Comments on the two-point string amplitudes
arXiv:2303.15658 · doi:10.1103/PhysRevD.107.106021
Abstract
The two-point string amplitude at tree level in flat spacetime reproduces the expected expression for free particles. This has been proven by Erbin, Maldacena and Skliros in [JHEP 07 (2019) 139] by two methods. Here, we provide an alternative proof of this result. Our method consists in considering a timelike Liouville direction as a regularization parameter, which suffices to break time translation invariance and, at the same time, to stabilize the residual conformal symmetry in the worldsheet. This allows taking a limit and restoring Poincare symmetry in a controlled way, thus reproducing the correct expression of the two-point amplitude.
13 pages. v3 references and comments added. Version accepted for publication