Physical world and mathematics

Normal matrix

A normal matrix is a square matrix that commutes with its conjugate transpose, AA = A*A; by the spectral theorem it has an orthonormal basis of eigenvectors, including Hermitian and unitary matrices.

Normal modal logic K

Normal modal logic K is the smallest normal modal logic, containing classical propositional logic, the Distribution Axiom, and the Necessitation Rule, named after Saul Kripke.

Normal mode

A normal mode, also called a vibrational mode, is a pattern of oscillation in which all parts of a system move at one fixed frequency; any motion is a superposition of modes.

Sep 29, 2026

Normal mode analysis

Normal mode analysis is a computational method that describes the vibrational modes of a molecular structure, typically a protein, and is used to study large-scale motions and flexibility.

Sep 29, 2026

Normal moveout

Normal moveout (NMO) is a seismic data processing correction that time-shifts each trace in a CMP gather by an offset-dependent amount, flattening reflections for stacking.

Normal operator

A normal operator is a linear operator on an inner product space that commutes with its adjoint, T*T = TT, the class for which the spectral theorem holds.

Normal shock

A normal shock is a shock wave perpendicular to the flow direction, across which a supersonic gas decelerates abruptly to subsonic speed as its pressure, temperature, and density rise.

Normal space

A normal space is a topological space in which any two disjoint closed sets can be separated by disjoint open neighborhoods; it underlies Urysohn's lemma and the Tietze extension theorem.

Normal stress difference

A normal stress difference is a difference between diagonal stress components that develops when a complex fluid is sheared; nonzero values signal elasticity and drive the rod-climbing effect.

Normal subgroup

A normal subgroup, also called an invariant subgroup, is a subgroup H of a group G with aH = Ha for every element, equivalently fixed under conjugation by all of G.

Normal surface

A normal surface is a properly embedded surface in a triangulated 3-manifold meeting each tetrahedron in standard disks, a theory introduced by Kneser and developed by Haken in the 1960s.

Normality (chemistry)

Normality is a measure of solution concentration, expressed as equivalents of solute per liter and denoted N, still common in titration despite being obsolete in SI.

Normality test

A normality test is a statistical procedure that assesses whether a sample of data plausibly comes from a normal distribution, including the Shapiro-Wilk and Anderson-Darling tests.

Normalization

Normalization, in statistics and machine learning, adjusts data or model activations to a common scale or range, using methods such as min-max scaling and z-score standardization.

Normalization (statistics)

Normalization in statistics, also called normalizing variables, covers methods such as Z-score standardization and min-max scaling that prevent features with large values from dominating learning.

Normalized Laplacian

The normalized Laplacian is a matrix associated with a graph, formed by scaling the combinatorial Laplacian by vertex degrees; Fan Chung developed it in her book Spectral Graph Theory.

Norman A. Phillips

Norman A. Phillips (1923–2019) was an American meteorologist who built the first general circulation model of the atmosphere, taught at MIT, and won the 2003 Benjamin Franklin Medal.

Norman Allinger

Norman Allinger (1928–2020) was an American computational chemist at the University of Georgia, senior author of the MM2, MM3, and MM4 molecular mechanics force fields for organic molecules.

Norman D. Newell

Norman D. Newell (1909–2005) was an American paleontologist at Columbia University and the American Museum of Natural History, known for his work on mass extinctions.

Norman F. Ness

Norman F. Ness (1933–2023) was an American space physicist at NASA Goddard who designed the Voyager magnetometers and led the discovery of the magnetic fields of Saturn, Uranus, and Neptune.

Norman F. Ramsey

Norman F. Ramsey (1915–2011) was an American Harvard physicist who shared the 1989 Nobel Prize in Physics for the separated oscillatory fields method behind atomic clocks.

Norman George Meyers (1930–2025) was an American mathematician who spent his career at the University of Minnesota and is best known for the 1963 higher-integrability result called the Meyers estimate.

Norman H. Anning

Norman H. Anning (Norman Herbert Anning, 1883–1963) was a Canadian-American mathematician who coauthored the 1945 Erdős–Anning theorem, proving that infinite planar integer-distance point sets must lie on a line.

Norman Hackerman

Norman Hackerman (1912–2007) was an American electrochemist known for corrosion science, who served as president of the University of Texas at Austin and Rice University.

Norman Haworth

Norman Haworth, or Walter Norman Haworth, was a British organic chemist who won the 1937 Nobel Prize in Chemistry for work on carbohydrates and vitamin C.

Norman Horowitz

Norman Horowitz (1915–2005) was an American geneticist, professor of biology at Caltech, who worked on the one-gene, one-enzyme experiments in Neurospora and designed the Viking lander's life-detection experiment for Mars.

Norman J. Dovic̀hi

Norman J. Dovic̀hi is an American bioanalytical chemist and Emeritus Professor at Notre Dame whose capillary array electrophoresis instruments sequenced the human genome; he edits Analyst.

Norman James Petch

Norman James Petch (1917–1992) was a British metallurgist whose 1953 paper on the cleavage strength of polycrystals gave the grain-size term of the Hall–Petch relation; he held metallurgy chairs at Leeds, Newcastle, and Strathclyde.

Norman Jarosik

Norman Jarosik is an American experimental cosmologist, a Senior Research Physicist at Princeton University who led the WMAP radiometer systems and shared the 2018 Breakthrough Prize in Fundamental Physics.