The One-Loop Five-Graviton Amplitude and the Effective Action

Understand

We consider the one-loop five-graviton amplitude in type II string theory calculated in the light-cone gauge.

• Although it is not possible to explicitly evaluate the integrals over the positions of the vertex operators, a low-energy expansion can be obtained, which can then be used to infer terms in the low-energy effective action.
• After subtracting diagrams due to known D^{2n}R^4 terms, we show the absence of one-loop R^5 and D^2R^5 terms and determine the exact structure of the one-loop D^4R^5 terms where, interestingly, the coefficient in front of the D^4R^5 terms is identical to the coefficient in front of the D^6R^4 term.
• Finally, we show that, up to D^6R^4 ~ D^4R^5, the \epsilon_{10} terms package together with the t_8 terms in the usual combination (t_8t_8\pm{1/8}\epsilon_{10}\epsilon_{10}).