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:
× 1099
if your question involves some type of (co)homology, including (but not limited to) simplicial, singular or group (co)homology. Consider the tag (homological-algebra) for more abstract as…
× 1091
for questions about cardinals and related topics such as cardinal arithmetics, regular cardinals and cofinality. Do not confuse with [large-cardinals] which is a technical concept about st…
× 1086
A vector space $E$, generally over the field $\mathbb R$ or $\mathbb C$ with a map $\lVert \cdot\rVert\colon E\to \mathbb R_+$ satisfying some conditions.
× 1077
For questions about the expectation of a random variable: computations, upper/lower bounds, etc.
× 1072
Computational complexity, a part of theoretical computer science that deals with understanding how efficiently a problem can be solved.
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the study of (classes of) mathematical structures (e.g. groups, fields, graphs, universes of set theory) using tools from mathematical logic. Objects of study in model theory are mode…
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Questions on the evaluation of integrals along a locus in the complex plane.
× 1016
For posts looking for feedback or verification of a proposed solution.
× 1001
Should be used with the (group-theory) tag. A group $(G,*)$ is said to be abelian if $a*b=b*a$ for all $a,b\in G.$
× 999
Questions on conic sections and their properties; the curves formed by the intersection of a plane and a cone. Circles, ellipses, hyperbolas, and parabolas are examples of conic sections.
× 997
"Mathematical physics consists of the application of mathematics to problems in physics and the development of mathematical methods suitable for such applications and for the formulation of physical t…
× 997
For questions about $L^p$ spaces, that is, given a measure space $(X,\mathcal F,\mu)$, the vector space of equivalence class of measurable functions with $p$-th power of the absolute value integrable.…
× 987
Questions on the use of the methods of real/complex analysis in the study of number theory.
× 986
a vector space equipped with an inner product. The inner product is a generalisation of the "dot" product often used in vector calculus.
× 985
Tensor products allow us to build "linear" objects from "multilinear" ones. It can refer to: basic ones from linear algebra/module theory, or more sophisticated versions from differential/algebraic ge…
× 978
used for problems where the goal is to find all functions satisfying the given equation (and maybe some other conditions). So in this case, solving the equation means…
× 958
For questions about finding factors of e.g. integers or polynomials
× 950
homotopic, if one of them can by continuously deformed to another. This gives rise to an equivalence relation. A group called homotopy group can be obtained from the equivalence clas…
× 942
Questions on the various algorithms used in linear algebra computations (matrix computations).
× 938
The study of competitive and non-competitive games, equilibrium concepts such as Nash equilibrium, and related subjects. Combinatorial games such as Nim are under (combinatorial-game-theory), and algo…
× 928
for questions about extension fields in abstract algebra. An extension field of a field K is just a field containing K as subfield, but interesting questions arise with them. Use this…
× 924
Questions on the factorial function, $n!=n\times(n-1)\times\cdots\times1$. Consider using the tag (gamma-function) if dealing with noninteger arguments.
× 919
Questions related to Brownian motion, a continuous stochastic process denoted by $W_t$, $t\geq 0$, with independent increments, such that $W(t)-W(s)$ is normally distributed, with $0$ mean and varianc…
× 908
structures which behave similar to a power set with complement, intersection and union. Questions regarding Boolean algebras as structures, or regarding functions defined from/to …
× 906
Questions on coordinate systems, a geometric method where a point in n-dimensions is assigned a corresponding n-tuple of numbers.
× 900
the probability that an event occurs given something else has already occurred.
× 872
any representation of a mathematical expression in terms of "known" functions, "known" usually being replaced with "elementary".
× 864
is for things related to 3-dimensions. For geometry of 3-dimensional solids, please use instead (solid-geometry). For geometry that is not on a plane, but otherwise agnostic of dimensions…
× 826
Questions asking for a "big list" of examples, illustrations, etc. Ask only when the topic is compelling, and please do not use this as the only tag for a question.
× 826
Questions about Turing computability and recursion theory, including the halting problem and other unsolvable problems. Questions about the resources required to solving particular problems should be …
× 800
for questions about Schwartz distributions, also known as Generalised Functions. For questions about "probability distributions", use (probability-distributions). For questions about dist…
× 781
Questions concerning predicate calculus, i.e. the logic of quantifiers.
× 779
an algebraic variety of dimension one. An affine algebraic curve can be described as the zero-locus of $n-1$ independent polynomials of $n$ variables in affine $n$-space over a f…
× 773
For questions about uniform convergence of a sequence or a series of functions on a set. Also used with the tag [convergence].
× 771
Questions on the calculus of variations, which deals with the optimization of functionals mostly defined on an infinite dimensional spaces.
× 770
a common set-theoretic axiom with many equivalents and consequences. This tag is for questions on where we use it in certain proofs, and how things would work without the assump…