Inter-universal Teichmuller Theory I: Construction of Hodge Theaters
Inter-universal Teichmuller Theory I: Construction of Hodge Theaters
Inter-universal Teichmuller Theory I: Construction of Hodge Theaters
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INTER-UNIVERSAL TEICHMÜLLER THEORY I 99<br />
That is to say, the portions <strong>of</strong> the diagram <strong>of</strong> Fig. 4.4 corresponding to † D > , † D ⊚<br />
differ quite fundamentally in structure. In particular, it is not surprising that the<br />
only “common ground” <strong>of</strong> these two fundamentally structurally different portions<br />
consists <strong>of</strong> an underlying set <strong>of</strong> cardinality l [i.e., the portion <strong>of</strong> the diagram <strong>of</strong><br />
Fig. 4.4 corresponding to † D J ].<br />
(iii) The bijection † ζ — or, perhaps more appropriately, its inverse<br />
( † ζ ) −1 : J ∼ → LabCusp( † D ⊚ )<br />
— may be thought <strong>of</strong> as relating arithmetic [i.e., if one thinks <strong>of</strong> the elements <strong>of</strong><br />
the capsule index set J as collections <strong>of</strong> primes <strong>of</strong> a number field] togeometry [i.e.,<br />
if one thinks <strong>of</strong> the elements <strong>of</strong> LabCusp( † D ⊚ ) as corresponding to the [geometric!]<br />
cusps <strong>of</strong> the hyperbolic orbicurve]. From this point <strong>of</strong> view,<br />
( † ζ ) −1 may be thought <strong>of</strong> as a sort <strong>of</strong> “combinatorial Kodaira-Spencer<br />
morphism” [cf. the point <strong>of</strong> view <strong>of</strong> [HASurI], §1.4].<br />
We refer to Remark 4.9.2, (iv), below, for another way to think about † ζ .<br />
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