Effective Field Theories for Neutron Stars Physics

TL;DR

This review surveys how chiral EFT, complemented by a variety of many-body techniques, yields a controlled neutron-star EOS at zero temperature that can be connected from the crust to high-density cores. It details MBPT, SCGF, QMC, in-medium χEFT, and lattice EFT as foundations for ab initio EOS calculations, and explains interpolation to bridge density gaps up to pQCD at asymptotically high densities. The authors analyze phase transitions, latent heat, and conformality signals in NS matter, and discuss how DM admixtures and two-fluid formalisms could imprint observable signatures in mass-radius and tidal deformabilities. The work emphasizes how multi-messenger observations, together with rigorous EFT-based modeling, constrain the EOS, probe new physics, and quantify uncertainties in NS structure and evolution.

Abstract

There is an increasing interest in the community for the Neutron Stars and what we can learn from them. In this review we show how chiral effective field theory, combined with many-body methods, can provide important results that connect Neutron Star properties at zero temperature to nuclear physics and allows to use these compact objects as laboratories of new physics.

Figures (31)

• Figure 1: Comparison of the naive scaling of the $\pi\pi$ scattering amplitude (left) with the $\pi N$ one (right). The red dots correspond to terms that break the power counting. One sees the contribution to all orders for any finite loop expansion.
• Figure 2: Diagrammatic representation two- and three-nucleon forces obtained in chiral effective field theory according to the Weinberg power counting when the $\Delta$ is included. Solid, dashed and double lines correspond to nucleon, pion and $\Delta(1232)$, respectively. Figure adapted from Ref. Piarulli:2019cqu.
• Figure 3: Example of the results obtained in MBPT using chiral potentials. This plot corresponds to Ref. Drischler:2017wtt. Reprinted figure with permission from C. Drischler, K. Hebeler and A. Schwenk, Phys. Rev. Lett. 122, no.4, 042501 (2019) Copyright 2019 by the American Physical Society https://doi.org/10.1103/PhysRevLett.122.042501.
• Figure 4: Example of the results obtained in SCGF using chiral potentials. Left figure corresponds to SNM and the right one to PNM. The plots are taken from Ref. Carbone:2014mja. Reprinted figures with permission from A. Carbone, A. Rios and A. Polls, Phys. Rev. C 90, no.5, 054322 (2014). Copyright 2014 by the American Physical Society. https://doi.org/10.1103/PhysRevC.90.054322.
• Figure 5: Example of the calculation of the energy per particle in pure neutron matter with QMC calculations using chiral potentials. This plot corresponds to Ref. Tews:2015ufa. Reprinted figure with permission from I. Tews, S. Gandolfi, A. Gezerlis and A. Schwenk, Phys. Rev. C 93, no.2, 024305 (2016). Copyright 2016 by the American Physical Society https://doi.org/10.1103/PhysRevC.93.024305.