On the phase diagram of a two-dimensional electron gas near integer fillings and fractions such as 1/5 and 1/7

The phase diagram of the 2DEG at high magnetic fields is discussed in the light of recent experiments showing the presence of crystalline phases around integer as well as certain fractional fillings. We suggest that a Hall crystal is a proper competing phase compatible with the odd denominator rule that characterizes the fractional quantum Hall effect, and that near integer filling a pinned crystal coexists with an incompressible fluid with no longitudinal resistance.