Tags
A tag is a keyword or label that categorizes your question with other, similar questions.
If $(X,\rho)$ is a metric space, then for any subset $S$, we have $$
H_\delta^d(S):=\inf\ \left\{ \sum_{i=1}^\infty ({\rm diam}\ U_i)^d |
S\subset \bigcup_{i=1}^\infty U_i,\ {\rm diam}\ U_i < \delta \right\}, $$
where the infimum is over all countable covers of $S$. Then we have $H^d(S):=\lim_{\delta \rightarrow 0 } H^d_\delta (S)$,
which is called the $d$-dimensional Hausdorff measure.
291 questions
Sieve theory deals with number theoretic sieves, and sifted sets. E.g. the Sieve of Eratosthenes, Brun sieve, and other modern sieves.
289 questions
Computational algebra is an area of algebra that seeks efficient algorithms to answer fundamental problems concerning basic algebraic objects (groups, rings, fields, etc.). For questions about generic computer algebra systems, use [tag:computer-algebra-systems].
287 questions
Diophantine equations where all of the terms are monomials of degree zero or one. For example, finding all integers $x$ satisfying $ax = b$, finding all integers $x,y$ such that $ax + by = c$, or finding all integers $x,y,z$ such that $ax + by + cz = d$. Probably appropriate with (elementary-number-theory).
286 questions
This tag is for questions relating to Eulerian paths in graphs. An "Eulerian path" or "Eulerian trail" in a graph is a walk that uses each edge of the graph exactly once. An Eulerian path is "closed" if it starts and ends at the same vertex.
286 questions
In the mathematical field of Topology, a uniform space is a generalization of the concept of metric spaces in which, unlike what happens in general topological spaces, it is possible to compare neighborhoods of distinct points. In uniform spaces, it is possible to define the concepts of uniform continuity, uniform convergence, and of complete space (as in the metric spaces, but unlike what happens in topological spaces in general).
285 questions
Even functions have reflective symmetry across the $y$-axis; odd functions have rotational symmetry about the origin.
284 questions
The condition number of a matrix is the ratio of the largest to the smallest singular value in the singular value decomposition of a matrix.
284 questions
For questions about Rolle's Theorem, or exercises that suggest the use of Rolle's Theorem. The theorem states that if a real-valued differentiable function has two distinct zeros, then the function has a vanishing derivative for some value between those two zeros.
283 questions
"The centroid or geometric center of a plane or solid figure is the arithmetic mean ("average") position of all the points in the shape. "
This tag is for questions about the centroid of a geometrical shape, its properties and computation.
283 questions
The uvw method is a very useful method for the proof of polynomial inequalities with three variables. Sometimes it works for more variables as well. This tag should be used for questions that could be tackled with this method, or questions about the method itself.
282 questions
This tag is meant for questions concerning the use of units in the measurement of a quantity.
282 questions
The study of geometry of manifolds without appealing to differential calculus. It includes studies of length spaces, Alexandrov spaces, and CAT(k) spaces. The techniques are often applicable to Riemannian/Finsler geometry (where differential calculus is used) and geometric group theory. For questions about plain-old metric spaces, please use (metric-spaces) instead.
282 questions
Questions relating to the representations of the absolute Galois group $\mathrm{Gal}(\overline K/K)$ of a number field or of a local field.
282 questions
A formal system is broadly defined as any well-defined system of abstract thought based on the model of mathematics. (Def: http://en.m.wikipedia.org/wiki/Formal_system)
282 questions
Question on minimal surfaces, or surfaces that have zero mean curvature.
281 questions
A linear group or matrix group is a group $G$ whose elements are invertible $n \times n$ matrices over a field $F$.
280 questions
Topological K-theory is a generalized cohomology theory, for which $K_0(X)$ is the Grothendieck group of isomorphism classes of vector bundles over topological space $X$. See also (algebraic-k-theory).
279 questions
For geometric questions about solving spherical triangles and spherical polygons on spheres.
279 questions
For questions about logistic regressions, a regression model where the dependent variable is categorical.
278 questions
A simple graph has a symmetric matrix L = D - A associated with it called the Laplacian matrix, where D is the diagonal matrix of degrees and A is the adjacency matrix, often studied for its spectrum (eigenvalues).
277 questions
A matrix associated to a transition of a Markov chain. The entries of this matrix represents a probability with the sum of a whole column being $1$.
276 questions
Gauss Divergence Theorem relates the flux of a vector field through a closed surface to the divergence of the field in the volume enclosed.
276 questions
For questions regarding formal decision problems. In contrast, questions involving strategic aspects (where the solution depends on the behavior of others) are discussed in game theory.
274 questions
The Ricci flow on a Riemannian manifold $(M,g)$ is determined by the geometric evolution equation $\partial_t g_{ij} = -2R_{ij}$ where $R_{ij}$ is the Ricci curvature. The Ricci flow is the main ingredient in Perelman's proof of the Poincaré conjecture.
273 questions
For topics of a combinatorial character in set theory. Topics belonging to "combinatorial set theory" may be tagged this way. These include: Partition calculus, diamond principles, square principles, combinatorial properties of infinite graphs or partial orders, etc.
273 questions
Use this tag for questions related to integers such that the only positive integer that divides them is 1.
273 questions
Numeric computation usually uses floating point numbers. Symbolic computations use symbols, and can give exact answers, such as $\sum_{n=1}^\infty \frac{1}{n^2} = \frac{\pi^2}{6}$. Mathematica, Maple, and Geometry Expressions all use symbolic computation, when desired. An online source is WolframAlpha.
272 questions
In number theory, the law of quadratic reciprocity is a theorem about modular arithmetic that gives conditions for the solvability of quadratic equations modulo prime numbers. (Ref: http://en.m.wikipedia.org/wiki/Quadratic_reciprocity)
272 questions
For question about matrices and their algebraic properties. Together with [tag:linear-algebra] if necessary.
272 questions
This tag is for questions about mean-square-error. In statistics, the mean squared error (MSE) of an estimator measures the average of the squares of the errors or deviations, that is, the difference between the estimator and what is estimated.
271 questions
Questions relating to the Gram–Schmidt process, which takes a set of input vectors and produces an orthonormal set of vectors that spans the same subspace as the input set.
271 questions
For questions relating to the computation, estimation and properties of extremely large finite quantities that are not usually used in mainstream mathematics. This is not for questions that just have large numbers; the fact that a number is very large has to affect the question.
270 questions