Beilinson's regulator conjecture for smooth projective curves

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Let XX be a smooth, projective, geometrically connected curve of genus gg defined over Q\mathbb{Q}. Let K4(3)(X)K_4^{(3)}(X) denote the third Adams eigenspace of K4(X)⊗QK_4(X)\otimes\mathbb{Q}, let rBr_B be the regulator map

rB:K4(3)(X)⟶H1(X(C),R(2))+,r_B:K_4^{(3)}(X)\longrightarrow H^1(X(\mathbb{C}),\mathbb{R}(2))^+,

and let H1(X(C),Q)+H_1(X(\mathbb{C}),\mathbb{Q})^+ be the fixed part under complex conjugation. Beilinson's conjecture. The following statements hold: K4(3)(X)K_4^{(3)}(X) is a Q\mathbb{Q}-vector space of dimension gg; and, if (Ξ1,…,Ξg)(\Xi_1,\ldots,\Xi_g) is a Q\mathbb{Q}-basis of K4(3)(X)K_4^{(3)}(X) and (γ1,…,γg)(\gamma_1,\ldots,\gamma_g) is a Q\mathbb{Q}-basis of H1(X(C),Q)+H_1(X(\mathbb{C}),\mathbb{Q})^+, then

L(g)(X,−1)=cπ−2gdet⁡(∫γirB(Ξj))1≤i,j≤gL^{(g)}(X,-1)=c\pi^{-2g}\det\left(\int_{\gamma_i}r_B(\Xi_j)\right)_{1\leq i,j\leq g}

for some c∈Q×c\in\mathbb{Q}^\times. This is the n=3n=3 case of Beilinson's conjecture, relating regulators in motivic or KK-theory to special values of the curve's LL-function; the source does not provide a resolution status.

References

Primary source

François Brunault, David T. -B. G. Lilienfeldt and Yusuke Nemoto, “Elements in K_4 and regulator maps of Fermat curves”, arXiv:2606.24532 (2026).

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