It is first order in space and time derivatives and has been shown to work but is impossible to prove.
In it each of the alpha's must be represented by a four by four matrix, one set of which obeys a similar anticommunication relation and are known as the Pauli matrices. P represents the three component momentum in this equation which sought to solve the problems of the Klein-Gordon equation. It is first order in space and time derivatives and has been shown to work but is impossible to prove. FTP, identify this relativistic wave equation named for the British physicist who formulated it.
In it each of the alpha's must be represented by a four by four matrix, one set of which obeys a similar anticommunication relation and are known as the Pauli matrices.
{Dirac} equation