Plasma Instabilities in Electron-Positron Pair Beams from Blazars
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- Institutt for fysikk 
The non-detection of an electromagnetic cascade in the electron-positron plasmabeams from blazars has led many physicists to invoke an intergalactic magneticeld that deects charged particles away from our eld of view. In this thesis welook at a dierent explanation. Namely that the beams loose their energy throughplasma instabilities rather than the inverse Compton scattering which would createthe cascade. We use a covariant formalism to calculate the linear response tensorof the plasma. Using this tensor we nd the absorption coecient for particlesdistributed according to the Jüttner distribution and for a dierent distributionbased on simulations. The absorption coecient is found to diverge for specicvalues of the phase velocity when the electric eld of the mode vanishes. This isunphysical, which means there is some issue with the calculations. The issue isidentied as the assumption that the imaginary part of the frequency, known as theabsorption coecient, is small. This assumption contradicts the results making thecalculations invalid. To solve this problem one would have to redo the calculationsavoiding this assumption.