Bar instabilities in disk galaxies: the role of the triaxial halo

We investigate the growth of bar instabilities inside a stellar-gaseous dis k using a smooth particle hydrodynamics code. We carried out several simula tions embedding the disk inside dark matter haloes with different masses, s hapes and different dynamical states. We aim to focus on the role of a non axisymmetric halo and its evolution on the bar triggering. Our approach all ows us to follow, for the first time in a self-consistent way, the effects of a live halo on the disk evolution. We point out that a massive halo not yet relaxed has a major role in triggering such an instability. Moreover, a relaxed halo with the same mass as that of the disk cannot avoid bar insta bility lasting at least 1 Gyr.