Taelman's class number conjecture for abelian t-modules

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Let KK be a finite separable extension of Fq(t)\mathbf{F}_q(t), let A=Fq[t]A=\mathbf{F}_q[t], and let K∞K_\infty and OKO_K denote the completions and the ring of integers used in the definition of the associated tt-module. Let EE be a uniformizable abelian tt-module over KK whose associated tt-motive MM has everywhere good reduction. Define

WE=Lie⁡E/(t−θ)Lie⁡EW_E=\operatorname{Lie}_E/(t-\theta)\operatorname{Lie}_E

and let w:Lie⁡E→WEw:\operatorname{Lie}_E\to W_E be the canonical projection. Taelman's class number conjecture. There exists a sub-AA-module Z⊂Lie⁡E(K∞)Z\subset\operatorname{Lie}_E(K_\infty) of rank dim⁡WE\dim W_E such that exp⁡E(Z)⊂E(OK)\exp_E(Z)\subset E(O_K) and

⋀Adim⁡WEw(Z)=L(E,0)⋅(⋀Adim⁡WEWE(OK))\bigwedge_A^{\dim W_E}w(Z)=L(E,0)\cdot\left(\bigwedge_A^{\dim W_E}W_E(O_K)\right)

as AA-lattices inside the one-dimensional F∞F_\infty-vector space

⋀K∞dim⁡WEWE(K∞).\bigwedge_{K_\infty}^{\dim W_E}W_E(K_\infty).

This is a function-field analogue of a class number formula: the special value L(E,0)L(E,0) is predicted to measure the covolume of an exponential lattice associated with integral points of EE. The source presents the claim as a conjecture and gives numerical evidence, but no resolution is supplied here.

References

Primary source

Lenny Taelman, “Special L-values of t-motives: a conjecture”, arXiv:0811.4522 (2008).

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