# Theoretical Cosmology

Our current research interests in theoretical cosmology include constructing dark energy models and understanding their cosmological implications; constructing modified gravity models; the construction and determination of the properties of various field theory solitons (Skyrmions, domain walls, cosmic strings, kinky and cosmic vortons). These tasks are undertaken using analytical techniques and numerical simulations. We have access to various supercomputers: COMA at JBCA and COSMOS/UNIVERSE at DAMTP, Cambridge University.

More information and publications are below.

- Constraining dark energy properties, developing the elastic dark energy model (more on the EDE model below, and our publications on domain walls)
*Publications*:*"Constraints on the anisotropy of dark energy"*(2009),*"Constraints on the solid dark universe model"*(2005).

**Modified gravity**

- Constructing and understanding
*f(R)*gravity models. *Publications*:*"Aspects of cosmological expansion in F(R) gravity models"*(2008),*"Do consistent F(R) models mimic General Relativity plus Lambda?"*(2007),*"Curing singularities in cosmological evolution of F(R) gravity"*(2009)

*Topological defects & field theory*

- Domain walls -- these are line defects in 2D. Their evolution in random scenarios and their stability properties are been studied, both numerically and analytically. Investigations have been performed in a variety of different models (scalar, vector and complex fields; Goldstone model, cubic anisotropy model, Carter's pentavac model).
*Publications*:*"Charge, junctions and the scaling dynamics of domain wall networks"*(2010),*"Scaling Dynamics of Domain Walls in the Cubic Anisotropy Model"*(2006)

- Cosmic strings -- using strings to constrain inflationary models, and to constrain the string tension
*Publications*:*"Constraints on Brane Inflation and Cosmic Strings"*(2007),*"Updated constraints on the cosmic string tension"*(2010)

- Kinky vortons -- these are domain walls with a superconducting symmetry current. Constructed from a modified version of Witten's U(1) x U(1) theory. Exact analytical solutions have been found, their stability investigated, and their formation in physically realistic scenarios has been established. Wall networks formed from kinky vortons have been shown to frustrate, meaning that they are candidates for an elastic dark energy model.
*Publications*:*"Kinky Vortons"*(2008),*"Stability and the equation of state for kinky vortons"*(2009),*"Formation and evolution of kinky vortons"*(2009)

- Cosmic vortons -- These are closed loops of cosmic strings with a superconducting charge living on the loop. Their construction and stability in a global field theory has been established for the first time, with ongoing work into their construction in a gauge field theory.
*Publications*:*"Vorton construction and dynamics"*(2008)

- Skyrmions -- rotation