Tags
A tag is a keyword or label that categorizes your question with other, similar questions.
For questions related to skew-symmetric (or antisymmetric or antimetric) matrix.
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Use this tag for questions about $p$-variation norms, the study of finiteness of the $p$- variation of functions, which is a generalization of the total variation.
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Nomography is a branch of mathematics which studies functional dependencies through graphical representation methods, called nomograms or nomographs.
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In mathematics, Lie algebroids serve the same role in the theory of Lie groupoids that Lie algebras serve in the theory of Lie groups: reducing global problems to infinitesimal ones.
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In abstract algebra, Green's relations are five equivalence relations that characterise the elements of a semigroup in terms of the principal ideals they generate. Use it along with (semi-group) and (abstract-algebra). DO NOT confuse it with (greens-theorem) or (greens-identities).
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Use for questions about embeddings of graphs in surfaces of genus greater than 0. For embeddings of graphs in planes, spheres, and other simply-connected spaces, use [planar-graphs].
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Use this tag for questions about combinatorial and geometric structures (buildings) that generalize simultaneously certain aspects of flag manifolds, finite projective planes, and Riemannian symmetric spaces.
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For questions related to bilinear operator. It's a function combining two elements of a vector space to yield a third element of the same space that is linear in each of its arguments.
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[Bicategories](https://en.wikipedia.org/wiki/Bicategory) are weak form of categories enriched over the category of categories that has a notion of $2$-morphisms (morphisms between ordinary morphisms). Primordial example for a bicategory is objects, spans, and morphisms of spans in any category with pullbacks. This concept is closely related with the notions of strict $2$-categories and double categories. Use conjunction with those tags as necessary.
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The mathematical analogue of the Bohr correspondence principle, which states that in the $\hbar\to 0$ limit quantum mechanics should approach classical mechanics. For many evolution equations, this suggests that the high frequency limit of partial differential equations should be able to be approximated by dynamical systems (ordinary differential equations). Semiclassical analysis aims at making these intuitions precise.
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Apt for questions related to reflection group (discrete group which is generated by a set of reflections of a finite-dimensional Euclidean space).
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For questions related to proper maps. A function between topological spaces is called proper if inverse images of compact subsets are compact.
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A homology sphere is an $n$-dimensional topological manifold that has the same integral homology as the $n$-sphere.
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Galois rings are a class of finite commutative rings generalizing both the finite fields and the integer residue rings modulo a prime power in a quite natural way. Their name stems from the fact that they share a lot of properties with the finite fields. A Galois ring $R$ is usually denoted by $\operatorname{GR}(p^m,r)$, where $p^m$ is the characteristic of $R$, $p$ is prime and $\left|R\right| = p^{mr}$.
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This tag is for questions relating to the Fermi-Dirac Integrals named after Enrico Fermi and Paul Dirac. Fermi–Dirac integrals arise in calculating pressure and density in degenerate matter, such as neutron stars; they also occur in the electronic density of semiconductors.
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For question concerning foliation theory in the holomorphic case: germs of foliation singularities, holomorphic foliations on complex manifolds, Pfaff fields, etc.
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The Hermite normal form is an analog of reduced echelon form for matrices over the integers $\mathbb Z$. It can solve problems about the solution to the linear system $Ax=b$ where $x$ is restricted to have integer coordinates only. To be Used with the subject tag [linear-algebra].
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The $h$-principle also known as homotopy principle applies to partial differential relations (PDRs) for which any underlying formal/algebraic solution is homotopic to a real one. The $h$-principle allows to boil down a differential topological problem to a topological one.
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For (a) questions on category theory regarding the notion of equivalence between categories (and any extensions of this concept) and (b) questions regarding the some specific equivalence between two particular categories (e.g., Gelfand duality, the equivalence between finite-dimensional real Lie algebras and simply connected Lie groups, the equivalence between commutative rings and affine schemes, etc.)
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In mathematics, a (left) coherent ring is a ring in which every finitely generated left ideal is finitely presented.
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For questions involving Tychonoff spaces, or topological spaces satisfying the $T_{3 \frac 1 2}$ separation axiom.
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For questions related to Morita equivalence. $2$ rings like $R, S$ are Morita equivalent (denoted by $R\approx S$) if their categories of modules are additively equivalent (denoted by ${}_{R}M\approx {}_{S}M$).
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A monomial order is a total order on the set of all (monic) monomials in a given polynomial ring, satisfying the property of respecting multiplication.
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Generalization of a Dirichlet character to construct a class of L-functions.
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A differential field is a commutative field equipped with derivations.
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A differential-algebraic system of equations (DAEs) is a system of equations that either contains differential equations and algebraic equations, or is equivalent to such a system.
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Dagger categories have a contravariant, involutive dagger functor which captures the idea of "adjoint maps". Hilbert spaces, *-algebras or sets and relations are examples.
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For questions about comodules over corings, coalgebras, bialgebras, Hopf algebras.
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For AlgGeom questions related to varieties, with or without the methods of scheme theory for their formulation or solution. Examples of the 'without' case are variety theory as understood by Serre in FAC and GAGA, or the study of algebraic subsets of the classical affine and projective spaces ₖⁿ=kⁿ, ℙₖⁿ=ₖⁿ⁺¹/k*, as exemplified in books such as W. Fulton, Algebraic Curves, J. Harris, Algebraic Geometry: a first course, or J. S. Milne, Algebraic Geometry
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For questions regarding groups of even prime power order, as distinct from p-groups in general. Topics include 2-groups of maximal class, 2-groups as Sylow subgroups, and the conjecture that almost all groups are 2-groups. Not intended for use with the p-groups tag.
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This tag concerns topics in ultrafinitist philosophy, its implications in mathematical logic, and the practical consequences to other areas of mathematics. Use (ultrafinitism) for ultrafinitism, and (finitism) for classical finitism and strict finitism.
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Strichartz estimates are a family of inequalities for linear dispersive partial differential equations, that arose out of contentions to the Fourier restriction problem. These inequalities establish size and decay of solutions in mixed norm Lebesgue spaces.
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For questions related to Schur's inequality. Schur's inequality is a classical inequality that relates three non-negative real numbers.
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