A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.

ag.algebraic-geometry× 14388

for questions on algebraic geometry, including algebraic varieties, stacks, sheaves, schemes, moduli spaces, complex geometry, quantum cohomology.

nt.number-theory× 10234

Prime numbers, diophantine equations, diophantine approximations, analytic or algebraic number theory, arithmetic geometry, Galois theory, transcendental number theory, continued fractions

co.combinatorics× 6260

Enumerative combinatorics, graph theory, order theory, posets, matroids, designs and other discrete structures. It also includes algebraic, analytic and probabilistic combinatorics.

dg.differential-geometry× 5581

Complex, contact, Riemannian, pseudo-Riemannian and Finsler geometry, relativity, gauge theory, global analysis.

at.algebraic-topology× 5466

Homotopy, stable homotopy, homology and cohomology, homotopical algebra.

fa.functional-analysis× 5322

Banach spaces, function spaces, real functions, integral transforms, theory of distributions, measure theory.

pr.probability× 5089

Theory and applications of probability and stochastic processes: e.g. central limit theorems, large deviations, stochastic differential equations, models from statistical mechanics, queuing theory.

rt.representation-theory× 4351

Linear representations of algebras and groups, Lie theory, associative algebras, multilinear algebra.

ct.category-theory× 3874

Categories and functors, universal properties, algebras and algebraic theories, topoi, enriched and internal categories, structured categories (abelian, monoidal, etc), higher categories.

linear-algebra× 3592

Questions about the properties of vector spaces and linear transformations, including linear systems in general.

ac.commutative-algebra× 3586

Commutative rings, modules, ideals, homological algebra, computational aspects, invariant theory, connections to algebraic geometry and combinatorics.

graph-theory× 3349

Questions about the branch of combinatorics called graph theory (not to be used for questions concerning the graph of a function). This tag can be further specialized via using it in combination with …

set-theory× 3278

forcing, large cardinals, descriptive set theory, infinite combinatorics, cardinal characteristics, forcing axioms, ultrapowers, measures, reflection, pcf theory, models of set theory, axioms of set t…

lo.logic× 3145

first-order and higher-order logic, model theory, set theory, proof theory, computability theory, formal languages, definability, interplay of syntax and semantics, constructive logic, intuitionism, p…

gn.general-topology× 2754

Continuum theory, point-set topology, spaces with algebraic structure, foundations, dimension theory, local and global properties.

gt.geometric-topology× 2627

Topology of cell complexes and manifolds, classification of manifolds (e.g. smoothing, surgery), low dimensional topology (e.g. knot theory, invariants of 4-manifolds), embedding theory, combinatorial…

real-analysis× 2400

Real-valued functions of real variable, analytic properties of functions and sequences, limits, continuity, smoothness of these.

ap.analysis-of-pdes× 2353

Partial differential equations (PDEs): Existence and uniqueness, regularity, boundary conditions, linear and non-linear operators, stability, soliton theory, integrable PDEs, conservation laws, qualit…

mg.metric-geometry× 2260

Euclidean, hyperbolic, discrete, convex, coarse geometry, comparisons in Riemannian geometry, symmetric spaces.

ca.classical-analysis-and-odes× 2131

Special functions, orthogonal polynomials, harmonic analysis, ordinary differential equations (ODE's), differential relations, calculus of variations, approximations, expansions, asymptotics.

matrices× 2032

Questions where the notion matrix has an important or crucial role (for the latter, note the tag matrix-theory for potential use). Matrices appear in various parts of mathematics, and this tag is typi…

ra.rings-and-algebras× 1942

Non-commutative rings and algebras, non-associative algebras, universal algebra and lattice theory, linear algebra, semigroups. For questions specific to commutative algebra (that is, rings that are a…

cv.complex-variables× 1924

Complex analysis, holomorphic functions, automorphic group actions and forms, pseudoconvexity, complex geometry, analytic spaces, analytic sheaves.

complex-geometry× 1912

the study of complex manifolds and complex algebraic varieties. It is a part of both differential geometry and algebraic geometry.

lie-groups× 1816

Groups that are additionally smooth manifolds such that the multiplication and the inverse maps are smooth.

homotopy-theory× 1747

an important sub-field of algebraic topology. It is mainly concerned with the properties and structures of spaces which are invariant under homotopy. Chief among these are the homot…

riemannian-geometry× 1659

a subfield of Differential Geometry, which specifically studies "Riemannian Manifolds", manifolds with "Riemannian Metrics", which means that they are equipped with continuous i…

soft-question× 1589

about research in mathematics, or about the job of a research mathematician, without being mathematical problems or statements in the strictest sense. In other words, questions that…

homological-algebra× 1550

(Co)chain complexes, abelian Categories, (pre)sheaves, (co)homology in various (possibly highly generalized) settings, spectra, derived functors, resolutions, spectral sequences, homotopy categories. …

measure-theory× 1528

Questions about abstract measure and Lebesgue integral theory. Also concerns such properties as measurability of maps and sets.

ds.dynamical-systems× 1514

Dynamics of flows and maps (continuous and discrete time), including infinite-dimensional dynamics, Hamiltonian dynamics, ergodic theory.

polynomials× 1501

Questions in which polynomials (single or several variables) play a key role. It is typically important that this tag is combined with other tags; polynomials appear in very different contexts. Please…

analytic-number-theory× 1487

A beautiful blending of real/complex analysis with number theory. The study involves distribution of prime numbers and other problems and helps giving asymptotic estimates to these.