# Symmetric nuclear matter from the strong interaction

## TL;DR

This paper investigates the equation of state of symmetric nuclear matter across a wide density range using chiral effective field theory at low densities and quantum chromodynamics-based functional renormalization group methods at high densities, revealing a maximum in the speed of sound linked to diquark formation.

## Contribution

It provides the first constraints on high-density nuclear matter directly from QCD using functional renormalization group techniques, complementing chiral EFT results at lower densities.

## Key findings

- Consistent results from two different theoretical approaches.
- Identification of a maximum in the speed of sound at supranuclear densities.
- Connection between the speed of sound maximum and diquark gap formation.

## Abstract

We study the equation of state of symmetric nuclear matter at zero temperature over a wide range of densities using two complementary theoretical approaches. At low densities up to twice nuclear saturation density, we compute the energy per particle based on modern nucleon-nucleon and three-nucleon interactions derived within chiral effective field theory. For higher densities we derive for the first time constraints in a Fierz-complete setting directly based on quantum chromodynamics using functional renormalization group techniques. We find remarkable consistency of the results obtained from both approaches as they come together in density and the natural emergence of a maximum in the speed of sound $c_S$ at supranuclear densities with a value beyond the asymptotic $c_S^2 = 1/3$. The presence of a maximum appears tightly connected to the formation of a diquark gap.