  Interband absorption and luminescence of quasi-two-dimensional, circularly
symmetric, N_e electron quantum dots are studied at high magnetic fields,
8<B<60 T, and low temperatures, T<<2 K. In the N_e=0 and 1 dots, the initial
and final states of such processes are fixed, and thus the dependence on B of
peak intensities is monotonic. For larger systems, ground state rearrangements
with varying magnetic field lead to substantial modifications of the absorption
and luminescence spectra. Collective effects are seen in the N_e=2 and 3 dots
at "filling factors" 1/2, 1/3 and 1/5.
