  The proton-neutron relativistic quasiparticle random phase approximation
(PN-RQRPA) is formulated in the canonical single-nucleon basis of the
relativistic Hartree-Bogoliubov (RHB) model, for an effective Lagrangian
characterized by density-dependent meson-nucleon couplings. The model includes
both the T=1 and T=0 pairing channels. Pair configurations formed from the
fully or partially occupied states of positive energy in the Fermi sea, and the
empty negative-energy states from the Dirac sea, are included in PN-RQRPA
configuration space. The model is applied to the analysis of charge-exchange
modes: isobaric analog resonances and Gamow-Teller resonances.
