Turnaround radius in $\Lambda$CDM, and dark matter cosmologies with
  shear and vorticity
  We determine the relationship between the turnaround radius, $R_{\rm t}$, and
mass, $M_{\rm t}$, in $\Lambda$CDM, and in dark energy scenarios, using an
extended spherical collapse model taking into account the effects of shear and
vorticity. We find a more general formula than that usually described in
literature, showing a dependence of $R_{\rm t}$ from shear, and vorticity. The
$R_{\rm t}-M_{\rm t}$ relation differs from that obtained not taking into
account shear, and rotation, especially at galactic scales, differing $\simeq
30\%$ from the result given in literature. This has effects on the constraint
of the $w$ parameter of the equation of state. We compare the $R_{\rm t}-M_{\rm
t}$ relationship obtained for the $\Lambda$CDM, and different dark energy
models to that obtained in the $f(R)$ modified gravity (MG) scenario. The
$R_{\rm t}-M_{\rm t}$ relationship in $\Lambda$CDM, and dark energy scenarios
are tantamount to the prediction of the $f(R)$ theories. Then, the $R_{\rm
t}-M_{\rm t}$ relationship is not a good probe to test gravity theories beyond
Einstein's general relativity.
