# Crossing Symmetry in the Planar Limit

### APA

Mizera, S. (2021). Crossing Symmetry in the Planar Limit. Perimeter Institute. https://pirsa.org/21050013

### MLA

Mizera, Sebastian. Crossing Symmetry in the Planar Limit. Perimeter Institute, May. 11, 2021, https://pirsa.org/21050013

### BibTex

@misc{ pirsa_PIRSA:21050013, doi = {10.48660/21050013}, url = {https://pirsa.org/21050013}, author = {Mizera, Sebastian}, keywords = {Quantum Fields and Strings}, language = {en}, title = {Crossing Symmetry in the Planar Limit}, publisher = {Perimeter Institute}, year = {2021}, month = {may}, note = {PIRSA:21050013 see, \url{https://pirsa.org}} }

Sebastian Mizera Institute for Advanced Study (IAS) - School of Natural Sciences (SNS)

## Abstract

Crossing symmetry asserts that particles are indistinguishable from anti-particles traveling back in time. In quantum field theory, this statement translates to the long-standing conjecture that probabilities for observing the two scenarios in a scattering experiment are described by one and the same function. Why could we expect it to be true? In this talk we examine this question in a simplified setup and take steps towards illuminating a possible physical interpretation of crossing symmetry. To be more concrete, we consider planar scattering amplitudes involving any number of particles with arbitrary spins and masses to all loop orders in perturbation theory. We show that by deformations of the external momenta, one can smoothly interpolate between the future and the past lightcones without encountering any singularities.