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: 
hilbertspaces× 215
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.

motives× 213
In algebraic geometry, a motive (or sometimes motif, following French usage) denotes 'some essential part of an algebraic variety'. One has a satisfactory description of pure motives, whereas the mixe…

stablehomotopy× 212
that part of homotopy theory (and thus algebraic topology) concerned with all structure and phenomena that remain after sufficiently many applications of the suspension funct…

computationalgeometry× 211
Using computers to solve geometric problems. Questions with this tag should typically have at least one other tag indicating what sort of geometry is involved, such as ag.algebraicgeometry or mg.metr…

hodgetheory× 210
The study of harmonic differential forms on complex projective varieties, their invariantly defined filtrations, their integrals over topological cycles, especially over subvarieties, the deformations…

randomwalk× 207 
birationalgeometry× 205
a field of algebraic geometry the goal of which is to determine when two algebraic varieties are isomorphic outside lowerdimensional subsets. This amounts to studying mappings …

algebraicsurfaces× 204
an algebraic variety of dimension two. In the case of geometry over the field of complex numbers, an algebraic surface has complex dimension two (as a complex manifold, when it…

limitsandconvergence× 203
Convergence of series, sequences and functions and different modes of convergence.

euclideangeometry× 202
a mathematical system attributed to the Alexandrian Greek mathematician Euclid, which he described in his textbook on geometry: the Elements. Euclid's method consists in assuming…

riemannzetafunction× 201
the function of one complex variable $s$ defined by the series $\zeta(s) = \sum_{n \geq 1} \frac{1}{n^s}$ when $\operatorname{Re}(s)>1$. It admits a meromorphic continuati…

manifolds× 200
a topological space that locally resembles Euclidean space near each point. More precisely, each point of an ndimensional manifold has a neighbourhood that is homeomorphic to the Euclid…

eigenvalues× 200 
teaching× 196
For questions related to teaching mathematics. For questions in Mathematics Education as a scientific discipline there is also the tag mathematicseducation. Note you may also ask your question on htt…

monoidalcategories× 193 
mathphilosophy× 193
Philosophical aspects of logic and set theory; truth status of mathematical axioms; Philosophy of Mathematics; philosophical aspects of mathematics in general; relation of mathematics to philosophy; e…

differentialoperators× 191
Elliptic, parabolic and hyperbolic operators. Laplace, LaplaceBeltrami, Schrödinger, Dirac. Exterior derivative and Lie derivative operators.

combinatorialgeometry× 191

characteristicp× 191 
textbookrecommendation× 190
Questions asking for recommendations of textbooks on some subject. It can be helpful to indicate whether the request is for selfstudy, for use in a course one teaches, for use accompanying a course o…

groupactions× 188 
graphcolorings× 187
Vertex colouring, Edge Colouring, List Colouring, Fractional Chromatic Number and other variants of graph colouring problems are all on topic.

calculusofvariations× 183 
kahlermanifolds× 182
Questions about Kähler manifolds and Kähler metrics.

semigroups× 179
a set $S$ together with a binary operation that is associative. Examples of semigroups are the set of finite strings over a fixed alphabet (under concatenation) and the positive intege…

lfunctions× 177
Questions about generalizations of the Riemann Zeta function of arithmetic interest whose definition relies on meromorphic continuation of special kinds of Dirichlet series, such as Dirichlet Lfuncti…

permutations× 176
Questions related to permutations, bijections from a finite (or sometimes infinite) set to itself.

geometricmeasuretheory× 176
Questions about geometric properties of sets using measure theoretic techniques; rectifiability of sets and measures, currents, Plateau problem, isoperimetric inequality and related topics.

prooftheory× 174
For question in Proof Theory, where "proofs" themselves are the object of mathematical investigation. It is not to be used to request a proof of some result.

planegeometry× 172 
computeralgebra× 172
Using computers to solve algebraic problems. Questions with this tag should typically include at least one other tag indicating what sort of algebraic problem is involved, such as ac.commutativealgeb…

spectralgraphtheory× 172
Questions related to the spectrum of graphs, defined using one of the possible variants of the discrete Laplace operator or Laplacian matrix.
See https://en.wikipedia.org/wiki/Discrete_Laplace_oper…

classfieldtheory× 170 
nonlinearoptimization× 167
Nonlinear objectives, nonlinear constraints, nonconvex objective, nonconvex feasible region.

discretemathematics× 166
Do NOT use this tag; instead you might use co.combinatorics or various more specific tags.

symmetricgroup× 164
the group of permutations of the set of integers $\{1,\dots,n\}$. This has $n!$ elements and is generated by the $n1$ involutions exchanging consecutive integers. The sym…
