  A low-energy perturbation theory is developed from the nonperturbative
framework of covariant Loop Quantum Gravity (LQG) by employing the background
field method. The resulting perturbation theory is a 2-parameter expansion in
the semiclassical and low-energy regime. The two expansion parameters are the
large spin and small curvature. The leading order effective action coincides
with the Einstein-Hilbert action. The subleading corrections organized by the
two expansion parameters give the modifications of Einstein gravity in quantum
and high-energy regime from LQG. The perturbation theory developed here shows
for the first time that covariant LQG produces the high curvature corrections
to Einstein gravity. This result means that LQG is not a naive quantization of
Einstein gravity, but rather provides the UV modification. The result of the
paper may be viewed as the first step toward understanding the UV completeness
of LQG.
