Particle theory

Abstract:

We identify a new mechanism in supergravity theories which leads to successful inflation without any need for fine tuning. The simplest model yields a spectrum of density fluctuations tilted away from scale-invariance and negligible gravitational waves. We demonstrate that this is consistent with the observed large-scale structure for a cold dark matter dominated, critical density universe. The model can be tested through measurements of microwave background anisotropy on small angular scales.

Abstract:

Discrete symmetries are commonplace in field theoretical models but pose a severe problem for cosmology since they lead to the formation of domain walls during spontaneous symmetry breaking in the early universe. However if one of the vacuua is favoured over the others, either energetically, or because of initial conditions, it will eventually come to dominate the universe. Using numerical methods, we study the evolution of the domain wall network for a variety of field configurations in two and three dimensions and quantify the rate at which the walls disappear. Good agreement is found with a recent analytic estimate of the termination of the scaling regime of the wall network.

Abstract:

This talk reviews briefly some of the main results of the small-x dipole formulation with regards to unitarity corrections. It illustrates the correspondence between unitarity and saturation corrections in the dipole approach and multiple t-channel pomeron exchange in the traditional BFKL view, and discusses how one can estimate and understand the effects of saturation.