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A. C. Davis

Publications and source records attributed to A. C. Davis.

45 records · Page 3Linked to original sources
arXiv1998

The Chern-Simons number as an order parameter : classical sphaleron transitions for SU(2)-Higgs field theories for a Higgs mass approximately equal to 120 GeV

The classical transitions between topologically distinct vacua in a SU(2)-Higgs model, using a Higgs field of mass approximately 120 GeV, is examined to probe the crossover region between the symmetric and broken phase. Assuming the Higgs mass is constant, we find the width of this crossover region is approximately 20% of the average temperature. We suggest that this observable is a better parameter to explore this region of phase space than equal-time correlation functions.

hep-ph↗
arXiv1996

Primordial Magnetic Fields in False Vacuum Inflation

We show that, during false vacuum inflation, a primordial magnetic field can be created, sufficiently strong to seed the galactic dynamo and generate the observed galactic magnetic fields. Considering the inflaton dominated regime, our field is produced by the Higgs-field gradients, resulting from a grand unified phase transition. The evolution of the field is followed from its creation through to the epoch of structure formation, subject to the relevant constraints. We find that it is possible to create a magnetic field of sufficient magnitude, provided the phase transition occurs during the final 5 e-foldings of the inflationary period.

astro-ph↗
arXiv1996

On the Evolution of Primordial Magnetic Fields

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, whose properties determine strongly the evolution of the field configuration. A number of other related issues such as the case of an electroweak plasma are also considered. Finally, as an example, the mechanism is applied to specific models.

astro-ph↗
arXiv1995

The Stability of Primordial Magnetic Fields Produced by Phase Transitions

Primordial magnetic fields seem to be a generic relic of phase transitions in the early universe. We consider a primordial electromagnetic field formed as a result of a second-order phase transition, and show that it is stable to thermal fluctuations in the period immediately following. We also show how such a field arises in first order phase transitions. In both cases there is a transitive electric field produced during the transition.

astro-ph↗
arXiv1994

Evolution of Fields in a Second Order Phase Transition

We analyse the evolution of scalar and gauge fields during a second order phase transition using a Langevin equation approach. We show that topological defects formed during the phase transition are stable to thermal fluctuations. Our method allows the field evolution to be followed throughout the phase transition, for both expanding and non-expanding Universes. The results verify the Kibble mechanism for defect formation during phase transitions.

hep-ph↗
arXiv1994

Electroweak Baryogenesis with Topological Defects

Electroweak baryogenesis has become a topic of much recent activity [1]. Here we discuss a new scenario which has the advantage of being insensitive to the order of the electroweak phase transition. We briefly review a mechanism [2] using unstable electroweak strings [3] and discuss in detail a mechanism [4] using topological defects (in particular cosmic strings) left behind after a previous phase transition.

hep-ph↗
arXiv1994

Charged Particle Scattering from Electroweak and Semi-Local Strings

The scattering of a charged fermion from an electroweak or semi-local string is investigated and a full solution obtained for both massive and massless cases. For the former, with fractional string flux, there is a helicity conserving and helicity-flip cross-section, of equal magnitude and of a modified Aharonov-Bohm form: for integer flux the strong interaction cross-section is suppressed by a logarithmic term. The results also apply for GUT cosmic strings and chiral fermions.

hep-ph↗
arXiv1994

Global Strings and the Aharonov-Bohm Effect

When a fermion interacts with a global vortex or cosmic string a solenoidal "gauge" field is induced. This results in a non-trivial scattering cross-section. For scalars and non-relativistic fermions the cross-section is similar to that of Aharonov and Bohm, but with corrections. A cosmological example is compared to one in liquid He$^{3}$-A and important differences are discovered.

hep-ph↗