A three-body force is a
force that does not exist in a system of two objects but appears in a three-body system. In general, if the behaviour of a system of more than two objects cannot be described by the two-body interactions between all possible pairs, as a first approximation, the deviation is mainly due to a three-body force.
The fundamental
strong interaction does exhibit such behaviour, the most important example being the stability experimentally observed for the
helium-3 isotope, which can be described as a 3-body quantum cluster entity of two protons and one neutron
NPin stable superposition. Direct evidence of a 3-body force in helium-3 is known
The existence of stable
NPcluster calls into question models of the atomic nucleus that restrict nucleon interactions within shells to 2-body phenomenon. The three-nucleon-interaction is fundamentally possible because
gluons, the mediators of the strong interaction, can couple to themselves. In
particle physics
Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) an ...
, the interactions between the three quarks that compose
hadron
In particle physics, a hadron (; grc, ἁδρός, hadrós; "stout, thick") is a composite subatomic particle made of two or more quarks held together by the strong interaction. They are analogous to molecules that are held together by the e ...
s can be described in a
diquark
In particle physics, a diquark, or diquark correlation/clustering, is a hypothetical state of two quarks grouped inside a baryon (that consists of three quarks) (Lichtenberg 1982). Corresponding models of baryons are referred to as quark–diquark ...
model which might be equivalent to the hypothesis of a three-body force. There is growing evidence in the field of
nuclear physics
Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter.
Nuclear physics should not be confused with atomic physics, which studies the ...
that three-body forces exist among the
nucleon
In physics and chemistry, a nucleon is either a proton or a neutron, considered in its role as a component of an atomic nucleus. The number of nucleons in a nucleus defines the atom's mass number (nucleon number).
Until the 1960s, nucleons were ...
s inside
atomic nuclei for many different isotopes (three-nucleon force).
See also
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Faddeev equation
The Faddeev equations, named after their inventor Ludvig Faddeev, are equations that describe, at once, all the possible exchanges/interactions in a system of three particles in a fully quantum mechanical formulation. They can be solved iterat ...
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Few-body systems
In mechanics, a few-body system consists of a small number of well-defined structures or point particles.
Quantum mechanics
In quantum mechanics, examples of few-body systems include light nuclear systems (that is, few-nucleon bound and scatter ...
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N-body problem
In physics, the -body problem is the problem of predicting the individual motions of a group of celestial objects interacting with each other gravitationally.Leimanis and Minorsky: Our interest is with Leimanis, who first discusses some histor ...
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Hydrogen molecular ion
The dihydrogen cation or hydrogen molecular ion is a cation (positive ion) with formula . It consists of two hydrogen nuclei (protons) sharing a single electron. It is the simplest molecular ion.
The ion can be formed from the ionization of a n ...
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Borromean nucleus
A Borromean nucleus is an atomic nucleus comprising three bound components in which any subsystem of two components is unbound. This has the consequence that if one component is removed, the remaining two comprise an unbound resonance, so that the ...
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Efimov state The Efimov effect is an effect in the quantum mechanics of few-body systems predicted by the Russian theoretical physicist V. N. Efimov in 1970. Efimov’s effect is where three identical bosons interact, with the prediction of an infinite series ...
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Chiral perturbation theory
References
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{{DEFAULTSORT:Three-Body Force
Force
Nuclear physics