Speaker: Dr. Yutaro Shoji from Nagoya University

Abstract:
The electroweak vacuum is not absolutely stable in the standard model and various models beyond the standard model. This is due to an appearance of another deeper vacuum, into which the electroweak vacuum can decay. The decay proceeds through quantum tunneling and the rate is expressed with an exponential suppression factor and a pre-factor. The suppression factor has been calculated in many papers, but a naive dimensional analysis has been usually adopted for the pre-factor.

We have pointed out that such an evaluation can suffer from large quantum corrections and it is important to calculate the pre-factor as well.

To calculate the pre-factor, we had problems in a gauge sector; its gauge invariance is not explicitly shown, and there appear zero modes, which we could not deal with.

We have solved these problems and made it possible to determine vacuum decay rates precisely.

As applications, we analyzed the decay rates in the standard model and its fermionic extensions. We also provide a public code, which can be used for models that exhibit classical scale invariance at a high energy scale.

Neural Computation Unit (Doya Unit)

Stable homotopy and differential topology

Speaker: Dr. Vincnezo Vitagliano from Keio University

Abstract:
External conditions have a dramatic impact on the way dynamical symmetry breaking occurs. I will review some recent (and some less recent) results of symmetry breaking in curved spacetime. Flirting with the contemporary interest toward 2D engineered material, I will then move on potential applications on geometrically deformed lattices. In a curved background, the natural expectation is that curvature works toward the restoration of an internal symmetry. I will show instead that, for topological defects, the competing action of the locally induced curvature and of boundary conditions generated by the non-trivial topology allows configurations where symmetries can be spontaneously broken close to the core.

[Topology and Geometry Seminar] "Solving Word Problems in finitely presented groups" by Robert Tang

"Ultra-strong light-matter interactions and super-radiant phase transitions" by Prof Motoaki Bamba, Osaka Univ

Speaker
Dr. Tomoaki Matsuura, Associate Professor at Department of Biotechnology, Graduate School of Engineering, Osaka University.

Topology and Geometry unit seminar

Dr. Sebastian Reinig, Postdoc, National Institute of Genetics.  Language: English

"Broadband plasmonics in the optical and THz range" by Prof. Venu Gopal Achanta, DCMP&MS, Tata Institute of Fundamental Research, Mumbai, India