Active Galactic Nuclei: The TeV Challenge
  Jets associated with Active Galactic Nuclei (AGN) have been observed for
almost a century, initially at optical and radio wavelengths. They are now
widely accepted as "exhausts" produced electromagnetically by the central,
spinning, massive black hole and its orbiting, accreting gas. Observations at
X-ray and, especially, gamma-ray energies have transformed our understanding of
how these jets evolve dynamically, accelerate electrons (and positrons) and
radiate throughout the entire electromagnetic spectrum. Some new approaches to
modeling the powerful and rapidly variable TeV emission observed from many
blazars are sketched. Observations at the highest TeV energies, to which the
High Altitude Water Cherenkov Gamma-Ray Observatory (HAWC) will contribute,
promise crucial discrimination between rival models of AGN jets.
