  We propose a brane-world setup based on gauge/gravity duality in which the
four-dimensional cosmological constant is set to zero by a dynamical
self-adjustment mechanism. The bulk contains Einstein gravity and a scalar
field. We study holographic RG flow solutions, with the standard model brane
separating an infinite volume UV region and an IR region of finite volume. For
generic values of the brane vacuum energy, regular solutions exist such that
the four-dimensional brane is flat. Its position in the bulk is determined
dynamically by the junction conditions. Analysis of linear fluctuations shows
that a regime of 4-dimensional gravity is possible at large distances, due to
the presence of an induced gravity term. The graviton acquires an effective
mass, and a five-dimensional regime may exist at large and/or small scales. We
show that, for a broad choice of potentials, flat-brane solutions are
manifestly stable and free of ghosts. We compute the scalar contribution to the
force between brane-localized sources and show that, in certain models, the
vDVZ discontinuity is absent and the effective interaction at short distances
is mediated by two transverse graviton helicities.
