  We study the energy spectrum and the electromagnetic response of Andreev
bound states in short Josephson junctions made of semiconducting nanowires. We
focus on the joint effect of Zeeman and spin-orbit coupling on the Andreev
level spectra. Our model incorporates the penetration of the magnetic field in
the proximitized wires, which substantially modifies the spectra. We pay
special attention to the occurrence of fermion parity switches at increasing
values of the field and to the magnetic field dependence of the absorption
strength of microwave-induced transitions. Our calculations can be used to
extract quantitative information from microwave and tunneling spectroscopy
experiments, such as the recently reported measurements in Van Woerkom et al.,
arXiv:1609.00333.
