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× 851
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× 820
Algebras of operators on Hilbert space, $C^*$algebras, von Neumann algebras, noncommutative geometry

algebraicgroups× 817 
st.statistics× 812
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× 750 
ho.historyoverview× 739
History and philosophy of mathematics, biographies of mathematicians, mathematics education, recreational mathematics, communication of mathematics.

stochasticprocesses× 737
a collection of random variables usually indexed by a totally ordered set.

primenumbers× 735
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…

arithmeticgeometry× 697 
na.numericalanalysis× 667
Numerical algorithms for problems in analysis and algebra, scientific computation

sg.symplecticgeometry× 657
Hamiltonian systems, symplectic flows, classical integrable systems

computationalcomplexity× 657
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× 641
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; …

differentialequations× 641
Ordinary or partial differential equations. Delay differential equations, neutral equations, integrodifferential equations. Wellposedness, asymptotic behavior, and related questions.

analyticnumbertheory× 632
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.

algebraicnumbertheory× 615
Algebraic number fields, Algebraic integers, Arithmetic Geometry, Elliptic Curves, Function fields, Local fields, Arithmetic groups, Automorphic forms, zeta functions, $L$functions, Quadratic forms, …

differentialtopology× 604
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…

fourieranalysis× 588  cohomology× 585 
modularforms× 579
Questions about modular forms and related areas

geometry× 554
Deprecated; please use a more specific tag.

biglist× 533
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…

banachspaces× 518
a complete normed vector space: A vector space equipped with a norm such that every Cauchy sequence converges.

oc.optimizationcontrol× 479
Operations research, linear programming, control theory, systems theory, optimal control, game theory

probabilitydistributions× 472 
modeltheory× 470
the branch of mathematical logic which deals with the connection between a formal language and its interpretations, or models.

algebraiccurves× 463 
discretegeometry× 458
Finite or discrete collections of geometric objects. Packings, tilings, polyhedra, polytopes, intersection, arrangements, rigidity.

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

knottheory× 441
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…

harmonicanalysis× 437
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 …

smoothmanifolds× 436
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…

modulispaces× 417
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 …

highercategorytheory× 413 
tagremoved× 410
to be used only when retagging highly(!) offtopic questions where none of the actual tags would make sense; all actual tags the questioner has used are removed and something is needed to…

sequencesandseries× 409 