Principle of equivalence, general covariance and the demand that the variation of the action functional should be well defined, lead to a generic Lagrangian for semiclassical gravity of the form L = Q bcd a Rbcd with ∇b Q bcd a = 0. The expansion of Q bcd a in terms of the derivatives of the metric tensor determines the structure of the theory uniquely. The zeroth order term gives the Einstein–...

The recent discovery, by the Chandra satellite, that jets of blazars are strong X–ray emitters at large scales (0.1–1 Mpc) bears support to the hypothesis that (also) on these scales the emitting plasma is moving at highly relativistic speeds. In this case in fact the emission via inverse Compton scattering off cosmic background photons is enhanced and the resulting predicted X–ray spectrum wel...

Ideal fluid dynamics is studied as a relativistic field theory with particular stress on its hamiltonian structure. The Schwinger condition, whose integrated version yields the stress tensor conservation, is explicitly verified both in equal-time and light-cone coordinate systems. We also consider the hamiltonian formulation of fluids interacting with an external gauge field. The complementary ...

We present new analytical self-similar solutions describing a collapse of a massless scalar field in scalar-tensor theories. The solutions exhibit a type of critical behavior. The black hole mass for the near critical evolution is analytically obtained for several scalar-tensor theories and the critical exponent is calculated. Within the framework of the analytical models we consider it is foun...

The condition for the vanishing of the Weyl tensor is integrated in the spherically symmetric case. Then, the resulting expression is used to find new, conformally flat, interior solutions to Einstein equations for locally anisotropic fluids. The slow evolution of these models is contrasted with the evolution of models with similar energy density or radial pressure distribution but non-vanishin...

We consider the radiative acceleration to relativistic bulk velocities of a cold, optically thin plasma which is exposed to an external source of γ-rays. The flow is driven by radiative momentum input to the gas, the accelerating force being due to Compton scattering in the relativistic Klein-Nishina limit. The bulk Lorentz factor of the plasma, Γ, derived as a function of distance from the rad...

We compute all 2-covariant tensors naturally constructed from a semiriemannian metric g which are divergence-free and have weight greater than −2. As a consequence, it follows a characterization of the Einstein tensor as the only, up to a constant factor, 2-covariant tensor naturally constructed from a semiriemannian metric which is divergence-free and has weight 0 (i.e., is independent of the ...

The relativistic second-rank tensor containing electric and magnetic polarization vectors of a medium is obtained based on the Maxwell equations determination charge density current structural microparticle. Using this electromagnetic field tensor, Lagrangian interaction with microparticle taking into account its elements. has been constructed considering polarizabilities.

The electric dipole moments of closed-shell atoms are sensitive to the parity and timereversal violating phenomena in the nucleus. The nuclear Schiff moment is one such property, it arises from the parity and time reversal violating quark-quark interactions and the quarkchromo electric dipole moments. We calculate the electric dipole moment of atomic Hg arising from the nuclear Schiff moment us...