Axion electrodynamics is based upon the Lagrangian of electromagnetic (EM) field plus its interaction with axions, and accordingly a physically open system. It means that four-divergence EM energy-momentum tensor different from zero, implying in turn total energy momentum (when integrated over all space) do not constitute four-vector. The force principle accessible to experimental detection, ju...

An analysis of one and two point functions of the energy momentum tensor on homogeneous spaces of constant curvature is undertaken. The possibility of proving a c-theorem in this framework is discussed, in particular in relation to the coefficients c, a, which appear in the energy momentum tensor trace on general curved backgrounds in four dimensions. Ward identities relating the correlation fu...

For the quark-gluon plasma, an energy-momentum tensor is found corresponding to the high-temperature Braaten-Pisarski effective action. The tensor is found by considering the interaction of the plasma with a weak gravitational field and the positivity of the energy is studied. In addition, the complete effective action in curved spacetime is written down. 1 Introduction The high-temperature pro...

By applying the Palatini approach to the 1/R-gravity model it is possible to explain the present accelerated expansion of the Universe. Investigation of the late Universe limiting case shows that: (i) due to the curvature effects the energy-momentum tensor of the matter field is not covariantly conserved; (ii) however, it is possible to reinterpret the curvature corrections as sources of the gr...