Interactions between three bodies

15:49 No time to pause, next talk is up.

15:50 Apparently there is time for pausing while some technical matters are attended to. Turn it off and on again!

15:51 Ok, We've got Jason Holt with Three-Nucleon Forces for Medium Mass Neutron Rich Nuclei. He starts with thanks to the conference organisers for letting us lie on a beach/do physics for two weeks.

15:52 The outline is up. The bullets of the bullet points are diamond shaped.

15:54 We start of by stating we will use many-body perturbation theory for the many body problem. Take that No-Core Shell Model!

15:55 MBPT truncates the model space, with the perturbative effective potential acting only between models within that space.

15:56 Make up for deficincies in MBPT that appear for more than a few particles or holes away from closed shell by some prudent adjustments of particular two-body matrix elements. Paticularly the monopole part - the angular average of the interactions.

15:58 Where are the adjustable parameters?

15:59 These monopoles drive the evolution of single particle energies. The differences between a phenomenological and micropscopic treatment on sp states (e.g. d3/2 state in Oxygen isotopes is bound above N = 10 up to N=28 but appear to be always unbound for Phenom. forces) - this is obviously important for dripline nuclei! Experimentally, dripline for O isotopes is at N=24. This is at odds with the above, and the finger is pointed at the lack of three body forces in the microscopic description. BOTTOM LINE: THREE BODY FORCES ARE IMPORTANT!

16:05 So: we need 3-body forces for valence shell theories. Hence the next slide is titled 3N forces for valence shell theories.

16:05 + 50 secs To make the 3N-force calculations tractable, an effective two-body force is derived from summation over one degree of freedom (or 1N degrees of freedom, I guess, in this case).

16:07 Some computational details are skipped over. Hurrah!

16:08 The 3N forces solve the O isotope dripline problem. Hurrah!

16:09 Fully microscopic binding energy calculations have been performed. And I think I caught mention of no free parameters. 3N + 1-body calculations with just NN (two-nucleon interaction) and 3N + monopoles (the matrix elements from minute 15:56) trailing in its wake.

16:14 I think I've now confused myself. There are 2 nucleon forces, 3 nucelon forces averaged to be two nucleon force, three nucleon forces that are three nucleon forces. Ok, think I've got it straight.

16:16 Conclusion: First Microscopic shell models using Chiral 3N forces, with excellent results that went by too fast for me to type.

16:18 I like the word chiral. It is very poetic. Although if this was a conference on quark matter I suspect I would get tired of it pretty quickly.

16:19 A question prompts Jason to repeat: what they have done, for the first time (I think) is add 3-body interactions into the shell model, which itself 'remains as messy as it always did' (the questioner's words). This leads to improvements, which is good, because it looks like a lot of work.

16:26 More Carlos: he urges us all to take buses whether we know Portugese or not - or at least that is what I think he said. City tour is cancelled, to be replaced by an early morining jog around the city limits, attendance compulsory.