Nuclear ``bubble'' structure in Si34

Bubble nuclei are characterized by a depletion of their central density. Their existence is examined within three different theoretical frameworks: the shell model and nonrelativistic and relativistic microscopic mean-field approaches. We analyze Si34 and O22 as possible candidates for proton and neutron bubble nuclei, respectively. In the case of O22, we observe a significant model dependence, thereby calling into question the bubble structure of O22. In contrast, an overall agreement among the models is obtained for Si34. Indeed, all models predict a central proton density depletion of about 40% and a central charge density depletion of 25%-30%. This result provides strong evidence in favor of a proton bubble in Si34.