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Lovász local lemma
The Lovász local lemma is a 1975 result of Erdős and Lovász: if bad events each have small probability and limited dependence, none may occur with positive probability.
Love number
A Love number is a dimensionless parameter measuring how much a self-gravitating body deforms in response to tidal forces, formulated by A. E. H. Love in 1909.
Love wave
A Love wave is a seismic surface wave in which the ground moves horizontally at right angles to the wave's travel direction, named for A.E.H. Love.
Lovell Telescope
The Lovell Telescope is a 76-meter fully steerable radio telescope at Jodrell Bank Observatory in Cheshire, England, completed in 1957 and named for Bernard Lovell, who conceived it.
Lovelock theorem
Lovelock's theorem, proven by David Lovelock in 1971, states that in four dimensions the only symmetric, divergence-free second-order metric tensors are the Einstein tensor and the metric.
Lovelock theory of gravity
Lovelock theory of gravity, or Lanczos–Lovelock gravity, is the most general metric theory with second-order field equations, formulated by David Lovelock in 1971. It reduces to general relativity in four dimensions.
Low-background steel
Low-background steel, also called pre-war or pre-nuclear steel, is steel made before atmospheric nuclear testing began in the 1940s, so it is free of fallout contamination and used to shield highly sensitive radiation detectors.
Low-carbon cement
Low-carbon cement is cement that replaces much of Portland clinker, the most carbon-intensive component, with materials like calcined clay and limestone, cutting CO2 emissions by 30–40%.
Low-density parity-check code
A low-density parity-check (LDPC) code is an error-correcting code defined by a sparse parity-check matrix, proposed by Robert G. Gallager at MIT in 1960 and used in 5G, Wi-Fi, and satellite broadcasting.
Low-density polyethylene
Low-density polyethylene, or PE-LD, is a branched, flexible form of polyethylene made from ethylene at high pressure, the first polyethylene produced commercially, in 1939, used mainly in film packaging.
Low-dose electron microscopy
Low-dose electron microscopy is a set of TEM and STEM practices that minimize electron dose so beam-sensitive specimens can be imaged before radiation damage destroys their structure.
Low-dose scanning transmission electron microscopy
Low-dose scanning transmission electron microscopy (low-dose STEM) is a set of electron microscopy methods that minimize electron dose, enabling atomic-resolution imaging of beam-sensitive materials such as zeolites and metal-organic frameworks.
Low-energy electron diffraction
Low-energy electron diffraction (LEED) is a surface science technique that fires 30–300 eV electrons at a crystal surface; the diffraction pattern reveals the surface's atomic structure, first observed by Davisson and Germer in 1925.
Low-energy electron microscopy
Low-energy electron microscopy (LEEM) images surfaces with electrons of 0–100 eV landing energy, following film growth and surface dynamics in real time with nanometer resolution.
Low-energy ion scattering
Low-energy ion scattering (LEIS), also called ion scattering spectroscopy, is a surface analysis technique that determines the elemental composition of a solid's outermost atomic layer using noble gas ions.
Low-energy upbend
The low-energy upbend, or low-energy enhancement, is a nuclear physics phenomenon in which γ-ray strength rises at low energy below about 2–4 MeV, first seen in iron isotopes.
Low-frequency electron spin resonance spectroscopy
Low-frequency electron spin resonance spectroscopy detects paramagnetic species at frequencies below X-band, where dielectric loss and shallow penetration defeat higher frequencies, enabling in vivo oximetry and whole-body imaging.
Low-level jet (meteorology)
A low-level jet is a wind speed maximum in the lowest kilometer of the atmosphere, with wind speed rising to a core and falling sharply above it.
Low-luminosity AGN
A low-luminosity active galactic nucleus (LLAGN) is a weak active galactic nucleus whose X-ray output falls below 10^42 erg/s, the most numerous AGN in the local Universe.
Low-pressure area
A low-pressure area, also called a low, depression, or cyclone, is a region of lower surface atmospheric pressure with converging rotating winds, generally bringing unsettled weather, cloud, wind, and precipitation.
Low-rank approximation
A low-rank approximation replaces a matrix with one of much lower rank that preserves its dominant structure, used for compression, denoising, and fast linear algebra on large data matrices.
Low-valent main-group chemistry
Low-valent main-group chemistry studies p-block compounds below their classical valences that activate H2, CO, and CO2; the field took shape after Philip Power's 2005 digermyne result.
Low-voltage electron microscopy
Low-voltage electron microscopy images specimens at reduced accelerating voltage, typically 20 to 80 kV in TEM and below 5 keV in SEM, to reduce radiation damage and increase contrast.
Lowell Observatory
Lowell Observatory is a private nonprofit observatory founded by Percival Lowell in 1894 on Mars Hill in Flagstaff, Arizona, best known for the 1930 discovery of Pluto.
Lowell Stott
Lowell Stott is a paleoceanographer and climate scientist, professor of Earth Sciences at the University of Southern California since 1989, known for deep-sea studies of past climate change.
Löwenheim–Skolem theorem
The Löwenheim–Skolem theorem is a pair of results in model theory of first-order logic, proved by Löwenheim in 1915 and Skolem in 1922.
Lower Centaurus Crux
Lower Centaurus Crux is one of three subgroups of the Scorpius-Centaurus OB association, the nearest site of recent massive star formation, about 118 parsecs away and roughly 17 million years old.
Lower envelope of functions
The lower envelope of functions is the pointwise minimum of a collection of functions, together with the subdivision showing which function is lowest in each region; it describes Voronoi diagrams in computational geometry.
Lower hybrid wave
A lower hybrid wave is an electrostatic oscillation of magnetized plasma between ion and electron cyclotron frequencies, used for efficient current drive and heating in tokamaks.
Lower mass gap
The lower mass gap is a hypothesized scarcity of compact objects with masses between roughly 2.5 and 5 solar masses, between the heaviest neutron stars and lightest black holes.