Time: 10:30-12:00  (Beijing time) Wednesday, 2025/12/10 (December 10)

Location: Room 401, Building 7, UCAS Zhongguancun Campus

Speaker: Liu Si-nong, YMSC Tsinghua



Abstract:

An interesting class of time dependent backgrounds in 1+1 dimensional string theory involves worldsheet Liouville walls which move in (target space) time. When a parameter in such a background exceeds a certain critical value, the speed of the Liouville wall exceeds the speed of light, and there is no usual S-Matrix. We examine such backgrounds in the dual c=1 matrix model from the point of view of fluctuations of the collective field, and determine the nature of the emergent space-time perceived by these fluctuations. We show that so long as the corresponding Liouville wall remains time-like, the emergent space time is conformal to full Minkowski space with a time-like wall. However, for the cases where the Liouville wall is superluminal, the emergent space-time has a space-like boundary where the collective field couplings diverge. This appears as a space-like singularity in perturbative collective field theory. We comment on the necessity of incorporating finite N, as well as finite (double-scaled) coupling, effects to understand the behavior of the exact theory near this boundary.

Link for Zoom meeting:

https://us06web.zoom.us/j/85715129440?pwd=QlJJRFBWWFRLMkxCVmcxZ1RKdlRxQT09