42,772 articles
Hilbert's sixth problem
Hilbert's sixth problem is one of the 23 problems David Hilbert posed at the International Congress of Mathematicians in Paris in 1900, asking that mathematics axiomatize probability and mechanics.
Hilbert's tenth problem
Hilbert's tenth problem is the 1900 challenge of finding an algorithm that decides whether any Diophantine equation has integer solutions; Matiyasevich proved in 1970 that none exists.
Hilbert's Theorem 90
Hilbert's Theorem 90 is an algebra theorem stating that for a finite cyclic field extension, every norm-one element is a quotient y/σ(y), proved as Satz 90 of Hilbert's 1897 Zahlbericht.
Hilbert's twelfth problem
Hilbert's twelfth problem, also known as Kronecker's Jugendtraum, was posed by David Hilbert in 1900 and asks for explicit constructions of all abelian extensions of a number field.
Hilda Hänchen
Hilda Hänchen was a German physicist at Hamburg's National Physical Institute who co-discovered the Goos–Hänchen effect, the lateral shift of light under total internal reflection, in 1947.
Hilding Faxén
Hilding Faxén (Olov Hilding Faxén) was a Swedish physicist known for the Faxén correction and Faxén's theorem, which describe the drag on a sphere in slowly varying viscous flow.
Hilkka I. Kenttämaa
Hilkka I. Kenttämaa, also written Hilkka Kenttamaa, is a Finnish-born chemist at Purdue University known for mass spectrometry studies of reactive intermediates and the LIAD technique.
Hill cipher
The Hill cipher is a classical polygraphic cipher invented by Lester S. Hill in 1929 that encrypts blocks of letters using an invertible key matrix modulo 26.
Hill differential equation
The Hill differential equation is a second-order linear differential equation with a periodic coefficient, introduced by George William Hill in 1878 to study the Moon's motion.
Hill sphere
The Hill sphere, also called the Roche sphere, is the region around a celestial body within which its gravity dominates the orbits of satellites against a more massive body.
Hill's lunar equations
Hill's lunar equations are the equations of motion introduced by George William Hill in his 1878 paper on the lunar theory, describing the Moon's motion around the Earth under solar perturbation.
Hill's spherical vortex
Hill's spherical vortex is an exact inviscid-fluid solution in which a sphere of vorticity translates steadily through otherwise irrotational fluid, found by M. J. M. Hill in 1894.
Hille–Yosida theorem
The Hille–Yosida theorem, proved independently by Einar Hille and Kôsaku Yosida in the late 1940s, characterizes which linear operators generate strongly continuous one-parameter semigroups on a Banach space.
Hillel Furstenberg
Hillel (Harry) Furstenberg, born 1935, is a mathematician who spent his career at the Hebrew University of Jerusalem, known for ergodic theory and for sharing the 2020 Abel Prize.
Hilmar Wendt
Hilmar Wendt (1913–2002) was a German mathematician who co-named the Hantzsche–Wendt manifold and held a chair of practical mathematics at the University of Bonn from 1948 to 1981.
Himalayan salt
Himalayan salt, also sold as Himalayan pink salt or pink rock salt, is a rock salt mined mainly at the Khewra Salt Mine in Punjab, Pakistan, with its pink color from iron oxides.
Himalia
Himalia, Jupiter VI, is the fifth largest moon of Jupiter, discovered by Charles Perrine in 1904; a dark, irregular body about 85 km in radius.
Himawari-8
Himawari-8 is a Japanese geostationary meteorological satellite launched in 2014 and operated by the Japan Meteorological Agency, observing East Asia and the western Pacific with a 16-band imager.
Himawari-9
Himawari-9 (ひまわり9号) is a Japanese geostationary weather satellite operated by the Japan Meteorological Agency, launched in 2016 and Japan's primary observation satellite since December 2022.
Hindcasting
Hindcasting, known in geosciences as reforecasting, runs a predictive model over a past period and compares its output with withheld observations to estimate forecast skill.
Hindley–Milner type system
The Hindley–Milner type system, also known as Hindley–Milner type inference, is a polymorphic type system for the lambda calculus, the foundation of type inference in ML, OCaml, and Haskell.
Hindu calendar (पञ्चाङ्ग)
The Hindu calendar, called Panchanga (पञ्चाङ्ग, "five limbs"), is a family of lunisolar and solar calendars across India and Nepal, chiefly used to fix dates of Hindu festivals and rituals.
Hindu units of time
Hindu units of time, also called Vedic timekeeping, are the traditional Indian measures of duration, from the nimeṣa blink up to the yuga and kalpa.
Hing Tong
Hing Tong was a mathematician who proved the Katětov–Tong insertion theorem, characterizing normal topological spaces, in a 1952 paper in Duke Mathematical Journal; Miroslav Katětov proved it independently in 1951.
Hinge
A hinge is a mechanical bearing connecting two rigid objects, typically a door and frame, allowing rotation about one fixed axis while blocking all other motion.
Hinode
Hinode (ひので, Japanese for "Sunrise"), known before launch as Solar-B, is a Japanese solar-observing satellite launched by JAXA in 2006 to study the Sun's magnetic field.
Hinokitiol
Hinokitiol (β-thujaplicin, 桧木醇) is a naturally occurring tropolone found in cypress wood, isolated by Tetsuo Nozoe in 1936 and known for chelating iron, copper, and zinc.
Hioki E.E. Corporation
Hioki E.E. Corporation (日置電機株式会社) is a Japanese manufacturer of electrical test and measuring instruments, founded in 1935 and headquartered in Ueda, Nagano Prefecture, known especially for battery testers and clamp-on power meters.
Hip strategy
The hip strategy is a balance-recovery technique using hip-joint torque instead of ankle torque, one of three classical postural strategies and a named control mode in humanoid robotics.
Hipparchus (Ἵππαρχος)
Hipparchus (Ἵππαρχος) was a Greek astronomer and mathematician born at Nicaea in Bithynia who discovered the precession of the equinoxes and is credited with the first known star catalog.