第11回 1/14 (木) (Zoomセミナー)
野崎 雄太氏 10:00-12:30 (GMT +09:00) (日本時間) [タイトル]ホモロジーシリンダーに関する Abel 商とクラスパー手術 [アブストラクト]
曲面の写像類群の研究において,Torelli 群と呼ばれる部分群が重要な役割を担っている.
そして Torelli 群の 3 次元類似としてホモロジーシリンダーの成すモノイドがあり,Dehn 手術の特別なクラスであるクラスパー手術を用いたフィルトレーションが入る.
本講演では,このフィルトレーションの次数商上に LMO 関手を用いて準同型写像を構成し,それが Johnson 準同型とは異なる情報を捉えていることを示す.
応用として,Torelli 群の部分群である Johnson 核について,その Abel 化にトーションが存在することを証明する.
本講演は佐藤正寿氏と鈴木正明氏との共同研究に基づく.
第10回 12/10 (木) (Zoomセミナー)
Oğuz Şavk 19:10-20:10 (GMT +09:00) (日本時間) [タイトル]Brieskorn spheres, homology cobordism and homology balls [アブストラクト]
A classical question in low-dimensional
topology asks which homology 3-spheres bound homology 4-balls. This
question is fairly addressed to Brieskorn spheres Σ(p,q,r), which are
defined to be links of singularities xp+yq+zr=0. Over the years,
Brieskorn spheres also have been the main objects for the understanding
of the algebraic structure of the integral homology cobordism group.
In this talk, we will present several families of Brieskorn spheres
which do or do not bound integral and rational homology balls via
Ozsváth-Szabó d-invariant, involutive Heegaard Floer homology, and Kirby
calculus. Also, we will investigate their positions in both integral and
rational homology cobordism groups.
slide
第1回4/10 (金) (online)
丹下 基生 10:00-12:30 [タイトル]Third term of lens surgery polynomial [アブストラクト]
For a Laurent polynomial Δ(t), if it is the Alexander polynomial of lens space knot K in S3, we say that Δ(t) is a lens surgery polynomial.
What condition does a lens surgery polynomial have?
This is the main question here.
By Ozsvath and Szabo it is well-known that any lens surgery polynomial is
flat and alternating.
The "flat" means that any coefficients are ±1 or 0.
The "alternating" means that any non-zero coefficients are alternating.
It is wel-known that the top term and the second term of any lens surgery polynomial are
1 and -1 respectively.
Teragaito conjectured that if the third term is non-zero, then the polynomial is the same
as (2,2g+1)-torus knot polynomial.
Here I proved the question is affirmative. Resume(13.7MB)