Kinematic Flow and the Emergence of Time
Journal
Physical Review Letters
Journal Volume
135
Journal Issue
3
Start Page
031602
ISSN
0031-9007
1079-7114
Date Issued
2025-07-18
Author(s)
Abstract
Perhaps the most basic question we can ask about cosmological correlations is how their strength changes as we smoothly vary kinematic parameters. The answer is encoded in differential equations that govern this evolution in kinematic space. In this Letter, we introduce a new perspective on these differential equations. We show that, in the simplified setting of conformally coupled scalars in power-law Friedmann-Robertson-Walker spacetimes, the equations for arbitrary tree-level processes can be obtained from a small number of simple combinatorial rules. While this "kinematic flow"is defined purely in terms of boundary data, it reflects the physics of bulk time evolution. The unexpected regularity of the equations suggests the existence of an autonomously defined mathematical structure from which cosmological correlations and the time evolution of the associated spacetime emerge.
Publisher
American Physical Society (APS)
Type
journal article