Bulge formation in disk galaxies with MOND
  The formation of galaxies and their various components can be stringent tests
of dark matter models and of gravity theories. In the standard cold dark matter
(CDM) model, spheroids are formed through mergers in a strongly hierarchical
scenario, and also in the early universe through dynamical friction in clumpy
galaxies. More secularly, pseudo-bulges are formed by the inner vertical
resonance with bars. The high efficiency of bulge formation is in tension with
observations in the local universe of a large amount of bulge-less spiral
galaxies. In the present work, the formation of bulges in very gas-rich
galaxies, as those in the early universe, is studied in the Milgrom's MOdified
Newtonian Dynamics (MOND), through multi-grid simulations of the non-linear
gravity, including the gas dissipation, star formation and feedback.
  Clumpy disks are rapidly formed, as in their Newtonian equivalent systems.
However, the dynamical friction is not as efficient, in the absence of dark
matter halos, and the clumps have no time to coalesce into the center to form
bulges, before they are eroded by stellar feedback and shear forces. Previous
work has established that mergers are less frequent in MOND, and classical
bulges are expected less massive. It is now shown that gas-rich clumpy galaxies
in the early universe do not form bulges.
  Since pseudo-bulges are formed with a similar rate as in the Newtonian
equivalent systems, it can be expected that the contribution of pseudo-bulges
is significantly higher in MOND.
