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Low Density Warm Stellar Matter with Light Clusters and Hyperclusters, Hyperons and Delta Isobars

Authors: Tiago Emanuel Anjo de Oliveira Custódio

Supervisors: Constança Providência; Helena Pais

MSc thesis, Estudo geral, Universidade de Coimbra (2021)

Abstract: The abundance of light nuclei, hyperons and ∆ isobars that are produced in stellar environments such as supernova or binary neutron star mergers, is calculated within both nonlinear and density-dependent relativistic mean-field models in low-density matter. Five purely nucleonic light nuclei (2H, 3H, 3He, 4He, 6He) are considered, together with three light hypernuclei (3ΛH ,4ΛH , 4ΛHe). We show that the presence of hyperons and ∆s shifts the dissolution of clusters to larger densities, and increases the amount of clusters. This effect is larger the smaller the charge fraction, and the higher the temperature. The abundance of hyperons and ∆s is also affected by the cluster formation: neutral and positively charged hyperons and ∆s suffer a reduction, and the negatively charged ones an increase. We also observe that the dissolution of the less-abundant clusters occurs at larger densities due to smaller Pauli-blocking effects. Overall, hypernuclei set in at temperatures above 25 MeV, and depending on the temperature and chemical composition, they may be more abundant than 4He, or even more abundant than other heavier clusters. It is also seen that for some values of the couplings of the ∆s, the nucleon effective mass becomes zero at too low densities, preventing the corresponding EoS of reaching the maximum mass star, therefore not being adequate to describe neutron stars. Keywords: Relativistic Nuclear Mean Field Theory, Supernova and Neutron Star Merger Matter, Light Nuclei and Hypernuclei, Heavy Baryons, Warm Non-homogeneous Hadronic Matter

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