Entanglement of quantum fluctuations in the inflationary universe

Yasusada Nambu

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)


We investigate quantum entanglement of a scalar field in the inflationary universe. By introducing a bipartite system using a lattice model of scalar field, we apply the separability criterion based on the partial transpose operation and numerically calculate the bipartite entanglement between separate spatial regions. We find that the initial entangled state becomes separable or disentangled when the size of the spatial regions exceed the Hubble horizon. This is a necessary condition for the appearance of classicality of the quantum fluctuation. We further investigate the condition for the appearance of the classical distribution function and find that the condition is given by the inequality for the symplectic eigenvalue of the covariance matrix of the scalar field.

Original languageEnglish
Article number044023
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Issue number4
Publication statusPublished - Aug 12 2008
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Physics and Astronomy (miscellaneous)


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