Entanglement content of quantum particle excitations. Part II. Disconnected regions and logarithmic negativity
Abstract
In this paper we study the increment of the entanglement entropy and of the (replica) logarithmic negativity in a zerodensity excited state of a free massive bosonic theory, compared to the ground state. This extends the work of two previous publications by the same authors. We consider the case of two disconnected regions and find that the change in the entanglement entropy depends only on the combined size of the regions and is independent of their connectivity. We subsequently generalize this result to any number of disconnected regions. For the replica negativity we find that its increment is a polynomial with integer coefficients depending only on the sizes of the two regions. The logarithmic negativity turns out to have a more complicated functional structure than its replica version, typically involving roots of polynomials on the sizes of the regions. We obtain our results by two methods already employed in previous work: from a qubit picture and by computing fourpoint functions of branch point twist fields in finite volume. We test our results against numerical simulations on a harmonic chain and find excellent agreement.
 Publication:

Journal of High Energy Physics
 Pub Date:
 November 2019
 DOI:
 10.1007/JHEP11(2019)058
 arXiv:
 arXiv:1904.01035
 Bibcode:
 2019JHEP...11..058C
 Keywords:

 Field Theories in Lower Dimensions;
 Integrable Field Theories;
 High Energy Physics  Theory;
 Condensed Matter  Statistical Mechanics;
 Mathematical Physics;
 Quantum Physics
 EPrint:
 45 pages, 17 figures