  Particle-hole instabilities are studied within a two dimensional model of
fermions interacting with antiferromagnetic spin fluctuations (spin-fermion
model). In contrast to previous works, we assume that neighboring hot spots
overlap due to a shallow dispersion of the electron spectrum in the antinodal
region and include in the consideration effects of a remnant low energy and
momentum Coulomb interaction. It turns out that this modification of the model
drastically changes the behavior of the system. The leading particle-hole
instability at not very weak fermion-fermion interaction is no longer a charge
density wave with a modulation along the diagonals of the Brillouin zone
predicted previously but a Pomeranchuk-type deformation of the Fermi surface
breaking the C$_{4}$ symmetry of the system. This order does not prevent from
further phase transitions at lower temperatures. We show that, depending on
parameters of the interaction, either d-wave superconductivity or charge
density wave with modulations along the bonds of the $CuO$ lattice is possible.
The low momentum remnant Coulomb interaction enhances the d-form factor of the
charge density wave. Comparison with experimental data allows us to conclude
that in many cuprate compounds the conditions for the proposed scenario are
indeed fulfilled. Our results may explain important features of the charge
modulations observed recently.
