Cutoff in the Lyman-$\alpha$ forest power spectrum: warm IGM or warm
  dark matter?
  We re-analyse high redshift and high resolution Lyman-$\alpha$ forest spectra
considered in (Viel et al 2013), seeking to constrain the properties of warm
dark matter particles. Compared to this previous work, we consider a wider
range of thermal histories of the intergalactic medium. We find that both warm
and cold dark matter models can explain the cut-off observed in the flux power
spectra of high-resolution observations equally well. This implies, however,
very different thermal histories and underlying re-ionisation models. We
discuss how to remove this degeneracy.
