Heavy ion collisions and neutron stars : dynamics and thermodynamics of QCD matter

This thesis deals with the phenomenology of QCD matter, its aspects in heavy ion collisions and in neutron stars. The first half of the work focuses on the hadronic phase of QCD matter. One focus is on how the hadronic phase shows itself in heavy ion collisions and how its dynamics can be simulated. The role of hadronic interactions is considered in the context of the lattice QCD data. The second part of this thesis presents a unified approach to QCD matter, the CMF model. The CMF model incorporates many aspects of QCD phenomenology which allows for a consistent description of the hadron-quark transition, making it applicable to the entire QCD phase diagram, i.e., to the cold nuclear matter and to the hot QCD matter. It is shown that a description of both the hot matter created in heavy ion collisions and the cold dense matter in neutron star interiors is possible within one single approach, the CMF model.

Neutron stars from crust to core within the Quark-meson coupling model

Recent years continue to be an exciting time for the neutron star physics, providing many new observations and insights to these natural ‘laboratories’ of cold dense matter. To describe them, there are many models on the market but still none that would reproduce all observed and experimental data. The quark-meson coupling model stands out with its natural inclusion of hyperons as dense matter building blocks, and fewer parameters necessary to obtain the nuclear matter equation of state. The latest advances of the QMC model and its application to the neutron star physics will be presented, within which we build the neutron star’s outer crust from finite nuclei up to the neutron drip line. The appearance of different elements and their position in the crust of a neutron star is explored and compared to the predictions of various models, giving the same quality of the results for the QMC model as for the models when the nucleon structure is not taken into account.

Role of Δs in determining the properties of neutron stars in parameterized hydrostatic equilibrium

The possible existence of [Formula: see text] resonances is inspected in the cold dense matter of neutron star (NS) core in the presence of hyperons. The diverse effects of variation in [Formula: see text] mass on their formation and the equation of state (EoS) are studied in this work with an effective chiral model and the resultant NS properties are calculated with the help of parameterized Tolman–Oppenheimer–Volkoff (PTOV) equations to bring out the two important features of pressure in the context of massive NSs. The [Formula: see text] puzzle is re-explored and resolved taking into account the concept of modified/parametrized inertial pressure and self-gravity in case of massive pulsars like PSR J1614−2230 and PSR J0348-0432. It is seen that although the presence of exotic matter like the hyperons and [Formula: see text] softens the EoS considerably, their presence in massive NSs can be successfully explained with the theory of parametrized hydrostatic equilibrium conditions. The results of this work also satisfy the constraints on [Formula: see text] and [Formula: see text] from the gravitational wave (GW170817) detection of binary NS merger. The constraint on baryonic mass from PSR J0737-3039 is also satisfied with the solutions of the PTOV equations for all the [Formula: see text] masses considered.

Neutron stars are gold mines

Neutron stars are not only mines for clues to dense matter physics but may also be the auspicious sources of half of all nuclei heavier than [Formula: see text] in the universe, including the auric isotopes. Although the cold dense matter above the nuclear saturation density cannot be directly explored in the laboratory, gilded constraints on the properties of matter from 1 to 10 times higher density can now be panned from neutron star observations. We show how upcoming observations, such as gravitational wave from mergers, precision timing of pulsars, neutrinos from neutron star birth and X-rays from bursts and thermal emissions, will provide the bullion from which further advances can be smelted.