Research
It’s becoming clear that, in a sense, the cosmos provides the only laboratory where sufficiently extreme conditions are ever achieved to test new ideas in particle physics. The energies in the Big Bang were far higher than we can ever achieve on Earth. So by looking at evidence for the Big Bang and studying things like compact stars, we are in effect learning something about fundamental physics.
Neutron Stars
Neutron stars are very dense objects. One teaspoon of their material would have a mass of five billion tons. Their gravitational force is so strong that if an object were to fall from just one meter high, it would hit the surface of the respective neutron star at two thousand kilometers per second. In such dense bodies, different particles from the ones present in atomic nuclei, the nucleons, can exist. These particles are hyperons, that contain non-zero strangeness and, if the density is high enough to deconfine them, quarks.
Constraints on QCD Phase Diagram
From a combination of lattice QCD results, pQCD calculations, and Chiral Effective Field Theory bands, we now have three theoretical points of reference (or rather regimes) in the QCD phase diagram, see Figure. Effective models and holography, some describing the microscopic degrees of freedom and their interactions, are used to connect these regimes in the phase diagram and even propose entirely new phases of dense and hot matter. These models are fixed to be in agreement with theoretical and experimental (low-energy nuclear physics, heavy-ion collisions, and astrophysics) results in the relevant regimes.
