Thermodynamic Behavior of a Perfect Fluid with Negative Energy Density
  Starting from a perfect cosmological fluid represented by the energy momentum tensor T_uv, one class of frequency metrics that satisfies both Einstein's general relativistic equation and the perfect fluid condition is: g_uv = e^iwt N_uv. Mathematically, such metrics indicate spacetime behaves locally like a simple harmonic oscillator. In the cosmological model presented here these small spacetime oscillations compress vacuum energy into a standing wave inside a dynamic Casimir cavity. At peak compression a phase shift occurs and the standing wave forms into a particle having relativistic mass-energy equal to the compressive work required to produce it. At this point the newly formed particle does isobaric work to expand the volume against the external pressure given T_ii. Equilibrium is achieved when the collision rate on the volume's internal and external surfaces equalizes. By treating spacetime as a classical thermodynamic problem and oscillator, such quantities as the mass of the compressed particle--that of an axion, the radii of the initial and final volume of compression, and the angular frequency of compression can be determined. During axion collision the photon frequency of the particle is calculated to be in the microwave range and inversely equal to that of the frequency of the spacetime compression that produced the particle. This suggests axion production is a source for the 2.7K cosmic background radiation and dark matter that pervades spacetime. 
Walter Christensen Jr