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- Karsten Bormann
- Presence
- 2005

- Karsten Bormann
- Virtual Reality
- 2006

- K. Bormann, Niels Bohr
- 2007

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)

For a Friedman-Robertson-Walker space-time in which the only contribution to the stress-energy tensor comes from the renormalised zero-point energy (i.e. the Casimir energy) of the fundamental fields the evolution of the universe (the scale factor) depends upon whether the universe is open, flat or closed and upon which fundamental fields inhabit the… (More)

- Karsten Bormann
- VR
- 2000

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 calculate the effective potentials for scalar, Dirac and Yang-Mills fields in curved backgrounds using a new method for the determination of the heat kernel involving a partial resummation of the Schwinger-DeWitt series. Self-interactions are treated both to one loop order as usual and slightly beyond one-loop order by means of a mean-field… (More)

We present a generic way of thinking about time machines from the view of a far away observer. In this model the universe consists of three (or more) regions: One containing the entrance of the time machine, another the exit and the remaining one(s) the rest of the universe. In the latter we know ordinary quantum mechanics to be valid and thus are able to… (More)

- Karsten Bormann
- Virtual Reality
- 2008

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)