Prediction for a four-neutron resonance
  We utilize various {\em ab initio} approaches to search for a low-lying resonance in the four-neutron ($4n$) system using the JISP16 realistic $NN$ interaction. Our most accurate prediction is obtained using a $J$-matrix extension of the No-Core Shell Model and suggests a $4n$ resonant state at an energy near $E_r = 0.8$ MeV with a width of approximately $\Gamma = 1.4$ MeV. 
A. M. Shirokov, G. Papadimitriou, A. I. Mazur, I. A. Mazur, R. Roth   and J. P. Vary
nucl-th nucl-ex