Microscopically constrained mean-field models from chiral nuclear thermodynamics

Abstract

We explore the use of mean field models to approximate microscopic nuclear equations of state derived from chiral effective field theory across the densities and temperatures relevant for simulating astrophysical phenomena such as core-collapse supernovae and binary neutron star mergers. We consider both relativistic mean field theory with scalar and vector meson exchange as well as energy density functionals based on Skyrme phenomenology and compare to thermodynamic equations of state derived from chiral two-and three-nucleon forces in many-body perturbation theory. Quantum Monte Carlo simulations of symmetric nuclear matter and pure neutron matter are used to determine the density regimes in which perturbation theory with chiral nuclear forces is valid. Within the theoretical uncertainties associated with the many-body methods, we find that select mean field models describe well microscopic nuclear thermodynamics. As an additional consistency requirement, we study as well the single-particle properties of nucleons in a hot/dense environment, which affect e.g., charged-current weak reactions in neutron-rich matter. The identified mean field models can be used across a larger range of densities and temperatures in astrophysical simulations than more computationally expensive microscopic models.

Unified equations of state for cold non-accreting neutron stars with Brussels-Montreal functionals. I. Role of symmetry energy

“…At the same time we recall from the discussion in Section IIIA of Goriely et al (2013) that the functionals of this paper are consistent with the quantum Monte Carlo calculations of Gandolfi, Carlson & Reddy (2012). In the time since our functionals were constructed in 2013, a number of new calculations of NeuM using chiral effective field theory (Roggero, Mukherjee & Pederiva 2014;Rrapaj, Roggero & Holt 2016;Drischler et al 2016;Tews et al 2016) have appeared. However, these calculations were restricted to densities below 0.3 fm −3 ; two of them at least (Roggero et al 2014;Rrapaj et al 2016) appear to favour LS2 over APR in this low-density regime, where LS2 is softer than APR.…”

Constraining the neutron-matter equation of state with gravitational waves

“…Neutron matter parameters have errors estimated from qmc calculations with various three-body interactions [15], and are consistent with recent qmc results based on chiral eft interactions [23][24][25]42]. Proton polaron parameters have errors estimated from the qmc calculations [43] and are consistent with estimates from chiral interactions [44]. The core parameters are chosen to allow for a 2M star at the extremes of all of our models except for the Soft eos which requires a lower core transition and are given large errors to be conservative with the exception of the parameter E c .…”

Open-source nuclear equation of state framework based on the liquid-drop model with Skyrme interaction

“…More microscopic treatments, such as chiral effective field theory, use interactions that obey symmetries of QCD and fit the small number of free parameters in the interaction based on observed properties of the nucleon-nucleon interaction [25]. These approaches are very accurate near nuclear saturation density and below and able to capture the properties of highly asymmetric matter [26]. However, difficult to calculate higher-order interactions become increasingly important with increasing density rendering the approach impractical well above nuclear saturation density.…”