The KGB obstruction conjecture for local extensions with cyclic p-Sylow subgroup

Let kk be an algebraically closed field of characteristic pp, and let GG be a finite group. A local GG-extension is a finite GG-Galois extension of formal power series rings over kk. The KGB obstruction is the obstruction to lifting such an extension to characteristic zero arising from the KGB invariant. A group is a local Oort group if every local extension with that group lifts to characteristic zero.

KGB obstruction conjecture. The KGB obstruction is the only obstruction to the local lifting problem for local GG-extensions where GG has cyclic pp-Sylow subgroup. In particular, DpnD_{p^n} is a local Oort group when pp is odd.

This conjecture generalizes the known result for metacyclic groups and would settle the local lifting problem for the groups DpnD_{p^n} in odd characteristic. It is known when the pp-Sylow subgroup of GG is Z/p{\mathbb Z}/p, but remains open in general.

Sources & referencesView supporting material

Primary source

Andrew Obus, “Lifting of curves with automorphisms”, arXiv:1703.01191 (2017).

Additional references

2 papers in this index state this conjecture (2015–2017). The statement above is taken from the most recent of them; the others are arXiv:1502.07623.

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