Conjecture F+ for fibrations with controlled Brauer classes

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Let kk be a number field. Let π+=(M,(Lm)m∈M,(bm)m∈M,(Km)m∈M)∈P+\pi_+=(M,(L_m)_{m\in M},(b_m)_{m\in M},(K_m)_{m\in M})\in{\mathscr P}_+, determining a variety WW, a smooth morphism p:W→Pk1p:W\to{\mathbf P}^1_k, and U=Pk1∖MU={\mathbf P}^1_k\setminus M. Let B⊆Br⁡(p−1(U))B\subseteq\operatorname{Br}(p^{-1}(U)) be the finite subgroup generated by the classes associated with the characters in Cm=Ker⁡(H1(Lm,Q/Z)→H1(Km,Q/Z))C_m=\operatorname{Ker}(H^1(L_m,{\mathbf Q}/{\mathbf Z})\to H^1(K_m,{\mathbf Q}/{\mathbf Z})). For c∈U(k)c\in U(k), let Wc(Ak)BW_c({\mathbf A}_k)^B be the adelic points orthogonal to the image of BB under restriction to Br⁡(Wc)\operatorname{Br}(W_c).

Conjecture F+. The subset

⋃c∈U(k)Wc(Ak)B\bigcup_{c\in U(k)}W_c({\mathbf A}_k)^B

is dense in W(Ak)W({\mathbf A}_k).

This is proposed as an improved substitute for Conjecture F and incorporates a prescribed Brauer–Manin condition on the fibres. Its status is not specified in the source.

References

Primary source

Yonatan Harpaz, Dasheng Wei and Olivier Wittenberg, “Rational points on fibrations with few non-split fibres”, arXiv:2109.03547 (2022).

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