Horava-Lifshitz gravity: detailed balance revisited
  We attempt a critical reconsideration of "detailed balance" as a principle
that can be used to restrict the proliferation of couplings in Horava-Lifshitz
gravity. We re-examine the shortcomings that have been usually associated with
it in the literature and we argue that easy remedies can be found for all of
them within the framework of detailed balance, and that the most persistent of
them are actually related to projectability. We show that, once projectability
is abandoned, detailed balance reduces the number of independent couplings by
roughly an order of magnitude and imposes only one restriction that constitutes
a phenomenological concern: the size of the (bare) cosmological constant is
unacceptably large. Remarkably, this restriction (which is present in the
projectable version as well) has been so far under-appreciated in the
literature. Optimists might prefer to interpret it as a potential blessing in
disguise, as it allows one to entertain the idea of a miraculous cancelation
between the bare cosmological constant and the (still poorly understood) vacuum
energy contribution.
