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在小振幅极限下,我们从时间相关的相对论平均场推导了相对论无规位相近似。在相对论平均场不考虑Dirac海的近似下,相对论无规位相近似的组态空间不仅包括通常的正能粒子-空穴对ph,还必须考虑Fermi海中占有态和Dirac海中负能态形成的对αh。用模型方法来研究负能态对相对论无规位相矩阵的贡献。对于Dirac海负能态对116Sn同位旋巨单极共振强度分布的很大的影响做了讨论。研究表明:由于矢量介子的类时分量的矩阵元中αh组态与ph对的耦合相对于标量介子大大地减弱,使得激发能在MeV能区的巨共振态中负能态的
At the small amplitude limit, we derive the relativistic random phase approximation from the time-dependent relativistic mean fields. In the approximation that the relativistic mean field does not consider the Dirac sea, the configuration space with the similar approximation of the relativity includes not only the normal positive-energy particle-hole pair ph, but also the pair formed by the state of Fermi and the negative energy of Dirac αh. The model method is used to study the contribution of negative energy states to the matrix of relativistic random phases. The great influence of the Dirac nodal energy on the monopole resonance intensity distribution of the 116Sn isospin is discussed. The results show that the coupling of αh configuration and ph pair in the matrix element of the quasi-time component of the vector meson decreases greatly relative to the scalar mesons, so that the excitation energy has a negative energy state in the giant resonance state of the MeV energy region