Spinor fields describing particles of zero rest mass satisfy the so-called zero rest mass equations. Examples of zero rest mass particles include the neutrino (a fermion) and the gauge bosons (as long as gauge symmetry is not violated) such as the photon. If ϕ^(A B...E) is the spinor field describing a particle of spin s (where upper case Latin indices are spinor indices which can take the values 0 and 1), then it is symmetric and has 2s indices. If the particle is also of zero rest mass, then ϕ^(A B...E) satisfies the zero rest mass equation del _(A')^A ϕ^(A B...E) = 0.

spinor | spinor field | twistor | twistor equation