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Here, we present our results of numerical simulations from the gravitational collapse of massive, magnetized molecular cloud cores. We show that massive stars assemble quickly with mass accretion rates exceeding 10^-3 M_sol/year and confirm that the mass accretion during the collapsing phase is much more efficient than predicted by selfsimilar collapse solutions,
dM/dt ~ c^3/G. We find that during protostellar assembly the mass accretion reaches 20 - 100 c^3/G. Furthermore, we determined the self-consistent structure of bipolar outflows that are produced in our three dimensional magnetized collapse simulations. These outflows produce cavities out of which radiation pressure can be released, thereby reducing the limitations on the final mass of massive stars formed by gravitational collapse. Moreover, we
argue that the extraction of angular momentum by disk-threaded magnetic fields and/or by the appearance of bars with spiral arms significantly enhance the mass accretion rate, thereby helping the massive protostar to assemble more quickly.
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