  Just comparing with the scenario that the (3+1)-dimensional "real world" of
the Calabi-Yau compactification has a tremendous landscape, we conjecture that
a (4+1)-dimensional holographic theory may also hold a landscape of its vacua.
Unlike the traditional studies of the AdS/CFT phenomenology where the vacua are
always constructive, we discuss the proper holographic vacua and their flux
compactification, starting from some general compact Einstein manifolds. The
proper vacua should be restricted by (i) a consistent worldsheet theory that
possesses the superconformal symmetry, (ii) some definite symmetries to
keep/break the corresponding symmetries of the dual field theory, (iii) certain
brane/flux configurations to cancel anomalies, and (iv) stabilities. We
consider diverse fundamental parameters of the dual field theory, fixed by some
special vacuum moduli.
  In an opposite way, if some field theory such as QCD holds an AdS dual, it
may also possesses various fundamental parameters by an "landscape" of its
vacuum. Different vacua may be adjacent with each other, and divided by domain
walls. If the size of a single vacuum region is smaller than the visible
universe, it may be testable. We discuss the consequences of this conjecture in
the astrophysical environments, include but not limit to: (i) consistency with
the critical energy density of the universe, (ii) the behaviors of cosmic rays,
(iii) the stability and abundance of deuterons and other nuclei in the big-bang
nucleosynthesis and the star burning scenarios, and (iv) the existence of
strange/charm stars.
