  The author was recently able to provide a cohomological interpretation of
Tate's Riemann-Roch formula for number fields using some new harmonic analysis
objects, ghost-spaces. When trying to investigate these objects in general, we
realized the importance of functions and measures on locally compact abelian
groups that are both positive and positive-definite at the same time.
  It looks like this class of functions and measures was not systematically
studied before. The goal of this paper is to partially fill in this gap. We
answer some of the natural questions involving these functions and measures,
especially those that satisfy some extra integrability conditions. We also
study some operations and constructions involving these functions and measures.
  There are several very interesting open questions, that we are only able to
point out at this moment. In particular, the structure of the cone of such
functions is not clear even when the group is just $\R.$
