The Structure of Rare Isotopes, Taka Otsuka

For me, this was one of the most awaited talks of the conference. I first watched Taka's talk at ENAM in 2008, in Poland. At the time people were digesting his ideas about the tensor force driving major shell structure changes. Not much was mentioned about the role of 3-body forces, not that I recall. Anyhow, I had no idea what he was talking about. I don't think I still do, but when I read that he was coming to PASI and was going to give a talk about his work. Since PASI talks are supposed to be at undergraduate level, I felt that was my chance to finally learn something from this guy. However, I knew it was impossible to review in 45 minutes such a tough subject using undergrad physics. But hey, Taka did a great job!

He started with a very pedagogical intro, showing how to construct many body systems from the basic nuclear forces. He spent some time discussing key features of the bare nn potential. He then moved on to single-particle potential, with our beloved harmonic oscillator potential, added L.S splitting and voilá, there you have the shell model and magic numbers. The universality of magic numbers has been challenged over the years, and he showed us some empirical evidence. As an example, he showed the now famous Tanihata's PRL in halo nuclei, which was published in 1985 - I was 2 years old when this happened, and to me at least it is impressive and scary to see that that this paradigm shift has been happening over my short lifetime.

I think the main message Taka was trying to pass across is that there is large evidence for two major mechanisms that are driving shell evolution a) tensor force, and 3-body force. His "intuitive" picture of the monopole effect of tensor force is starting to sink in my mind, but I have to confess that his discussion on 3-body force was beyond me. I'll definitely need need another couple of years to come to terms with these recent developments.