12 research outputs found

### Anabelian Geometry for Henselian Discrete Valuation Fields with Quasi-finite Residues

Let p, l be prime numbers. In anabelian geometry for p-adic local fields [i.e., finite extension fields of the field of p-adic numbers], many topics have been discussed. In the present paper, we generalize two of the topics --discovered by S. Mochizuki-- to more general complete discrete valuation fields. One is the mono-anabelian reconstruction, under a certain indeterminacy, of the cyclotomic rigidity isomorphism between the usual cyclotome Ẑ(1) associated to a p-adic local field and the cyclotome constructed, in a purely group-theoretic way, from [the underlying topological group structure of] the absolute Galois group of the p-adic local field. The other is the Neukirch-Uchida-type result, i.e., the field-theoreticity of an outer isomorphism between the absolute Galois groups of p-adic local fields that preserves the respective ramification filtrations. For our generalizations, we first discuss l-local class field theory for Henselian discrete valuation fields with strongly l-quasi-finite residue fields [i.e., perfect fields such that the maximal pro-l quotients of the absolute Galois groups of their finite extension fields are isomorphic to Ẑl] of characteristic p via Artin-Tate's class formation. This theory enables us to reconstruct the l-cyclotomes from the absolute Galois groups of such fields. With regard to cyclotomic rigidity, under a certain assumption, we establish mono-anabelian group/monoid-theoretic reconstruction algorithms for cyclotomic rigidity isomorphisms associated to Henselian discrete valuation fields with quasi-finite residue fields [i.e., perfect residue fields whose absolute Galois groups are isomorphic to Ẑ]. As an application of the reconstructions of cyclotomic rigidity isomorphisms, we determine the structure of the groups of Galois-equivariant automorphisms of various algebraically completed multiplicative groups that arise from complete discrete valuation fields with quasi-finite residues. Moreover, as a byproduct of the argument applied in this determination [especially, in the positive characteristic case], we also determine, in a generalized situation, the structure of a certain indeterminacy “(Ind2)” that appears in S. Mochizuki's inter-universal Teichmüller theory. With regard to the Neukirch-Uchida-type result, by combining the reconstruction result of p-cyclotomes above [in the case where l = p] with a recent result due to T. Murotani, together with a computation concerning norm maps, we prove an analogous result for mixed characteristic complete discrete valuation fields whose residue fields are [strongly] p-quasi-finite and algebraic over the prime fields

### Anabelian Group-theoretic Properties of the Pro-p Absolute Galois Groups of Henselian Discrete Valuation Fields

Let p be a prime number; K a Henselian discrete valuation field of characteristic 0 such that the residue field is an infinite field of characteristic p. Write GK for the absolute Galois group of K. In our previous papers, under the assumption that K contains a primitive p-th root of unity ζp, we proved that any almost pro-p-maximal quotient of GK satisfies certain “anabelian” group-theoretic properties called very elasticity and strong internal indecomposability. In the present paper, we generalize this result to the case where K does not necessarily contain ζp. Then, by applying this generalization, together with some facts concerning Hilber-tian fields, we prove the semiabsoluteness of isomorphisms between thepro-p etale fundamental groups of smooth varieties over certain classes offields of characteristic 0. Moreover, we observe that there are various sim-ilarities between the maximal pro-p quotient GpK of GK and non abelianfree pro-p groups. For instance, we verify that every topologically finitely generated closed subgroup of GpK is a free pro-p group. One of the key ingredients of our proofs is “Artin-Schreier theory in characteristic zero”introduced by MacKenzie and Whaples

### Indecomposability of various profinite groups arising from hyperbolic curves

In this paper, we prove that the etale fundamental group of a hyperbolic curve over an arithmetic field [e.g., a finite extension field of Q or Qp] or an algebraically closed field is indecomposable [i.e., cannot be decomposed into the direct product of nontrivial profinite groups]. Moreover, in the case of characteristic zero, we also prove that the etale fundamental group of the configuration space of a curve of the above type is indecomposable. Finally, we consider the topic of indecomposability in the context of the comparison of the absolute Galois group of Q with the Grothendieck-Teichmuller group GT and pose the question: Is GT indecomposable? We give an affirmative answer to a pro-l version of this questio

### On Generalizations of Anabelian Group-theoretic Properties

In the present paper, we discuss certain generalizations on two anabelian group-theoretic properties --strong internal indecomposability and elasticity. More concretely, by replacing the normality conditions appearing in characterizations of strong internal indecomposability and elasticity by the subnormality conditions, we introduce the notions of strong sn-internal indecomposability and sn-elasticity and prove that various profinite groups appearing in anabelian geometry satisfy these properties

