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Inter-universal Teichmuller Theory I: Construction of Hodge Theaters

Inter-universal Teichmuller Theory I: Construction of Hodge Theaters

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associated to † F ⊩ mod and ‡ F ⊩ mod .<br />

INTER-UNIVERSAL TEICHMÜLLER THEORY I 15<br />

(iii) (Frobenius-/Étale-Pictures) Let { n HT Θ±ell NF } n∈Z be a collection <strong>of</strong><br />

distinct Θ ±ell NF-<strong>Hodge</strong> theaters [relative to the given initial Θ-data] indexed<br />

by the integers. Then the infinite chain<br />

...<br />

Θ<br />

−→ (n−1) HT Θ±ell NF Θ<br />

−→ n HT Θ±ell NF Θ<br />

−→ (n+1) HT Θ±ell NF Θ<br />

−→ ...<br />

<strong>of</strong> Θ-linked Θ ±ell NF-<strong>Hodge</strong> theaters will be referred to as the Frobeniuspicture<br />

[associated to the Θ-link] — cf. Fig. I1.5. The Frobenius-picture fails<br />

to admit permutation automorphisms that switch adjacent indices n, n+1,but<br />

leave the remaining indices ∈ Z fixed. The Frobenius-picture induces an infinite<br />

chain <strong>of</strong> full poly-isomorphisms<br />

...<br />

∼<br />

→ (n−1) D ⊢ ><br />

∼<br />

→ n D ⊢ ><br />

∼<br />

→ (n+1) D ⊢ ><br />

∼<br />

→ ...<br />

between the various D ⊢ -prime-strips n D ⊢ >, i.e., in essence, the D ⊢ -prime-strips<br />

associated to the F ⊢× -prime-strips n F ⊢×<br />

mod<br />

. The relationships <strong>of</strong> the various D-<br />

Θ ±ell NF-<strong>Hodge</strong> theaters n HT D-Θ±ellNF to the “mono-analytic core” constituted<br />

by the D ⊢ -prime-strip “ (−) D ⊢ >” regarded up to isomorphism — relationships that are<br />

depicted by spokes in Fig. I1.6 — are compatible with arbitrary permutation<br />

symmetries among the spokes [i.e., among the labels n ∈ Z <strong>of</strong> the D-Θ ±ell NF-<br />

<strong>Hodge</strong> theaters]. The diagram depicted in Fig. I1.6 will be referred to as the étalepicture.<br />

In addition to the main result discussed above, we also prove a certain technical<br />

result concerning tempered fundamental groups —cf. TheoremBbelow—<br />

that will be <strong>of</strong> use in our development <strong>of</strong> the theory <strong>of</strong> <strong>Hodge</strong>-Arakelov-theoretic<br />

evaluation in [IUTchII]. This result is essentially a routine application <strong>of</strong> the theory<br />

<strong>of</strong> maximal compact subgroups <strong>of</strong> tempered fundamental groups developed in<br />

[SemiAnbd] [cf., especially, [SemiAnbd], Theorems 3.7, 5.4]. Here, we recall that<br />

this theory <strong>of</strong> [SemiAnbd] may be thought <strong>of</strong> as a sort <strong>of</strong> “Combinatorial Section<br />

Conjecture” [cf. Remark 2.5.1 <strong>of</strong> the present paper; [IUTchII], Remark 1.12.4] —<br />

a point <strong>of</strong> view that is <strong>of</strong> particular interest in light <strong>of</strong> the historical remarks made<br />

in §I5 below. Moreover, Theorem B is <strong>of</strong> interest independently <strong>of</strong> the theory <strong>of</strong> the<br />

present series <strong>of</strong> papers in that it yields, for instance, a new pro<strong>of</strong> <strong>of</strong> the normal<br />

terminality <strong>of</strong> the tempered fundamental group in its pr<strong>of</strong>inite completion, a result<br />

originally obtained in [André], Lemma 3.2.1, by means <strong>of</strong> other techniques [cf. Remark<br />

2.4.1]. This new pro<strong>of</strong> is <strong>of</strong> interest in that, unlike the techniques <strong>of</strong> [André],<br />

which are only available in the pr<strong>of</strong>inite case, this new pro<strong>of</strong> [cf. Proposition 2.4,<br />

(iii)] holds in the case <strong>of</strong> pro-̂Σ-completions, for more general ̂Σ [i.e., not just the<br />

case <strong>of</strong> ̂Σ =Primes].<br />

Theorem B. (Pr<strong>of</strong>inite Conjugates <strong>of</strong> Tempered Decomposition and<br />

Inertia Groups) Let k be a mixed-characteristic [nonarchimedean] local<br />

field, X a hyperbolic curve over k. Write<br />

Π tp X

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