新着情報
2018年9月の記事一覧
代数特別セミナー
kimurak日時: 10月15日 16:00-17:30
場所: D814
講演者: Andrew William Macpherson (IPMU)
題目: A Yoneda philosophy of correspondencesAbstract: Cohomology is bivariant, which means that to a morphism f it associates not only a pullback map f^*, but also (under certain conditions) an Umkehr map in the opposite direction. These maps satisfy a "push-pull" or "base change" identity. Everyone knows that this implies that cohomology can be thought of as a functor out of a certain category CORR of "correspondences", whose morphisms are "rooves" and whose composition law is defined by taking a fibre product of kernels.
In higher category theory, specifying objects by describing the morphism spaces and composition law explicitly --- as we just did with correspondences --- is rather inconvenient. Rather, it is better to define things via their universal properties. In this talk, I will give a universal interpretation for CORR in terms of "bivariant functors" into an (∞,2)-category, which takes out the pain from constructing functors out of CORR.
連絡先: 木村健一郎
トポロジーセミナー（2018/10/30）
topology日時：2018年10月30日（火）16：00〜17：00
場所：筑波大学自然系学系D棟D814
講演者：Jung Hoon Lee 氏 （Chonbuk National University）
講演題目：A necessary condition for constituent knots of reducible genus two handlebody-knots
アブストラクト：A knot K is a constituent knot of a genus two handlebody-knot H if there is a non-separating disk D in H such that the core of cl(H-N(D)) is K.
We characterize constituent knots of a non-trivial reducible genus two handlebody-knot in terms of an incompressible torus (or two incompressible tori) in the exterior of the handlebody-knot.場所：筑波大学自然系学系D棟D814
講演者：Jung Hoon Lee 氏 （Chonbuk National University）
講演題目：A necessary condition for constituent knots of reducible genus two handlebody-knots
アブストラクト：A knot K is a constituent knot of a genus two handlebody-knot H if there is a non-separating disk D in H such that the core of cl(H-N(D)) is K.
