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.

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injective if $\hom_{R}({-},I)$ is exact. The notion of injective modules is dual to the notion of a projective module. In homological algebra injective modules are used…
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In the mathematical field of topology, a uniform space is a set with a uniform structure. (Def: http://en.m.wikipedia.org/wiki/Uniform_space)
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The operator which best approximates a solution to a linear system with a singular (non-invertible) matrix.: e.g., the Moore-Penrose pseudoinverse. Use when a question concerns a matrix that is probab…
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Questions concerning the Cantor set, which consists of those real numbers in [0,1] that remain after repeatedly removing the open middle third of every interval; it contains those numbers which may be…
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For questions about strictly stationary or stationary in the wide sense sequences or processes. Questions about deterministic stationary processes (in the case of discrete dynamical systems) are welco…
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the mathematical study of changes in the qualitative or topological structure of a given family, such as the integral curves of a family of vector fields, and the solutions of a …
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the property shared by many binary operations including group operations. For a binary operation $\cdot$, associativity holds if $(x\cdot y)\cdot z = x \cdot(y\cdot z)$.
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For questions on prime twins.
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about questions regarding Initial value problems. In the field of differential equations, an initial value problem is an ordinary differential equation together with a specified value, cal…
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For questions about categorical limits and colimits.
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Questions on finding integer solutions to bivariate equations of the form $x^2-Dy^2=a$.
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In mathematics, a monotonic function (or monotone function) is a function between ordered sets that preserves or reverses the given order. This concept first arose in calculus, and was later generaliz…
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For questions about hash functions: functions from a big set to a smaller one such that the same output $f(x_1)=f(x_2)$ for different input $x_1\ne x_2$ is unlikely, especially if $x_2$ differs from $…
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In mathematics, particularly in algebraic geometry, complex analysis and number theory, an abelian variety is a projective algebraic variety that is also an algebraic group, i.e., has a group law that…
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In mathematics, especially in algebraic geometry and the theory of complex manifolds, coherent sheaves are a specific class of sheaves having particularly manageable properties closely linked to the g…
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for questions about Green's theorem. Green's theorem gives the relationship between a line integral around a simple closed curve $C$ and a double integral over the plane region $D$ bounded…
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For question regarding the notion of orientation both in topology and in global analysis.
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The function that maps a real number $x$ to the smallest integer greater than or equal to $x$ (which is often denoted $\lceil x\rceil$. See also (floor-function).
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when posting questions related to the concept of convexity and geometry. For example, for convex polygons.
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For questions relating to the computation, estimation and properties of extremely large quantities that are not usually used in mainstream mathematics.
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Regularization, in mathematics and statistics and particularly in the fields of machine learning and inverse problems, refers to a process of introducing additional information in order to solve an il…
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For questions concerning the mathematical software system SageMath. Consider whether your question would be a better fit at [ask SageMath](http://ask.sagemath.org/).
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In formal language theory, a grammar (when the context is not given, often called a formal grammar for clarity) is a set of production rules for strings in a formal language. A formal grammar is a set…
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For questions involving the Borel-Cantelli Lemma or the second Borel-Cantelli Lemma. Use this tag along with (probability-theory), (real-analysis) or (measure-theory)
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an area in the intersection of game theory and algorithm design, whose objective is to design algorithms in strategic environments. (Def: http://en.m.wikipedia.org/wiki/Al…
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Clifford algebras over the real numbers. They are applied in geometry and theoretical physics.
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the term for the theory in which mathematics is formalized (often PA, ZFC or similar theories). Meta-mathematical statements are statements which are evaluated at the level of the meta-…
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For questions related to conversion of units.
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a discrete analogue to the Laplace transform, in that it maps a time domain signal into a representation in complex frequency plane.
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For question about the Schwartz space, a vector space of smooth functions stable under the Fourier transform.
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for questions regarding semidefinite programming (SDP) which is a subfield of convex optimization concerned with the optimization of a linear objective function (an objective function is a…
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In mathematical optimization, the Karush–Kuhn–Tucker (KKT) conditions are first order necessary conditions for a solution in nonlinear programming to be optimal, provided that some regularity conditio…