The goldstino is the
Nambu−Goldstone fermion
In particle physics, a fermion is a particle that follows Fermi–Dirac statistics. Generally, it has a half-odd-integer spin: spin , spin , etc. In addition, these particles obey the Pauli exclusion principle. Fermions include all quarks an ...
emerging in the
spontaneous breaking of
supersymmetry
In a supersymmetric theory the equations for force and the equations for matter are identical. In theoretical and mathematical physics, any theory with this property has the principle of supersymmetry (SUSY). Dozens of supersymmetric theories e ...
. It is the close fermionic analog of the
Nambu−Goldstone boson
In particle and condensed matter physics, Goldstone bosons or Nambu–Goldstone bosons (NGBs) are bosons that appear necessarily in models exhibiting spontaneous breakdown of continuous symmetries. They were discovered by Yoichiro Nambu in part ...
s controlling the spontaneous breakdown of ordinary bosonic symmetries.
As in the case of Goldstone bosons, it is massless, unless there is, in addition, a small explicit supersymmetry breakdown involved, on top of the basic spontaneous breakdown; in this case it develops a ''small'' mass, analogous to that of
Pseudo-Goldstone bosons of chiral symmetry breaking.
In theories where supersymmetry is a
global symmetry
In physics, a symmetry of a physical system is a physical or mathematical feature of the system (observed or intrinsic) that is preserved or remains unchanged under some transformation.
A family of particular transformations may be ''continuo ...
, the goldstino is an ordinary particle (possibly the lightest supersymmetric particle, responsible for
dark matter).
In theories where supersymmetry is a
local symmetry, the goldstino is absorbed by the
gravitino, the
gauge field it couples to, becoming its longitudinal component, and giving it nonvanishing mass. This mechanism
is a close analog of the way the
Higgs field gives nonzero mass to the
W and Z bosons.
Vestigial bosonic superpartners of the goldstinos, called ''
sgoldstinos'', might also appear, but need not, as
supermultiplets have been reduced to arrays.
In effect, SSB of supersymmetry, by definition, implies a
nonlinear realization of the supersymmetry in the
Nambu−Goldstone mode, in which the goldstino couples ''identically to all particles'' in these arrays, and is thus the superpartner of ''all of them'', equally.
References
Supersymmetric quantum field theory
Hypothetical elementary particles
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