Getting the tiger by the tail: Probing the turnaround radius of
  structures with outer halo density profiles
  In this paper we develop a new semianalytical approach to quantifying the
density profile of outer dark matter halos, motivated by the remarkable
universality those profiles, for a wide range of dynamical parameters of the
inner halos. We show that our minimalist model is robust under significant
variations of its input parameters around the currently known values and we
identify the turnaround radius as the most important scale of the problem.
Based on that observation, we argue that the turnaround radius accurately
represents the transition to the external density profile, and we provide a
universal test based on geometrical characteristics of the outer profile as a
proposal for measuring the turnaround radius of structures.
