  A cosmological event horizon develops in a vacuum-dominated Friedmann
universe. The Schwarschild radius of the vacuum energy within the horizon
equals the horizon radius. Black hole thermodynamics and the holographic
conjecture indicate a finite number of degrees of freedom within the horizon.
The average energy per degree of freedom equals the energy of a massless
quantum with wavelength of the horizon circumference. This suggests identifying
the degrees of freedom with the presence or absence, in each Planck area on one
horizon quadrant, of a 0S2 vibrational mode of the horizon with the z axis
passing through that area. Pressure waves on the horizon (the superposition of
0S2 vibrational modes) can be envisioned to propagate into the observable
universe within the horizon at the speed of light. So, the vacuum energy and
pressure throughout the observable universe could (in principle) be determined
from the vacuum equation of state.
