Abstract
We study the entanglement entropy resulting from tracing out local degrees of freedom of a quantum scalar field in an expanding universe. It is known that when field modes become superhorizon during inflation they evolve to increasingly squeezed states. We argue that this causes the entanglement entropy to grow continuously as successive modes cross the horizon. The resulting entropy is proportional to the total duration of inflation. It is preserved during a subsequent radiation or matter dominated era, and thus it may be relevant for today’s universe. We demonstrate explicitly these features in a toy model of a scalar field in 1+1 dimensions.
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Acknowledgments
We would like to thank A. Karanikas and D. Katsinis for useful discussions. The research of K. Boutivas and N. Tetradis was supported by the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the “First Call for H.F.R.I. Research Projects to support Faculty members and Researchers and the procurement of high-cost research equipment grant” (Project Number: 824).
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Boutivas, K., Pastras, G. & Tetradis, N. Entanglement and expansion. J. High Energ. Phys. 2023, 199 (2023). https://doi.org/10.1007/JHEP05(2023)199
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DOI: https://doi.org/10.1007/JHEP05(2023)199