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: 
kt.ktheoryhomology× 364
Algebraic and topological Ktheory, relations with topology, commutative algebra, and operator algebras

sequencesandseries× 360 
vectorbundles× 352
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…

forcing× 351
a method first used to prove the continuum hypothesis is independent of the classical axioms of set theory

inequalities× 350 
convexpolytopes× 342
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…

abelianvarieties× 342
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× 333
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.

sheaftheory× 329 
ergodictheory× 325
Dynamical systems on measure spaces, invariant measures, ergodic averages, mixing properties.

simplicialstuff× 322 
openproblem× 319
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× 318 
sp.spectraltheory× 318
Schrodinger operators, operators on manifolds, general differential operators, numerical studies, integral operators, discrete models, resonances, nonselfadjoint operators, random operators/matrices…

examples× 311 
lattices× 307
used in number theory. (Not to be confused with lattice theory or lattices as used in physics!)

galoistheory× 302  groupcohomology× 298  terminology× 296  integration× 295 
specialfunctions× 281
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.

convexity× 278  riemannsurfaces× 272 
geometricgrouptheory× 269
Large scale properties of groups; growth functions; Dehn functions; small cancellation properties; hyperbolicity and CAT(0); actions and representations; combinatorial group theory; presentations

convexgeometry× 265  diophantineequations× 259 
it.informationtheory× 258
Covers theoretical and experimental aspects of information theory and coding.

deformationtheory× 255 
modelcategories× 253  automorphicforms× 250 
cstaralgebras× 246
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…

stochasticcalculus× 245
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× 244  etalecohomology× 242 
schemes× 235
the geometrical study of solutions of algebraic systems of equations, not only over the real/complex numbers, but also over integer numbers (and more generally o…

galoisrepresentations× 233 