## 2. Symbols and Conventions

The following standard symbols are used: L and L^{-1} for the matrices corresponding to the direct and the reciprocal Lorentz transformation, F for the matrix expressing the electromagnetic field, J^{i} for the charge/current-density four-vector and J_{i} for his

dual four-form, V^{i} for the four-velocity and, finally, G for the Gauss matrix characterizing the metric:

In addition, we introduce another matrix M representing the electro-magnetic field and a Nabla-operator as a four-form:

M (more precisely G·M) can be found in literature under the name 'dual fieldtensor' and is denoted with F* oder *F.

The Nabla-operator corresponds to the ∂_{µ} of tensor calculus.

The matrices L , L^{-1} and G do not change, if they are transposed, and for G holds G^{-1} = G .

Further we have L^{-1} = G·L·G and L^{-1} = G^{-1}·L·G as well as L = G·L^{-1}·G und L = G^{-1}·L^{-1}·G .