Models for Type Ia Supernovae and Cosmology

From the spectra and light curves it is clear that SNIa events are thermonuclear explosions of white dwarfs. However, details of the explosion are highly under debate. Here, we present detailed models which are consistent with respect to the explosion mechanism, the optical and infrared light curves (LC), and the spectral evolution. This leaves the description of the burning front and the structure of the white dwarf as the only free parameters. The explosions are calculated using onedimensional Lagrangian codes including nuclear networks. Subsequently, optical and IR-LCs are constructed. Detailed NLTE-spectra are computed for several instants of time using the density, chemical and luminosity structure resulting from the LCs (sect.2). Different models for the thermonuclear explosion are discussed including detonations, deflagrations, delayed detonations, pulsating delayed detonations (PDD) and helium detonations (sect.3). Comparisons between theoretical and observed LCs and spectra provide an insight into details of the explosion and nature of the progenitor stars (sect. 4 & 5). We try to answer several related questions. Are subluminous SNe Ia a group different from ‘normal’ SN Ia (sect. 4)? Can we understand observed properties of the LCs and spectra (sect. 5)? What can we learn from infrared spectra? Can we determine Ho independently from primary distance indicators, and how do the results compare with empirical methods (sect.6)? What do we learn about the progenitor evolution and its metallicity? What are the systematic effects for the determination of the cosmological parameters ΩM and Λ and how can we recognize this potential ’pitfalls’ and correct for evolutionary effects (sect.7)?