P 4 is the generator of time translations (Hamiltonian), P i is the generator of spatial translations (momentum operator), K i is the generator of Galilean boosts, and J i stands for a generator of rotations (angular momentum operator). The generator P 5 is a Casimir invariant and P 2 − − 2 P 4 P 5 is an additional Casimir invariant. This algebra is isomorphic to the extended Galilean Algebra in (3+1) dimensions with P 5 = − − M , The central charge, interpreted as mass, and P 4 = − − H .