  An alternative cosmological model is presented, which avoids the requirement
of dark energy and dark matter. Based on the proposition that energy
conservation should be valid not only locally but also globally, the energy
tensor of general relativity has to be corrected, including potential energy of
matter explicitly. This leads to the consequence that a homogeneous universe
must be static, as potential energy acts as a field with negative pressure. In
this static universe cosmological red shift can be understood as energy loss by
gravitational radiation. There exists a continuous matter cycle, beginning from
hot intergalactic plasma, which is replenished by the jets of quasars, the
formation of large web-like structures, the formation of galaxies and stars, to
the final collapse into quasars again. The model is confirmed qualitatively by
the observed size distribution of cosmic structures. Quantitative confirmation
is obtained from the diffuse x-ray background and from observations of
supernovas. As the total energy content of the universe (trace of the energy
tensor) is zero in this model, creation ex nihilo is possible, but requires
changes of our elementary particle models. An idea of a modified model is
presented.
