Date:             26th December, 2025 (Fri.)

Place:            Tokyo University of Science (Kagurazaka Campus, building 7, 751 room)

Address:      1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan 

Access:         Access Map (751 room is in the building 7 in the campus map)

※ Registrationはありません。直接会場にお越しください。研究集会後に懇親会を行います。懇親会に参加希望の場合は、できるだけ早めに（遅くても１週間前までに）石川までご連絡ください。

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Program: 

13:30 -14:20   Thi Ngoc Giao Nguyen (Tokyo University of Science)

                                On the lengths of plane Cremona transformations

14:40 - 15:30  Masayuki Kawashima (Okayama University of Science)

                                Some examples of Quasi-Toric Relations for plane curves of degree 6 

15:50 - 16:40  Kazumasa Inaba (Okayama University of Science)

                                Good stratifications of nondegenerate locally tame complete intersection varieties 

17:00 - 17:50  Atsuko Katanaga (Iwate University)

                                Zeta Functions of Isolated cDV Singularities of type cD 

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Abstract: 

Thi Ngoc Giao Nguyen (Tokyo University of Science)

Title: On the lengths of plane Cremona transformations

Abstract: Click here

Masayuki Kawashima (Okayama University of Science)

Title: Some examples of Quasi-Toric Relations for plane curves of degree 6

Abstract: 

Let C={F=0} be a plane curve of degree d. We are interested in the topology of C. It is known that several factors affect it — for example, the number of irreducible components, singularities, and the form of the defining polynomial. In this talk, we focus on the form of the defining polynomial, which is called quasi-toric relations. We give an example of a plane curve of degree 6 that admits two decompositions: one as a classical torus curve and another as a quasi-toric relation.

Kazumasa Inaba (Okayama University of Science)

Title: Good stratifications of nondegenerate locally tame complete intersection varieties

Abstract:

Let fj be a nonconstant polynomial function for j = 1, . . . , k. Assume that the germ at 0 of the variety V = { fj = 0, j = 1, . . . , k} is a germ of nondegenerate locally tame complete intersection variety in the sense of Eyral–Oka. By a result of Eyral–Oka, we can explicitly construct a stratification S of V which satisfies Whitney (b)-regularity. In this talk, under a certain assumption, we show that S satisfies Thom’s af-condition. As an application, we study a variation of Milnor fibrations. 

Atsuko Katanaga (Iwate University)

Title: Zeta Functions of Isolated cDV Singularities of type cD

Abstract:

A compound Du Val (cDV)  singularity is a complex three-dimensional singularity which has a Du Val surface singularity as a hypersurface section. In this talk, we focus on certain isolated Newton non-degenerate singularities of type cD. The associated zeta function can be obtained from a resolution of the singularity using A'Campo's formula. We show that the second homology group of the singularity link has no torsion except possibly  Z/2Z factors if the singularity is weighted homogeneous. This is joint work with Masaharu Ishikawa.

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Organizers:  

Masaharu Ishikawa (Keio University)

Mutsuo Oka (Tokyo University of Science)

Contact:       ishikawa   at   keio   .   jp