Physical world and mathematics

Harmon Craig

Harmon Craig (1926–2003) was an American isotope geochemist who spent his career at Scripps Institution of Oceanography, pioneering carbon isotope and radiocarbon studies of the global carbon cycle.

Harmon Northrop Morse

Harmon Northrop Morse (1848–1920) was an American chemist at Johns Hopkins University whose fifteen-year osmotic-pressure campaign supplied experimental support for van 't Hoff's theory of solutions.

Harmonic

A harmonic, also called a flageolet tone or harmonic partial, is a component of a periodic sound at a whole-number multiple of the fundamental, and the pattern of harmonics gives a note its timbre.

Harmonic analysis

Harmonic analysis is the branch of mathematics that decomposes functions and signals into sine and cosine waves, the idea behind Fourier series and the Fourier transform.

Sep 29, 2026

Harmonic balance

Harmonic balance, or the harmonic balance method, is a frequency-domain numerical method for the periodic steady-state response of nonlinear circuits, used for amplifiers, mixers, and oscillators.

Harmonic coordinate condition

The harmonic coordinate condition, also called the harmonic gauge or De Donder gauge, is a gauge choice in general relativity requiring each coordinate function to satisfy the wave equation.

Harmonic coordinates

Harmonic coordinates, also known as the harmonic coordinate system or wave coordinates, are a coordinate system in general relativity where each coordinate satisfies the wave equation.

Harmonic form

A harmonic form is a differential form on a Riemannian manifold lying in the kernel of the Hodge Laplacian, central to Hodge theory, which links analysis and topology.

A harmonic function is a twice continuously differentiable function satisfying the Laplace equation, describing steady-state temperatures, electrostatic potentials, and ideal fluid flows; it obeys the mean value property.

Harmonic map

A harmonic map is a mapping between Riemannian manifolds that is a critical point of a natural energy integral, generalizing Dirichlet's integral; the theory was begun systematically by Eells and Sampson in 1964.

Harmonic mean

The harmonic mean is a type of average, one of the three Pythagorean means, calculated as the number of values divided by the sum of their reciprocals.

Harmonic measure

Harmonic measure is a probability measure on a domain's boundary giving where Brownian motion from an interior point first exits, equivalently how boundary values determine solutions of the Dirichlet problem.

Harmonic number

A harmonic number is the sum of the reciprocals of the first n positive integers, a partial sum of the divergent harmonic series that grows like the natural logarithm.

Harmonic oscillator

A harmonic oscillator is any physical system in which a restoring force proportional to displacement from equilibrium produces oscillation, exemplified by a mass on a spring obeying Hooke's law.

Harmonic oscillator model of aromaticity

The harmonic oscillator model of aromaticity (HOMA) is a geometric index, introduced in 1972 by Kruszewski and Krygowski, that measures the aromaticity of cyclic molecules from bond lengths.

Harmonic series (mathematics)

The harmonic series is the infinite sum of 1 + 1/2 + 1/3 + 1/4 + …, which diverges even though its terms tend to zero.

Harmonic superspace

Harmonic superspace is an extension of ordinary superspace, adding harmonic variables on the sphere S², introduced in 1984 by Galperin, Ivanov, Kalitzin, Ogievetsky, and Sokatchev.

HARMONIE-AROME

HARMONIE-AROME is a kilometer-scale, non-hydrostatic numerical weather prediction model for limited-area regional forecasting in which convection is treated explicitly, built on the shared ALADIN-HIRLAM code framework.

Harold Agnew

Harold Agnew was an American physicist who helped build the first nuclear reactor, flew on the Hiroshima mission, and directed Los Alamos from 1970 to 1979.

Harold Baily Dixon

Harold Baily Dixon (1852–1930) was a British chemist who held the Chair of Chemistry at Owens College, Manchester, and became a leading authority on flames in gaseous explosions.

Harold Brown (physicist)

Harold Brown (1927–2019) was an American nuclear physicist who directed Lawrence Livermore, led Caltech, and was the first scientist to serve as U.S. Secretary of Defense.

Harold C. Urey

Harold Clayton Urey was an American chemist who won the 1934 Nobel Prize in Chemistry for discovering deuterium, then founded isotope geochemistry and cosmochemistry, studying the Moon into the 1970s.

Harold Davenport

Harold Davenport (1907–1969) was a British mathematician and leading figure of the mid-century British school of number theory, working on Waring's problem, additive group theory, and Diophantine approximation.

Harold Delos Babcock

Harold Delos Babcock (1882–1968) was an American astronomer at Mount Wilson Observatory known for precision solar spectroscopy, ruled diffraction gratings, and the first measurement of the Sun's general magnetic field.

Harold Edwards (mathematician)

Harold Mortimer Edwards, Jr. (1936–2020) was an American mathematician at New York University whose books on Riemann's zeta function, Fermat's Last Theorem, and Galois theory won the 1980 Steele Prize.

Harold Edwin Hurst

Harold Edwin Hurst (1880–1978) was a British hydrologist who spent some 60 years studying the Nile for the Egyptian government and discovered the Hurst phenomenon, quantified by the Hurst exponent.

Harold Ewen

Harold Irving Ewen was an American radio astronomer and microwave engineer who, as a Harvard graduate student with Edward Purcell, first detected the 21-centimeter line of neutral hydrogen in 1951.

Harold Exton

Harold Exton (born 20 June 1928) is a mathematician who wrote books on multiple and q-hypergeometric functions, including q-Hypergeometric Functions and Applications (1983), and whose name is attached to the Hahn–Exton q-Bessel function.

Sep 20, 2026

Harold F. Levison

Harold F. Levison, known as Hal Levison, is an American planetary scientist at the Southwest Research Institute in Boulder, Colorado, and principal investigator of NASA's Lucy mission.