42,772 articles
Group divisible design
A group divisible design (GDD) is a combinatorial design whose point set is split into groups, with cross-group pairs of points appearing together in a constant number of blocks.
Group extension
A group extension is a group E containing a given group N as a normal subgroup with quotient group Q, usually written as a short exact sequence.
Group field theory
Group field theory is a quantum field theory defined on a group manifold whose Feynman diagrams are spin foams, proposed as a non-perturbative formulation of quantum gravity.
Group homomorphism
A group homomorphism, also called a group morphism or morphism of groups, is a function between two groups that preserves the group operation; its kernel and image underlie the first isomorphism theorem.
Group IV color centers in diamond
Group IV color centers in diamond are atom-like quantum defects where silicon, germanium, tin, or lead sits between two vacancies, used as spin-photon interfaces and quantum-network nodes.
Group IV monochalcogenide
Group IV monochalcogenides are layered van der Waals semiconductors with formula MX, where M is Ge or Sn and X is S, Se, or Te; GeS, GeSe, SnS, and SnSe are best studied.
Group IV monochalcogenides
Group IV monochalcogenides are layered semiconductors with the formula MX, including GeS, GeSe, SnS, and SnSe, crystallizing in a puckered lattice analogous to black phosphorus and valued for ferroelectricity and thermoelectric performance.
Group lasso
The group lasso is a regularization method for linear and generalized linear regression that keeps or removes whole predefined groups of coefficients, introduced by Yuan and Lin in 2005.
Group of Lie type
A group of Lie type is a finite group of rational points of a reductive algebraic group over a finite field, including the classical matrix groups.
Group presentation
A group presentation is a description of a group by a set of generators and relators, written ⟨S | R⟩, giving a compact way to define infinite groups.
Group representation
A group representation, the subject of group representation theory, realizes an abstract group as invertible linear transformations of a vector space, with applications in chemistry, physics, and quantum mechanics.
Group ring
A group ring R[G] is a ring of formal finite sums of group elements with coefficients in a ring R; when R is a field it is a group algebra.
Group scheme
A group scheme is a scheme with a group structure given by morphisms for multiplication, inverse, and identity, so its points form groups for every base scheme.
Group testing
Group testing is a statistical method that tests pooled samples instead of individual ones, introduced by Robert Dorfman in 1943 to screen US army conscripts for syphilis.
Group theory
Group theory is the branch of mathematics studying groups, algebraic structures that capture symmetry and operations like addition, founded in Galois's 1830s work on equations.
Group velocity
Group velocity, or group speed, is the speed at which a wave packet's envelope travels, carrying its energy and signal, in contrast with the phase velocity of individual crests.
Group velocity dispersion
Group velocity dispersion, quantified by the parameter β₂, is the variation of group velocity with frequency that makes optical pulses spread as they travel through a medium or fiber.
Group-IV monochalcogenide monolayers
Group-IV monochalcogenide monolayers are single-layer two-dimensional semiconductors of a group-IV metal (Ge, Sn) and a chalcogen (S, Se, Te), with a puckered lattice like black phosphorus.
Groupoid
A groupoid is a small category in which every morphism is an isomorphism, equivalently a set with a partial multiplication, introduced by Heinrich Brandt in 1926.
Grove Karl Gilbert
Grove Karl Gilbert (1843–1918) was an American geologist who served the USGS for 39 years and became a founder of geomorphology, the study of how landforms are shaped.
Grover's algorithm
Grover's algorithm, also called the Grover search algorithm, is a quantum algorithm proposed by Lov Grover at Bell Labs in 1996 that finds a marked item in an unstructured search space using O(√N) queries.
Growth and division of active droplets
Growth and division of active droplets is a phenomenon in which chemically driven liquid droplets grow and split like living cells, proposed as a model for prebiotic protocells.
Growth curve analysis
Growth curve analysis is a statistical method for modeling how an outcome changes over time, using repeated measures to estimate individual trajectories and their differences.
Growth index (cosmology)
The growth index is a cosmological parameter, written γ, that summarizes how fast cosmic structures grow; it is about 0.55 in general relativity and differs in modified gravity.
Growth mixture model
A growth mixture model is a latent-variable statistical method that identifies unobserved subgroups, called latent classes, each with its own developmental trajectory, in longitudinal data.
Growth mixture modeling
Growth mixture modeling is a statistical method for longitudinal data that divides a population into latent classes with different trajectories, introduced by Muthén and Shedden in 1999.
Growth rate (group theory)
In group theory, the growth rate of a finitely generated group measures how quickly the number of elements reachable by short words grows with word length.
Growth rate hypothesis
The growth rate hypothesis is a proposition in ecological stoichiometry, introduced by James Elser and colleagues around 2000, holding that rapid growth requires phosphorus-rich ribosomal RNA, raising body phosphorus.
GRS 1915+105
GRS 1915+105 is a Galactic X-ray binary containing a stellar-mass black hole that ejects plasma in relativistic jets, the first Milky Way source with observed superluminal motion, seen in 1994.
GRUAN
GRUAN, the GCOS Reference Upper-Air Network, is an international network of sites measuring climate variables from the surface into the stratosphere, envisaged by the WMO in 2007 to calibrate satellites and radiosonde data.