Vinatier's freeness conjecture for the square root of the inverse different

Let L/KL/K be a finite weakly ramified Galois extension of number fields, with G=Gal(L/K)G=\operatorname{Gal}(L/K), ring of integers OL\mathcal{O}_L, and different DL/K\mathcal{D}_{L/K}. When it exists, let AL/K\mathcal{A}_{L/K} be the unique fractional ideal satisfying

(AL/K)2=(DL/K)1.(\mathcal{A}_{L/K})^2=(\mathcal{D}_{L/K})^{-1}.

For an extension of odd degree, this ideal exists and is a Z[G]\mathbb{Z}[G]-module. Vinatier's conjecture. If L/KL/K is a weakly ramified Galois extension of number fields of odd degree, then AL/K\mathcal{A}_{L/K} is a free Z[G]\mathbb{Z}[G]-module. The conjecture extends the known result for tamely ramified extensions, where the square root of the inverse different is free over the integral group ring. Its status is not resolved in the supplied source.

Sources & referencesView supporting material

Primary source

Y. Kuang, “On Galois-Gauss sums and the square root of the inverse different”, arXiv:2210.10347 (2022).

Additional references

2 papers in this index state this conjecture (2022). The statement above is taken from the most recent of them; the others are arXiv:2203.14131.

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