Every idea

Ideas 19501–19650 of 19934.

Name	Kind	Subject
Undecidability of the halting problem	Theorem	Mathematical logic and foundations
Morris–Lecar model	Concept	Biology and other natural sciences
Symmetric and self-reciprocal kernels	Definition	Integral transforms, operational calculus
Curve-shortening flow	Definition	Differential geometry
Variable-mass system	Concept	Mechanics of particles and systems
Almost periodic sequence	Concept	Difference and functional equations
Tensor decomposition	Definition	Linear and multilinear algebra; matrix theory
Word problem for free lattices	Theorem	Order, lattices, ordered algebraic structures
Stone–von Neumann theorem	Theorem	Topological groups, Lie groups
Essentially self-adjoint operator	Definition	Operator theory
Euler integral for the gamma function	Theorem	Special functions
Gravitational memory effect	Fact	Relativity and gravitational theory
Vibration of plates	Concept	Mechanics of deformable solids
Finite-rank operator	Concept	Operator theory
Synge's theorem	Theorem	Differential geometry
Monogenic function	Definition	Functions of a complex variable
Hopf manifold	Example	Several complex variables and analytic spaces
Fourier series of Bernoulli polynomials	Example	Harmonic analysis on Euclidean spaces
Martin's axiom	Definition	Mathematical logic and foundations
Christoffel symbols	Definition	Differential geometry
Metamaterial cloaking	Definition	Optics, electromagnetic theory
Congruence lattice	Definition	General algebraic systems
Reeb stability theorem	Theorem	Manifolds and cell complexes
Riemann problem for gas dynamics	Problem	Fluid mechanics
Bellman equation	Concept	Operations research, mathematical programming
Kervaire invariant problem	Problem	Algebraic topology
Parametrix	Concept	Global analysis, analysis on manifolds
Kasparov product	Definition	K-theory
McEliece cryptosystem	Definition	Information and communication theory, circuits
Weil divisor	Concept	Algebraic geometry
Topological manifold	Definition	Manifolds and cell complexes
Aizenman–Higuchi theorem	Theorem	Statistical mechanics, structure of matter
Flag variety	Definition	Algebraic geometry
Zinbiel algebra	Definition	Nonassociative rings and algebras
Steinberg group	Definition	K-theory
Young–Laplace equation	Theorem	Fluid mechanics
Prime ring	Concept	Associative rings and algebras
Short-rate model	Definition	Game theory, economics, finance, and other social and behavioral sciences
Symbol class	Definition	Partial differential equations
Hurewicz theorem	Theorem	Algebraic topology
Transform pair	Concept	Integral transforms, operational calculus
Dehn surgery	Concept	Manifolds and cell complexes
CSP dichotomy theorem	Theorem	General algebraic systems
S-wave	Definition	Mechanics of deformable solids
Singular perturbation	Definition	Ordinary differential equations
Boutet de Monvel's embedding theorem	Theorem	Several complex variables and analytic spaces
Curvature form	Concept	Differential geometry
Prim's algorithm	Concept	Combinatorics
Well-founded order	Definition	Order, lattices, ordered algebraic structures
Diversity index	Definition	Biology and other natural sciences
Allen–Cahn equation	Definition	Partial differential equations
Moment map	Concept	Differential geometry
Heat potential	Concept	Partial differential equations
Linear discriminant analysis	Concept	Statistics
Subadditive function	Definition	Difference and functional equations
Ramsey problem of optimal taxation	Problem	Game theory, economics, finance, and other social and behavioral sciences
Steiner conic	Definition	Geometry
Skin effect	Definition	Optics, electromagnetic theory
First and second variation of arc length	Theorem	Differential geometry
Relativistic mechanics	Concept	Relativity and gravitational theory
Modern portfolio theory	Concept	Game theory, economics, finance, and other social and behavioral sciences
Costas array	Definition	Combinatorics
Gowers norm	Concept	Number theory
Theta correspondence	Concept	Number theory
Fundamental groupoid	Concept	Algebraic topology
Lattice gauge theory	Concept	Quantum theory
Category of posets	Concept	Category theory; homological algebra
Cauchy's functional equation	Problem	Difference and functional equations
Power series in several variables	Definition	Several complex variables and analytic spaces
Cartan matrix of an algebra	Concept	Associative rings and algebras
Kohn Laplacian	Concept	Several complex variables and analytic spaces
Bernstein's theorem on monotone functions	Theorem	Real functions
Radial basis function	Concept	Approximations and expansions
