# Strings on the Keldysh Contour

### APA

Mogni, C. (2019). Strings on the Keldysh Contour. Perimeter Institute. https://pirsa.org/19100043

### MLA

Mogni, Christopher. Strings on the Keldysh Contour. Perimeter Institute, Oct. 15, 2019, https://pirsa.org/19100043

### BibTex

@misc{ pirsa_19100043, doi = {10.48660/19100043}, url = {https://pirsa.org/19100043}, author = {Mogni, Christopher}, keywords = {Quantum Fields and Strings}, language = {en}, title = {Strings on the Keldysh Contour}, publisher = {Perimeter Institute}, year = {2019}, month = {oct}, note = {PIRSA:19100043 see, \url{https://pirsa.org}} }

Christopher Mogni University of California

## Abstract

There is a fundamental tension between what string theory computes (S-matrix elements) and what you can compute in QFT on a time-dependent backgrounds (real time operator expectation values). The prescription for computing time dependent expectation values in QFT involves a path integral defined on a closed time path, known as the Keldysh contour. In this talk, we'll discuss how a worldsheet formulation of string theory must perceive the Keldysh contour and how this modifies critical string theory at tree level in the string coupling.