always worked with logic and symbols, but for centuries the underlying laws of logic were taken for granted, and never expressed symbolically. Mathematical logic, also known as symbolic logic, was developed when people finally realized that the tools of mathematics can be used to study the structure of logic itself. Areas of research in this field have expanded rapidly, and are usually subdivided into several distinct departments.
 Model theory (MSC 03C)

 Model theory studies mathematical structures in a general framework. Its main tool is firstorder logic.
 03D Computability theory and recursion theory
 Set theory (MSC 03E)

 A set can be thought of as a collection of distinct things united by some common feature. Set theory is subdivided into three main areas. Naive set theory is the original set theory developed by mathematicians at the end of the 19th century. Axiomatic set theory is a rigorous axiomatic theory developed in response to the discovery of serious flaws (such as Russell's paradox) in naive set theory. It treats sets as "whatever satisfies the axioms", and the notion of collections of things serves only as motivation for the axioms. Internal set theory is an axiomatic extension of set theory that supports a logically consistent identification of illimited (enormously large) and infinitesimal (unimaginably small) elements within the real numbers. See also List of set theory topics.
 Proof theory and constructive mathematics (MSC 03F)

 Proof theory grew out of David Hilbert's ambitious program to formalize all the proofs in mathematics. The most famous result in the field is encapsulated in Gödel's incompleteness theorems. A closely related and now quite popular concept is the idea of Turing machines. Constructivism is the outgrowth of Brouwer's unorthodox view of the nature of logic itself; constructively speaking, mathematicians cannot assert "Either a circle is round, or it is not" until they have actually exhibited a circle and measured its roundness.
Algebra
The study of structure starting with numbers, first the familiar natural numbers and integers and their arithmetical operations, which are recorded in elementary algebra. The deeper properties of whole numbers are studied in number theory. The investigation of methods to solve equations leads to the field of abstract algebra, which, among other things, studies rings and fields, structures that generalize the properties possessed by everyday numbers. Long standing questions about compass and straightedge construction were finally settled by Galois theory. The physically important concept of vectors, generalized to vector spaces, is studied in linear algebra.
 Combinatorics (MSC 05)
 Studies finite collections of objects that satisfy specified criteria. In particular, it is concerned with "counting" the objects in those collections (enumerative combinatorics) and with deciding whether certain "optimal" objects exist (extremal combinatorics). It includes graph theory, used to describe interconnected objects (a graph in this sense is a collection of connected points). See also the list of combinatorics topics, list of graph theory topics and glossary of graph theory. While these are the classical definitions, a combinatorial flavour is present in many parts of problemsolving.
 Order theory (MSC 06)
 Any set of real numbers can be written out in ascending order. Order Theory extends this idea to sets in general. It includes notions like lattices and ordered algebraic structures. See also the order theory glossary and the list of order topics.
 General algebraic systems (MSC 08)
 Given a set, different ways of combining or relating members of that set can be defined. If these obey certain rules, then a particular algebraic structure is formed. Universal algebra is the more formal study of these structures and systems.
 Number theory (MSC 11)
 Number theory is traditionally concerned with the properties of integers. More recently, it has come to be concerned with wider classes of problems that have arisen naturally from the study of integers. It can be divided into elementary number theory (where the integers are studied without the aid of techniques from other mathematical fields); analytic number theory (where calculus and complex analysis are used as tools); algebraic number theory (which studies the algebraic numbers  the roots of polynomials with integer coefficients); geometric number theory; combinatorial number theory and computational number theory. See also the list of number theory topics.
 Field theory and polynomials (MSC 12)
 Field theory studies the properties of fields. A field is a mathematical entity for which addition, subtraction, multiplication and division are welldefined. A polynomial is an expression in which constants and variables are combined using only addition, subtraction, and multiplication.
 Commutative rings and algebras (MSC 13)
 In ring theory, a branch of abstract algebra, a commutative ring is a ring in which the multiplication operation obeys the commutative law. This means that if a and b are any elements of the ring, then a×b=b×a. Commutative algebra is the field of study of commutative rings and their ideals, modules and algebras. It is foundational both for algebraic geometry and for algebraic number theory. The most prominent examples of commutative rings are rings of polynomials.
 15: Linear and multilinear algebra; matrix theory
 16: Associative rings and associative algebras
 17: Nonassociative rings and nonassociative algebras
 18: Category theory; homological algebra
 19: Ktheory
 20: Group theory and generalizations
 22: Topological groups, Lie groups, and analysis upon them
(Also transformation groups, abstract harmonic analysis)
Analysis
Within the world of mathematics, analysis is the branch that focuses on change: rates of change, accumulated change, and multiple things changing relative to (or independently of) one another.
Modern analysis is a vast and rapidly expanding branch of mathematics that touches almost every other subdivision of the discipline, finding direct and indirect applications in topics as diverse as number theory, cryptography, and abstract algebra. It is also the language of science itself and is used across chemistry, biology, and physics, from astrophysics to Xray crystallography.
 26: Real functions, including derivatives and integrals
 28: Measure and integration
 30: Complex functions, including approximation theory in the complex domain
 31: Potential theory
 32: Several complex variables and analytic spaces
 33: Special functions
 34: Ordinary differential equations
 35: Partial differential equations
 Dynamical systems (MSC 27)
