Low regularity local well-posedness of the Derivative Nonlinear Schr\"odinger Equation with periodic initial data

The Cauchy problem for the derivative nonlinear Schr"odinger equation with periodic boundary condition is considered. Local well-posedness for periodic initial data u_0 in the space ^H^s_r, defined by the norms ||u_0||{^H^s_r}=||<xi>^s ^u_0||{l^r’} is shown in the parameter range s>= 1/2, 2>r>4/3. The proof is based on an adaptation of the gauge transform to the periodic setting and an appropriate variant of the Fourier restriction norm method.