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: 
finitefields× 281
a field with a finite number of elements. For each prime power $q^k$, there is a unique (up to isomorphism) finite field with $q^k$ elements. Up to isomorphism, these are the only …

ordertheory× 279 
topologicalgroups× 273
a group $G$ together with a topology on the elements of $G$ such that the group operation and group inverse function are both continuous (with respect to the topology).

schemes× 272
the geometrical study of solutions of algebraic systems of equations, not only over the real/complex numbers, but also over integer numbers (and more generally o…

ellipticpde× 272
Questions about partial differential equations of elliptic type. Often used in combination with the toplevel tag ap.analysisofpdes.

abstractalgebra× 271  etalecohomology× 269  galoisrepresentations× 268 
stacks× 267 
randommatrices× 264
Statistics of spectral properties of matrixvalued random variables.

axiomofchoice× 263  3manifolds× 256 
additivecombinatorics× 253
Questions on the subject additive combinatorics, also known as arithmetic combinatorics, such as questions on: additive bases, sum sets, inverse sum set theorems, sets with small doubling, Sidon sets,…

derivedcategory× 252
For questions about the derived categories of various abelian categories and questions regarding the derived category construction itself.

fields× 248
Fields as algebraic objects. For vector and tensor fields, use eg. [dg.differentialgeometry]. For physical fields, use eg. [mp.mathematicalphysics] or [quantumfieldtheory].

modules× 247
For questions on modules over rings.

quadraticforms× 245 
descriptivesettheory× 245
the study of definable subsets of Polish spaces, where definable is taken to mean from the Borel or projective hierarchies. Other topics include infinite games and determinac…

bigpicture× 245
Questions designed to get an overview of a specific subject or body of results or to understand the relations among similar definitions, techniques or concepts appearing in different subfields of mat…

singularitytheory× 244 
matrixanalysis× 241
The study of the properties of real and complex matrices that are more close to analysis and operator theory. For instance: the properties of positive definite matrices, matrix inequalities, perturbat…

commutativerings× 239 
quantumgroups× 237
Questions about algebraic structures known as quantum groups, and their categories of representations. Quasitriangular Hopf algebras and their Drinfel'd twists, triangular Hopf algebras, $C^\star$ qua…

topostheory× 237 
projectivegeometry× 235 
intuition× 235
Questions asking for the intuition behind some definition, conjecture, proof etc. In other words, questions designed to improve or to acquire understanding on a conceptual or intuitive level, as oppos…

vonneumannalgebras× 233
Subtag of [tag:oa.operatoralgebras] for questions about von Neumann algebras, that is, weak operator topology closed, unital, *subalgebras of bounded operators on a Hilbert space.

noncommutativealgebra× 232 
linearprogramming× 231
the study of optimizing a linear function over a set of linear inequalities. The Simplex Method, Ellipsoid Method and Interior Point Method are popular algorithms to solve linea…

noncommutativegeometry× 229
Noncommutative geometry in the sense of Connes and beyond: noncommutative algebras viewed as functions on a noncommutative space.

algebraicktheory× 226 
hopfalgebras× 221
a vector space $H$ over a field $k$ endowed with an associative product $\times:H\otimes_k H\to H$ and a coassociative coproduct $\Delta:H\to H\otimes_k H$ which is a morphism of alg…

approximationtheory× 217 
convexoptimization× 217
Optimization with convex constraints and convex objectives; notions related to convex optimization such as subgradients, normal cones, separating hyperplanes

mathematicseducation× 216
For questions in Mathematics Education as a scientific discipline. For more handson questions on teaching Mathematics, please use the tag teaching. There is also a Stack Exchange community http://mat…

markovchains× 215 