42,772 articles
Hyperbolic shear polaritons
Hyperbolic shear polaritons are hybrid light-matter quasiparticles arising in low-symmetry monoclinic and triclinic crystals, first demonstrated in beta-phase gallium oxide and reported in Nature in February 2022.
Hyperbolic surface
A hyperbolic surface is a two-dimensional surface with constant Gaussian curvature −1, locally like the hyperbolic plane, existing on closed orientable surfaces of genus at least 2.
Hypercomplex number
A hypercomplex number, also called a hypercomplex system, is an element of a finite-dimensional algebra with identity over the real numbers; examples include the quaternions, octonions, and Clifford algebras.
Hyperconjugation
Hyperconjugation, also called σ-conjugation or no-bond resonance, is the stabilizing interaction of a sigma bond, usually C−H or C−C, with an adjacent empty or partially filled p, π, or π orbital.
Hypercrosslinked polymer CO2 sorbents
Hypercrosslinked polymer CO2 sorbents are porous organic adsorbents in which heavily crosslinked aromatic networks bind carbon dioxide, a cheap, stable class of solid sorbents for carbon capture.
Hypercube
A hypercube, also called an n-cube or measure polytope, is the generalization of the ordinary three-dimensional cube to n dimensions; the sequence runs point, segment, square, cube, and tesseract, each step doubling the vertex count.
Hypercube graph
The hypercube graph, also called the n-cube or Boolean cube, is the graph formed by binary strings of length n, with edges between strings differing in one bit.
Hyperelastic material
A hyperelastic material, also called a Green elastic material, is an elastic material whose stress-strain relationship derives from a single strain energy density function, typical of rubber and soft tissues.
Hyperferroelectricity
Hyperferroelectricity is a proposed class of proper ferroelectricity, introduced in 2014, in which materials keep switchable polarization despite an unscreened depolarization field; no candidate is yet experimentally confirmed.
Hyperfine structure
Hyperfine structure, also called hyperfine splitting or hyperfine interaction, is the small splitting of atomic energy levels by magnetic interaction between the nuclear spin and the electrons.
Hyperfine sublevel correlation spectroscopy
Hyperfine sublevel correlation (HYSCORE) spectroscopy is a two-dimensional pulsed EPR experiment, reported in 1986, that identifies nuclei coupled to an electron spin and measures their hyperfine couplings.
Hyperfinite type II factor
The hyperfinite type II₁ factor, usually written R, is a von Neumann algebra approximated by finite-dimensional matrix algebras, unique of its type, introduced by Murray and von Neumann in 1943.
Hyperfinite type II₁ factor
The hyperfinite type II₁ factor R is the unique infinite-dimensional von Neumann algebra that is a factor, carries a finite trace, and is a limit of matrix algebras.
Hyperfocal distance
Hyperfocal distance is the focus distance at which a lens's depth of field extends from half that distance to infinity, widely used in landscape, street, and documentary photography.
Hypergeometric distribution
The hypergeometric distribution is a discrete probability distribution counting successes in a random sample drawn without replacement from a finite population, used in acceptance sampling and Fisher's exact test.
Hypergeometric function
The hypergeometric function, also known as the Gauss hypergeometric function or ₂F₁, is a special function defined by a power series that solves a broad class of differential equations.
Hypergeometric series
A hypergeometric series is a power series in which the ratio of consecutive coefficients is a rational function of the index, named by Euler in 1769 and made rigorous by Gauss in 1812.
Hypergiant
A hypergiant is an extremely luminous, massive star showing very high mass loss through stellar winds, classed 0 or Ia+ and lacking an official definition.
Hypergraph
A hypergraph is a generalization of a graph in which an edge may join any number of vertices rather than exactly two; an ordinary graph is a 2-uniform case.
Hypergraph matching
Hypergraph matching is the problem of finding a largest collection of pairwise disjoint edges in a hypergraph; it is NP-hard when edges contain 3 or more vertices.
Hypergraph regularity method
The hypergraph regularity method is an extremal combinatorics technique decomposing any large hypergraph into pseudorandom blocks. It extends Szemerédi's regularity lemma and yields the hypergraph removal lemma.
Hypergraph removal lemma
The hypergraph removal lemma is a theorem of extremal combinatorics stating that a hypergraph with few copies of a fixed hypergraph F can be made F-free by deleting few edges.
Hypericin
Hypericin is a photosensitizing pigment produced by St John's wort (Hypericum perforatum), first isolated in 1939, used as a herbal medicine marker and in photodynamic therapy of cancer.
Hyperlens
A hyperlens is a curved optical device made of a hyperbolic metamaterial that images below the diffraction limit by converting evanescent waves into propagating ones.
Hypermassive neutron star
A hypermassive neutron star (HMNS) is a briefly stable merger remnant whose mass exceeds the maximum nonrotating neutron star mass, supported only by differential rotation and heat.
Hypernova
A hypernova is an exceptionally energetic stellar explosion, generally a broad-lined Type Ic supernova with energy about ten times that of a typical supernova, often accompanying long-duration gamma-ray bursts.
Hypernucleus
A hypernucleus is a subatomic bound system in which a nucleus of protons and neutrons contains at least one hyperon, a baryon with strange quarks.
Hyperon puzzle
The hyperon puzzle is the conflict in neutron star physics between the predicted appearance of hyperons in stellar cores and observed masses above two solar masses, which hyperons make hard to explain.
HyperPhysics
HyperPhysics is a free web-based physics reference built as concept maps of linked cards, created by Georgia State University physicist Rod Nave and online since 1998.
Hyperplane
A hyperplane is a subspace of one dimension less than its space: a plane in 3D, a line in 2D, generalizing the plane to any dimension.