  We explore thermodynamic contributions to the three-dimensional de Sitter
horizon originating from metric and Chern-Simons gauge field fluctuations. In
Euclidean signature these are computed by the partition function of gravity
coupled to matter semi-classically expanded about the round three-sphere
saddle. We investigate a corresponding Lorentzian picture - drawing inspiration
from the topological entanglement entropy literature - in the form of an
edge-mode theory residing at the de Sitter horizon. We extend the discussion to
three-dimensional gravity with positive cosmological constant, viewed
(semi-classically) as a complexified Chern-Simons theory. The putative
gravitational edge-mode theory is a complexified version of the chiral
Wess-Zumino-Witten model associated to the edge-modes of ordinary Chern-Simons
theory. We introduce and solve a family of complexified Abelian Chern-Simons
theories as a way to elucidate some of the more salient features of the
gravitational edge-mode theories. We comment on the relation to the
AdS$_4$/CFT$_3$ correspondence.