Fuchsian equation	Concept	Ordinary differential equations
Hirsch conjecture	Counterexample	Convex and discrete geometry
K2 of the integers	Example	K-theory
Littlewood–Paley square function	Definition	Harmonic analysis on Euclidean spaces
Quadratic variation	Definition	Probability theory and stochastic processes
Normal form	Definition	Ordinary differential equations
Universal bundle	Definition	Algebraic topology
Principle of virtual work	Theorem	Mechanics of particles and systems
Beth number	Definition	Mathematical logic and foundations
Travel-time curve	Definition	Geophysics
Spacetime	Definition	Relativity and gravitational theory
CR manifold	Concept	Several complex variables and analytic spaces
Lawson topology	Concept	Order, lattices, ordered algebraic structures
Functional equation of the gamma function	Theorem	Special functions
Moishezon manifold	Definition	Several complex variables and analytic spaces
Nonlinear Schrödinger equation in optics	Definition	Optics, electromagnetic theory
Hermite equation	Example	Ordinary differential equations
Alexandrov's theorem on polyhedra	Theorem	Convex and discrete geometry
Regular cardinal	Definition	Mathematical logic and foundations
Mathieu function	Definition	Special functions
Global optimization	Concept	Operations research, mathematical programming
Amenable group action	Concept	Abstract harmonic analysis
Karp's 21 NP-complete problems	Example	Computer science
Infinitesimal strain theory	Definition	Mechanics of deformable solids
Varifold	Definition	Calculus of variations and optimal control; optimization
Minimum-variance unbiased estimator	Concept	Statistics
Microcanonical ensemble	Definition	Statistical mechanics, structure of matter
Top trading cycle	Concept	Game theory, economics, finance, and other social and behavioral sciences
Boolean network	Definition	Biology and other natural sciences
Lagrange basis polynomials	Definition	Approximations and expansions
Immersion	Definition	Manifolds and cell complexes
Division with remainder for natural numbers	Theorem	Number theory
Concrete category of algebras	Concept	General algebraic systems
Roche lobe	Definition	Mechanics of particles and systems
Primary decomposition	Concept	Commutative algebra
Birational map	Definition	Algebraic geometry
Barratt–Priddy–Quillen theorem	Theorem	Algebraic topology
Sklar's theorem	Theorem	Statistics
Blocking set	Concept	Geometry
Ehrhart–Macdonald reciprocity	Theorem	Convex and discrete geometry
Bareiss algorithm	Theorem	Numerical analysis
Semilocal ring	Concept	Associative rings and algebras
Manifold of smooth mappings	Definition	Global analysis, analysis on manifolds
Kolmogorov microscales	Definition	Fluid mechanics
Harmonic majorant	Concept	Potential theory
Permutation group	Concept	Group theory and generalizations
Continuous lattice	Definition	Order, lattices, ordered algebraic structures
Integral equation of the first kind	Concept	Integral equations
Fluid dynamics	Definition	Fluid mechanics
Colombeau algebra	Definition	Functional analysis
Spin factor	Example	Nonassociative rings and algebras
Potential of a measure	Definition	Potential theory
Tikhonov regularization	Definition	Operator theory
Hartley transform	Definition	Integral transforms, operational calculus
Isothermal process	Definition	Classical thermodynamics, heat transfer
Barrelled space	Concept	Functional analysis
Anti-equivalence of affine schemes and rings	Theorem	Algebraic geometry
Fundamental class	Concept	Manifolds and cell complexes
Smirnov's theorem on conformal invariance of percolation	Theorem	Statistical mechanics, structure of matter
Join	Concept	General topology
E-theory	Definition	K-theory
Haldane conjecture	Conjecture	Statistical mechanics, structure of matter
Ocean wave spectrum	Definition	Geophysics
Support of a measure	Definition	Measure and integration
Method of images	Definition	Potential theory
Hartogs lemma for subharmonic functions	Lemma	Potential theory
Many-sorted algebra	Definition	General algebraic systems
Cosmological principle	Definition	Relativity and gravitational theory
Irreducible matrix	Definition	Linear and multilinear algebra; matrix theory
Haar measure on the circle	Example	Abstract harmonic analysis
Variogram	Concept	Statistics
Dirac operator	Definition	Global analysis, analysis on manifolds
Δ-complex	Concept	Algebraic topology
BCM theory	Definition	Biology and other natural sciences
Fundamental groupoid	Definition	Algebraic topology
Stochastic game	Definition	Game theory, economics, finance, and other social and behavioral sciences
Kirby calculus	Definition	Manifolds and cell complexes