Galilean superconformal symmetries

We consider the non-relativistic c→∞ contraction limit of the (N=2k)-extended D=4 superconformal algebra su(2,2;N), introducing in this way the non-relativistic (N=2k)-extended Galilean superconformal algebra. Such a Galilean superconformal algebra has the same number of generators as su(2,2|2k). The usp(2k) algebra describes the non-relativistic internal symmetries, and the generators from the coset u(2k)usp(2k) become central charges after contraction.