Accelerated expansion of the Universe driven by dynamic self - interaction

We establish a new model, which takes into account a dynamic (inertial) self-interaction of gravitating systems. The model is formulated by introduction of a new function depending on the square of the covariant derivative of the velocity four-vector of the system as a whole into the Lagrangian. This term is meant for description of both self-action of the system irregularly moving in the gravitational field, and back-reaction of the motion irregularities on the gravity field. We discuss one example of exact solution to the extended master equations in the framework of cosmological model of the FLRW type with vanishing cosmological constant. It is shown that accelerated expansion of the Universe can be driven by traditional matter with positive pressure (e.g., dust, ultrarelativistic fluid) due to the back-reaction of the gravity field induced by irregular motion of the system as a whole; this back-reaction is shown to be characterized by the negative effective pressure.