Stable solutions of inflation driven by vector fields
  Many models of inflation driven by vector fields alone have been known to be
plagued by pathological behaviors, namely ghost and/or gradient instabilities.
In this work, we seek a new class of vector-driven inflationary models that
evade all of the mentioned instabilities. We build our analysis on the
Generalized Proca Theory with an extension to three vector fields to realize
isotropic expansion. We obtain the conditions required for quasi de-Sitter
solutions to be an attractor analogous to the standard slow-roll one and those
for their stability at the level of linearized perturbations. Identifying the
remedy to the existing unstable models, we provide a simple example and
explicitly show its stability. This significantly broadens our knowledge on
vector inflationary scenarios, reviving potential phenomenological interests
for this class of models.
