标题： 三粒子顶点的梯子方程及其近似解 显示英文标题

标题： Ladder equation for the three-particle vertex and its approximate solution

摘要： 我们将三个两粒子Bethe-Salpeter方程推广到十个三粒子阶梯。 这些方程是精确的，并且如果我们知道其中一种通道的三粒子顶点不可约，就能得到精确的三粒子顶点。 然而，由于我们无法获得这种三粒子不可约顶点，因此通过两个两粒子不可约顶点的和来近似阶梯中的这一基本构建块，每个两粒子不可约顶点连接两个费米子线。 与精确解的比较表明，这种近似仅在相互作用较弱时有效，而且即使在这种情况下也只是定性地有效——至少对于分析的非线性响应函数而言。 显示英文摘要

摘要： We generalize the three two-particle Bethe-Salpeter equations to ten three-particle ladders. These equations are exact and yield the exact three-particle vertex, if we knew the three-particle vertex irreducible in one of the ten channels. However, as we do not have this three-particle irreducible vertex at hand, we approximate this building block for the ladder by the sum of two-particle irreducible vertices each connecting two fermionic lines. The comparison to the exact solution shows that this approximation is only good for rather weak interactions and even than only qualitatively - at least for the non-linear response function analyzed.