Chiral effective field theory for few-nucleon systems

Some recent developments in the description of nuclear forces and few--nucleon systems within the effective field theory approach are reviewed.Comment: 9 pages, 6 figures, plenary talk at 17th International IUPAP Conference on Few-body Problems in Physics, June 5-10, 2003, Durham, North Carolina, US

Effective Field Theory and Isospin Violation in Few-Nucleon Systems

I discuss the leading and subleading isospin--breaking three--nucleon forces in the chiral effective field theory framework.Comment: 5 pages, 2 figures. Invited lead talk at the 19th European Conference on Few-Body Problems in Physics, Groningen, The Netherlands, August 23-27, 200

Regularization, renormalization and "peratization" in effective field theory for two nucleons

We discuss conceptual aspects of renormalization in the context of effective field theories for the two-nucleon system. It is shown that, contrary to widespread belief, renormalization scheme dependence of the scattering amplitude can only be eliminated up to the order the calculations are performed. We further consider an effective theory for an exactly solvable quantum mechanical model which possesses a long- and short-range interaction to simulate pionful effective field theory. We discuss the meaning of low-energy theorems in this model and demonstrate their validity in calculations with a finite cutoff $\Lambda$ as long as it is chosen of the order of the hard scale in the problem. Removing the cutoff by taking the limit $\Lambda \to \infty$ yields a finite result for the scattering amplitude but violates the low-energy theorems and is, therefore, not compatible with the effective field theory framework.Comment: 22 pages, 2 figures, to appear in Eur. Phys. J.

The three-nucleon system as a laboratory for nuclear physics: the need for 3N forces

Recent experimental results in three-body systems have unambiguously shown that calculations based on nucleon-nucleon forces fail to accurately describe many experimental observables and one needs to include effects which are beyond the realm of the two-body potentials. This conclusion owes its significance to the fact that experiments and calculations can both be performed with a high accuracy. In this short review, a sample of recent experimental results along with the results of the state-of-the-art calculations will be presented and discussed.Comment: Commissioned article for Nuclear Physics News, 8 pages, 6 figure

Four-nucleon force in chiral effective field theory

We derive the leading contribution to the four-nucleon force within the framework of chiral effective field theory. It is governed by the exchange of pions and the lowest-order nucleon-nucleon contact interaction and includes effects due to the nonlinear pion-nucleon couplings and the pion self interactions constrained by the chiral symmetry of QCD. The resulting four-nucleon force does not contain any unknown parameters and can be tested in few- and many-nucleon studies.Comment: 4 pages, 4 figure

Nuclear forces with Delta-excitations up to next-to-next-to-leading order I: peripheral nucleon-nucleon waves

We study the two-nucleon force at next-to-next-to-leading order in a chiral effective field theory with explicit Delta degrees of freedom. Fixing the appearing low-energy constants from a next-to-leading order calculation of pion-nucleon threshold parameters, we find an improved convergence of most peripheral nucleon-nucleon phases compared to the theory with pions and nucleons only. In the delta-full theory, the next-to-leading order corrections are dominant in most partial waves considered.Comment: 16 pages, 10 figure

Chiral dynamics of few-nucleon systems

I discuss some recent developments in chiral effective field theory for few-nucleon systems.Comment: 8 pages, 6 figures, invited talk, International Nuclear Physics Conference (INPC 2007), Tokyo, Japan, June 3-8, 200