# Tags

A tag is a keyword or label that categorizes your question with other, similar questions.

A power automorphism of a group is an automorphism that takes each subgroup of the group to within itself.

A matrix pencil in mathematics is a linear equation system, which consists of matrices with complex elements

Use this tag for a general type of quadratic variation of two stochastic processes.

A Chaitin constant, Chaitin omega, or halting probablity is the real number representing the probability a randomly generated program will halt in a specific encoding. It is a normal and transcendental uncomputable number.

For questions concerning the Alexandroff compactification of a locally compact topological space, which is a compact topological space which contains the original space and one extra point.

For questions about the st-connectivity problem in computer science.

The Nichols algebra of a braided vector space is a braided Hopf algebra named after the mathematician Warren Nichols. It takes the role of quantum Borel part of a pointed Hopf algebra.

Multivalued logic is a propositional calculus in which there are more than two truth values.

A group in which every finitely generated subgroup is cyclic.

For questions about the half-normal distribution. It's a non-negative distribution based on the normal distribution.

Given a $S_n$-stable family $F$ of homogeneous polynomials in the variables $x_{ij}$ with $1≤i≤\ell$ and $1≤j≤n$, the polarization module generated by the family $F$ is the smallest vector space closed under taking partial derivatives and closed under the action of polarization operators that contains $F$.

A fusion system of a $p$-group $P$ is the category of subgroups of $P$ and injective group homomorphisms induced by conjugation in $P$. Example topics include control of fusion, blocks, centric and radical subgroups, subsystems and quotients, Alperin's fusion theorem, and normal fusion systems.

Herstein's theory is the study of the nonassociative structures and objects arising from associative rings

Geometric complexity theory aims to solve problems in complexity theory by translating them into problems written in the language of algebraic geometry and representation theory to use the algebro-geometric techniques to solve them.

Use this for questions on the spread of disease through a population resulting in an epidemic or epidemics. These questions often encompass the study of differential equations, stochastic processes, markov chains, and machine learning.

Use for anything related to Judea Pearl's do calculus, in which a quantity of primary interest is a probability of the form $P(x|\operatorname{do}(y)),$ involving the $\operatorname{do}$ operator. Related topics include the back-door criterion, back-door adjustment formula, front-door adjustment formula.

For questions about co-hopfian groups, rings, modules, etc. Namely, objects which are not isomorphic to any proper subobject.