  The effects of adiabatic phonons on a spin-fermion model for high T_c
cuprates are studied using numerical simulations. In the absence of
electron-phonon interactions (EPI), stripes in the ground state are observed
for certain dopings while homogeneous states are stabilized in other regions of
parameter space. Different modes of adiabatic phonons are added to the
Hamiltonian:breathing, shear and half-breathing modes. Diagonal and
off-diagonal electron-phonon couplings are considered. It is observed that
strong diagonal EPI generate stripes in previously homogeneous states, while in
striped ground states an increase in the diagonal couplings tends to stabilize
the stripes, inducing a gap in the density of states (DOS) and rendering the
ground state insulating. The off-diagonal terms, on the other hand, destabilize
the stripes creating inhomogeneous ground states with a pseudogap at the
chemical potential in the DOS. The breathing mode stabilizes static diagonal
stripes; while the half-breathing (shear) modes stabilize dynamical (localized)
vertical and horizontal stripes. The EPI induces decoherence of the
quasi-particle peaks in the spectral functions.
