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arXiv · 2608.19334

Breakdown of Hydrodynamic Universality in Neutron Star Oscillations

Gabriel S. Denicol·Amanda Guerrieri·João V. M. Muniz·Gabriel S. Rocha·Raissa F. P. Mendes
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Abstract

Hydrodynamic universality refers to the property that different formulations of relativistic dissipative hydrodynamics yield identical predictions in the asymptotic long-wavelength regime. We show that neutron-star oscillations need not reach this regime. Because the finite stellar radius limits the accessible wavelengths and causality imposes a lower bound on microscopic relaxation times, the separation between microscopic and macroscopic scales can become insufficient for hydrodynamic universality to emerge. Comparing linear oscillations in relativistic Navier--Stokes and Israel--Stewart theories, we find that realistic bulk viscosities can produce sizeable modifications of the oscillation spectrum, even at the longest wavelengths. These results identify neutron-star oscillations as a direct probe of microscopic nonequilibrium dynamics beyond the leading hydrodynamic description.

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Gabriel S. Denicol, Amanda Guerrieri, João V. M. Muniz, Gabriel S. Rocha, Raissa F. P. Mendes. 2026-08-19. Breakdown of Hydrodynamic Universality in Neutron Star Oscillations. https://arxiv.org/abs/2608.19334

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