content_image/353776.jpg
<img src='content_image/353776.jpg'>

need to use reduction factors [29]. Therefore in order to exam whether the spin symmetry still persist in the face of these effects, the Dirac negative energy spectrum is calculated with the coupling constants g$_{i}$ ¯ N ¯ N = g$_{i}$ ¯ NN = g$_{iN}$ ¯ N = 0 . 3 g$_{iNN}$ , where i = σ, ω, ρ . In Fig. 7, all the bound single neutron states in the Dirac sea thus obtained are shown, together with the spin-orbit splitting as well as its Hartree and Fock contributions. It is found that the spin symmetry is still well conserved even in the case where significant deviations from the G-parity values of the meson-antinucleon couplings due to the strong annihilation channels and various many-body effects occur. 

## IV. SUMMARY 

In summary, the spin symmetry in the negative energy spectrum and its mechanism are investigated within the DDRHF theory by taking the nucleus $^{16}$O as an example. 

Similarly to RMF, the spin symmetry in the negative energy spectrum is found to be 

