A note on quantum field theories with a minimal length scale

The aim of this note is to address the low energy limit of quantum field theories with a minimal length scale. The essential feature of these models is that the mininal length acts as a regulator in the asymptotic high energy limit which is incorporated through an infinite series of higher order derivatives. If one investigates a perturbative expansion in inverse powers of the Planck mass, one generically obtains extra poles in the propagator, and instabilities connected with the higher order derivative Lagrangian, which are however artifacts of truncating the series.