Medium modifications of antikaons in dense matter.
Technische Universität, Darmstadt
[Ph.D. Thesis], (2004)
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|Item Type:||Ph.D. Thesis|
|Title:||Medium modifications of antikaons in dense matter|
In this work the properties of antikaons in dense hadronic matter are investigated. The aim is a description of the kaon propagator in the medium including its full energy and momentum dependence over a wide energy-momentum range. The interaction of the antikaon with other hadrons are given by the Lagrangian of chiral perturbation theory in the SU(3) sector. In a first step the Bethe-Salpeter scattering equation is solved for a system of coupled channels of mesons (kaon, pion, eta) and baryons (nucleon, Lambda, Sigma). The pi-Sigma channel proves to be of special importance as its coupling to K-N produces a resonance in the isospin I=0 scattering amplitude which is called Lambda(1405). The existence of this resonance slightly below the K-N threshold is the reason the calculation of the scattering amplitudes cannot be done in a perturbative way. Instead one has to sum up all orders in the Bethe-Salpeter equation. In the medium changes in the T-matrix are caused by the existence of a 'Fermi-sea' of occupied states. The strong medium modification of the pions has to be taken into account in the propagators of the pion scattering channels. In the next step the in-medium T-matrix is used to calculate the selfenergy of the antikaon in the medium. The resulting modified kaon propagator then serves as input to the scattering equation. A iterative scheme results which is carried to selfconsistency in the scattering amplitude as well as the kaon propagator. The procedure is applied to symmetric and asymmetric nuclear matter. The latter is typically found in neutron stars. Given the full propagator of the antikaon, the question of kaon condensation in neutron stars can be addressed. Here one thinks of a possible transition of electrons into negative kaons at sufficiently large density, when the kaon mass, lowered by the interactions with the medium,falls below the electron chemical potential. The kaons will then form a Bose-condensate. The reduced number of electrons leads to a reduction of their degeneracy pressure. The system has to be charge neutral and in beta-equilibrium. Data for nuclear matter including a realistic nuclear equation of state can be taken from the literature. However, up to five times nuclear matter density the obtained mass of the antikaons is found to be significantly larger than the given electrochemical potential. Thus kaon condensation is not possible. Finally, possible extensions of the scheme with respect to thermodynamic selfconsistency are discussed.
|Place of Publication:||Darmstadt|
|Divisions:||05 Department of Physics|
|Date Deposited:||17 Oct 2008 09:21|
|Last Modified:||07 Dec 2012 11:50|
|Referees:||Roth, Prof.Dr. Robert|
|Advisors:||Wambach, Prof.Dr. Jochen|
|Refereed:||7 July 2004|