Abundance gradients along the Galactic disc from chemical evolution
  models
  In this paper, we study the formation and chemical evolution of the Milky Way
disc with particular focus on the abundance patterns ([$\alpha$/Fe] vs. [Fe/H])
at different Galactocentric distances, the present-time abundance gradients
along the disc and the time evolution of abundance gradients. We consider the
chemical evolution models for the Galactic disc developed by Grisoni et al.
(2017) for the solar neighborhood, both the two-infall and the one-infall ones,
and we extend our analysis to the other Galactocentric distances. In
particular, we examine the processes which mainly influence the formation of
the abundance gradients: the inside-out scenario, a variable star formation
efficiency, and radial gas flows. We compare our model results with recent
abundance patterns obtained along the Galactic disc from the APOGEE survey and
with abundance gradients observed from Cepheids, open clusters, HII regions and
PNe. We conclude that the inside-out scenario is a key ingredient, but cannot
be the only one to explain abundance patterns at different Galactocentric
distances and abundance gradients. Further ingredients, such as radial gas
flows and variable star formation efficiency, are needed to reproduce the
observed features in the thin disc. The evolution of abundance gradients with
time is also shown, although firm conclusions cannot still be drawn.
