Particle with torsion on 3d null-curves

We consider a (2 + 1)-dimensional mechanical system with the Lagrangian lin ear in the torsion of a light-like curve. We give Hamiltonian formulation o f this system and show that its mass and spin spectra are defined by one-di mensional nonrelativistic mechanics with a cubic potential. Consequently, t his system possesses the properties typical of resonance-like particles.