学术报告（9月8日）

主持人：张宏浩 副教授

欢迎广大师生踊跃参加！

摘要：

近年来，通过利用正Grassmann流形、在壳图与振幅多面体的优美的几何图像，特别是在转换到动量扭量空间后，N=4 SYM散射振幅的研究取得了惊人的突破。在树图层次以上，研究N=4 SYM的圈图积分函数需要对正Grassmann流形进行精巧的推广，从而产生了振幅多面体的概念。在这次报告中，我们将回顾三种相关但又不同的推导圈图积分函数的方法：BCFW递推关系、局域展开与振幅多面体的三角剖分。

 Loop Integrands in Momentum Twistor Space and Amplituhedron

Abstract: For scattering amplitudes of N=4 SYM, tremendous progress had been made in the last a few years through the novel formulation of positive Grassmannian, on-shell diagrams and the elegant geometric picture of amplituhedron, especially after transforming to the (super) momentum twistor space. Beyond tree level, loop integrands of N=4 SYM demands an intricate generalization of positive Grassmannian, which is the amplituhedron. In this seminar we will review three related different ways to derive loop integrands: the BCFW recursion relation, local expansion and the amplituhedron triangulation.