Many-body Problems in the Theory of Stellar Collapse and Neutron Stars

When modelling the collapse of massive stars leading to supernova explosions and the cooling of neutron stars, understanding the microphysical processes, such as the interaction of neutrinos within a dense medium are of vital importance. The interaction of neutrinos with nucleons (neutrons and protons) is altered by the presence of the medium, compared to the same process with free nucleons. Neutrino scattering and production processes may be characterized in terms of the excitations that are created or destroyed in the nuclear medium. One way to analyse the effects of the medium is by using Landau’s theory of normal Fermi liquids. This theory gives simple relationships between physical quantities such as the spin susceptibility or the response to a weak interaction probe in terms of Landau parameters, that are measures of the interaction between quasiparticles. One problem when using Landau Fermi liquid theory for nucleon matter is that the interaction has a tensor component. The tensor interaction does not conserve the total spin and, as a consequence, there are generally contributions to long-wavelength response functions from states that have more than one quasiparticle-quasihole pair in the intermediate state. Such contributions cannot be calculated in terms of Landau parameters alone, since in the usual formulation of Landau theory, only singlepair excitations are considered. In this thesis three problems are addressed. First, we obtain bounds on the contributions from more than one quasiparticle-quasihole pair by using sum-rule arguments. Second, we derive expressions for static response functions allowing for the tensor components of the interaction…


1 Introduction
1.1 Outline
2 Neutron stars and core-collapse supernovae
2.1 Stellar collapse and supernovae
2.1.1 The pre-supernova star
2.1.2 Collapse
2.1.3 Core-bounce
2.1.4 The prompt shock
2.1.5 The delayed explosion
2.2 Neutron stars
2.2.1 Neutron star structure
2.2.2 Neutron star cooling
3 Neutrino interactions in dense matter
3.1 Leptonic processes
3.2 Semi-leptonic processes
3.2.1 Neutrino-nucleus interactions
3.2.2 Neutrino interactions in nuclear matter
3.2.3 Other neutrino interactions in dense matter
4 Linear response theory
4.1 Response at zero temperature
4.2 The role of conservation laws
4.3 Response functions at non-zero temperature
5 Introduction to Landau Fermi-liquid theory
5.1 Note on conservation laws
5.2 The tensor interaction
5.3 The kinetic equation
5.4 Asymmetric nuclear matter
6 Summary and Outlook
6.1 Summary of papers
6.1.1 Paper I – Multipair contributions to the spin response of nuclear matter
6.1.2 Paper II – Static response of Fermi liquids with tensor in- teractions
6.1.3 Paper III – Long-wavelength spin- and spin-isospin corre-lations in nucleon matter
6.2 Outlook
7 Acknowledgments
8 Summary

Author: Olsson, Emma

Source: Uppsala University Library

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