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.
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oa.operatoralgebras× 691
Algebras of operators on Hilbert space, C^*algebras, von Neumann algebras, noncommutative geometry

algebraicgroups× 689  finitegroups× 682 
riemanniangeometry× 665
a subfield of Differential Geometry, which specifically studies "Riemannian Manifolds", manifolds with "Riemannian Metrics", which means that they are equipped with continuous i…

ho.historyoverview× 661
Biographies, philosophy of mathematics, mathematics education, recreational mathematics, communication of mathematics

algorithms× 645 
geometry× 622
Deprecated; please use a more specific tag.

primenumbers× 611
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× 610 
na.numericalanalysis× 585
Numerical algorithms for problems in analysis and algebra, scientific computation

stochasticprocesses× 585
a collection of random variables usually indexed by a totally ordered set.

computationalcomplexity× 579
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…

sg.symplecticgeometry× 560
Hamiltonian systems, symplectic flows, classical integrable systems

differentialequations× 554
Ordinary or partial differential equations. Delay differential equations, neutral equations, integrodifferential equations. Wellposedness, asymptotic behavior, and related questions.

ellipticcurves× 548
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; …

fourieranalysis× 505 
algebraicnumbertheory× 498 
differentialtopology× 494
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…

modularforms× 486
Questions about modular forms and related areas

analyticnumbertheory× 485
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.

biglist× 477
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…

cohomology× 465 
tagremoved× 435
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…

oc.optimizationcontrol× 431
Operations research, linear programming, control theory, systems theory, optimal control, game theory

banachspaces× 426
a complete normed vector space: A vector space equipped with a norm such that every Cauchy sequence converges.

modeltheory× 419
the branch of mathematical logic which deals with the connection between a formal language and its interpretations, or models.

qa.quantumalgebra× 407
Quantum groups, skein theories, operadic and diagrammatic algebra, quantum field theory

complexanalysis× 391 
algebraiccurves× 383 
knottheory× 380
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…

probabilitydistributions× 369 
modulispaces× 352
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× 350 
computabilitytheory× 346
computable sets and functions, Turing degrees, c.e. degrees, models of computability, primitive recursion, oracle computation, models of computability, decision problems, undecidability, Turing jump, …

kt.ktheoryhomology× 343
Algebraic and topological Ktheory, relations with topology, commutative algebra, and operator algebras

harmonicanalysis× 340 