【ガロアの逆問題入門セミナー(I, II)】 (1) June 1 (Thu) [理E404] 15:00-16:00+ (introductory talk 1) (2) Junu 2 (Fri) [理D505] 11:00-12:00+ (introductory talk 2) Title: Introduction to Inverse Galois Theory (I and II) Abstract: The aim is to give an introduction to inverse Galois theory and to some number theoretical topics involved in inverse Galois theory. We will discuss the following topics: the Inverse Galois problems, the geometric approach, the Riemann existence theorem, Hilbert's irreducibility theorem, the Beckmann-Black problem, the Grunwald problem, the Malle conjecture, generic and parametric extensions, etc. NB: this is a basic introduction intended for graduate students or interested colleagues. (3)【大阪大学整数論・保形型式セミナー】 June 2 (Fri) [理D505] 16:30-17:30 (seminar talk) Title: Some perspectives on the Inverse Galois Problem Abstract: The work I will talk about is motivated by the Regular Inverse Galois Problem: show that every finite group G is the Galois group of a Galois extension F/Q(T) with Q algebraically closed in F. I will discuss two types of results. First, some strong variants of the RIGP related to the notion of parametric extensions, which will be shown to fail. Second, a strong consequence of the RIGP related to a conjecture of Malle on the number of Galois extensions with a given group and with bounded discriminant. (4)【ガロアの逆問題特論セミナー(I)】 June 5 (Mon) [理D505] 13:30-14:30+ (advanced talk 1) Title: On the Malle conjecture and the self-twisted cover Abstract: The Malle conjecture predicts that the number of Galois extensions of Q with given group G and discriminant bounded by some real number y > 0 grows like y^a, for some exponent a > 0. This statement is known for nilpotent groups. The work I will present establishes it for Sn, An, many simple groups and more generally all regular Galois groups overQ. The constructed extensions can be further requested to satisfy some notable local conditions. Our method uses a new version of Hilbert's Irreducibility Theorem that counts specialized extensions and not just the specialization points. A new ingredient is the self-twisted cover that we will introduce. (5)【ガロアの逆問題特論セミナー(II)】 June 6 (Tue) [理D505] 15:00-16:00+ (advanced talk 2) Title: Genus zero pull-backs of Galois covers Abstract: Pulling back a Galois cover $X\to \P^1$ of group $G$ along a cover $\P^1\to \P^1$ yields ``most of the time'' a new Galois cover of $\P^1$ with the same group. This operation provides a natural tool for Inverse Galois Theory and induces a pre-order on the set of Galois covers. We will present questions that arise from this double perspective, and some answers. |