Aspects of self-dual Yang-Mills and self-dual gravity

TL;DR

This thesis investigates all same helicity loop amplitudes in self-dual Yang-Mills and gravity, proposing new formulas and exploring their implications for anomalies and UV divergences in quantum gravity.

Contribution

It introduces a new all-multiplicity formula for one-loop amplitudes in self-dual Yang-Mills and analyzes their anomaly and UV divergence implications.

Findings

Four-point one-loop amplitude reduces to shifts, suggesting an anomaly.

Proposed a new formula for all-multiplicity one-loop amplitudes.

Validated the formula through explicit computations at 3, 4, and 5 points.

Abstract

In this thesis, we study the all same helicity loop amplitudes in self-dual Yang-Mills and self-dual gravity. These amplitudes have long been conjectured to be interpreted as an anomaly and are recently linked to the UV divergence of two-loop quantum gravity. In the first part of the thesis, we study the loop amplitudes in self-dual Yang-Mills. We show that the four point one-loop amplitude can be reduced to a computation of shifts, which strongly suggests a case for an anomaly interpretation. We next propose a new formula for the one-loop amplitudes at all multiplicity, in terms of the Berends-Giele currents connected by an effective propagator. We prove the formula by observing that it readily implies the correct collinear properties. To demonstrate the validity of our formula, we do an explicit computation at 3, 4 and 5 points and reproduce the known results. The region momenta variables play an important role in our formula and thus it points to both the worldsheet and the momentum twistor interpretations. In the second part of the thesis, we study the one loop behaviour of chiral Einstein-Cartan gravity and the one-loop amplitudes in self-dual gravity.