# Universal Entanglement and Boundary Geometry in Conformal Field Theory

**Authors:** Christopher P. Herzog, Kuo-Wei Huang, Kristan Jensen  
**arXiv:** [1510.00021](https://arxiv.org/abs/1510.00021)  
**Date:** 2015-09-30  
**Summary page:** https://www.summarizepaper.com/fr/paper/1510.00021v3/

## Abstract

Employing a conformal map to hyperbolic space cross a circle, we compute the universal contribution to the vacuum entanglement entropy (EE) across a sphere in even-dimensional conformal field theory. Previous attempts to derive the EE in this way were hindered by a lack of knowledge of the appropriate boundary terms in the trace anomaly. In this paper we show that the universal part of the EE can be treated as a purely boundary effect. As a byproduct of our computation, we derive an explicit form for the A-type anomaly contribution to the Wess-Zumino term for the trace anomaly, now including boundary terms. In d=4 and 6, these boundary terms generalize earlier bulk actions derived in the literature.