Bigger Rip with No Dark Energy
  By studying a modified Friedmann equation which arises in an extension of general relativity which accommodates a time-dependent fundamental length $L(t)$, we consider cosmological models where the scale factor diverges with an essential singularity at a finite future time. Such models have no dark energy in the conventional sense of energy possessing a truly simple pressure-energy relationship. Data on supernovae restrict the time from the present until the Rip to be generically longer than the current age of the Universe. 
Paul H. Frampton and Tomo Takahashi