Physics and Astronomy, Nuclear and High Energy Physics, General Physics and Astronomy, Theoretical Computer Science
2
Scopus Publications
42
Scholar Citations
2
Scholar h-index
2
Scholar i10-index
Scopus Publications
Effect of causality constraints on Bayesian analyses of heavy-ion collisions Thiago S. Domingues, Renata Krupczak, Jorge Noronha, Tiago Nunes da Silva, Jean-François Paquet, Matthew Luzum Physical Review C, 2024 There have long been questions about the limits to the validity of relativistic fluid dynamics and whether it is being used outside its regime of validity in modern simulations of relativistic heavy-ion collisions. An important new tool for answering this question is a causality analysis in the nonlinear regime---if the solutions of the evolution equations do not respect relativistic causality, then they are not a faithful representation of the underlying relativistic theory (in this case, quantum chromodynamics). Using this nonlinear criterion, it has recently been shown that hydrodynamics is indeed being used outside its regime of validity in simulations, at least sometimes. Here we explore the phenomenological implications, particularly the quantitative effects of demanding limits on acausality in modern Bayesian parameter estimation. We find that, while typically only a small fraction of the system's energy is initially in an acausal regime, placing strict limits on the allowed energy fraction significantly changes the preferred properties of the initial condition, which in turn alters the extracted medium properties such as bulk viscosity, where large values are no longer favored. These findings highlight the importance of developing better theoretical descriptions of the early-time, out-of-equilibrium dynamics of relativistic heavy-ion collisions.
Causality violations in simulations of large and small heavy-ion collisions Renata Krupczak, Tiago Nunes da Silva, Thiago S. Domingues, Matthew Luzum, Gabriel S. Denicol, Fernando G. Gardim, Andre V. Giannini, Mauricio N. Ferreira, Mauricio Hippert, Jorge Noronha, David D. Chinellato, Jun Takahashi, and Physical Review C, 2024 Heavy-ion collisions, such as Pb-Pb or p-Pb, produce extreme conditions in temperature and density that make the hadronic matter transition to a new state, called quark-gluon plasma (QGP). Simulations of heavy-ion collisions provide a way to improve our understanding of the QGP's properties. These simulations are composed of a hybrid description that results in final observables in agreement with accelerators like LHC and RHIC. However, recent works pointed out that these hydrodynamic simulations can display acausal behavior during the evolution in certain regions, indicating a deviation from a faithful representation of the underlying QCD dynamics. To pursue a better understanding of this problem and its consequences, this work simulated two different collision systems, Pb-Pb and p-Pb at $\sqrt{{s}_{NN}}=5.02$ TeV. In this context, our results show that causality violation, even though always present, typically occurs on a small part of the system, quantified by the total energy fraction residing in the acausal region. In addition, the acausal behavior can be reduced with changes in the prehydrodynamic factors and the definition of the bulk-viscous relaxation time. Since these aspects are fairly arbitrary in current simulation models, without solid guidance from the underlying theory, it is reasonable to use the disturbing presence of acausal behavior in current simulations to guide improvements towards more realistic modeling. While this work does not solve the acausality problem, it sheds more light on this issue and also proposes a way to solve this problem in simulations of heavy-ion collisions.
RECENT SCHOLAR PUBLICATIONS
Scaled transverse-momentum spectra as a probe of collective dynamics in heavy-ion collisions TS Domingues, M Luzum arXiv preprint arXiv:2603.15891 , 2026 2026.0 Citations: 1
The shape of transverse momentum spectra in hybrid hydrodynamic models TS Domingues, FG Gardim, CD Muncinelli, AV Giannini, GS Denicol, ... arXiv preprint arXiv:2602.22490 , 2026 2026.0 Citations: 1
Probing the onset of collectivity via scaled particle spectra in ultrarelativistic nuclear collisions TS Domingues, FG Gardim, DD Chinellato, GS Denicol, AV Giannini, ... EPJ Web of Conferences 364, 04011 , 2025 2025.0 Citations: 1
The effect of causality constraints on Bayesian analyses of heavy-ion collisions TS Domingues, R Krupczak, J Noronha, TN Da Silva, JF Paquet, ... arXiv preprint arXiv:2409.17127 , 2024 2024.0 Citations: 14
Introdu\c {c}\~ ao\a infer\^ encia Bayesiana: t\'ecnicas estat\'isticas para an\'alise de dados de\'ions pesados relativ\'isticos L Santos, T Domingues arXiv preprint arXiv:2406.18734 , 2024 2024.0
Causality violations in simulations of large and small heavy-ion collisions R Krupczak, T Nunes da Silva, TS Domingues, M Luzum, GS Denicol, ... Physical Review C 109 (3), 034908 , 2024 2024.0 Citations: 25
Introduction to Bayesian inference: statistical techniques for relativistic heavy ion data analysis L Santos, T Domingues 2024.0
3–9 Sept 2023 Hilton of the Americas, 1600 Lamar, Houston, Texas, 77010, USA US/Central timezone TS Domingues
The Effect of Acausality on Bayesian Analyses TS Domingues, M Luzum, R Krupczak, TJN da Silva, JF Paquet, ...
Houston, we have a problem: Causality! TS Domingues
MOST CITED SCHOLAR PUBLICATIONS
Causality violations in simulations of large and small heavy-ion collisions R Krupczak, T Nunes da Silva, TS Domingues, M Luzum, GS Denicol, ... Physical Review C 109 (3), 034908 , 2024 2024.0 Citations: 25
The effect of causality constraints on Bayesian analyses of heavy-ion collisions TS Domingues, R Krupczak, J Noronha, TN Da Silva, JF Paquet, ... arXiv preprint arXiv:2409.17127 , 2024 2024.0 Citations: 14
Scaled transverse-momentum spectra as a probe of collective dynamics in heavy-ion collisions TS Domingues, M Luzum arXiv preprint arXiv:2603.15891 , 2026 2026.0 Citations: 1
The shape of transverse momentum spectra in hybrid hydrodynamic models TS Domingues, FG Gardim, CD Muncinelli, AV Giannini, GS Denicol, ... arXiv preprint arXiv:2602.22490 , 2026 2026.0 Citations: 1
Probing the onset of collectivity via scaled particle spectra in ultrarelativistic nuclear collisions TS Domingues, FG Gardim, DD Chinellato, GS Denicol, AV Giannini, ... EPJ Web of Conferences 364, 04011 , 2025 2025.0 Citations: 1
Introdu\c {c}\~ ao\a infer\^ encia Bayesiana: t\'ecnicas estat\'isticas para an\'alise de dados de\'ions pesados relativ\'isticos L Santos, T Domingues arXiv preprint arXiv:2406.18734 , 2024 2024.0
Introduction to Bayesian inference: statistical techniques for relativistic heavy ion data analysis L Santos, T Domingues 2024.0
3–9 Sept 2023 Hilton of the Americas, 1600 Lamar, Houston, Texas, 77010, USA US/Central timezone TS Domingues
The Effect of Acausality on Bayesian Analyses TS Domingues, M Luzum, R Krupczak, TJN da Silva, JF Paquet, ...
Houston, we have a problem: Causality! TS Domingues