Singularity in Potential, Perturbation and Variational Methods

Yi-Bing Ding, Xue-Qian Li, Peng-Nian Shen

In this work, we carefully study the energy eigen-values and splitting of heavy quarkonia as there exist $1/r^3$ and ${\delta }^3(\vec{r})$ singular terms in the potential which make a dire…