Preheating and phase transitions in gauge theories

It has recently been suggested that the baryon washout problem of the standard electroweak baryogenesis scenario could be avoided if inflation ends with a period of parametric resonance at a low enough energy density. I present results of numerical simulations in which this process was studied in the Abelian Higgs model. Our results show that because of the masslessness of the gauge field, the parametric resonance takes place naturally, and that the system reaches a quasi-equilibrium state in which the long-wavelength part of the spectrum has a high effective temperature. This enhances baryon number violation and makes baryogenesis more efficient.Comment: Talk given at SEWM2000. 5 pages, 1 figur

Formation of Magnetic Monopoles in Hot Gauge Theories

In this talk, I discuss the formation of magnetic monopoles in a phase transition from the confining SU(2) phase to the Coulomb phase in a hot Georgi-Glashow model. I argue that monopoles are formed from long-wavelength thermal fluctuations, which freeze out after the phase transition.Comment: 5 pages, talk given at Strong and Electroweak Matter 2002, Heidelberg, October 2-5, 200

Defect formation in the early universe

Topological defects are common in many everyday systems. In general, they appear if a symmetry is broken at a rapid phase transition. In this article, I explain why it is believed that they should have also been formed in the early universe and how that would have happened. If topological defects are found, this will provide a way to study observationally the first fractions of a second after the Big Bang, but their apparent absence can also tell us many things about the early universe.Comment: 26 pages, 10 figures. Updated to match the version published in Contemporary Physics (http://taylorandfrancis.metapress.com/link.asp?id=dcvj45hv41kr7xf7

Non-equilibrium dynamics of hot Abelian Higgs model

The real-time dynamics of finite-temperature gauge theories can be approximated, to leading-order accuracy in the coupling constants, by a classical field theory with the hard thermal loop Lagrangian. I show how this approach can be used in numerical lattice simulations to study dynamics of the Abelian Higgs model in or slightly out of equilibrium.Comment: 4 pages, talk given at COSMO' 99, Trieste, Italy, September 27 - October 2, 199

Massive scalar field evolution in de Sitter

The behaviour of a massive, non-interacting and non-minimally coupled quantised scalar field in an expanding de Sitter background is investigated by solving the field evolution for an arbitrary initial state. In this approach there is no need to choose a vacuum in order to provide a definition for particle states. We conclude that the expanding de Sitter space is a stable equilibrium configuration under small perturbations of the initial conditions. Depending on the initial state, the energy density can approach its asymptotic value from above or below, the latter of which implies a violation of the weak energy condition. The backreaction of the quantum corrections can therefore lead to a phase of super-acceleration also in the non-interacting massive case.Comment: 22 pages, 5 figures. v2: References added. v3: Expanded text, added references. Version accepted by JHE