Observational constraints on cosmological future singularities
  In this work we consider a family of cosmological models featuring future
singularities. This type of cosmological evolution is typical of dark energy
models with an equation of state violating some of the standard energy
conditions (e.g. the null energy condition). Such kind of behavior, widely
studied in the literature, may arise in cosmologies with phantom fields,
theories of modified gravity or models with interacting dark matter/dark
energy. We briefly review the physical consequences of these cosmological
evolution regarding geodesic completeness and the divergence of tidal forces in
order to emphasize under which circumstances the singularities in some
cosmological quantities correspond to actual singular spacetimes. We then
introduce several phenomenological parameterizations of the Hubble expansion
rate to model different singularities existing in the literature and use SN Ia,
BAO and H(z) data to constrain how far in the future the singularity needs to
be (under some reasonable assumptions on the behaviour of the Hubble factor).
We show that, for our family of parameterizations, the lower bound for the
singularity time can not be smaller than about 1.2 times the age of the
universe, what roughly speaking means about 2.8 Gyrs from the present time.
