- Quantum Chromodynamics under Extreme Conditions
- Quark Matter, and signatures in compact stars
- Quark-Gluon Plasma
The matter of the universe some few microseconds after the Big Bang was made up of a mixture or soup of quarks and gluons, the so called quark gluon plasma (QGP). The temperature then was so high that not only the atoms, but also all the protons and neutrons were melted into their fundamental constituents. This thermal period of the Universe might be recreated in terrestrial accelerators, such as the Relativistic Heavy Ion Collider (RHIC), in Brookhaven National Laboratory (USA), or in the Large Hadron Collider (LHC) of CERN (Switzerland). These accelerator facilities are the best instruments we have to understand the thermal evolution of the Universe and the thermal transition that took place to form all the protons, neutrons and other baryons of our present Universe.
Quantum Chromodynamics (QCD) is the theory that describes the strong nuclear interactions among quarks and gluons, which are the constituents of hadrons. In Figure 1, a schematic description of the phases of the theory is shown. The region of low temperatures and low density is the hadron phase, where all quarks are confined to the interior of hadrons.At very high temperature the hadrons melt forming a plasma of quarks and gluons. At very high density and relatively low temperature quarks pair to form the phase of color superconductivity. This phase may be present in the core of compact stars, or still in the hypothetical quark stars, objects ranging in density between neutron stars and black holes.
Our basic research line aims is to study how quarks and gluons behave in these very extreme conditions that took place either in the Early Universe, or in astrophysical scenarios.
Neutron stars as laboratories for dense nuclear and quark matter
Neutron stars are the densest stars known. They are supposed to be composed by neutrons, protons and electrons, although they might also contain unconfined quark matter in their core. With measurements of the macroscopic properties of compact stars, such as the mass, radius, frequency of rotation, value of the magnetic field, we can infer properties of the fundamental interactions of their constituents, and learn about the equation of state of dense matter. If strange quark matter is absolutely stable and has lower energy per baryon than nuclear matter, quark stars might be realised in Nature. We provide theoretical predictions of the macroscopic behavior of a chunk of quark matter (cooling rate, response to magnetic fields, rotational and vibrational properties), so as to provide signatures of the yet undetected quark stars.