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Gravitational instability model
The gravitational instability model, also called disk instability, is a planet-formation theory in which giant planets form rapidly from the self-gravity of a young star's gas disk.
Gravitational instanton
A gravitational instanton is a complete, non-singular solution of the Euclidean Einstein equations in four dimensions that approaches flat space at infinity, analogous to Yang–Mills instantons.
Gravitational lens
A gravitational lens, also called a gravity lens, is a massive galaxy or galaxy cluster whose gravity bends light passing near it, distorting and magnifying the image of a distant source behind it.
Gravitational lensing formalism
The gravitational lensing formalism is the set of equations describing how a mass distribution deflects, distorts, magnifies, and delays light, centered on the lens equation and Fermat potential.
Gravitational lensing of the cosmic microwave background
CMB weak lensing is the gravitational distortion of the cosmic microwave background by intervening matter, which traces the universe's projected mass distribution and constrains dark energy and neutrino mass.
Gravitational microlensing
Gravitational microlensing, also called microlensing, is a form of gravitational lensing in which a foreground star briefly magnifies a distant background star's light, producing no resolvable image.
Gravitational path-integral methods
Gravitational path-integral methods quantize general relativity by summing over all spacetime geometries; central issues include the conformal-factor problem, gauge fixing, and whether an asymptotic-safety fixed point exists.
Gravitational potential
Gravitational potential, also called gravity potential, is the gravitational potential energy of a unit test mass at a point, a scalar equal to -GM/r for a point mass.
Gravitational quantum states of neutrons
Discrete energy levels of ultracold neutrons bouncing in Earth's gravity above a mirror, first observed in 2002; gravity resonance spectroscopy tests gravity at micrometer scales.
Gravitational redshift
Gravitational redshift, also called the Einstein shift, is the shift of light's frequency between points at different gravitational potential, a classical test of general relativity verified from Harvard's tower to satellites.
Gravitational redshift experiments
Gravitational redshift experiments compare identical clocks at different heights in a gravitational field against general relativity's prediction, from the 1960 Harvard tower tests to satellite and atomic-clock tests.
Gravitational singularity
A gravitational singularity is a location in spacetime, predicted by general relativity, where curvature and density grow without bound, as at black hole centers and the Big Bang.
Gravitational slip
Gravitational slip is the difference between the two scalar metric potentials in a perturbed expanding universe. A nonzero slip signals a departure from general relativity or anisotropic stress, altering structure growth and lensing.
Gravitational time dilation
Gravitational time dilation is the general relativity prediction that clocks run more slowly deeper in a gravitational field; near Earth the effect is about 10⁻¹⁶ per meter of height.
Gravitational wave
A gravitational wave, also called gravitational radiation, is a ripple in spacetime moving at the speed of light, predicted by Einstein in 1916 and first detected by LIGO in 2015.
Gravitational wave background
A gravitational wave background is a stochastic, noise-like signal from many overlapping, unresolved gravitational waves; in 2023 pulsar timing arrays reported evidence for a nanohertz background, likely from supermassive black hole binaries.
Gravitational wave background from SMBH binaries
The gravitational wave background from supermassive black hole binaries is a stochastic nanohertz signal from binaries in merged galaxies, detected by pulsar timing arrays in June 2023.
Gravitational wave echo
A gravitational wave echo is a hypothesized delayed, repeating pulse of gravitational radiation following a merger's ringdown if the remnant lacks a true event horizon.
Gravitational-wave astronomy
Gravitational-wave astronomy studies cosmic sources through gravitational waves, ripples in spacetime predicted by Einstein and first detected by the LIGO detectors in 2015, when they recorded the binary black hole merger GW150914.
Gravitational-wave early warning alert
A gravitational-wave early warning alert is a notice from the LIGO–Virgo–KAGRA detectors sent before a compact binary merger, giving telescopes a head start on the flash that follows.
Gravitational-wave echoes
Gravitational-wave echoes are hypothetical delayed pulses of gravitational radiation after a merger that would appear if the remnant is an exotic compact object rather than a black hole.
Gravitational-wave lensing
Gravitational-wave lensing is the deflection, delay, and distortion of gravitational waves by massive objects like galaxies and black holes; no lensed signal has yet been confirmed.
Gravitational-wave memory
Gravitational-wave memory is a permanent, non-oscillatory change in spacetime left behind by a burst of gravitational waves, first predicted by Zel'dovich and Polnarev in 1974 and still undetected.
Gravitational-wave polarizations
Gravitational-wave polarizations are the independent strain patterns a passing wave imposes on matter; general relativity allows two tensor modes, while general metric theories allow up to six.
Gravitational-wave recoil
Gravitational-wave recoil is the kick a compact-object merger remnant receives when gravitational waves emit momentum anisotropically; black hole kicks can reach thousands of kilometers per second.
Gravitational-wave transient catalog
The Gravitational-Wave Transient Catalog (GWTC) is the running list of gravitational-wave signals detected by the LIGO, Virgo, and KAGRA collaborations, growing from 11 events in 2019 to hundreds of compact binary mergers.
Gravitationally induced entanglement
Gravitationally induced entanglement (GIE) is the predicted entanglement between two masses interacting only through gravity, proposed in 2017 as a laboratory test of whether the gravitational field is quantum.
Gravitino
The gravitino is the hypothetical spin-3/2 superpartner of the graviton predicted by supergravity. It is extremely weakly coupled, possibly stable dark matter, and has never been observed.
Gravitoelectromagnetism
Gravitoelectromagnetism, also called gravitomagnetism, is a weak-field, slow-motion approximation of general relativity rewritten in a form resembling Maxwell's equations, with mass current generating frame dragging, the Lense–Thirring effect.
Graviton
The graviton is the hypothetical quantum particle of the gravitational field, a massless spin-2 boson whose exchange would mediate gravity; no graviton has ever been detected, and 2024 proposals suggest single-graviton detection may be within reach.