Tags
A tag is a keyword or label that categorizes your question with other, similar questions.
An ellipsoid is a convex set defined by $\mathcal{E} := \left\{ x \in \mathbb R^n \mid (x - x_c)^T P^{-1} (x - x_c) \leq 1 \right\}$ where matrix $P$ is symmetric and positive definite.
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Rigid transformations are mappings from one reference frame to another reference frame in the Euclidean space $\mathbb R^n$. They comprise translation, rotation (and sometimes reflection).
More formally, rigid transformation are elements of the matrix Lie group SE($n$), the specially Euclidean group. If reflection is included, these proper rigid transformations are elements of the matrix Lie group E($n$), the Euclidean group.
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Cayley graphs are graphs obtained from a group $G$ in a such way that vertices are elements of the group and edges are added using some generating set $S\subseteq G$.
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This tag is for questions relating to Total Variation.The concept of total variation for functions of one real variable was first introduced by Camille Jordan in the paper (Jordan 1881). He used the new concept in order to prove a convergence theorem for Fourier series of discontinuous periodic functions whose variation is bounded. The extension of the concept to functions of more than one variable however is not simple for various reasons.
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The entries of a Toeplitz matrix are constant along the diagonals parallel to the main diagonal.
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The general linear group of order $n$, $GL_n(\mathbb{F})$, over a field $\mathbb{F}$ (usually $\mathbb{R}$ or $\mathbb{C}$) is the group of $n\times n$ invertible matrices over $\mathbb{F}$. The operation is the usual matrix multiplicatoin.
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For questions about winding numbers. The winding number of a continuous curve counts how many times it "loops" around a given point.
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Questions concerning morphisms of functors or unnatural isomorphisms.
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A quadratically constrained quadratic program (QCQP) is an optimization problem in which both the objective function and the constraints are quadratic.
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For problems related to involutions , that is functions that are their own inverses .
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For questions about triangulated categories. A triangulated category is an additive category with an additive auto-equivalence called a translation (or shift) functor, and a class of distinguished triangles satisfying various axioms.
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L-functions are meromorphic functions on $\mathbb C$ that are used extensively in number theory.
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Use this tag for questions related to array data structures that compactly store bits.
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Tag for problems about comparing explicitly given numbers, often by hand calculation only.
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For questions on the Young tableau, a combinatorial object useful in representation theory and Schubert calculus. It provides a convenient way to describe the group representations of the symmetric and general linear groups and to study their properties.
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For questions concerning sequent calculus, a formal proof system originally introduced by Gerhard Gentzen in 1933/1935 and studied in the framework of proof theory.
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Euler's method is a numerical method to solve first-order first-degree differential equations with a given initial value.
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Questions about delayed differential equations which are a type of differential equation in which the derivative of the unknown function at a certain time is given in terms of the values of the function at previous times.
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For questions about almost complex structures on manifolds or vector spaces.
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For questions about or using the Weierstrass approximation theorem (or the Stone-Weierstrass theorem). The Weierstrass theorem states that if $f:[a,b]\to\mathbb R$ is continuous and if $\epsilon>0$, then there exists a polynomial $p$ such that
$$
|f(x)-p(x)|<\epsilon $$ for all $x$ in $[a,b]$. In words, any continuous function on a closed and bounded interval can be uniformly approximated on that interval by polynomials to any degree of accuracy.
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A right stochastic matrix is a nonnegative square matrix with each row summing to 1. A left stochastic matrix is a nonnegative square matrix with each column summing to 1. A doubly stochastic matrix is both right stochastic and left stochastic.
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Use this tag for questions regarding sparse matrices, that is matrices with relatively few entries compared to their size. Related: [numerical-methods] and [numerical-linear-algebra].
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A magma is a set together with a binary operation on this set. (For questions about the computer algebra system named Magma, use the [magma-cas] tag instead.)
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For question about fisher information that appears in mathematical statistics.
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For questions related to Yoneda lemma in category theory, which *basically* says (among many other things it says) that every locally small category can be embedded nicely into it's functor category into the category of Sets. Use this tag along with (abstract-algebra) or (category-theory).
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For questions about second-countable topological spaces, i.e., space with countable base.
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For questions involving rings of positive characteristic, particularly those questions whose statements and hypotheses heavily rely on positive characteristic. Consider using the ring-theory tag for questions that apply to rings of all characteristics.
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Magma is a computer algebra system distributed by the University of Sydney, and designed for solving problems in algebra, number theory, geometry and combinatorics.
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