Conjecture F+ for fibrations with controlled Brauer classes

Let kk be a number field. Let π+=(M,(Lm)mM,(bm)mM,(Km)mM)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:WPk1p:W\to{\mathbf P}^1_k, and U=Pk1MU={\mathbf P}^1_k\setminus M. Let BBr(p1(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 cU(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

cU(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.

Sources & referencesView supporting material

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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