Entanglement in descendants

TL;DR

This paper investigates the entanglement properties of conformal descendants in 2D CFT, revealing non-trivial entanglement structures and universal features in their corrections and relative entropies.

Contribution

It provides a detailed analysis of entanglement entropy and relative entropy for descendants in 2D CFT, including their short interval expansions and universal dressing factors.

Findings

Descendants exhibit non-trivial entanglement entropy.

First sub-leading corrections are determined by dressing factors.

Relative entropy relates to differences in dressing factors.

Abstract

We study the single interval entanglement and relative entropies of conformal descendants in 2d CFT. Descendants contain non-trivial entanglement, though the entanglement entropy of the canonical primary in the free boson CFT contains no additional entanglement compared to the vacuum, we show that the entanglement entropy of the state created by its level one descendant is non-trivial and is identical to that of the $U(1)$ current in this theory. We determine the first sub-leading corrections to the short interval expansion of the entanglement entropy of descendants in a general CFT from their four point function on the n-sheeted plane. We show that these corrections are determined by multiplying squares of appropriate dressing factors to the corresponding corrections of the primary. Relative entropy between descendants of the same primary is proportional to the square of the difference of their dressing factors. We apply our results to a class of descendants of generalized free fields and descendants of the vacuum and show that their dressing factors are universal.