A Common Type II Origin of Galilean and Carroll Superstrings

Abstract

We show that the relativistic Type-II superalgebras, once the fundamental-string winding charge is retained alongside the momentum, admit a single non-Lorentzian contraction whose two translation ideals carry Galilean and magnetic-Carroll supersymmetry, respectively. The complementary vector charge required for this structure is thus intrinsic to string theory. The IIA realization is particle-like and the IIB realization string-like, a distinction fixed by chirality, and spacelike T-duality relates the two while preserving each non-Lorentzian structure. The same contraction is finite on the doubled Green--Schwarz action, including all fermion terms and local kappa symmetry, where the two supersymmetries appear as the two polarizations of a single worldsheet theory. These results unify two distinct non-Lorentzian corners of string theory within a common Type-II origin and open a route toward a broader web of non-Lorentzian dualities and possible holographic generalizations.