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Meng Fai Lim

Publications and source records attributed to Meng Fai Lim.

50 records · Page 3Linked to original sources
arXiv2017

$\mathfrak{M}_H(G)$-property and congruence of Galois representations

In this paper, we study the Selmer groups of two congruent Galois representations over an admissible $p$-adic Lie extension. We will show that under appropriate congruence condition, if the dual Selmer group of one satisfies the $\M_H(G)$-property, so will the other. In the event that the $\M_H(G)$-property holds, and assuming certain further hypothesis on the decomposition of primes in the $p$-adic Lie extension, we compare the ranks of the $π$-free quotient of the two dual Selmer groups. We then apply our results to compare the characteristic elements attached to the Selmer groups. We also study the variation of the ranks of the $π$-free quotient of the dual Selmer groups of specialization of a big Galois representation. We emphasis that our results \textit{do not} assume the vanishing of the $μ$-invariant.

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arXiv2016

Comparing the $π$-primary submodules of the dual Selmer groups

In this paper, we compare the structure of Selmer groups of certain classes of Galois representations over an admissible $p$-adic Lie extension. Namely, we show that the $π$-primary submodules of the Pontryagin dual of the Selmer groups of two Galois representations have the same elementary representations when the two Galois representations in question are either Tate dual to each other or are congruent to each other. In the first situation, our result gives a partial answer to the question of Greenberg on whether the Pontryagin dual of the Selmer groups of two Galois representations that are Tate dual to each other are pseudo-isomorphic (up to a twist of the Iwasawa algebra). In the second situation, our result will be applied to study the variation of the $π$-primary submodules of the dual Selmer groups of certain specialization of a big Galois representation. One of the important ingredient in our proofs is an asymptotic formula for $π$-primary modules over a noncommutative Iwasawa algebra which can be viewed as a generalization of a weak analog of the classical Iwasawa asymptotic formula.

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arXiv2016

On the complete faithfulness of the $p$-free quotient modules of dual Selmer groups

In this paper, we consider the question of the complete faithfulness of the $p$-free quotient module of the dual Selmer groups of elliptic curves defined over a noncommutative $p$-adic Lie extension. Our question will refine previous questions on the complete faithfulness of dual Selmer groups. We also consider the question of the triviality of the central torsion submodules of these Iwasawa modules and we see that this latter question is intimately related to the former. We will also formulate and study analogous questions for the dual Selmer groups of Hida deformations. We then give positive answer to our questions, and establish "control theorem" results between the questions in certain cases.

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arXiv2015

Comparing the Selmer group of a $p$-adic representation and the Selmer group of the Tate dual of the representation

The main conjecture of Iwasawa theory is a conjecture on the relation between a Selmer group and a conjectural $p$-adic $L$-function. This conjectural $p$-adic $L$-function is expected to satisfy a conjectural functional equation in a certain sense. In view of the main conjecture and this conjectural functional equation, one would expect to have certain algebraic relationship between the Selmer group attached to a Galois representation and the Selmer group attached to the Tate twist of the dual of the Galois representation. It is precisely a component of this algebraic relationship that this paper aims to investigate. Namely, for a given "ordinary" $p$-adic representation, we compare its Selmer group with the Selmer group of its Tate dual over an admissible $p$-adic Lie extension, and show that the generalized Iwasawa $μ$-invariants associated to the Pontryagin dual of the two said Selmer groups are the same. We should mention that in proving the said equality of the $μ$-invariants, we do not assume the main conjecture nor the conjectural functional equation.

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arXiv2015

On the pseudo-nullity of the dual fine Selmer groups

In this paper, we will study the pseudo-nullity of the fine Selmer group and its related question. Namely, we investigate certain situations, where one can deduce the pseudo-nullity of the dual fine Selmer group of a general Galois module over a admissible $p$-adic Lie extension $F_{\infty}$ from the knowledge that pseudo-nullity of the Galois group of the maximal abelian unramified pro-$p$ extension of $F_{\infty}$ at which every prime of $F_{\infty}$ above $p$ splits completely. In particular, this gives us a way to construct examples of the pseudo-nullity of the dual fine Selmer group of a Galois module that is unramified outside $p$. We will illustrate our results with many examples.

