Do multineutrons exist?

Abstract

Following recent work in which events which may correspond to a bound tetraneutron ($^4$n) were observed, it is pointed out that from the theoretical perspective the two-body nucleon-nucleon (NN) force cannot by itself bind four neutrons, even if it could bind a dineutron. Unrealistic modifications of the NN force or introduction of unreaslistic four-nucleon force would be needed in order to bind the tetraneutron. The existence of other multineutron systems is discussed.