2015/04/06 by Javier M. Magán, Javier M. Magan, Stefan Vandoren
Mathematics · Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Degrees of freedom (physics and chemistry) #Fock space #Massless particle #Mathematics #Physics #Quantum #Quantum entanglement #Quantum field theory #Quantum many-body systems #Quantum mechanics #Scalar (mathematics) #Scalar field #Statistical physics #Theoretical physics #gr-qc #hep-th #quant-ph
paper · pdf · doi:10.1007/jhep07(2015)150
45 pages, 6 Figures
arxiv created 2015/04/06 · openalex publication_date 2015/07/01 · arxiv updated 2015/09/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Entanglement in random states has turned into a useful approach to quantum thermalization and black hole physics. In this article, we refine and extend the ‘random unitaries framework’ to quantum field theories (QFT), and to include conserved charges. We show that in QFT, the connection between typical states, reduced subsystems and thermal dynamics is more transparent within the Fock basis. We provide generic formulae for the typical reduced density matrices and entanglement entropies of any given subset of particles. To illustrate our methods, we apply the generic framework to the simplest but non trivial cases, a massless scalar field in two dimensions and its generalization to the case of N scalar fields, including the large N limit. We find the effective temperature, by matching the reduced dynamics to a Gibbs ensemble, and derive the equation of state of the QFT. The deviations from perfect thermality are shown to be of order 1 /S instead of exp(− S ), a result which might be relevant for black hole physics. Finally we describe the analogue of the so-called ‘Page curve’ in the QFT scenario as a function of the energy scale which divides high from low energy degrees of freedom.