  We investigate the effect of rotating, triaxial halos on disk galaxies
through an extensive set of numerical N-body simulations. Our simulations use a
rigid potential field for the halos and bulges and collisionless particles for
the disks. The triaxiality and the rotation rate of the halo are varied, as
well as the masses of all three galaxy components. We analyze both the bar
stability and spiral response of the disk under these conditions.
  We characterize most of our models by the mass ratio of the disk to the halo
at 2.3 disk scale lengths, (M_d/M_h)_Rsun. For models with a mass ratio greater
than 0.8, a halo pattern speed Omega_h = 6.7 km/s/kpc, and an
intermediate-to-major axis ratio q_b=0.85, a strong bar will develop within 3
Gyr, even for models with a bulge mass M_b=0.3M_d. Models in which the bulge
mass is reduced by half develop bars earlier and with lower Omega_h.
  We create an artificial Hubble sequence of galaxies by varying the
bulge-to-disk ratio of our models from 0 to 2.5. The torque induced by a
rotating, non-axisymmetric halo creates bisymmetric spiral structure in the
disk. We find the the pitch angle of the spiral arms in these models follows
the same general trend found in observations of spiral galaxies, namely that
later type galaxies have higher pitch angles. Our simulations follow closely
the observational relation of spiral pitch angle with maximum rotational
velocity of the disk, where galaxies with faster rotation have more tightly
wound spiral arms. This relation is followed in our simulations regardless of
whether the dominating mass component of the galaxy is the disk, the halo, or
the bulge.
