We discuss recent developments in assessing heavy-quark interactions in the quark-gluon plasma (QGP). While induced gluon radiation is expected to be the main energy-loss mechanism for fast-moving quarks, we focus on elastic scattering which prevails towards lower energies, evaluating both perturbative (gluon-exchange) and nonperturbative (resonance formation) interactions in the QGP. The latter are treated within an effective model for D- and B-meson resonances above T-c as motivated by current QCD lattice calculations. Pertinent diffusion and drag constants, following from a Fokker-Planck equation, are implemented into an expanding fireball model for Au-Au collisions at RHIC using relativistic Langevin simulations. Heavy quarks are hadronized in a combined fragmentation and coalescence framework, and resulting electron-decay spectra are compared to recent RHIC data. A reasonable description of both nuclear suppression factors and elliptic flow up to momenta of similar to 5 GeV supports the notion of a strongly interacting QGP created at RHIC. Consequences and further tests of the proposed resonance interactions are discussed.
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