EFFECTIVE FIELD THEORY FOR NUCLEAR PHYSICS

I summarize the motivation for the effective field theory approach to nuclear physics, and some of its recent accomplishments. 1 Why effective field theory, why nuclear physics? Low energy data is generally insensitive to the details of interactions at short distance. It is therefore difficult to learn about short rangeinteractions; yet by the same token, complete knowledge of the physics at short distances is not required for an accurate understanding of experiments. Effective field theory exploits this fact. The effects of nonlocal interactions at short distance may be represented in terms of local operators in a derivative expansion — the effective Lagrangian. The higher an operator’s dimension, the smaller the effect it has on low energy physics, and hence one can obtain a useful phenomenological theory by retaining operators only up to some dimension, fitting their coefficients to data. Some effective theories arequite useful, such as chiral perturbation theory; some are wildly successful, such as the standard model of particle physics. In this talk I will discuss a new application currently being developed, nuclear effective theory. The utility of effective field theory (EFT) depends on the existence of an energy gap so that “short” and “long” distance physics can be distinguished. It is probably not a useful technique for describing turbulence, or protein folding, for example. In 1990, Weinberg suggested that nuclear physics could be a subject that would benefit from an EFT treatment 1 . In nucleon-nucleon interactions, one can identify the low scales to be m� = 140 MeV, and the nucleon momentum (pF ≃ 280 MeV in nuclear matter), while the high scales