Research Projects

The proposed project aims to study two singular limits of string theory: a Carrollian limit and a Galilean limit on the worldsheet. The Carrollian limit leads to a theory of null string, where the worldsheet metric becomes degenerate and the underlying Riemannian geometry is replaced by a Carrollian geometry. This is particularly relevant to the worldsheet formulation of bosonic and supersymmetric theories of tensionless open strings. The non-relativistic limit of tensile string theory is studied from the worldsheet perspective, where the underlying worldsheet degenerates and the spacetime structure is best described by Newton-Cartan geometry. The project also plans to apply the worldsheet analysis of Carrollian string to compute scattering amplitudes of perturbative string theory at high energy and investigate the relationship between null string and the Ambitwistor string, a worldsheet narrative of the S-matrix formalism of scattering theory developed by Cachazo, He, and Yuan.