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Title: Astrophysical consequences of phase transitions in the early universe : primordial magnetic fields and superconducting cosmic strings
Author: Dimopoulos, K.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1997
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A new mechanism for the evolution of primordial magnetic fields is described and analysed. The field evolution is followed from the time of its creation until the epoch of structure and galaxy formation. The mechanism takes into account the turbulent behaviour of the early universe plasma. Of crucial importance are the plasma opacity and conductivity which inhibit the field evolution through Alfven wave propagation and Thomson scattering effects. A number of other related issues such as the case of an electro-weak plasma are also considered. For demonstrational reasons the mechanism is applied to two specific toy models of primordial field generation. An attempt to create a primordial magnetic field using a realistic model the above mechanism is employed in the context of False Vacuum Inflation. Considering the inflation dominated regime, the field is produced by the Higgs-field gradients, resulting from a grand unified phase transition, which occurs during the inflationary period. The evolution of the field is followed from its creation through to the epoch of structure formation, subject to the relevant constraints. Particular attention is paid to the reheating period and also to the inflation's quantum fluctuations at the time of phase transition, since both the above could jeopardise the stability of the magnetic field. It is found that it is possible to create a magnetic field of sufficient magnitude. Another approach to the problem of seed field generation involves superconducting cosmic strings. It is a growing belief that, for a wide range of theoretical models, cosmic strings may be superconducting and carry substantial currents. A network of charged-current carrying cosmic strings may generate a primordial magnetic field through dynamical friction between the strings and the plasma. The field is created by vorticity, generated in the primordial plasma due to the strings' motion and gravitational pull.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available