  We show that the near-horizon energy introduced by Frodden, Ghosh and Perez
arises from the action for general relativity as a horizon boundary term. Spin
foam variables are used in the analysis. The result provides a derivation of
the horizon boost Hamiltonian introduced by one of us to define the dynamics of
the horizon degrees of freedom, and shows that loop gravity provides a
realization of the horizon Schrodinger equation proposed by Carlip and
Teitelboim.
