# Effective Field theory and the many-body problem

May 2014 **PROGRAM** ESNTNuclForcesManyBody.pdf

**Organizers:** T. Duguet (SPhN), B. Long (Sichuan Univ.), M. P Valderrama (IPNO), V. Somà (SPhN), U. van Kolck (IPNO and Univ. Of Arizona).

**The goals of the project** are

- to extend the analysis of power counting from the two-nucleon to the few- and many-nucleon systems,
- to discuss how to implement these ideas in concrete calculations and
- to review the reasons leading to the existence of different power counting schemes in the two-nucleon sector and whether they can be solved by looking at the larger picture provided by the A-nucleon systems.

Specifically, we aim to answer the following questions:

- What are the remaining discrepancies in power counting in the 2N system ? Can any of them be eliminated based on pure theoretical considerations rather than the quality of the fit ?
- How to investigate the counting of contact 3N forces ? Given the difficulty of analytic calculations, a numerical method needs to be developed, preferably based on available many-body calculation frameworks.
- How should SCGGF (self-consistent Gorkov-Green function) calculations be modified to handle interactions generated by the correct power counting ?

Addressing the latter point in particular will act as a jump-start for a new collaboration between us that is meant to

lead to full-edged numerical tests based on modified SCGGF calculations.

**Scientific issues and schedule ***see program file*

The project involves the visit of Professor Bingwei Long to Saclay for about four weeks. His expertise will be highly beneficial for all the points raised above. In particular, he is expected to engage in specific discussions on nucleon-nucleon scattering with M. Pavón Valderrama and

U. van Kolck, and on the implementation of the new power counting in A-body ab-initio structure calculations with T. Duguet, M. Pavón Valderrama, V. Somà and U. van Kolck.

** Program of the half-day workshop scheduled on Friday, May 16th, Room 135**

The meeting will be dedicated to introducing interested nuclear experimentalists and theoreticians to the challenges and perspective related to the application of effective field theories to the many-nucleon systems. The relevant issues will be introduced and the results of the project will be reported on, followed by a round-table discussion.

- 9h00-9h45
*Welcome* - 9h45-11h00 B Long,
*Renormalization and power counting of chiral nuclear forces*Talk_Long_ESNT16may14.pdf - 11h00-11h15
*Break* - 11h15-12h30 V. Somà,
*Towards many-body calculations on the basis of a consistent chiral power counting* - 12h30-13h30 Lunch

*Retour accueil ESNT **Back to the ESNT page*