Does modified gravity predict fast stellar bars in spiral galaxies?
  The evolution of disk galaxies in modified gravity is studied by using
high-resolution N-body simulations. More specifically, we use the weak field
limit of two modified gravity theories, i.e., nonlocal gravity (NLG) and
scalar-tensor-vector gravity known as MOG, and ignore the existence of dark
matter halo. On the other hand, we construct the same models in the standard
dark matter model and compare their dynamics with the galactic models in
modified gravity. It turns out that there are serious differences between
galactic models in these different viewpoints. For example, we explicitly show
that the galactic models in modified gravity, host faster bars compared to the
dark matter case. On the other hand, final stellar bars are weaker in modified
gravity. These facts are not new and have already been reported in our previous
simulations for exponential galactic models. Therefore, our main purpose in
this study is to show that the above-mentioned differences, with emphasis on
the speed of the bars, are independent of the initial density profile of the
adopted disk/halo. To do so, we employ different profiles for the disk and halo
and show that the results remain qualitatively independent of the initial
galactic models. Moreover, a more accurate method has been used to quantify the
kinematic properties of the stellar bar. Our results imply that contrary to the
dark matter models, bars in modified gravity are fast rotators which never
leave the fast-bar region until the end of the simulation.
