Karsten Bormann

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The procedure of solving the direct problem for a transonic gas outtow from the surface of a slowly rotating star is formulated within 2D ideal hydrodynamics. The nonrelativistic Grad-Shafranov equation describing a 2D stellar wind is written down. It is shown that the existence of an exact analytical solution-a spherically symmetrical stellar wind-allows(More)
The free energy due to the vacuum fluctuations of matter fields on a classical gravitational background is discussed. It is shown explicitly how this energy is calculated for a non-minimally coupled scalar field in an arbitrary gravitational background, using the heat kernel method. The treatment of (self-)interacting fields of higher spin is outlined,(More)
We demonstrate how to obtain explicitly the propagators for quantum fields residing in curved space-time using the heat kernel for which a new construction procedure exists. Propagators are determined for the case of Rindler, Friedman-Robertson-Walker, Schwarzschild and general conformally flat metrics, both for scalar, Dirac and Yang-Mills fields. The(More)