Relativistic quantum mechanics
https://en.wikipedia.org/wiki/Relativistic_quantum_mechanicsDirac equation : for relativistic spin ½ massive parity-symetrical particles
https://en.wikipedia.org/wiki/Dirac_equationKlein–Gordon equation : for relativistic spinless massive particles
https://en.wikipedia.org/wiki/Klein–Gordon_equationRepresentation theory of the Lorentz group & Relativistic wave functions
https://en.wikipedia.org/wiki/Representation_theory_of_the_Lorentz_group#Relativistic_quantum_mechanicsDoes relativistic quantum mechanics really violate causality? - Physics Stack Exchange
https://physics.stackexchange.com/questions/346780/does-relativistic-quantum-mechanics-really-violate-causality