報(bào)告人：李定平 （北京大學(xué)）

時(shí) 間：2026年1月5日（周一）上午14:00-16:00

地 點(diǎn)：良鄉(xiāng)校區(qū)，理學(xué)樓B203會(huì)議室

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.

簡(jiǎn)歷：

李定平，北京大學(xué)物理學(xué)院教授，清華大學(xué)本科畢業(yè)，1993年獲得意大利高等研究學(xué)院博士學(xué)位。長(zhǎng)期專注于多體場(chǎng)論非微擾方法的研究，及其在高溫超導(dǎo)體宏觀相圖和高溫超導(dǎo)的微觀機(jī)理等方向的應(yīng)用，相關(guān)論文發(fā)表在Reviews of Modern Physics, Physical Review Letters, Physical Review B, Physical Review A, Nuclear Physics B等刊物.

聯(lián)系方式：dizhou@bit.edu.cn

邀請(qǐng)人：周迪 教授

網(wǎng) 址：http://www.5130unyq.cn/

承辦單位：物理學(xué)院、先進(jìn)光電量子結(jié)構(gòu)設(shè)計(jì)與測(cè)量教育部重點(diǎn)實(shí)驗(yàn)室