Elliptic curves of rank two and generalised Kato classes

Abstract

Heegner points play an outstanding role in the study of the Birch and Swinnerton-Dyer conjecture, providing canonical Mordell–Weil generators whose heights encode first derivatives of the associated Hasse–Weil L-series. Yet the fruitful connection between Heegner points and L-series also accounts for their main limitation, namely that they are torsion in (analytic) rank \(>1\). This partly expository article discusses the generalised Kato classes introduced in Bertolini et al. (J Algebr Geom 24:569–604, 2015) and Darmon and Rotger (J AMS 2016), stressing their analogy with Heegner points but explaining why they are expected to give non-trivial, canonical elements of the idoneous Selmer group in settings where the classical L-function (of Hasse–Weil–Artin type) that governs their behaviour has a double zero at the centre. The generalised Kato class denoted \(\kappa (f,g,h)\) is associated to a triple (f, g, h) consisting of an eigenform f of weight two and classical p-stabilised eigenforms g and h of weight one, corresponding to odd two-dimensional Artin representations \(V_g\) and \(V_h\) of \(\mathrm {Gal\,}(H/\mathbb {Q})\) with p-adic coefficients for a suitable number field H. This class is germane to the Birch and Swinnerton-Dyer conjecture over H for the modular abelian variety E over \(\mathbb {Q}\) attached to f. One of the main results of Bertolini et al. (2015) and Darmon and Rotger (J AMS 2016) is that \(\kappa (f,g,h)\) lies in the pro-p Selmer group of E over H precisely when \(L(E,V_{gh},1)=0\), where \(L(E,V_{gh},s)\) is the L-function of E twisted by \(V_{gh}:= V_g\otimes V_h\). In the setting of interest, parity considerations imply that \(L(E,V_{gh},s)\) vanishes to even order at \(s=1\), and the Selmer class \(\kappa (f,g,h)\) is expected to be trivial when \({\mathrm {ord}}_{s=1}L(E,V_{gh},s) >2\). The main new contribution of this article is a conjecture expressing \(\kappa (f,g,h)\) as a canonical point in \((E(H)\otimes V_{gh})^{G_\mathbb {Q}}\) when \({\mathrm {ord}}_{s=1} L(E,V_{gh},s)=2\). This conjecture strengthens and refines the main conjecture of Darmon et al. (Forum Math Pi 3:e8, 2015) and supplies a framework for understanding the results of Darmon et al. (2015), Bertolini et al. (2015) and Darmon and Rotger (J AMS 2016).