Schwarzian transformations at null infinity

TL;DR

This paper explores the Schwarzian behavior of the gravitational field at null infinity under superrotations, highlighting its nature as an unobservable gauge artifact and discussing implications for celestial holography.

Contribution

It introduces the Schwarzian behavior at null infinity as a gauge artifact and connects it to celestial holography and the AdS$_3$/CFT$_2$ correspondence.

Findings

Schwarzian behavior is an unobservable gauge artifact at null infinity.

The News tensor characterizes gravitational radiation in this context.

Potential links between celestial holography and AdS/CFT correspondence are proposed.

Abstract

I describe the Schwarzian behavior of the gravitational field at null infinity under superrotations, to be understood as an \textit{unobservable} gauge artifact. To this end I review the induced geometry of null infinity and the construction of the gauge-invariant News tensor that characterizes gravitational radiation. I discuss potentially important implications for the celestial holography program, suggesting in particular that the uplift of the AdS$_3$/CFT$_2$ correspondence directly relates to the unobservable gauge sector.