Extended supersymmetric BMS3 algebras and their free field realisations

We study N = (2, 4, 8) supersymmetric extensions of the three dimensional BMS algebra (BMS3) with most generic possible central extensions. We find that N-extended supersymmetric BMS3 algebras can be derived by a suitable contraction of two copies of the extended superconformal algebras. Extended algebras from all the consistent contractions are obtained by scaling left-moving and right-moving supersymmetry generators symmetrically, while Virasoro and R-symmetry generators are scaled asymmetrically. On the way, we find that the BMS/ GCA correspondence does not in general hold for supersymmetric systems. Using the beta-gamma and the b-c systems, we construct free field realisations of all the extended super-BMS3 algebras.