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: 
inequalities× 429 
forcing× 421
a method first used to prove the continuum hypothesis is independent of the classical axioms of set theory

computabilitytheory× 419
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× 418
Algebraic and topological Ktheory, relations with topology, commutative algebra, and operator algebras

tagremoved× 418
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…

convexpolytopes× 416
the convex hulls of a finite set of points in Euclidean spaces. They have rich combinatorial, arithmetic, and metrical theory, and are related to toric varieties and to linear pr…

terminology× 407
Questions of the kind "What's the name for a X that satisfies property Y?"

ergodictheory× 388
Dynamical systems on measure spaces, invariant measures, ergodic averages, mixing properties.

sp.spectraltheory× 378
Schrodinger operators, operators on manifolds, general differential operators, numerical studies, integral operators, discrete models, resonances, nonselfadjoint operators, random operators/matrices…

abelianvarieties× 376
projective algebraic varieties endowed with an Abelian group structure. Over the complex numbers, they can be described as quotients of a vector space by a lattice of full rank. …

computerscience× 370
For question borderline with, or having application to, computer science. Consider also posting http://cs.stackexchange.com/ or http://cstheory.stackexchange.com/ instead of here, if appropriate.

hyperbolicgeometry× 370 
integration× 368  simplicialstuff× 359  sheaftheory× 359 
geometricgrouptheory× 355
Large scale properties of groups; growth functions; Dehn functions; small cancellation properties; hyperbolicity and CAT(0); actions and representations; combinatorial group theory; presentations

galoistheory× 349  groupcohomology× 348 
openproblem× 343
equivalent to a known open problem, then the openproblem tag is added. After that, the question essentially becomes, "What is known about this problem? What are some…

examples× 342 
convexgeometry× 338 
lattices× 336
used in number theory. (Not to be confused with lattice theory or lattices as used in physics!)

diophantineequations× 325
polynomial equations $F=0$, or systems of polynomial equations $F_1=\ldots=F_k=0$, where $F,F_1,\ldots,F_k$ are polynomials in either $\mathbb{Z}[X_1,\ldots,X_n]$ of $\mathbb…

specialfunctions× 323
Many special functions appear as solutions of differential equations or integrals of elementary functions. Most special functions have relationships with representation theory of Lie groups.

sobolevspaces× 323  modelcategories× 305 
stochasticcalculus× 304
Stochastic calculus provides a consistent theory of integration for stochastic processes and is used to model random systems. Its applications range from statistical physics to quantitative finance.

convexity× 303 
riemannsurfaces× 301  asymptotics× 298  deformationtheory× 296  largecardinals× 295 
automorphicforms× 292 
cstaralgebras× 291
a complex Banach algebra together with an isometric antilinear involution satisfying (a b)* = b* a* and the C*identity ‖a* a‖ = ‖a‖². Related tags: [tag:banachalgebras], [tag:vonne…

operatortheory× 286
Spectrum, resolvent, numerical range, functional calculus, operator semigroups. Special classes of operators: compact, Fredholm, dissipative, differential, integral, pseudodifferential, etc.

it.informationtheory× 281
Covers theoretical and experimental aspects of information theory and coding.
