The (p,q) inflation model
  In this paper we propose a new inflation model named (p,q) inflation model in which the inflaton potential contains both positive and negative powers of inflaton field in the polynomial form. We will show that such a simple model can easily generate a large amplitude of tensor perturbation and a negative running of spectral index with large absolute value. 
Qing-Guo Huang
astro-ph.CO gr-qc hep-ph hep-th