Non-Hermitian SUSY Hydrogen-like Hamiltonians with real spectra

It is shown that the radial part of the Hydrogen Hamiltonian factorizes as the product of two not mutually adjoint first order differential operators plus a complex constant epsilon. The 1-susy approach is used to construct non-hermitian Hamiltonians with hydrogen spectra. Other non-hermitian Hamiltonians are shown to admit an extra `complex energy' at epsilon. New self-adjoint hydrogen-like Hamiltonians are also derived by using a 2-susy transformation with complex conjugate pairs epsilon, (c.c) epsilon.Comment: LaTeX2e file, 13 pages, 6 EPS figures. New references added. The present is a reorganized and simplified versio

The Sommerfeld precursor in photonic crystals

We calculate the Sommerfeld precursor that results after transmission of a generic electromagnetic plane wave pulse with transverse electric polarization, through a one-dimensional rectangular N-layer photonic crystal with two slabs per layer. The shape of this precursor equals the shape of the precursor that would result from transmission through a homogeneous medium. However, amplitude and period of the precursor are now influenced by the spatial average of the plasma frequency squared instead of the plasma frequency squared for the homogeneous case.

The electromagnetic Brillouin precursor in one-dimensional photonic crystals

We have calculated the electromagnetic Brillouin precursor that arises in a one-dimensional photonic crystal that consists of two homogeneous slabs which each have a single electron resonance. This forerunner is compared with the Brillouin precursor that arises in a homogeneous double-electron resonance medium. In both types of medium, the precursor consists of the components of the applied pulse that have their frequencies below the lowest of the two electron resonances. In the inhomogeneous medium however, the slab contrast starts affecting the precursor field after a certain rise time of the precursor: its spectrum starts to peak at the geometric scattering resonances of the medium whereas minima appear at the Bragg-scattering frequencies.

Diffusion theory for light propagation in biological tissue:limitations and adaptations

Diffusion theory is an approximation of the equation of radiative transport, that is used to describe light propagation in turbid media. This approximation is very popular because of its simplicity, possibilities to describe time-resolved light propagation, and for its appeal to physical intuition. However, it has also its restrictions. It is the aim of this contribution to discuss this method, and to evaluate what can be undertaken to avoid the deviations caused by its restrictions, based on results obtained with the equation of radiative transport.</p