Two years ago, Joel Friedman submitted a paper purporting to prove the Hanna Neumann Conjecture, which eventually turned out to contain a fatal bug and was withdrawn. Quite recently, Friedman repeated his attempt at proof with paper "Sheaves on Graphs and a Proof of the Hanna Neumann Conjecture": http://arxiv.org/abs/1105.0129 . Has this attempt been verified by anyone or is still under review?
closed as off topic by Gerald Edgar, Qiaochu Yuan, Noah Snyder, Kevin Buzzard, Mark Sapir Jun 5 '11 at 12:08
Questions on MathOverflow are expected to relate to research level mathematics within the scope defined by the community. Consider editing the question or leaving comments for improvement if you believe the question can be reworded to fit within the scope. Read more about reopening questions here.If this question can be reworded to fit the rules in the help center, please edit the question.
I don't think that this latest round has been independently verified.
Igor Mineyev has also announced a solution. See http://www.math.uiuc.edu/~mineyev/math/