Inferring Three-Nucleon Couplings from Multimessenger Neutron Star Observations

Concetti Chiave

Neutron star observations can be used to directly constrain the couplings that govern three-nucleon interactions in chiral effective field theory.

Sintesi

The authors develop a framework that enables the inference of three-nucleon couplings in dense matter directly from astrophysical neutron star observations. They apply this formalism to the LIGO/Virgo gravitational-wave event GW170817 and the X-ray measurements from NASA's Neutron-Star Interior Composition Explorer (NICER) to establish direct constraints for the couplings c1 and c3 that govern three-nucleon interactions in chiral effective field theory.

The authors employ recent advances in machine learning to overcome the computational challenges associated with translating microscopic nuclear interactions to macroscopic neutron star observables. They use a parametric matrix model to rapidly calculate the equation of state of neutron matter and an ensemble of neural networks to predict the tidal deformability of neutron stars.

The authors find that existing neutron star observations do not yet provide high-precision constraints on the three-nucleon couplings due to significant statistical uncertainties. However, they demonstrate that next-generation gravitational-wave detectors, such as the Einstein Telescope and Cosmic Explorer, can offer stringent constraints on c3, potentially at a level comparable to those from laboratory data on pion-nucleon scattering. This would enable a direct connection between microscopic couplings in quantum field theories and macroscopic observations of neutron stars, providing a nontrivial test of the consistency between low-energy couplings inferred from terrestrial and astrophysical data.

Statistiche

The average (maximum) size of the third-order many-body perturbation theory correction is 252 (790) keV across all densities and for all low-energy coupling combinations.
The average (maximum) deviation between the parametric matrix model and the many-body perturbation theory calculation, averaged over density and the 70 validation samples, is 15 keV (158 keV).

Citazioni

"Neutron stars are fascinating systems that access higher densities and greater neutron excess than nuclei accessible in terrestrial experiments. Therefore, they offer an unparalleled laboratory for nuclear matter in regions of high density and isospin asymmetry."
"Our work directly connects the microscopic couplings in quantum field theories to macroscopic observations of neutron stars, providing a way to test the consistency between low-energy couplings inferred from terrestrial and astrophysical data."

Approfondimenti chiave tratti da

Inferring three-nucleon couplings from multi-messenger neutron-star observations

by Rahul Somasu... alle arxiv.org 10-02-2024

https://arxiv.org/pdf/2410.00247.pdf

Domande più approfondite

How can the framework developed in this work be extended to constrain other low-energy couplings in the nuclear Hamiltonian, such as those governing two-nucleon interactions?

The framework developed in this work can be extended to constrain other low-energy couplings (LECs) in the nuclear Hamiltonian, particularly those governing two-nucleon interactions, by leveraging the same multi-messenger astrophysical observations that were utilized for three-nucleon couplings. The key steps involve:

Incorporating Two-Nucleon Interactions: The existing Bayesian inference framework can be adapted to include LECs associated with two-nucleon interactions, such as those governing the nucleon-nucleon (NN) potential. This would involve defining a new set of parameters that represent the strengths of these interactions, which can be constrained using the same observational data from neutron stars.

Utilizing Gravitational Wave and X-ray Data: Similar to how the framework used data from the LIGO/Virgo gravitational-wave event GW170817 and X-ray measurements from NASA’s NICER mission to infer three-nucleon couplings, the same data can be analyzed to extract information about two-nucleon interactions. The tidal deformability and mass-radius relationships of neutron stars are sensitive to the underlying nuclear interactions, allowing for the extraction of constraints on two-nucleon LECs.

Machine Learning Emulators: The use of machine learning emulators, as demonstrated in this work, can be applied to model the relationship between the two-nucleon LECs and the resulting neutron-star observables. By training emulators on high-fidelity calculations of the equation of state (EOS) that include two-nucleon interactions, the computational burden can be significantly reduced, enabling efficient sampling of the posterior distributions for these couplings.

Comparative Analysis: The framework allows for a comparative analysis between the constraints obtained from neutron star observations and those derived from terrestrial nuclear experiments. This cross-validation can help identify discrepancies and refine the understanding of nuclear interactions at different density regimes.

