Bjoern S. Schmekel

Self-renormalization of the classical quasilocal energy

Pointlike objects cause many of the divergences that afflict physical theories. For instance, the gravitational binding energy of a point particle in Newtonian mechanics is infinite. In general relativity, the analog of a point particle is a black hole and the notion of binding energy must be replaced by quasilocal energy (QLE). The QLE derived by York, and elaborated by Brown and York, is finite outside the horizon but it was not considered how to evaluate it inside the horizon. We present a prescription for finding the QLE inside a horizon, and show that it is finite at the singularity for a variety of types of black holes. The energy is typically concentrated just inside the horizon, not at the central singularity.

Path integral over black hole fluctuations

Evaluating a functional integral exactly over a subset of metrics that represent the quantum fluctuations of the horizon of a black hole, we obtain a Schroedinger equation in null coordinate time for the key component of the metric. The equation yields a current that preserves probability if we use the most natural choice of functional measure. This establishes the existence of blurred horizons and a thermal atmosphere. It has been argued previously that the existence of a thermal atmosphere is a direct concomitant of the thermal radiation of black holes when the temperature of the hole is greater than that of its larger environment, which we take as zero.

Simulation of coherent synchrotron radiation emission from rotating relativistic electron layers

The electromagnetic radiation of rotating relativistic electron layers is studied numerically using particle-in-cell simulation. This system is general enough to be applied to problems involving the coherent synchrotron radiation (CSR) instability in bunch compressors and possibly in radio pulsars where the CSR instability may be used to explain the high brightness temperature and the observed spectra. The results of the simulation confirm all relevant scaling properties predicted by theoretical models and suggest that their range of validity is bigger than conservative estimates indicate. This is important for radio pulsars where the allowed parameter range is unknown.

Coherent synchrotron radiation for laminar flows

We investigate the effect of shear in the flow of charged particle equilibria that are unstable to the coherent synchrotron radiation (CSR) instability. Shear may act to quench this instability because it acts to limit the size of the region with a fixed phase relation between emitters. The results are important for the understanding of astrophysical sources of coherent radiation where shear in the flow is likely.