Quantum relativistic string and multiplicative dual model

A classical and quantum covariant description of the relativistic string is made using new dynamical variables. The excited states of the string lie along the straight-line Regge trajectories with a quantized slope parameter J + β1 = (β0 + α'M2)/m, where J is the spin, M is the mass of the state, β1, β0 and α' are fixed constants, m is a positive integer. The found new multiplicative dual models have a similar spectrum which is narrower than the one given by the traditional model. The found models involve free of ''ghosts'' models with the leading Regge trajectory intercept equaling 1/2