Non-linear spherical collapse in tachyon models, and a comparison of
  collapse in tachyon and quintessence models of dark energy
  We study evolution of perturbations in dark matter and dark energy for
spherical collapse. We study Tachyon models of dark energy using the approach
outlined in Rajvanshi and Bagla (2018). We work with models that are allowed by
current observations. We find that as with Quintessence models allowed by
observations, dark energy perturbations do not affect evolution of
perturbations in dark matter in a significant manner. Perturbations in dark
energy remain small for such models. In order to compare different classes of
dark energy models, we use reconstruction of potentials and study dark matter
and dark energy perturbations for same expansion history in the two models. We
find that dark matter perturbations carry no imprint of the class of dark
energy models for the same expansion history: this is significant in that we
can work with any convenient model to study clustering of dark matter. We find
that the evolution of dark energy perturbations carries an imprint of the class
of models in that these grow differently in Tachyon models and Quintessence
models. However, the difference between these diminishes for (1+w)<<1 and hence
prospects for differentiating between models using characteristics of
perturbations are limited in our Universe.
