Reply to the Comment of X. Ji on "Spin and orbital angular momentum in gauge theories" [PRL 100:232002 (2008)]

TL;DR

This paper provides a detailed response to a comment on their previous work, clarifying issues related to gauge-invariant descriptions of spin and orbital angular momentum in gauge theories.

Contribution

It defends and clarifies the gauge-invariant framework for quark and gluon angular momentum against critiques, emphasizing locality and measurability.

Findings

Reaffirms the gauge-invariant approach's validity.

Addresses concerns about locality and Lorentz covariance.

Clarifies the measurability of angular momentum components.

Abstract

We reply to the Comment of X. Ji [arXiv:0810.4913] on our paper [PRL 100:232002 (2008)], concerning angular momentum algebra, locality, Lorentz covariance, and measurability of our gauge-invariant description of the spin and orbital angular momentum of quarks and gluons.