  Using Relativistic Quantum Geometry we study back-reaction effects of
space-time inside the causal horizon of a static de Sitter metric, in order to
make a quantum thermodynamical description of space-time. We found a finite
number of discrete energy levels for a scalar field from a polynomial condition
of the confluent hypergeometric functions expanded around $r=0$. As in the
previous work, we obtain that the uncertainty principle is valid for each
energy level on sub-horizon scales of space-time. We found that temperature and
entropy are dependent on the number of sub-states on each energy's level and
the Bekenstein-Hawking temperature of each energy level is recovered when the
number of sub-states of a given level tends to infinity. We propose that the
primordial state of the universe could be described by a de Sitter metric with
Planck energy $E_p=m_p\,c^2$, and a B-H temperature:
$T_{BH}=\left(\frac{\hbar\,c}{2\pi\,l_p\,K_B}\right)$.
