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Title: Scattering, absorption and emission by black holes
Author: Dolan, S. R.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2007
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In the first three chapters we consider a Direc plane wave impinging upon a Schwarzschild black hole. The interaction is characterised by three quantities: the absorption cross section, the scattering cross section, and the partial polarization. If the wavelength λ of the incident wave is much smaller than the event horizon s, these quantities may be approximated classically. If λ ≫ rs then the black hole may be treated parturbatively, and these quantities may be approximated through a Born series expansion. In the intermediate regime, λ ~ rs, a partial wave expansion is necessary. We consider all three regimes and present significant new results for absorption, scattering and Mott polarization. In the next chapter we show the existence of a spectrum of normalisable fermionic bound states on the Schwarzschild background. These states are the gravitational analogues of the hydrogenic electron orbitals. We compute their energy levels, decay times and wavefunctions, and discuss their potential significance. Two further chapters treat wave interaction with the rotating (Kerr) black hole. As a preliminary step, we review the theory of spin-weighted spheroidal harmonics and methods for their calculation. These functions are used to separate the Dirac field on the Kerr background into angular and radial parts. The radial equations are then solved numerically to find phase shifts and transmission coefficients. We extend the partial wave analysis to the rotating case, and present accurate scattering and absorption cross sections.  The effect of spin-rotation coupling on the cross sections is discussed. The final chapter is a study of fermionic emission from higher-dimensional rotating black holes. If theories with large extra dimensions are well-founded then black holes may arise at TeV energies. Black holes created through high-energy particle collisions would decay via the emission of standard model fields on the brane, and gravitons in the bulk. Their emission spectra would provide a clear signature of the underlying higher-dimensional spacetime. Motivated by this intriguing possibility, we apply numerical methods to compute the spectra and angular profiles of fermionic emission on the brane. We show that the net emission is greatly enhanced by the addition of extra dimensions; that the emission is concentrated in the plane of rotation; and that neutrinos are emitted preferentially into the southern hemisphere. Finally, the effect of fermionic emission on the evolution of a 5D black hole is considered in detail.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available