Using high resolution N-body simulations of stellar disks embedded in cosmologically motivated dark matter halos , we study the evolution of bars and the transfer of angular momentum between halos and bars .
We find that dynamical friction results in some transfer of angular momentum to the halo , but the effect is much smaller than previously found in low resolution simulations and is incompatible with early analytical estimates .
After 5 Gyrs of evolution the stellar component loses only 5 % – 7 % of its initial angular momentum .

Mass and force resolutions are crucial for the modeling of bar dynamics .
In low resolution ( 300 – 500 pc ) simulations we find that the bar slows down and angular momentum is lost relatively fast .
In simulations with millions of particles reaching a resolution of 20-40 pc , the pattern speed may not change over billions of years .
Our high resolution models produce bars which are fast rotators , where the ratio of the corotation radius to the bar major semi-axis lies in the range \R = 1.2 - 1.7 , marginally compatible with observational results .
In contrast to many previous simulations , we find that bars are relatively short .
As in many observed cases , the bar major semi-axis is close to the exponential length of the disk .

The transfer of angular momentum between inner and outer parts of the disk plays a very important role in the secular evolution of the disk and the bar .
The bar formation increases the exponential length of the disk by a factor of 1.2 -1.5 .
The transfer substantially increases the stellar mass in the center of the galaxy and decreases the dark matter-to-baryons ratio .
As the result , the central 2 kpc region is always strongly dominated by the baryonic component .
At intermediate ( 3 – 10 kpc ) scales the disk is sub-dominant .
These models demonstrate that the efficiency of angular momentum transfer to the dark matter has been greatly overestimated .
More realistic models produce bar structure in striking agreement with observational results .