Lorentz invariant and Lorentz non invariant aspects of a scalar tachyon field Lagrangian and the scalar tachyon Feynman propagator
A consistent theory of faster than light particles (tachyons) can be built replacing the standard Lorentz invariant approach to the quantum field theory of tachyons by the Lorentz covariant one, invoking a concept of the preferred reference frame. This is a mandatory condition imposed by the causality conservation. In this article some features of a Lorentz violating (but Lorentz covariant) Lagrangian of a scalar tachyon field are considered. It is shown that the equation of motion and Feynman propagator resulting from it are Lorentz invariant, while the Lorentz symmetry of the suggested tachyon field model can be defined as covariantly broken.