报告人：李定平 （北京大学）

时 间：2026年1月5日（周一）上午14:00-16:00

地 点：良乡校区，理学楼B203会议室

摘要：

In many-body theory, fundamental symmetries-such as the Ward-Takahashi identity (WTI),the Fluctuation-Dissipation theorem (FDT), and the Pauli exclusion principle-must be satisfied. However, widely used approximate theories struggle to fulfill these symmetries simultaneously.

By employing the GW method (beyond the mean-field approximation) and a covariance scheme -- both of which strictly satisfy WTI and FDT -- we numerically demonstrate that the violation of the Pauli exclusion principle is significantly smaller than that in mean-field theory. Furthermore, we achieve the restoration of the Pauli exclusion principle without breaking WTI or FDT. To validate the numerical accuracy of our approach, we calculate the symmetrized one-body Green's function and two-body correlation function for the half-filled Hubbard model, comparing the results with high-precision data from Determinant Quantum Monte Carlo (DQMC). This comparison confirms the method's reliability at low temperatures and strong coupling regimes.

Preliminary results are also presented for the cuprate Hubbard model at various filling fractions, laying the groundwork for the development of a microscopic many body theory of high-temperature superconductivity in cuprate superconductors.

简历：

李定平，北京大学物理学院教授，清华大学本科毕业，1993年获得意大利高等研究学院博士学位。长期专注于多体场论非微扰方法的研究，及其在高温超导体宏观相图和高温超导的微观机理等方向的应用，相关论文发表在Reviews of Modern Physics, Physical Review Letters, Physical Review B, Physical Review A, Nuclear Physics B等刊物.

联系方式：dizhou@bit.edu.cn

邀请人：周迪 教授

网 址：http://physics.bit.edu.cn/

承办单位：物理学院、先进光电量子结构设计与测量教育部重点实验室