  A modified-gravity-type model of two hypothetical massless vector fields is
presented. These vector fields are gravitationally coupled to standard matter
and an effective cosmological constant. Considered in a cosmological context,
the vector fields dynamically cancel an arbitrary cosmological constant, and
flat Minkowski spacetime appears as the limit of attractor-type solutions of
the field equations. Asymptotically, the field equations give rise to a
standard Friedmann-Robertson-Walker universe and standard Newtonian
gravitational dynamics of small systems.
