Date

2026年10月20日 (火) 13:30

Language: English

Date

2026年9月24日 (木) 15:00 〜 16:00

Title: The Obstruction of Orientability of Real Monopole Floer Homology

Abstract: The Real Seiberg-Witten theory is one of a stong tool in knot theory and surface knot theory. For example, that can detect exotic P^2-knot and Kang-Park-Taniguchi proved that any non trivial cable of figure eight knot is not slice using Real Seiberg-Witten theory. This theory is also provide interesting phenomena in index theory, since Real Seiberg-Witten theory can be seen as a "non-linear version" of Atiya's Real K-theory. For example, there is an obstruction to orient moduli space of Real Seiberg-Witten eqations on closed 4-manifolds. Recently, Bonciocat obtained a obstruction to lift the real Heegaard Floer homology from mod 2 coefficient to Z-coefficient. In this talk, we give a canonical way to obtain Z- coefficient real monopole Floer homology of double branced cover of a link in homology S^3 in the case when the obstruction vanishes. We also proved that the Bonciocat's obstruction is also obstract Z-coefficient in real monopole, however the proof is different. This is joint work with Jiakai Li.

Date

2026年10月20日 (火) 15:00
 
 
Speaker: Shogo Ozaki,
Associate Professor, Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Kyushu University 
 
 
Title: 
Flexibility in Bacterial Replication Origins: Molecular Mechanisms and Evolutionary Implications
 
Abstract:
Chromosomal DNA replication begins at a specific genomic locus, the replication origin (oriC). While the initiator protein DnaA is highly conserved among bacteria, replication origin sequences are remarkably diverse. This raises a fundamental question: how can bacterial replication initiation remain robust despite extensive evolutionary changes in origin architecture?
In this seminar, I will present our studies of DNA replication origins from evolutionarily distant bacteria, including Escherichia coli, the hyperthermophile Thermotoga maritima, and the alphaproteobacterium Caulobacter crescentus. Comparison of these species reveals striking differences in origin architecture, providing a unique opportunity to explore how replication initiation systems evolve while maintaining the same fundamental function. By combining biochemical, genetic, and comparative approaches, we uncovered unexpected flexibility in DnaA-dependent origin function.
Our findings reveal that bacterial replication origins can tolerate variation in the orientation of DnaA-binding sites, the sequence of unwound DNA, and the spacing between essential origin elements. Together, these observations suggest that DnaA-dependent initiation complexes possess intrinsic flexibility that enables replication origins to diversify during evolution while preserving reliable replication initiation. These findings provide new insight into the molecular mechanisms that underlie both the robustness and the evolutionary diversification of bacterial chromosome replication.

 
Reference:
Kiyohara N, Wakasugi Y, Ihara K, Kubaru A, Maruki S, Kojima N, Yoshitomi S, Katayama T, Ozaki S. Origin flexibility governs robust ssDNA engagement by the DnaA initiator. Proc Natl Acad Sci U S A. 2026 Sep 22;123(38):e2615469123. doi: 10.1073/pnas.2615469123. 
 
Lu C, Yoshida R, Katayama T, Ozaki S. Thermotoga maritima oriC involves a DNA unwinding element with distinct modules and a DnaA-oligomerizing region with a novel directional binding mode. J Biol Chem. 2023 Jul;299(7):104888. doi: 10.1016/j.jbc.2023.104888. 
 
 
 

Date

2026年10月29日 (木) 14:00 〜 15:00

Seminar by JSPS Fellow: Asa Conover

Date

2026年9月29日 (火) 10:00 〜 11:00

Title: Strong positivity property for subdiffusion equations and applications to related inverse problems

Speaker: Prof. Yikan Liu (Kyoto University)

Date

2026年9月28日 (月) 14:00 〜 15:00

Title: From image generation to three-dimensional turbulence: a physically interpretable diffusion-model from the perspective of deterministic PDEs

Speaker: Prof. Tsuyoshi Yoneda (Hitotsubashi University)

Date

2026年9月28日 (月) 10:00 〜 11:00

Title: Mathematical analysis of generalized fractional viscoelastic models

Speaker: Prof. Hiromichi Itou (Chuo University)

Date

2026年10月13日 (火) 13:00 〜 14:00

Seminar by Kwabena Boahen, Stanford University

Date

2026年9月17日 (木) 14:00 〜 15:00

Title: Designing Complex Fluids: Leveraging Rheology for Advanced Manufacturing

Speaker: Dr. Chaimongkol Saengow, Lecturer, the Sirindhorn International Institute of Technology, Thammasat University

This seminar is co-hosted by the Mechanics and Materials Unit and the Micro/Bio/Nanofluidics Unit

Date

2026年9月16日 (水) 14:30 〜 15:30

Title: Signs in real monopole Floer homology

 

Abstract: 

The computation of the 3-dimensional framed real Seiberg–Witten invariant of the branched double cover of a knot K is instrumental in Miyazawa's construction of exotic P^2-knots. This invariant, known as Miyazawa's degree invariant deg(K), is the Euler characteristic χ(HMR) of framed real monopole Floer homology (HMR).  A priori deg(K) is defined only up to an overall sign, since the real Dirac operator has no complex orientation. Worse, signs associated to distinct real spin^c structures are not comparable. Resolving the latter issue is essential for developing computational techniques for real Seiberg--WItten invariants.

 

I will explain how to fix the sign of the 3-dimensional count, in other words, define an absolute mod-two grading, via a mod-two index-theoretic correction term. This yields a total Euler characteristic \tilde{χ} that sums over all real spin^c structures, the analogue of \hat{χ} in real Heegaard Floer homology (HFR). Recent work of Srivastava provides the motivating results: an absolute mod-two grading in \hat{HFR} and the evaluation of \hat{χ} in terms of the Alexander polynomial at \sqrt{-1}. This is joint work with Ciprian Manolescu.

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