Primordial fluctuations and non-Gaussianities in sidetracked inflation
  Heavy scalar fields can undergo an instability during inflation as a result
of their kinetic couplings with the inflaton. This is known as the geometrical
destabilization of inflation, as it relies on the effect of the negative
curvature of the field-space manifold overcoming the stabilizing force of the
potential. This instability can drive the system away from its original path in
field space into a new inflationary attractor, a scenario that we dub
sidetracked inflation. We study this second phase and its observable
consequences in several classes of two-field models. We show that cosmological
fluctuations exhibit varied behaviours depending on the potential and the field
space geometry, and that they can be captured by single-field effective
theories with either a modified dispersion relation, a reduced speed of sound,
or an imaginary one --- the latter case describing a transient tachyonic growth
of the fluctuations. We also numerically calculate the bispectrum with the
transport approach, finding large non-Gaussianities of equilateral and
orthogonal shapes. In the hyperbolic geometry the potentials of our models
present a pole at the boundary of the Poincar\'e disk and we discuss their
relationships with $\alpha$-attractors.
