Conservation of energy, thermodynamics and cosmology models

Lamba CDM and similar cosmology models apparently do not conserve energy, but it is unresolved whether this is correct and consistent with theory. Conservation of energy in the context of the Friedmann equations is discussed including whether energy is a well-defined quantity and what condition for energy conservation would apply. The evidence for conservation of energy includes that the first law of thermodynamics can be derived directly from the Friedmann equations, and from consideration of Noether’s theorem. An expanding volume of photons loses energy, and a similar volume of dark energy gains energy which is inconsistent with conservation of energy. The source and possible resolution for this apparent contradiction are discussed in terms of the thermodynamics of an expanding volume of the universe. ΛCDM and other similar models do not properly account for the thermodynamic pdV work done during the adiabatic expansion. Quantitative analysis shows that the pdV work released by photons is remarkably close to the known quantity of dark matter, indicating that there is a direct connection.