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Abstract

Interpreting high-energy, astrophysical phenomena, such as supernova
explosions or neutron-star collisions, requires a robust understanding of
matter at supranuclear densities. However, our knowledge about dense matter
explored in the cores of neutron stars remains limited. Fortunately, dense
matter is not only probed in astrophysical observations, but also in
terrestrial heavy-ion collision experiments. In this work, we use Bayesian
inference to combine data from astrophysical multi-messenger observations of
neutron stars and from heavy-ion collisions of gold nuclei at relativistic
energies with microscopic nuclear theory calculations to improve our
understanding of dense matter. We find that the inclusion of heavy-ion
collision data indicates an increase in the pressure in dense matter relative
to previous analyses, shifting neutron-star radii towards larger values,
consistent with recent NICER observations. Our findings show that constraints
from heavy-ion collision experiments show a remarkable consistency with
multi-messenger observations and provide complementary information on nuclear
matter at intermediate densities. This work combines nuclear theory, nuclear
experiment, and astrophysical observations, and shows how joint analyses can
shed light on the properties of neutron-rich supranuclear matter over the
density range probed in neutron stars.