By extending the framework in this manner, researchers can gain deeper insights into the role of two-nucleon interactions in dense matter and their implications for nuclear structure and astrophysical phenomena.

What are the potential implications if the constraints on three-nucleon couplings from neutron star observations were found to be inconsistent with those from nuclear physics experiments?

If the constraints on three-nucleon couplings derived from neutron star observations were found to be inconsistent with those obtained from nuclear physics experiments, several significant implications could arise:

Breakdown of Effective Field Theories (EFTs): Such inconsistencies might indicate a breakdown of the current effective field theories used to describe nuclear interactions. If the three-nucleon couplings inferred from astrophysical data do not align with those derived from laboratory experiments, it could suggest that the EFT framework is not adequately capturing the complexities of nuclear forces in extreme environments, such as those found in neutron stars.

New Physics: The discrepancies could point to the presence of new physics beyond the standard nuclear models. This might include the need to incorporate additional degrees of freedom, such as hyperons or other exotic states of matter, which could alter the dynamics of nuclear interactions at high densities.

Reevaluation of Nuclear Models: Inconsistencies would necessitate a reevaluation of the nuclear models and the assumptions underlying the extraction of LECs from both terrestrial and astrophysical data. This could lead to a refinement of the models used in nuclear structure calculations and a better understanding of the underlying physics.

Impact on Neutron Star Properties: The implications would extend to the macroscopic properties of neutron stars, such as their mass, radius, and stability. If the three-nucleon forces inferred from neutron stars are significantly different, it could affect predictions regarding the equation of state (EOS) of neutron-rich matter, potentially leading to revised estimates of neutron star masses and radii.

Guidance for Future Experiments: Finally, such findings would provide critical guidance for future experimental and observational efforts. They could inform the design of new nuclear experiments aimed at probing the relevant couplings more precisely, as well as the development of next-generation gravitational wave observatories to further investigate neutron star mergers.

How might the insights gained from this work on the interplay between microscopic nuclear physics and macroscopic neutron star properties inform our understanding of the role of three-nucleon forces in other astrophysical contexts, such as core-collapse supernovae?

The insights gained from this work on the interplay between microscopic nuclear physics and macroscopic neutron star properties can significantly enhance our understanding of the role of three-nucleon forces in other astrophysical contexts, including core-collapse supernovae, in several ways:

Understanding Dense Matter Behavior: The framework developed for inferring three-nucleon couplings from neutron star observations provides a robust method for understanding the behavior of dense nuclear matter. This knowledge is crucial for modeling the conditions present during core-collapse supernovae, where matter is subjected to extreme densities and pressures, similar to those found in neutron stars.

Influence on Supernova Dynamics: Three-nucleon forces play a critical role in determining the equation of state (EOS) of nuclear matter, which directly influences the dynamics of core-collapse supernovae. By establishing reliable constraints on these forces, researchers can improve simulations of supernova explosions, leading to better predictions of explosion mechanisms, nucleosynthesis processes, and the resulting remnant structures.

Connection to Neutrino Physics: The insights into three-nucleon interactions can also inform our understanding of neutrino interactions in dense matter, which are pivotal during the supernova explosion phase. The behavior of neutrinos in the dense environment of a collapsing core is influenced by the EOS, and thus, a better understanding of three-nucleon forces can lead to improved models of neutrino transport and energy deposition.

Implications for Nucleosynthesis: The role of three-nucleon forces in shaping the EOS can affect the nucleosynthesis pathways during supernova explosions. By constraining these forces, researchers can refine models of element formation in supernovae, enhancing our understanding of the chemical evolution of the universe.

Broader Astrophysical Context: Finally, the framework's ability to connect microscopic nuclear interactions with macroscopic astrophysical phenomena can be applied to other contexts beyond core-collapse supernovae, such as neutron star mergers and the formation of heavy elements in kilonovae. This holistic approach can lead to a more comprehensive understanding of the fundamental processes governing the universe's evolution.

In summary, the insights gained from this work not only advance our understanding of neutron stars but also have far-reaching implications for various astrophysical phenomena, particularly those involving extreme conditions of density and temperature.