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In theoretical physics, the Rarita–Schwinger equation is the relativistic field equation of spin-3/2 fermions. It is similar to the Dirac equation for spin-1/2 fermions. This equation was first introduced by William Rarita and Julian Schwinger in 1941. In modern notation it can be written as:〔S. Weinberg, "The quantum theory of fields", Vol. 3, Cambridge p. 335〕 : where is the Levi-Civita symbol, and are Dirac matrices, is the mass, , and is a vector-valued spinor with additional components compared to the four component spinor in the Dirac equation. It corresponds to the representation of the Lorentz group, or rather, its part.〔S. Weinberg, "The quantum theory of fields", Vol. 1, Cambridge p. 232〕 This field equation can be derived as the Euler–Lagrange equation corresponding to the Rarita–Schwinger Lagrangian:〔S. Weinberg, "The quantum theory of fields", Vol. 3, Cambridge p. 335〕 : where the bar above denotes the Dirac adjoint. This equation controls the propagation of the wave function of composite objects such as the delta baryons () or for the conjectural gravitino. So far, no elementary particle with spin 3/2 has been found experimentally. The massless Rarita–Schwinger equation has a sermonic gauge symmetry: is invariant under the gauge transformation , where is an arbitrary spinor field. "Weyl" and "Majorana" versions of the Rarita–Schwinger equation also exist. ==Equations of motion in the massless case== Consider a massless Rarita-Schwinger field described by the Lagrangian density : where the sum over spin indices is implicit, are Majorana spinors, and : To obtain the equations of motion we vary the Lagrangian with respect to the fields , obtaining: : using the Majorana flip properties〔Pierre Ramond - Field theory, a Modern Primer - p.40〕 we see that the second and first terms on the RHS are equal, concluding that : plus unimportant boundary terms. Imposing we thus see that the equation of motion for a massless Majorana Rarita-Schwinger spinor reads: : 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Rarita–Schwinger equation」の詳細全文を読む スポンサード リンク
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