# Tags

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:
 operator-theory× 164 Spectrum, resolvent, numerical range, functional calculus, operator semigroups. Special classes of operators: compact, Fredholm, dissipative, differential, integral, pseudodifferential, etc. matrix-analysis× 163 The study of real and complex matrices and their algebraic and analytical properties, including: eigenvalues and eigenvectors, positive definite matrices, matrix inequalities, invariant subspaces, per… projective-geometry× 160 elliptic-pde× 160 Questions about partial differential equations of elliptic type. Often used in combination with the top-level tag ap.analysis-of-pdes. stable-homotopy× 160 manifolds× 159 algebraic-surfaces× 157 approximation-theory× 156 math-philosophy× 156 birational-geometry× 150 computational-geometry× 148 Using computers to solve geometric problems. Questions with this tag should typically have at least one other tag indicating what sort of geometry is involved, such as ag.algebraic-geometry or mg.metr… hilbert-spaces× 148 euclidean-geometry× 142 semigroups× 142 riemann-zeta-function× 142 the function of one complex variable $s$ defined by the series $\zeta(s) = \sum_{n \geq 1} \frac{1}{n^s}$ when $\operatorname{Re}(s)>1$. It admits a meromorphic continuati… random-walk× 141 proof-theory× 140 For question in Proof Theory, where "proofs" themselves are the object of mathematical investigation. It is not to be used to request a proof of some result. monoidal-categories× 140 computer-algebra× 140 Using computers to solve algebraic problems. Questions with this tag should typically include at least one other tag indicating what sort of algebraic problem is involved, such as ac.commutative-algeb… textbook-recommendation× 140 Questions asking for recommendations of textbooks on some subject. It can be helpful to indicate whether the request is for self-study, for use in a course one teaches, for use accompanying a course o… langlands-conjectures× 139 Higher reciprocity laws zeta-functions× 135 homology× 133 books× 133 Questions in which books play a key-role, such as questions on antique books, e-books, difference between various editions of a book, etc. For questions asking for recommendations of books on some sub… universal-algebra× 131 calculus-of-variations× 130 l-functions× 130 Questions about generalizations of the Riemann Zeta function of arithmetic interest whose definition relies on meromorphic continuation of special kinds of Dirichlet series, such as Dirichlet L-functi… gm.general-mathematics× 128 group-actions× 127 class-field-theory× 125 intersection-theory× 124 convex-optimization× 123 career× 121 differential-operators× 121 Elliptic, parabolic and hyperbolic operators. Laplace, Laplace-Beltrami, Schrödinger, Dirac. Exterior derivative and Lie derivative operators. graph-colorings× 117 permutations× 116 Questions related to permutations, bijections from a finite (or sometimes infinite) set to itself.