Exploring extra dimensions through observational tests of dark energy
  and varying Newton's constant
  We recently presented a series of dark energy theorems that place constraints
on the equation of state of dark energy ($\wdark$), the ime-variation of
Newton's constant ($\dot G$), and the violation of energy conditions in
theories with extra dimensions. In this paper, we explore how current and
future measurements of $\wdark$ and $\dot G$ can be used to place tight limits
on large classes of these theories (including some of the most well-motivated
examples) independent of the size of the extra dimensions. As an example, we
show that models with conformally Ricci-flat metrics obeying the null energy
condition (a common ansatz for Kaluza-Klein and string constructions) are
highly constrained by current ata and may be ruled out entirely by future dark
energy and pulsar observations.
