The Débes–Deschamps conjecture on finite split embedding problems

Let kk be a Hilbertian field. A finite split embedding problem over kk is an epimorphism

α:GGal(L/k),\alpha:G\rightarrow \operatorname{Gal}(L/k),

where GG is finite, L/kL/k is Galois, and there is an embedding α:Gal(L/k)G\alpha':\operatorname{Gal}(L/k)\rightarrow G with αα=idGal(L/k)\alpha\circ\alpha'=\operatorname{id}_{\operatorname{Gal}(L/k)}. A solution is an isomorphism β:Gal(F/k)G\beta:\operatorname{Gal}(F/k)\rightarrow G for a Galois extension F/kF/k containing LL, such that αβ\alpha\circ\beta is the restriction map to Gal(L/k)\operatorname{Gal}(L/k). Débes–Deschamps conjecture. Each finite split embedding problem over any Hilbertian field has a solution. The conjecture would imply the inverse Galois problem over every Hilbertian field and the Shafarevich conjecture for the maximal cyclotomic extension of Q\mathbb{Q}. It is known in some important cases, including when the base field is a rational function field in one variable over an ample field, but is not established in general.

Sources & referencesView supporting material

Primary source

François Legrand, “On finite embedding problems with abelian kernels”, arXiv:2112.12170 (2022).

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