Signature of the interaction between dark sectors in the reionization
  process
  We consider the reionization process in a cosmological model in which dark
matter interacts with dark energy. Using a semi-analytical reionization model,
we compute the evolution of the ionized fraction in terms of its spatial
average and linear perturbations. We show that certain types of interactions
between dark matter and dark energy can significantly affect the reionization
history. We calculate the 21 cm signals in the interaction models, and compare
the results with the predictions of the ${\rm \Lambda CDM}$ model.
