Shear viscosity to entropy density ratio: A powerful tool for gravity theories and strongly coupled fluids
Abstract In this perspective review, we present a concise yet multifaceted overview of the pivotal role played by the shear viscosity to entropy density ratio across various physical contexts. After summarizing some of the main aspects of the bound obtained by Kovtun, Son and Starinets, we examine potential sources of its violation, exploring the insights these may offer and their connections to fundamental causality conditions. We also review a range of experimental tests conducted in diverse, yet complementary, physical systems, discussing the prospects opened by upcoming measurements.
Authors
- Dario Grasso (ORCID: https://orcid.org/0000-0001-7761-7242)
- Massimo Mannarelli (ORCID: https://orcid.org/0000-0003-0211-5250)
- Maria Luisa Chiofalo (ORCID: https://orcid.org/0000-0002-6992-5963)
- Stefano Liberati (ORCID: https://orcid.org/0000-0002-7632-7443)
Institutions
- Scuola Internazionale Superiore di Studi Avanzati (IT)
- University of Trieste (IT)
- Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Gran Sasso (IT)
- Istituto Nazionale di Fisica Nucleare, Sezione di Trieste (IT)
- Institute for Fundamental Physics of the Universe (IT)
- Istituto Nazionale di Fisica Nucleare, Sezione di Pisa (IT)
Publication Details
- Journal
- Europhysics Letters (EPL)
- Published
- 2025-09-01
- DOI
- https://doi.org/10.1209/0295-5075/ae0365
- Primary Topic
- Phase Equilibria and Thermodynamics
- Type
- article
- Field-Weighted Citation Impact
- 0.00