# Tags

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:
 finite-fields× 309 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 … it.information-theory× 304 Covers theoretical and experimental aspects of information theory and coding. order-theory× 299 abstract-algebra× 294 Do NOT use this tag. Instead you could consider gr.group-theory, ac.commutative-algebra, ra.rings-and-algebras or various more specific tags. schemes× 292 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… etale-cohomology× 288 the étale cohomology groups of an algebraic variety or scheme are algebraic analogues of the usual cohomology groups with finite coefficients of a topological space, introduced by Grothendieck in orde… random-matrices× 286 Statistics of spectral properties of matrix-valued random variables. galois-representations× 285 frequently used when the G-module is a vector space over a field or a free module over a ring, but can also be used as a synonym for G-module. The study of Galois mod… quantum-groups× 282 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… topological-groups× 282 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). stacks× 280 modules× 280 For questions on modules over rings. derived-category× 279 For questions about the derived categories of various abelian categories and questions regarding the derived category construction itself. axiom-of-choice× 277 An important and fundamental axiom in set theory sometimes called Zermelo's axiom of choice. It was formulated by Zermelo in 1904 and states that, given any set of mutually disjoint nonempty sets, the… 3-manifolds× 272 additive-combinatorics× 271 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,… fields× 268 Fields as algebraic objects. For vector and tensor fields, use eg. [dg.differential-geometry]. For physical fields, use eg. [mp.mathematical-physics] or [quantum-field-theory]. matrix-analysis× 267 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… descriptive-set-theory× 266 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… commutative-rings× 263 big-picture× 260 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 sub-fields of mat… singularity-theory× 259 quadratic-forms× 258 projective-geometry× 258 noncommutative-algebra× 255 noncommutative-geometry× 250 Noncommutative geometry in the sense of Connes and beyond: noncommutative algebras viewed as functions on a noncommutative space. intuition× 250 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… topos-theory× 249 linear-programming× 248 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… markov-chains× 247 hopf-algebras× 246 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… von-neumann-algebras× 246 Subtag of [tag:oa.operator-algebras] for questions about von Neumann algebras, that is, weak operator topology closed, unital, *-subalgebras of bounded operators on a Hilbert space. algebraic-k-theory× 245 convex-optimization× 244 Optimization with convex constraints and convex objectives; notions related to convex optimization such as sub-gradients, normal cones, separating hyperplanes approximation-theory× 230 hilbert-spaces× 227 a real or complex vector space endowed with an inner product such that $H$ is a complete metric space when endowed with the norm induced by this inner product.