## 釜山国立大‐北大ジョイントシンポジウム／PNU-HU Joint Symposium

2017年 　 12月 19日 10時 00分 ～ 2017年 　 12月 19日 17時 50分

１．講演会（場所：理学部４号館　4-501）
10:00-10:30　古畑　仁　氏（北海道大学）
10:40-11:10　正宗　淳　氏（北海道大学）
11:20-11:50　Siomona Settepanella　氏（北海道大学）

２．ポスターセッション（場所：理学部３号館５階コモンスペース）
13：30-14：30

Tan Nhat Tran（Ｄ１）、植田優基（Ｄ１）、福田一貴（Ｄ１）

３．数学教室談話会（場所：理学部４号館4-501）
14：45-15：35　Young-Jun Choi　氏（釜山国立大学）
16：00-16：50　Ji-Hun Yoon　氏（釜山国立大学）
17：00-17：50　Juncheol Pyo　氏（釜山国立大学）

・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・
１．講演会　10：00-11：50　＠4-501

“Sasakian statistical manifolds and hypersurfaces”
A differential-geometric review on statistical manifolds will be given.We introduce a notion of Sasakian statistical structure and construct it on an odd-dimensional sphere, which is a rare example of compact statistical manifolds. This talk is based on a recent joint work with Hasegawa I., Okuyama Y., Sato K. and Shahid, M.H.

“On the construction of non-trivial harmonic functions under certain integrable conditions”
It is well known that any complete manifold enjoys the $L^p$ Liouville property with any 1<p<infinity but not with p=1. 　We will show how the L2 Liouville property fails on an incomplete manifold and we will provide a systematic way to break the L1 Liouville property of a complete manifold.

Simona Settepanella　氏
“Pappus's Variety in Grassmannian Gr(3,n). ”
In 1989 Manin and Schechtman considered a family of arrangements of hyperplanes generalizing classical braid arrangements which they called discriminantal arrangements. Such an arrangement depends on a choice $\A=\{H^0_1,...,H^0_n\}$ of collection of hyperplanes in general position in $\CC^k$. It consists of parallel translates $H_1^{t_1},...,H_n^{t_n}, (t_1,...,t_n) \in \CC^n$
which fail to form a generic arrangement in $\CC^k$. Recently, in 2016, Libgober and Settepanella gave a necessary and sufficient condition on generic arrangement $\A=\{H^0_1,...,H^0_n\}$ in
$\CC^k$ for multiplicity $3$ intersections of rank $2$ to appear in the intersection lattice of the associated discriminantal arrangement. Arrangements $\A$ in $\CC^k$ verifying this condition are called "non very generic".
In 2017, Sawada, Settepanella and Yamagata proved that, in case $k=3$ the non very generic arrangements $\A$ of cardinality $n$ in $\CC^3$ are points in a well defined degree $2$ hypersurface in the projective Grassmannian $Gr(3,n)$. In particular they showed that this hypersurface is product of quadrics and that points in certain intersection of those quadrics correspond to arrangement containing $6$ lines in Pappus's configuration or $12$ lines in Hesse configuration. They also provided a new proof of Pappus's Theorem. This is a joint work with S. Sawada and S. Yamagata.

２．ポスターセッション　13：30-14：30＠５階コモンスペース

３．数学教室談話会　14：45-17：50＠4-501