Gravitoner

Gravitioner, or gravitoner in Swedish, are hypothetical elementary particles that would mediate the gravitational force in quantum theories of gravity. In most models they are massless spin-2 bosons with two physical helicity states. They would couple universally to energy and momentum, with effects that become significant only at very high energies or very short distances near the Planck scale.

Relation to classical gravity: Gravity is described classically by general relativity as curvature of spacetime. A linearized, weak-field approximation treats fluctuations of the metric as a quantum field, yielding gravitoner quanta. In this picture, long-range gravity and Newton's law arise from the exchange of many virtual gravitons.

Experimental status: Gravitoner have not been observed directly. Gravitational waves detected by LIGO and other observatories are classical predictions of general relativity; they could be viewed as coherent states of a very large number of gravitons. If gravitoner had mass, gravity would acquire a Yukawa-like term and the propagation would differ from general relativity; observational constraints place extremely small upper bounds on any graviton mass and on deviations from general relativity.

Theoretical context: Gravitoner appear in perturbative quantum gravity and in string theory. The standard perturbative quantization of gravity is nonrenormalizable, so the graviton is typically treated within an effective field theory at low energies. Other approaches to quantum gravity include loop quantum gravity and various string-theoretic frameworks, where the graviton emerges as a specific excitation of fundamental degrees of freedom.

Notes: The concept remains theoretical, guiding research in quantum gravity and phenomenology, rather than a confirmed particle in experiments.