Tsuyoshi KOBAYASHI Home Page

2005 Nara Topology Seminar

12月2日（金）午後 4：20～ 午後5：20

場所：奈良女子大学理学部Ｃ棟４階　C435（第一セミナー室）

講演者：Prof. Ben Burton (RMIT University)

講演題目：「Minimal Triangulations of Non-Orientable 3-Manifolds」

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Date: December 2(Fri.) 16:20-17:20

Room: Nara Women's University C435

Speaker: Prof. Ben Burton (RMIT University)

Title: Minimal Triangulations of Non-Orientable 3-Manifolds

Abstract: A minimal triangulation is a method of building a 3-manifold using
the smallest possible number of tetrahedra. In this talk,
using new data from the 9-tetrahedron non-orientable census, we examine
the constructions used in the smallest minimal non-orientable
triangulations. In particular we focus on non-orientable Seifert
fibred spaces, showing how these triangulations are built using
tools such as layerings and saturated blocks. The software package
Regina will be illustrated, including both a general tour of its
features and its specific use in analysing minimal triangulations.

11月25日(金)16:20-17:50

場所：奈良女子大学理学部Ｃ棟４階　C431 （数学演習室）

講演者：Prof. Akhil Ranjan (Indian Institute of Technology)

講演題目：「Harmonic manifolds with minimal horospheres」

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Date: November 25(Fri.) 16:20-17:50

Room: Nara Women's University C431

Speaker: Prof. Akhil Ranjan (Indian Institute of Technology)

Title: Harmonic manifolds with minimal horospheres

11月4日(金)14:40-16:10

場所：奈良女子大学理学部Ｃ棟４階　C434 （数学小講義室）

講演者：Prof. Song Won Taek (Korea Inst. for Advanced Study)

講演題目：「The minimum dilataion of pseudo-Anosov 5-braids」

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Date: November 4(Fri.) 14:40-16:10

Room: Nara Women's University C434

Speaker: Prof. Song Won Taek (Korea Inst. for Advanced Study)

Title: The minimum dilataion of pseudo-Anosov 5-braids

Abstract: The minimum dilatation of pseudo-Anosov 5-braids
is shown to be the largest zero $\lambda_5 \approx 1.72208$
of $x^4 - x^3 - x^2 - x + 1$ which is attained by
$\sigma_1\sigma_2\sigma_3\sigma_4\sigma_1\sigma_2$.
The proof involves a lemma which bounds the norm of
a Perron-Frobenius matrix in term of its spectral radius,
and a computer-aided search in a finite but big set of
candidate braids with bounded lengths for the minimum dilatation.

4月19日(火)14:40-15:40

場所：奈良女子大学理学部Ｃ棟４階　C431-2 （数学演習室）

講演者：平澤美可三氏 (学習院大学)

講演題目：「The flat basket presentation of Seifert surfaces and
a new coding algorithm for links」

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Date: April 19(Tue.) 14:40-15:40

Room: Nara Women's University C431-2

Speaker: Prof. Mikami Hirasawa (Gakushuin Univ.)

Title: The flat basket presentation of Seifert surfaces and
a new coding algorithm for links

Abstract: This is a joint work with T. Kobayashi (Nara Women's Univ) and
Rei Furihata (Yosami Junior High School).
We introduce a new standard form of a Seifert surface F. In that
standard form, F is obtained by successively plumbing flat annuli
to one disk, where the gluing regions are all in the disk.
We show that any link has a Seifert surface in the standard form,
and thereby present a new way of coding a link.