Physical world and mathematics

Helix

A helix is a smooth space curve that winds around a fixed axis at constant distance while advancing at a constant rate, like a screw thread.

Helix Nebula

The Helix Nebula (NGC 7293), nicknamed the Eye of God, is a planetary nebula in Aquarius about 700 light-years away, cast off by a dying Sun-like star.

Hell Creek Formation

The Hell Creek Formation is a rock unit in Montana, Wyoming, and the Dakotas famous for its dinosaur fossils, including Tyrannosaurus rex, and preserving the Cretaceous–Paleogene extinction boundary.

The Hellinger distance, or Hellinger metric, is a metric on probability distributions that compares square-root densities, named after Ernst Hellinger and widely used in statistical lower bounds and decision trees.

Hellmut Fritzsche

Hellmut Fritzsche (1927–2018) was a German-born American experimental physicist and Louis Block Professor at the University of Chicago, a leading experimenter on amorphous semiconductors who confirmed Ovshinsky's switching effect and co-developed the Cohen–Fritzsche–Ovshinsky band model.

Hellmuth Kneser

Hellmuth Kneser (1898–1973) was a German mathematician best known for proving the prime decomposition of 3-manifolds in 1929 and constructing a half-iterate of the exponential function in 1950.

Helma Wennemers

Helma Wennemers (born 1969) is a German organic chemist and professor of organic chemistry at ETH Zurich, known for peptide catalysts, synthetic collagen, and supramolecular chemistry.

Helmholtz coil

A Helmholtz coil, also called a Helmholtz pair, is two identical coaxial coils separated by a distance equal to their radius, producing a nearly uniform magnetic field for calibration.

Helmholtz decomposition

The Helmholtz decomposition, also called the fundamental theorem of vector calculus, states that any vector field splits into a curl-free part given by a scalar potential and a divergence-free part given by a vector potential.

Helmholtz equation

The Helmholtz equation is the elliptic partial differential equation describing the spatial amplitude of a harmonically oscillating wave; it is the time-independent form of the wave equation.

Helmholtz free energy

The Helmholtz free energy, also called the Helmholtz energy or Helmholtz function, is a thermodynamic potential, A = U − TS, minimized at equilibrium at constant temperature and volume.

Helmholtz resonance

Helmholtz resonance, also known as wind throb, is the acoustic resonance of air in a cavity with a constricted neck, such as blowing across a bottle mouth.

Helmut Cölfen

Helmut Cölfen (1965–2023) was a German physical and colloid chemist, professor of physical chemistry at the University of Konstanz from 2010, known for discovering stable pre-nucleation clusters and the concept of mesocrystals.

Helmut Grunsky

Helmut Grunsky (1904–1986) was a German mathematician whose 1939 Grunsky inequalities became a standard tool of geometric function theory and work on the Bieberbach conjecture.

Helmut Hasse

Helmut Hasse (1898–1979) was a German mathematician who shaped 20th-century number theory with the local–global principle, the Brauer–Hasse–Noether theorem, and the Hasse bound for elliptic curves.

Helmut Hofer

Helmut Hofer is a German and American mathematician at the Institute for Advanced Study, a founder of symplectic topology known for Hofer geometry and the Hofer–Zehnder capacity.

Helmut Landsberg

Helmut Erich Landsberg (1906–1985) was a German-born American climatologist who directed the U.S. Weather Bureau's Office of Climatology, wrote Physical Climatology, and received the National Medal of Science in 1985.

Sep 20, 2026

Helmut Schwarz

Helmut Schwarz, born in 1943, is a German chemist at TU Berlin known for gas-phase mass spectrometry, two-state reactivity, and methane activation; he won the 2025 Wolf Prize.

Helmut Wielandt

Helmut Wielandt (1910–2001) was a German mathematician trained in Berlin under Issai Schur, known for the Wielandt inequality, the Collatz–Wielandt formula, and his 1950 proof of the Perron–Frobenius theorem.

Helmut Zeisel

Helmut Zeisel is an Austrian mathematician and industrial researcher known for the Zeisel numbers, squarefree integers whose prime factors follow a linear recurrence, introduced in 1994.

Sep 20, 2026

Helmuth Möhwald

Helmuth Möhwald (1946–2018) was a German physicist and physical chemist, founding director of the Max Planck Institute of Colloids and Interfaces, known for layer-by-layer film assembly and hollow capsule templating.

Hemamala I. Karunadasa

Hemamala I. Karunadasa is a Sri Lankan-born materials chemist, Professor of Chemistry at Stanford with a joint appointment at SLAC, known for lead-free halide perovskites for solar cells and lighting.

Oct 22, 2026

Hematene

Hematene is a two-dimensional material of iron oxide, Fe₂O₃, first reported in 2018 by Rice University researchers who exfoliated atomic-scale sheets from natural hematite ore; it founded a family of non-van der Waals 2D materials.

Hematite

Hematite is an iron oxide mineral, Fe₂O₃, and the most important ore of iron; most formed in Precambrian banded iron formations, and it also occurs on Mars.

Hematoporphyrin

Hematoporphyrin, also known as hematoporphyrin IX, is a porphyrin first isolated from blood in 1841 that acts as a photosensitizer and parent compound of the photodynamic therapy drug Photofrin.

Hematoxylin

Hematoxylin is a natural compound extracted from the heartwood of the logwood tree, used worldwide as the nuclear stain in histology and, with eosin, in the routine H&E stain of diagnostic pathology.

Hemiacetal

A hemiacetal is a functional group in which one carbon bears both a hydroxyl and an alkoxy group, formed when an alcohol adds to an aldehyde; ketone-derived analogs are hemiketals.

Hemicholinium-3

Hemicholinium-3 (HC-3) is a synthetic bis-quaternary ammonium compound that inhibits the high-affinity choline transporter, blocking acetylcholine synthesis; discovered in 1954, it is a research tool, not a drug.

Hemispherical power asymmetry

The hemispherical power asymmetry is a cosmic microwave background anomaly where temperature fluctuations are larger on one hemisphere, first seen in WMAP data in 2004.