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Entanglement content of quantum particle excitations. Part II. Disconnected regions and logarithmic negativity

Research output: Contribution to journalArticle

Olalla A. Castro-Alvaredo, Cecilia De Fazio, Benjamin Doyon, Istvan Szecsenyi

Original languageEnglish
Article number58
JournalJournal of High Energy Physics
Issue number11
Early online date11 Nov 2019
Publication statusPublished - Nov 2019


King's Authors


In this paper we study the increment of the entanglement entropy and of the (replica) logarithmic negativity in a zero-density 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 four-point functions of branch point twist fields in finite volume. We test our results against numerical simulations on a harmonic chain and find excellent agreement.

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