D=4 extended Galilei superalgebras with central charges

We perform a nonrelativistic contraction of N-extended Poincaré superalgebra with internal symmetry U(N) and general set of N(N−1) real central charges. We show that for even N=2k and particular choice of the dependence of Zij on light velocity c one gets the N-extended Galilei superalgebra with unchanged number of central charges and compact internal symmetry algebra U(k;H)=USp(2k). The Hamiltonian positivity condition is modified only by one central charge. If we put all the central charges equal to zero one gets the 2k-extended Galilei superalgebra as the subalgebra of recently introduced extended Galilei conformal superalgebra (de Azcárraga, Lukierski (2009) [1] and Sakaguchi [2]).