# Which cases of Beilinson-Bloch-Kato for elliptic motives are known?

Let $$V$$ be a semisimple geometric Galois representation of a number field. Then the Bloch-Kato conjectures state that $$\operatorname{ord}_{s=0}{L(V^*(1),s)} = \operatorname{dim}{H^1_f(G_k,V)}-\operatorname{dim}{H^0(G_k,V)}.$$

Beilinson has similar conjectures relating the LHS to algebraic K-theory rather than Selmer groups.

If $$E$$ is an elliptic curve, and we set $$V=h_1(E)=h^1(E)(1)$$, then the conjecture above is equivalent to the statement that the analytic rank is the same as the rank of the $$p$$-adic Selmer group. Beilinson's conjecture in this case is equivalent to the assertion that the analytic rank equals the Mordell-Weil rank.

For $$V$$ of non-negative weight, the conjecture simply asserts that the Selmer group vanishes. Assuming the conjectured properties of $$L$$-functions, the conjectures for $$V$$ and $$V^*(1)$$ are equivalent (in particular, the case of weight $$\le -2$$ follows from the case of weight $$\ge 0$$).

My question is: which cases of this conjecture are known for $$V=\operatorname{Sym}^k{h^1(E)}(n)$$ for $$E$$ an elliptic curve? I know that many cases are known when $$k=n=1$$ due to the theory of Heegner points, Gross-Zagier, etc, but I'd like to know what's known outside that range. (I'm especially interested in cases where $$w=k-2n=-2, -3, -4$$).

Feel free to give reference, or even better, specific elliptic curves in LMFDB.

• One way to construct elements in $H^1_f(V)$ is to use the $p$-adic realization map from motivic cohomology. In you particular situation, elements in motivic cohomology have been constructed by Deninger for $n=k+1$ using torsion points of $E$ (see Higher regulators and Hecke L-series of imaginary quadratic fields I & II). One can show that these elements are linearly independent by computing the archimedean regulator (but the relation with the $L$-function is not known). I don't know if computing the $p$-adic regulator has ever been implemented. – François Brunault Sep 3 '20 at 16:45
• Recarding the case $k=1$, the motivic elements have been constructed by Beilinson. Gealy has computed their $p$-adic realisation in his PhD thesis. He also shows a result of the form ''$H^1(V)$ has rank $1$'' (as expected) but it's conditional on the Leopoldt-type conjecture that $H^2(V)$ is finite, and on Kato's main conjecture for $E$. – François Brunault Sep 3 '20 at 16:53
• You probably want some assumptions on the base number field. If it's not totally real or CM, then we know basically nothing. – David Loeffler Sep 4 '20 at 7:18
• To be honest, I was really interested in elliptic curves over $\mathbb{Q}$ or maybe a quadratic imaginary field. So that's no issue – David Corwin Sep 6 '20 at 2:44

## 1 Answer

There are three approaches I know of to studying $$H^1_{\mathrm{f}}(K, V)$$, where $$V = Sym^k(h^1(E))(n))$$. All rely on $$E$$ being modular, so let me assume this henceforth (of course, this is no assumption if $$K = \mathbf{Q}$$, or for some other small-degree fields).

• Via "anticyclotomic" Euler systems, such as Heegner points (and the closely-related method of "arithmetic level-raising"). This works extremely well when $$k = n = 1$$, and $$K$$ is totally real (or $$K$$ is CM and $$E$$ is base-extended from $$K^+$$); under these hypotheses we know the BK conjecture holds, for any $$p$$, whenever the analytic rank is 0 or 1 (Zhang, Nekovar). More generally, this might potentially be accessible for any $$n$$ and $$k = 2n-1$$, although huge amounts of work would be needed to carry that out. However, it's entirely impossible to generalise this approach beyond the case of motivic weight $$w = -1$$.

• Via modularity-lifting theorems. This gives a way of studying Selmer groups of representations that have the shape $$W \otimes W^*$$, where $$W$$ is irreducible. More generally, if $$W$$ has some extra structure (e.g. self-duality) which forces $$W \otimes W^*$$ to be reducible, then you can get some information about the cohomology of the pieces. This gives you very nice control over $$Sym^k(h^1(E))(n)$$ for $$k = 2$$ and $$n = 1$$ (or by duality $$n = 2$$) (Diamond--Flach--Guo). More generally, one should be able to get some information about general $$n$$ and $$k = 2n$$ or $$2n-2$$ using the recent work of Newton--Thorne; Theorem 5.6 of this paper tells you something about $$W\otimes W^*$$ where $$W = Sym^k(h^1(E))$$, and this representation breaks up as a sum of $$Sym^{2m}(h^1(E))(m)$$ for $$0 \le m \le k$$. [Caveat: I'm not sure exactly what their method gives; it's possible that you need to twist by an odd quadratic character at some point.] However, this is again restricted to specific values of $$w$$; it won't tell you anything unless $$w = 0$$ or $$w = -2$$.

• Via "cyclotomic" Euler systems, such as Kato's Euler system. This method has the advantage that it can tell you something about general motivic weights (i.e. a fixed $$k$$ and any $$n \in \mathbf{Z}$$). However, it gives you a criterion for vanishing of the $$H^1$$ in terms of p-adic L-functions, and these are only indirectly related to complex $$L$$-functions outside the critical range (i.e. away from $$w = -1$$ in your case). Nonetheless, these p-adic L-functions are computable, so you can check explicitly whether they vanish in examples. For elliptic curves over $$\mathbf{Q}$$, an Euler system for $$Sym^k E$$ exists for $$k = 1$$ due to Kato, and for $$k = 2$$ [*] and $$k = 3$$ due to Zerbes and myself (building on work of lots of other people). So, for example, if $$K = \mathbf{Q}$$, and $$k = 1, 2, 3$$, this would give an approach to proving the vanishing of $$H^1_{\mathrm{f}}(\mathbf{Q}, Sym^k(h^1(E))(n))$$ for your favourite elliptic curve and a specific but arbitrary value of $$n$$ (and $$p$$), using only a finite amount of computation.

[*] Actually there is a caveat here -- embarrassingly, I forgot the statement of my own theorem! -- so the result as published only applies to $$Sym^2(E)$$ twisted by a non-trivial Dirichlet character. But the un-twisted case might also be accessible with some extra work.

• Thanks! What about over an imaginary quadratic field? In one case, I have a specific curve of rank $0$, and I'm interested in it over imaginary quadratic fields over which it has rank $1$. If I can show it explicitly for $k=2,3$, that's really all I need. (But I'm also interested in other cases, e.g., for certain rank $1$ curves over $\mathbb{Q}$.) – David Corwin Sep 6 '20 at 2:48
• I'd be happy to discuss this further but MO isn't really the place for extended conversations -- feel free to get in touch via my warwick.ac.uk email. – David Loeffler Sep 6 '20 at 7:36
• To add to the second bullet-point, it seems that $\operatorname{Sym}^2{h^1(E)}(1)$ is covered by arxiv.org/abs/1411.7661 under some mild assumptions when the curve is modular (known in general e.g., over $\mathbb{Q}$ or a real quadratic field). – David Corwin Dec 30 '20 at 22:58
• Is it fair to say that $k=3$ would use something like Theorem D of arxiv.org/pdf/2003.05960.pdf? – David Corwin Jan 6 at 1:20
• Morally yes, although there are some mildly fiddly technical issues meaning we don't have a full proof written out yet for Sym^3 of an elliptic curve. See arxiv.org/abs/2005.04786 for Sym^3 of modular forms of level 1 and big weight. – David Loeffler Jan 6 at 9:38