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arXiv2015

Notes on the fine Selmer groups

In this paper, we study the fine Selmer groups attached to a Galois module defined over a commutative complete Noetherian ring with finite residue field of characteristic p. Namely, we are interested in its properties upon taking residual representation and within field extensions. In particular, we will show that the variation of the fine Selmer group in a cyclotomic $\Zp$-extension is intimately related to the variation of the class groups in the cyclotomic tower. We also discuss some examples of pseudo-nullity of fine Selmer groups.

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arXiv2015

Akashi series, characteristic elements and congruence of Galois representations

In this paper, we compare the Akashi series of the Pontryagin dual of the Selmer groups of two Galois representations over a strongly admissible p-adic Lie extension. Namely, we show that whenever the two Galois representations in question are congruent to each other, the Akashi series of one is a unit if and only if the Akashi series of the other is also a unit. We will also obtain similar results for the Euler characteristics of the Selmer groups and the characteristic elements attached to the Selmer groups.

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arXiv2015

The growth of fine Selmer groups

Let A be an abelian variety defined over anumber field F. In this paper, we will investigate the growth of p-rank of the fine Selmer group in three situations. In particular, in each of these situations, we show that there is a strong analogy between the growth of the p-rank of the fine Selmer group and the growth of the p-rank of the class groups.

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arXiv2015

On the homology of Iwasawa cohomology groups

A fundamental observation of Iwasawa gives a criterion for a module over the classical Iwasawa algebra to be torsion. In this paper, we study a certain extension of this criterion. We will then apply this to study the structure of the homology of the "Iwasawa cohomology groups" and dual fine Selmer groups.

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arXiv2015

On completely faithful Selmer groups of elliptic curves and Hida deformations

In this paper, we study completely faithful torsion $\mathbb{Z}_p[[G]]$-modules with applications to the study of Selmer groups. Namely, if $G$ is a nonabelian group belonging to certain classes of polycyclic pro-$p$ group, we establish the abundance of faithful torsion $\mathbb{Z}_p[[G]]$-modules, i.e., non-trivial torsion modules whose global annihilator ideal is zero. We then show that such $\mathbb{Z}_p[[G]]$-modules occur naturally in arithmetic, namely in the form of Selmer groups of elliptic curves and Selmer groups of Hida deformations. It is interesting to note that faithful Selmer groups of Hida deformations do not seem to appear in literature before. We will also show that faithful Selmer groups have various arithmetic properties. Namely, we show that faithfulness is an isogeny invariant, and we prove "control theorem" results on the faithfulness of Selmer groups over a general admissible $p$-adic Lie extension.

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arXiv2014

A remark on the $\mathfrak{M}_H(G)$-conjecture and Akashi series

In this article, we give a criterion for the dual Selmer group of an elliptic curve which has either good ordinary reduction or multiplicative reduction at every prime above $p$ to satisfy the $\M_H(G)$-conjecture. As a by-product of our calculations, we are able to define the Akashi series of the dual Selmer groups assuming the conjectures of Mazur and Schneider. Previously, the Akashi series are defined under the stronger assumption that the dual Selmer group satisfies the $\M_H(G)$-conjecture. We then establish a criterion for the vanishing of the dual Selmer groups using the Akashi series. We will apply this criterion to prove some results on the characteristic elements of the dual Selmer groups. Our methods in this paper are inspired by the work of Coates-Schneider-Sujatha and can be extended to the Greenberg Selmer groups attached to other ordinary representations, for instance, those coming from an $p$-ordinary modular form.

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arXiv2013

Nekovar duality over p-adic Lie extensions of global fields

Poitou-Tate duality for the Galois group of an extension of a global field with appropriately restricted ramification can be seen as taking place between the cohomology of a compact or discrete module and the compactly-supported cohomology of its Pontryagin dual. Nekovar proved a derived variant of this in which the module is replaced by a bounded complex of modules over the group ring of R that are finitely generated over R, where R is a complete commutative local Noetherian ring with finite residue field. Here, the Pontryagin dual is replaced by the Grothendieck dual, which is itself a bounded complex of modules with finitely generated cohomology. Nekovar's duality then takes place in the derived category of R-modules. We extend Nekovar's result to the setting of noncommutative Iwasawa theory. That is, we exhibit a duality between complexes computing Iwasawa cohomology and its compactly supported variant in the derived category of finitely generated modules over the Iwasawa algebra over R of a p-adic Lie extension.

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