Abstract:
Foldy–Wouthuysen transformation for the equations connected with the De Sitter
group $SO(1,4)$ is considered. The general transformation contains the usual Foldy–Wouthuysen transformation and the Cini–Touschek transformation. It is shown that
the usual Foldy–Wouthuysen transformation is equivalent to the Lorentz transformation
only for the edge weight points with $h=\pm\, n_1$ of the De Sitter group representation
($n_1,n_2$). An equation in the Cini–Touschek representation is for $h=\pm\, n_1$ equivalent
to equations for the zero rest mass particles. From the known equations connection
between the Foldy–Wouthuysen and Lorentz transformations exists for the
Dirac, Kemmer–Duffin and Bargmann–Wigner equations. For the Rarita–Schwinger
equation in the $SO(1,4)$-form there is no equivalence.