Low regularity data for the periodic Kawahara equation
  In this paper, we consider the well-posedness for the Cauchy problem of the Kawahara equation with low regularity data in the periodic case. We obtain the local well-posedness for $s \geq -3/2$ by a variant of the Fourier restriction norm method. On the other hand, we show the ill-posedness for $s <-3/2$ in weak sense. Moreover, the local solutions can be extended globally in time for $s \geq -1$ by the I-method. This is a shape contrast to the results in the non-periodic setting, where the critical exponent is equal to -2. 
Takamori Kato
math.AP