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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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INTER-UNIVERSAL TEICHMÜLLER THEORY I 67<br />

for the resulting characteristic splitting <strong>of</strong> the Frobenioid Cv<br />

⊢ def<br />

= C v , i.e., so that we<br />

may think <strong>of</strong> the pair (O ⊲ (Cv ⊢ ),τv ⊢ ) as the object <strong>of</strong> TM ⊢ determined by K v ;<br />

D ⊢ v<br />

for the object <strong>of</strong> TM ⊢ determined by A Dv ;<br />

F ⊢ v<br />

def<br />

=(C ⊢ v , D ⊢ v ,τ ⊢ v )<br />

for the [ordered] triple consisting <strong>of</strong> Cv ⊢ , Dv ⊢ ,andτv ⊢ . Thus, the object (O ⊲ (Cv ⊢ ),τv ⊢ )<br />

<strong>of</strong> TM ⊢ is isomorphic to Dv ⊢ .Moreover,Cv ⊢ (respectively, Dv ⊢ ; Fv ⊢ )maybealgorithmically<br />

reconstructed from F v<br />

(respectively, D v ; F v<br />

).<br />

(iii) Next, let us observe that p v ∈ K v [cf. §0] may be thought <strong>of</strong> as a(n) [nonidentity]<br />

element <strong>of</strong> the noncompact factor Φ C ⊢<br />

v<br />

[i.e., the factor denoted by a “→” in<br />

the definition <strong>of</strong> TM ⊢ ] <strong>of</strong> the object (O ⊲ (Cv ⊢ ),τv ⊢ )<strong>of</strong>TM ⊢ . This noncompact factor<br />

Φ C ⊢ v<br />

is isomorphic, as a topological monoid, to R ≥0 ;letuswriteΦ C ⊢ v<br />

additively<br />

and denote by log(p v ) the element <strong>of</strong> Φ C ⊢ v<br />

determined by p v . Thus, relative to<br />

the natural action [by multiplication!] <strong>of</strong> R ≥0 on Φ C<br />

⊢<br />

v<br />

, it follows that log(p v )isa<br />

generator <strong>of</strong> Φ C<br />

⊢<br />

v<br />

. In particular, we may form a new topological monoid<br />

Φ C Θ<br />

v<br />

def<br />

= R ≥0 · log(p v ) · log(Θ)<br />

isomorphic to R ≥0 that is generated by a formal symbol “log(p v )·log(Θ) = log(p log(Θ)<br />

v )”.<br />

Moreover, if we denote by O × the compact factor <strong>of</strong> the object (O ⊲ (C ⊢ Cv<br />

⊢ v ),τv ⊢ )<strong>of</strong><br />

TM ⊢ , and set O × def<br />

= O × , then we obtain a new split Frobenioid (C Θ Cv<br />

Θ Cv<br />

⊢ v ,τv Θ ), isomorphic<br />

to (Cv ⊢ ,τv ⊢ ), such that<br />

O ⊲ (C Θ v )=O × C Θ v<br />

× Φ C Θ<br />

v<br />

— where we note that this equality gives rise to a natural isomorphism <strong>of</strong> split Frobenioids<br />

(C ⊢ v ,τ ⊢ v ) ∼ → (C Θ v ,τ Θ v ), obtained by “forgetting the formal symbol log(Θ)”. In<br />

particular, we thus obtain a natural isomorphism<br />

F ⊢ v<br />

∼<br />

→F Θ v<br />

—wherewewriteFv<br />

Θ def<br />

= (Cv Θ , Dv Θ ,τv Θ ) for the [ordered] triple consisting <strong>of</strong> Cv Θ ,<br />

Dv<br />

Θ def<br />

= Dv ⊢ , τv Θ . Finally, we observe that Fv Θ may be algorithmically reconstructed<br />

from F v<br />

.<br />

Remark 3.4.1. A similar remark to Remark 3.2.1 [i.e., concerning the phrase<br />

“reconstructed category-theoretically”] applies to the phrase “algorithmically reconstructed”<br />

that was applied in the discussion <strong>of</strong> Example 3.4.

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