 The study of the solutions to the equations of motion of systems that are primarily mechanical in nature; although this ranges from planetary orbits through the behaviour of electronic circuits to the solutions of partial differential equations that arise in biology. Much of modern research is focused on the study of chaotic systems. See also the list of dynamical system topics
 37: Ergodic theory
 39: Difference equations and functional equations
 40: Sequences, series, summability
 41: Approximations and expansions
 42: Fourier analysis, including Fourier transforms, trigonometric approximation, trigonometric interpolation, and orthogonal functions
 43: Abstract harmonic analysis
 44: Integral transforms, operational calculus
 45: Integral equations
 46: Functional analysis, including infinitedimensional holomorphy, integral transforms in distribution spaces
 47: Operator theory
 49: Calculus of variations and optimal control; optimization (including geometric integration theory)
 58: Global analysis, analysis on manifolds (including infinitedimensional holomorphy)
(Also: probabilistic potential theory, numerical approximation, representation theory, analysis on manifolds)
Geometry
Geometry (MSC 51) deals with spatial relationships, using fundamental qualities or axioms. Such axioms can be used in conjunction with mathematical definitions for points, straight lines, curves, surfaces, and solids to draw logical conclusions. See also List of geometry topics
 Convex geometry and discrete geometry (MSC 52)
 Includes the study of objects such as polytopes and polyhedra. See also List of convexity topics
 Discrete or combinatorial geometry (MSC 52)
 The study of geometrical objects and properties that are discrete or combinatorial, either by their nature or by their representation. It includes the study of shapes such as the Platonic solids and the notion of tessellation.
 Differential geometry (MSC 53)
 The study of geometry using calculus, and is very closely related to differential topology. Covers such areas as Riemannian geometry, curvature and differential geometry of curves. See also the glossary of differential geometry and topology.
 Algebraic geometry (MSC 14)
 Given a polynomial of two real variables, then the points on a plane where that function is zero will form a curve. An algebraic curve extends this notion to polynomials over a field in a given number of variables. Algebraic geometry may be viewed the study of these curves. See also the list of algebraic geometry topics and list of algebraic surfaces.
 Topology
 Deals with the properties of a figure that do not change when the figure is continuously deformed. The main areas are point set topology (or general topology), algebraic topology, and the topology of manifolds, defined below.
 General topology (MSC 54)
 Also called point set topology. Properties of topological spaces. Includes such notions as open and closed sets, compact spaces, continuous functions, convergence, separation axioms, metric spaces, dimension theory. See also the glossary of general topology and the list of general topology topics.
 Algebraic topology (MSC 55)
 Properties of algebraic objects associated with a topological space and how these algebraic objects capture properties of such spaces. Contains areas like homology theory, cohomology theory, homotopy theory, and homological algebra, some of them examples of functors. Homotopy deals with homotopy groups (including the fundamental group) as well as simplicial complexes and CW complexes (also called cell complexes). See also the list of algebraic topology topics.
 Manifolds (MSC 57)
 A manifold can be thought of as an ndimensional generalization of a surface in the usual 3dimensional Euclidean space. The study of manifolds includes differential topology, which looks at the properties of differentiable functions defined over a manifold. See also complex manifolds.
Applied mathematics
Probability and statistics
See also glossary of probability and statistics
 Probability theory (MSC 60)
 The study of how likely a given event is to occur. See also Category:probability theory, and the list of probability topics.
 Stochastic processes (MSC 60G/H)
 Considers with aggregate effect of a random function, either over time (a time series) or physical space (a random field). See also List of stochastic processes topics, and Category:Stochastic processes.
 Statistics (MSC 62)
 Analysis of data, and how representative it is. See also the list of statistical topics.
Computational sciences
 Numerical analysis, (MSC 65)
 Many problems in mathematics cannot in general be solved exactly. Numerical analysis is the study of algorithms to provide an approximate solution to problems to a given degree of accuracy. Includes numerical differentiation, numerical integration and numerical methods. See also List of numerical analysis topics
 68: Computer science
Physical sciences
 Mechanics
 Addresses what happens when a real physical object is subjected to forces. This divides naturally into the study of rigid solids, deformable solids, and fluids, detailed below.
 Particle mechanics (MSC 70)
 In mathematics, a particle is a pointlike, perfectly rigid, solid object. Particle mechanics deals with the results of subjecting particles to forces. It includes celestial mechanics — the study of the motion of celestial objects.
 Mechanics of deformable solids (MSC 74)
 Most realworld objects are not pointlike nor perfectly rigid. More importantly, objects change shape when subjected to forces. This subject has a very strong overlap with continuum mechanics, which is concerned with continuous matter. It deals with such notions as stress, strain and elasticity. See also continuum mechanics.
 Fluid mechanics (MSC 76)
 Fluids in this sense includes not just liquids, but flowing gases, and even solids under certain situations. (For example, dry sand can behave like a fluid). It includes such notions as viscosity, turbulent flow and laminar flow (its opposite). See also fluid dynamics.
 78: Optics, electromagnetic theory
 80: Classical thermodynamics, heat transfer
 81: Quantum theory, including quantum optics
 82: Statistical mechanics, structure of matter
 83: Relativity and gravitational theory, including relativistic mechanics
 85: Astronomy and astrophysics
 86: Geophysics
Nonphysical sciences
 90: Operations research, mathematical programming
 91: Game theory, economics, social and behavioral sciences
 92: Biology (see also mathematical biology) and other natural sciences
 93: Systems theory; control, including optimal control
 94: Information and communication, circuits
 97: Mathematics education
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