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.
Type to find tags: 
ag.algebraicgeometry× 9836
Algebraic varieties, stacks, sheaves, schemes, moduli spaces, complex geometry, quantum cohomology.

nt.numbertheory× 6592
Prime numbers, Diophantine equations, analytic number theory, algebraic number theory, arithmetic geometry, Galois theory, transcendental number theory, continued fractions

referencerequest× 5471
used if a reference is needed in a paper or textbook on a specific result.

co.combinatorics× 3885
Enumerative combinatorics, graph theory, order theory, posets, matroids, designs and other discrete structures. It also includes algebraic, analytic and probabilistic combinatorics.

at.algebraictopology× 3763
Homotopy, stable homotopy, homology and cohomology, homotopical algebra.

gr.grouptheory× 3677
Questions about the branch of abstract algebra that deals with groups.

dg.differentialgeometry× 3622
Complex, contact, Riemannian, pseudoRiemannian and Finsler geometry, relativity, gauge theory, global analysis.

pr.probability× 3271
Theory and applications of probability and stochastic processes: e.g. central limit theorems, large deviations, stochastic differential equations, models from statistical mechanics, queuing theory.

fa.functionalanalysis× 3158
Banach spaces, function spaces, real functions, integral transforms, theory of distributions, measure theory.

rt.representationtheory× 2759
Linear representations of algebras and groups, Lie theory, associative algebras, multilinear algebra.

ct.categorytheory× 2588
Categories and functors, universal properties, algebras and algebraic theories, topoi, enriched and internal categories, structured categories (abelian, monoidal, etc), higher categories.

ac.commutativealgebra× 2383
Commutative rings, modules, ideals, homological algebra, computational aspects, invariant theory, connections to algebraic geometry and combinatorics.

linearalgebra× 2312
Questions about the properties of vector spaces and linear transformations, including linear systems in general.

lo.logic× 2141
firstorder and higherorder logic, model theory, set theory, proof theory, computability theory, formal languages, definability, interplay of syntax and semantics, constructive logic, intuitionism, p…

settheory× 2131
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…

graphtheory× 2109
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 …

gt.geometrictopology× 1774
Topology of cell complexes and manifolds, classification of manifolds (e.g. smoothing, surgery), low dimensional topology (e.g. knot theory, invariants of 4manifolds), embedding theory, combinatorial…

gn.generaltopology× 1749
Continuum theory, pointset topology, spaces with algebraic structure, foundations, dimension theory, local and global properties.

ca.analysisandodes× 1524
Special functions, orthogonal polynomials, harmonic analysis, ODE's, differential relations, calculus of variations, approximations, expansions, asymptotics.

mg.metricgeometry× 1416
Euclidean, hyperbolic, discrete, convex, coarse geometry, comparisons in Riemannian geometry, symmetric spaces.

ap.analysisofpdes× 1338
Existence and uniqueness, regularity, boundary conditions, linear and nonlinear operators, stability, soliton theory, integrable PDEs, conservation laws, qualitative dynamics.

ra.ringsandalgebras× 1255
Noncommutative rings and algebras, nonassociative algebras, universal algebra and lattice theory, linear algebra, semigroups.

softquestion× 1241
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…

cv.complexvariables× 1225
Complex analysis, holomorphic functions, automorphic group actions and forms, pseudoconvexity, complex geometry, analytic spaces, analytic sheaves.

complexgeometry× 1195
the study of complex manifolds and complex algebraic varieties. It is a part of both differential geometry and algebraic geometry.

matrices× 1182
Questions where the notion matrix has an important or crucial role (for the latter, note the tag matrixtheory for potential use). Matrices appear in various parts of mathematics, and this tag is typi…

liegroups× 1151
Groups that are additionally smooth manifolds such that the multiplication and the inverse maps are smooth.

realanalysis× 1143
Realvalued functions of real variable, analytic properties of functions and sequences, limits, continuity, smoothness of these.

homotopytheory× 1115
an important subfield 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…

ds.dynamicalsystems× 969
Dynamics of differential equations and flows, mechanics, classical fewbody problems, iterations, complex dynamics, delayed differential equations.

mp.mathematicalphysics× 942
Mathematical methods in quantum field theory, quantum mechanics, statistical mechanics, condensed matter, nuclear and atomic physics.

measuretheory× 940
Questions about abstract measure and Lebesgue integral theory. Also concerns such properties as measurability of maps and sets.

homologicalalgebra× 895
(Co)chain complexes, abelian Categories, (pre)sheaves, (co)homology in various (possibly highly generalized) settings, spectra, derived functors, resolutions, spectral sequences, homotopy categories. …

polynomials× 889
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…

finitegroups× 871 
riemanniangeometry× 868
a subfield of Differential Geometry, which specifically studies "Riemannian Manifolds", manifolds with "Riemannian Metrics", which means that they are equipped with continuous i…
