In this talk we will discuss the classic soft photon radiation theorems due to Low and Weinberg. We will review Low’s arguments, and discuss the assumptions made in arriving at the classic “Low’s theorem” result.
We will show that when a soft photon is radiated from an Infrared pinched subgraph, the leading soft photon theorem is corrected by higher order graphs. We will discuss the connection between the leading soft photon theorem and soft subgraphs.
We will then discuss a complete classification of pinch surfaces, and modifications to classic factorization theorems in the presence of a radiative subgraphs. At next-leading to power, we will find new effects from soft-subgraphs. Here, we will also review the connection between next-to-leading power radiative amplitudes and next-to-leading power factorization. This will enable us to arrive at a matrix element form for the leading and subleading soft photon theorems that is expected to hold to all orders.
Finally, I will describe an explicit calculation to verify that the leading power soft photon theorem is modified in four dimensions at starting at three loops.