  Realizing dark energy and the observed de Sitter spacetime in quantum gravity
has proven to be obstructed in most every usual approach. We argue that
additional degrees of freedom of the left- and right-movers in string theory
and a resulting doubled, non-commutatively generalized geometric formulation
thereof can lead to an effective model of dark energy consistent with de Sitter
spacetime. In this approach, the curvature of the canonically conjugate dual
space provides for the dark energy inducing a positive cosmological constant in
the observed spacetime, whereas the size of the above dual space is the
gravitational constant in the same observed de Sitter spacetime. As a hallmark
relation owing to a unique feature of string theory which relates short
distances to long distances, the cosmological constant scale, the Planck scale,
and the effective TeV-sized particle physics scale must satisfy a see-saw-like
formula---precisely the generic prediction of certain stringy cosmic brane type
models.