### Explicit estimates in inter-universal Teichmuller theory

In the final paper of a series of papers concerning inter-universal Teichmuller theory, Mochizuki verified various numerically non-effective versions of the Vojta, ABC, and Szpiro Conjectures over number fields. In the present paper, we obtain various numerically effective versions of Mochizuki’s results. In order to obtain these results, we first establish a version of the theory of etale theta functions that functions properly at arbitrary bad places, i.e., even bad places that divide the prime “2”. We then proceed to discuss how such a modified version of the theory of etale theta functions affects inter-universal Teichmuller theory. Finally, by applying our slightly modified version of inter-universal Teichmuller theory, together with various explicit estimates concerning heights, the j-invariants of “arithmetic” elliptic curves, and the prime number theorem, we verify the numerically effective versions of Mochizuki’s results referred to above. These numerically effective versions imply effective diophantine results such as an effective version of the ABC inequality over mono-complex number fields [i.e., the rational number field or an imaginary quadratic field] and effective versions of conjectures of Szpiro. We also obtain an explicit estimate concerning “Fermat’s Last Theorem” (FLT) — i.e., to the effect that FLT holds for prime exponents > 1.615·1014 — which is sufficient, in light of a numerical result of Coppersmith, to give an alternative proof of the first case of FLT. In the second case of FLT, if one combines the techniques of the present paper with a recent estimate due to Mihailescu and Rassias, then the lower bound “1.615·1014” can be improved to “257”. This estimate, combined with a classical result of Vandiver, yields an alternative proof of the second case of FLT. In particular, the results of the present paper, combined with the results of Vandiver, Coppersmith, and Mihailescu-Rassias, yield an unconditional new alternative proof of Fermat’s Last Theore

### Internal Indecomposability of Various Profinite Groups in Anabelian Geometry

It is well-known that various profinite groups appearing in anabelian geometry satisfy distinctive group-theoretic properties such as the slimness [i.e., the property that every open subgroup is center-free] and the strong indecomposability [i.e., the property that every open subgroup has no nontrivial product decomposition]. In the present paper, we consider another group-theoretic property on profinite groups, which we shall refer to as strong internal indecomposability --this is a stronger property than both the slimness and the strong indecomposability-- and prove that various profinite groups appearing in anabelian geometry [e.g., the étale fundamental groups of hyperbolic curves over number fields, p-adic local fields, or finite fields; the absolute Galois groups of Henselian discrete valuation fields with positive characteristic residue fields or Hilbertian fields] satisfy this property. Moreover, by applying the pro-prime-to-p version of the Grothendieck Conjecture for hyperbolic curves over finite fields of characteristic p [established by Saidi and Tamagawa], together with some considerations on almost surface groups, we also prove that the Grothendieck-Teichmüller group satisfies the strong indecomposability . This gives an affirmative answer to an open problem posed in a first author's previous work

### 双曲的曲線から生じる様々な副有限群の非分解性

京都大学0048新制・課程博士博士(理学)甲第20158号理博第4243号新制||理||1610(附属図書館)京都大学大学院理学研究科数学・数理解析専攻(主査)教授 望月 新一, 教授 岡本 久, 教授 玉川 安騎男学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDFA

### Explicit Estimates in Inter-universal Teichmüller Theory

In the final paper of a series of papers concerning inter- universal Teichmüller theory, Mochizuki verified various numerically non-effective versions of the Vojta, ABC, and Szpiro Conjectures over number fields. In the present paper, we obtain various numerically effective versions of Mochizuki's results. In order to obtain these results, we first establish a version of the theory of étale theta functions that functions properly at arbitrary bad places, i.e., even bad places that divide the prime "2". We then proceed to discuss how such a modified version of the theory of étale theta functions affects inter-universal Teichmüller theory. Finally, by applying our slightly modifed version of inter-universal Teichmüller theory, together with various explicit estimates concerning heights, the j-invariants of "arithmetic" elliptic curves, and the prime number theorem, we verify the numerically effective versions of Mochizuki's results referred to above. These numerically effective versions imply effective diophantine results such as an effective version of the ABC inequality over mono-complex number fields [i.e., the rational number field or an imaginary quadratic field] and an effective version of a conjecture of Szpiro. We also obtain an explicit estimate concerning "Fermat's Last Theorem" (FLT) - i.e., to the effect that FLT holds for prime exponents > 1.615・1014 - which is sufficient to give an alternative proof of the first case of Fermat's Last Theorem