Effective field theory changed the way in which quantum interactions are thought and developed. Nuclear physics is not an exception to this. The possibility of exchanging pions between nucleons makes the expansion of the interaction around nucleonic and pionic degrees of freedom the most natural choice. However, this procedure introduces some technical difficulties for example, the one-pion-exchange results to be not easily renormalizable and the powercounting orders are not trivial to be determined.
Although, in many nuclear processes, the momenta involved are very soft and can not resolve the pion exchange. This opens the possibility to use contact EFT instead of meson exchanges. While limited in the momentums that can be described, this class of theories preserve renormalizability and has a very limited number of inputs that need to be fitted. Despite his simplicity, this theory still retains predictive power on non-trivial few- and many-body effects. In this seminar, I am going to describe how Contact EFT for nuclear physics (which takes the name of Pionless theory) is constructed and what are the features, strengths, and limitations of this approach in few- and many-body systems.
This theory has proven to work well for several few-body nuclear calculations, but it is not limited to the nuclear regime. It is, in fact, appropriate for all the systems that are close to unitarity (as cold atoms), namely that have a two-body effective rage much smaller than the relative scattering length. The extension of this theory to different systems will be commented together with some of our latest results in applying it to physical systems that can hardly be described with the standard approaches as single- and double-lambda hypernuclei and Lattice nuclei.