ИСТИНА

A low-lying resonance in the system of four neutrons (tetraneutron) was first observed recently by Kisamori et al. The so-called SS-HORSE method was developed to extract resonance energies and widths from the results of the No-Core Shell Model (NCSM) calculations. An extension of the SS-HORSE-NCSM formalism to the case of democratic decays was able to explain the tetraneutron resonance in calculations with the JISP16 NN interaction. I discuss the above theoretical approach and new results obtained with various other inter-nucleon interactions in extended model spaces.