  A modification of the Einstein-Hilbert theory, the Covariant Canonical Gauge
Gravity (CCGG), leads to a cosmological constant that represents the energy of
the space-time continuum when deformed from its (A)dS ground state to a flat
geometry. CCGG is based on the canonical transformation theory in the De
Donder-Weyl (DW) Hamiltonian formulation. That framework modifies the
Einstein-Hilbert Lagrangian of the free gravitational field by a quadratic
Riemann-Cartan concomitant. The theory predicts a total energy-momentum of the
system of space-time and matter to vanish, in line with the conjecture of a
"Zero-Energy-Universe" going back to Lorentz (1916) and Levi-Civita (1917).
Consequently a flat geometry can only exist in presence of matter where the
bulk vacuum energy of matter, regardless of its value, is eliminated by the
vacuum energy of space-time.% $\lambda_0$. The observed cosmological constant
$\Lambda_{\mathrm{obs}}$ is found to be merely a small correction %of the order
$10^{-120} \,\lambda_0$ attributable to deviations from a flat geometry and
effects of complex dynamical geometry of space-time, namely torsion and
possibly also vacuum fluctuations of matter and space-time. That quadratic
extension of General Relativity, anticipated already in 1918 by Einstein
\cite{einstein18}, thus provides a significant and natural contribution to
resolving the %$120$ orders of magnitude miss-estimate called the "cosmological
constant problem".
