  Classic inflation, the theory described in textbooks, is based on the idea
that, beginning from typical initial conditions and assuming a simple inflaton
potential with a minimum of fine-tuning, inflation can create exponentially
large volumes of space that are generically homogeneous, isotropic and flat,
with nearly scale-invariant spectra of density and gravitational wave
fluctuations that are adiabatic, Gaussian and have generic predictable
properties. In a recent paper, we showed that, in addition to having certain
conceptual problems known for decades, classic inflation is for the first time
also disfavored by data, specifically the most recent data from WMAP, ACT and
Planck2013. Guth, Kaiser and Nomura and Linde have each recently published
critiques of our paper, but, as made clear here, we all agree about one thing:
the problematic state of classic inflation. Instead, they describe an
alternative inflationary paradigm that revises the assumptions and goals of
inflation, and perhaps of science generally.
