  The thermodynamics of general relativistic systems with boundary, obeying a
Hamiltonian constraint in the bulk, is argued to be determined solely by the
boundary quantum dynamics, and hence by the area spectrum. Assuming, for large
area of the boundary, (a) an area spectrum as determined by Non-perturbative
Canonical Quantum General Relativity (NCQGR), (b) an energy spectrum that bears
a power law relation to the area spectrum, (c) an area law for the leading
order microcanonicai entropy, leading thermal fluctuation corrections to the
canonical entropy are shown to be logarithmic in area with a universal
coefficient. Since the microcanonical entropy also has univeral logarithmic
corrections to the area law (from quantum spacetime fluctuations, as found
earlier) the canonical entropy then has a universal form including logarithmic
corrections to the area law. This form is shown to be independent of the index
appearing in assumption (b). The index, however, is crucial in ascertaining the
domain of validity of our approach based on thermal equilibrium.
