  We study the Hamiltonian formulation of the generally covariant theory
defined by the Lagrangian 4-form L=e_I e_J F^{IJ}(\omega) where e^I is a tetrad
field and F^{IJ} is the curvature of a Lorentz connection \omega^{IJ}. This
theory can be thought of as the limit of the Holst action for gravity for the
Newton constant G goes to infinity and Immirzi parameter goes to zero, while
keeping their product fixed. This theory has for a long time been conjectured
to be topological. We prove this statement both in the covariant phase space
formulation as well as in the standard Dirac formulation. In the time gauge,
the unconstrained phase space of theory admits an SU(2) connection formulation
which makes it isomorphic to the unconstrained phase space of gravity in terms
of Ashtekar-Barbero variables. Among possible physical applications, we argue
that the quantization of this topological theory might shed new light on the
nature of the degrees of freedom that are responsible for black entropy in loop
quantum gravity.
