论文标题
关于树级字符串振幅的单位性
On Unitarity of Tree-Level String Amplitudes
论文作者
论文摘要
弦理论中的四颗粒子树级散射幅度与单位性具有神奇的一致，反映在一个非平凡的事实中，即在临界维度下，在大型杆上振幅的残基可以与所有阳性系数一起在部分波中扩展。尽管这是从无轴测定理（而不是间接）的，但陈述的简单性及其对字符串理论的物理一致性的基本意义乞求更直接和基本的理解。在本说明中，我们通过为弦振幅的部分波系数提供新的表达式迈出了一个步骤，这是由开放/闭合字符串的惊人简单的双/三重轮廓积分给出的。这种表示使我们能够直接证明$ d \ leq 6 $时空维度的所有超弦理论的单位性，也可以用于确定大质量水平下部分波的各种渐近波。
Four-particle tree-level scattering amplitudes in string theory are magically consistent with unitarity, reflected in the non-trivial fact that beneath the critical dimension, the residues of the amplitudes on massive poles can be expanded in partial waves with all positive coefficients. While this follows (rather indirectly) from the no-ghost theorem, the simplicity of the statement and its fundamental importance for the physical consistency of string theory begs for a more direct and elementary understanding. In this note we take a step in this direction by presenting a new expression for the partial wave coefficients of string amplitudes, given by surprisingly simple double/triple contour integrals for open/closed strings. This representation allows us to directly prove unitarity of all superstring theories in $D \leq 6$ spacetime dimensions, and can also be used to determine various asymptotics of the partial waves at large mass levels.
