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Identifier 000380673
Title Vorticity production and survival in radiative Friedman universe
Alternative Title Παραγωγή και εξέλιξη της περιστροφής σε μοντέλα Friedman την εποχής της ακτινοβολίας
Author Δοσοπούλου, Φανή
Thesis advisor Τομαράς, Θεόδωρος
Abstract Although most astrophysical objects rotate, whether the universe itself rotates or not is as yet unknown. Is is conceivable that some observational data, such as the large-scale asymmetry observed in the CMB as well as several anomalies detected on large angular scales, could be attributed to rotation. Nevertheless, the issue is still open to discussion. In this thesis, we examine the effect the presence of a magnetic field has on vorticity in a Friedman universe during the radiation period. We select a Friedman background with a weak random $B$-field and perturbe it. We derive the linear form of the vorticity evolution equation and analyze what effect the matter and magnetic energy densities, as well the magnetic tension have on vorticity production and survival. We find that both the matter and the magnetic pressure help vorticity to survive, acting against its reduction caused by the expansion of the universe. We then find a linear analytical solution for the evolution of the vorticity vector during the radiation era. The solution shows that the presence of a magnetic field reduces the standard decay rate of the vorticity and in the long term tends to keep it constant. Finally, we examine the effect of magnetic perturbations on vortex-like distortions in the density distribution of the radiative matter and conclude again that the $B$-field does help the latter to survive.
Language English
Issue date 2013-07-19
Collection   School/Department--School of Sciences and Engineering--Department of Physics--Post-graduate theses
  Type of Work--Post-graduate theses
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