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: 
liealgebras× 872
algebraic structures which were introduced to study the concept of infinitesimal transformations. The term "Lie algebra" (after Sophus Lie) was introduced by Hermann Weyl in the 1930s…

oa.operatoralgebras× 839
Algebras of operators on Hilbert space, $C^*$algebras, von Neumann algebras, noncommutative geometry

algebraicgroups× 835 
st.statistics× 826
Applied, computational and theoretical statistics: e.g. statistical inference, regression, time series, multivariate analysis, data analysis, Markov chain Monte Carlo, design of experiments, case stud…

algorithms× 774 
primenumbers× 762
Questions where prime numbers play a keyrole, such as: questions on the distribution of prime numbers (twin primes, gaps between primes, Hardy–Littlewood conjectures, etc); questions on prime numbers…

stochasticprocesses× 756
a collection of random variables usually indexed by a totally ordered set.

ho.historyoverview× 755
History and philosophy of mathematics, biographies of mathematicians, mathematics education, recreational mathematics, communication of mathematics.

arithmeticgeometry× 707 
na.numericalanalysis× 688
Numerical algorithms for problems in analysis and algebra, scientific computation

analyticnumbertheory× 672
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.

computationalcomplexity× 671
computational complexity theory; complexity classes, such as P, NP, PSPACE, and so on; resourcelimited computation; NPcompleteness and other completeness concepts; oracle analogues of complexity cla…

ellipticcurves× 659
an algebraic curve of genus one with some additional properties. Questions with this tag will often have the toplevel tags nt.numbertheory or ag.algebraicgeometry in addition; …

sg.symplecticgeometry× 658
Hamiltonian systems, symplectic flows, classical integrable systems

differentialequations× 657
Ordinary or partial differential equations. Delay differential equations, neutral equations, integrodifferential equations. Wellposedness, asymptotic behavior, and related questions.

algebraicnumbertheory× 639
Algebraic number fields, Algebraic integers, Arithmetic Geometry, Elliptic Curves, Function fields, Local fields, Arithmetic groups, Automorphic forms, zeta functions, $L$functions, Quadratic forms, …

differentialtopology× 616
The study of differentiable manifolds and differentiable maps. One fundamental problem is that of classifying manifolds up to diffeomorphism. Differential topology is what Poincaré understood as topol…

cohomology× 600  fourieranalysis× 596 
modularforms× 596
Questions about modular forms and related areas

geometry× 560
Deprecated; please use a more specific tag.

banachspaces× 550
a complete normed vector space: A vector space equipped with a norm such that every Cauchy sequence converges.

biglist× 540
Questions designed to generate a "big list" of certain results, examples, conjectures, etc. via many individual answers, each contributing one or a few instances. Such a question should typically be i…

probabilitydistributions× 502 
oc.optimizationcontrol× 492
Operations research, linear programming, control theory, systems theory, optimal control, game theory

discretegeometry× 483
Finite or discrete collections of geometric objects. Packings, tilings, polyhedra, polytopes, intersection, arrangements, rigidity.

modeltheory× 481
the branch of mathematical logic which deals with the connection between a formal language and its interpretations, or models.

algebraiccurves× 475 
harmonicanalysis× 452
a generalisation of Fourier analysis that studies the properties of functions. Check out this tag for abstract harmonic analysis (on abelian locally compact groups), or Euclidean …

qa.quantumalgebra× 446
Quantum groups, skein theories, operadic and diagrammatic algebra, quantum field theory

smoothmanifolds× 446
Smooth manifolds and smooth functions between them. For manifolds with additional structure, see more specific tags, such as [riemanniangeometry]. For more topological aspects, see [differentialtopo…

knottheory× 445
dealing with embedding of curves in manifolds of dimension 3. A knot is a single circle embedded in the affine space of dimension 3 as a smooth curve not crossing itself. Many knot inva…

highercategorytheory× 424 
modulispaces× 423
Given a concrete category C, with objects denoted Obj(C), and an equivalence relation ~ on Obj(C) given by morphisms in C. The moduli set for Obj(C) is the set of equivalence classes with respect to …

vectorbundles× 422
A continuously varying family of vector spaces of the same dimension over a topological space. If the vector spaces are onedimensional, the term line bundle is used and has the associated tag linebu…

sequencesandseries× 420 