Stable and causal frames for BDNK hydrodynamics
Abstract
We establish the existence of families of linearly stable and causal Bemfica-Disconzi-Noronha-Kovtun (BDNK) frames for arbitrary equation of state and set of physical transport coefficients. By developing a method based on simplification of Routh-Hurwitz criteria and telegrapher factorisation of polynomials, we provide six concrete examples of such families, three of which admit conformal limits, for both neutral and charged fluids. These frames have adjustable characteristic speeds and can serve as a starting point for numerical implementations of relativistic hydrodynamics in various settings. In the process we uncover a map between stable and causal frames in neutral fluids and stable and causal frames in charged fluids. We also develop an AI research protocol that can be used to search for such frames in any hydrodynamic theory.
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BibTeX
@misc{armas2026stable,
title = {{Stable and causal frames for BDNK hydrodynamics}},
author = {Jay Armas},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.28984},
eprint = {2610.28984},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.28984},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Stable and causal frames for BDNK hydrodynamics
AU - Jay Armas
PY - 2026
DA - 2026/10/20
PB - arXiv
DO - 10.48550/arxiv.2610.28984
UR - https://arxiv.org/abs/2610.28984
AB - We establish the existence of families of linearly stable and causal Bemfica-Disconzi-Noronha-Kovtun (BDNK) frames for arbitrary equation of state and set of physical transport coefficients. By developing a method based on simplification of Routh-Hurwitz criteria and telegrapher factorisation of polynomials, we provide six concrete examples of such families, three of which admit conformal limits, for both neutral and charged fluids. These frames have adjustable characteristic speeds and can serve as a starting point for numerical implementations of relativistic hydrodynamics in various settings. In the process we uncover a map between stable and causal frames in neutral fluids and stable and causal frames in charged fluids. We also develop an AI research protocol that can be used to search for such frames in any hydrodynamic theory.
ER -