  The Press-Schechter theory of the cosmological mass function and its
modifications allow to constraint cosmological scenarios of the structure
formation. Recently a few new models have been suggested that explored the
influence of anisotropic collapse on the shape of the mass function. I discuss
in more detail a particular model that assumes that a fluid particle becomes a
part of a gravitationally bound halo when the smallest eigenvalue of the
deformation tensor of the filtered initial density field reaches a certain
threshold (like the filtered density contrast reaches the threshold in the
Press-Schechter formalism). Choosing the smallest eigenvalue guarantees that
the fluid particle in question experiences collapse along all three axes. The
model shows a better agreement with the N-body simulations than the standard
Press-Schechter model.

Astrophysics