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: 
discretegeometry× 354
Finite or discrete collections of geometric objects. Packings, tilings, polyhedra, polytopes, intersection, arrangements, rigidity.

kt.ktheoryhomology× 353
Algebraic and topological Ktheory, relations with topology, commutative algebra, and operator algebras

sequencesandseries× 350 
forcing× 334
a method first used to prove the continuum hypothesis is independent of the classical axioms of set theory

abelianvarieties× 334
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. …

vectorbundles× 331
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…

inequalities× 328 
computerscience× 325
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.

convexpolytopes× 323
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…

sheaftheory× 320 
ergodictheory× 316
Dynamical systems on measure spaces, invariant measures, ergodic averages, mixing properties.

openproblem× 315
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…

hyperbolicgeometry× 310  examples× 309 
sp.spectraltheory× 304
Schrodinger operators, operators on manifolds, general differential operators, numerical studies, integral operators, discrete models, resonances, nonselfadjoint operators, random operators/matrices…

simplicialstuff× 303 
lattices× 302
used in number theory. (Not to be confused with lattice theory or lattices as used in physics!)

galoistheory× 296  terminology× 286  integration× 284 
groupcohomology× 281  convexity× 271 
specialfunctions× 268
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.

riemannsurfaces× 266 
diophantineequations× 260  convexgeometry× 255 
geometricgrouptheory× 253
Large scale properties of groups; growth functions; Dehn functions; small cancellation properties; hyperbolicity and CAT(0); actions and representations; combinatorial group theory; presentations

it.informationtheory× 248
Covers theoretical and experimental aspects of information theory and coding.

deformationtheory× 247  automorphicforms× 245  modelcategories× 244  etalecohomology× 241 
stochasticcalculus× 236
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.

stacks× 235  galoisrepresentations× 230  axiomofchoice× 230 