Conformal invariant tensionless strings

We study a string theory with action proportional to the linear size of surfaces. This property makes the theory very close to the Feynman path integral for a point-like relativistic particle. It is a tensionless string theory because for the flat Wilson loop the action reduces to its perimeter. We solved and quantized this high-derivative nonlinear two-dimensional conformal field theory. The absence of conformal anomaly requires the space–time to be 13-dimensional. We have found that all particles, with arbitrary large spin, are massless. This pure massless spectrum is consistent with the tensionless character of the theory and we speculate that it may describe unbroken phase of standard string theory when α′→∞.