Many-particle many-hole states near the magic number 20: deformed and   superdeformed states
  Many-particle many-hole states near the magic number 20 have been investigated in the relativistic mean field formalism using the fixed configuration method. Neutron particle-hole states in neutron-rich nuclei with $N\sim 20$, {\em i.e.} $^{30,32,34}$Mg,and $^{28,30}$Ne are studied to find out the ground state configuration. The ground state of $^{32}$Ne,Mg as well as possibly $^{34}$Mg comes out actually as particle-hole states. Proton-neutron excitation across the shell gap at 20 in nuclei with $N=Z$, {\em i.e.} $^{32}$S, $^{36}$Ar, $^{40}$Ca and $^{44}$Ti is investigated as possible origins of superdeformed configuration. Observed superdeformed bands in $^{36}$Ar and $^{40}$Ca can be described as many-particle many-hole states. 
Samit Bhowal, Sankha Das and G. Gangopadhyay