Bloch–Kato dimension formula for étale cohomology Selmer groups

Let XX be as above, let pp be a prime of good reduction, and let m<2r1m<2r-1. Write Heˊtm(XQ,Qp(r))H^m_{\operatorname{\acute{e}t}}(X_{\overline{\mathbb{Q}}},\mathbb{Q}_p(r)) for the pp-adic étale cohomology representation, and let Hf1H^1_f and H0H^0 denote the corresponding Bloch–Kato Selmer and invariant groups. Let VV^* denote the dual representation. Bloch–Kato dimension formula.

dimHf1(Q,Heˊtm(XQ,Qp(r)))=dimHf1(Qp,Heˊtm(XQ,Qp(r)))dimH0(R,Hm(XQ,Qp(r)))dimH0(Q,Hm(XQ,Qp(r1))).\begin{aligned} \dim H^1_f(\mathbb{Q},H^m_{\operatorname{\acute{e}t}}(X_{\overline{\mathbb{Q}}},\mathbb{Q}_p(r))) ={}&\dim H^1_f(\mathbb{Q}_p,H^m_{\operatorname{\acute{e}t}}(X_{\overline{\mathbb{Q}}},\mathbb{Q}_p(r)))\\ &-\dim H^0(\mathbb{R},H^m(X_{\overline{\mathbb{Q}}},\mathbb{Q}_p(r)))\\ &-\dim H^0(\mathbb{Q},H^m(X_{\overline{\mathbb{Q}}},\mathbb{Q}_p(r-1))^*). \end{aligned}

This is presented as a form of part of the Bloch–Kato conjectures, obtained using Poitou–Tate duality. Its validity is not established in general.

Sources & referencesView supporting material

Primary source

Netan Dogra, “2-descent for Bloch–Kato Selmer groups and rational points on hyperelliptic curves I”, arXiv:2312.04996 (2026).

Additional references

2 papers in this index state this conjecture (2010–2023). The statement above is taken from the most recent of them; the others are arXiv:1010.3833.

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