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  • Letter
  • Open Access

Entanglement viscosity: From unitarity to irreversibility in accelerated frames

G. Yu. Prokhorov*

  • *Contact author: prokhorov@theor.jinr.ru
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Phys. Rev. D 114, L041703 – Published 21 August, 2026

DOI: https://doi.org/10.1103/2f7b-l381

Abstract

We demonstrate that the unitarity of quantum field theory, through the positivity of spectral densities, underlies thermodynamic irreversibility for a subsystem separated by a horizon, in direct analogy with the irreversibility of renormalization-group flows. To this end, we explicitly find the shear and bulk viscosities—the entanglement viscosities—for thermal radiation in Rindler space using the universal spectral representation. A direct consequence of the obtained general formulas is the relationship between the acceleration-induced shear viscosity in flat space and the conformal quantum anomaly in curved space, pointing to a possible novel probe of the conformal anomaly in systems with extreme acceleration. Moreover, for conformal field theories, we explicitly show that globally entanglement viscosity saturates the Kovtun-Son-Starinets bound.

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Phys. Rev. D 114, L041703– Published 21 August, 2026
  • Received 28 February 2026
  • Accepted 30 July 2026
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