Towards geometric inflation: the cubic case
  We present an up to cubic curvature correction to General Relativity with the
following features: (i) its vacuum spectrum solely consists of a graviton and
is ghost-free, (ii) it possesses well-behaved black hole solutions which
coincide with those of Einsteinian cubic gravity, (iii) its cosmology is
well-posed as an initial value problem and, most importantly, (iv) it entails a
geometric mechanism triggering an inflationary period in the early universe
(driven by radiation) with a graceful exit to a late-time cosmology arbitrarily
close to $\Lambda$CDM.
