Theoretical research on charge radii in exotic nuclei

Charge radii are fundamental properties in describing atomic nuclei．Precise determination of charge radii of exotic nuclei can be influenced, for example, by shape deformation, pairing correlation, and shell closure effect．Therefore it is important to develop a unified theoretical model．Available descriptions of charge radii can disclose effective nucleon-nucleon interactions and make constraints on theoretical parameterization sets．Reliable data of nuclear charge radii serve as inputs in astrophysics study．This paper reviews recent progress of theoretical research regarding charge radii in exotic nuclei．The source of shell closures and odd-even staggering in charge radii are analyzed through various theoretical models．Trends in systematic change of charge radii along Ca and Rb isotopic chains are used as examples to emphasize that neutron-proton correlations and spin-orbit interactions play an important role in describing charge radii of exotic nuclei．