Aspects of universal extra dimensional models and their latticized versions

In this work some aspects of models with universal extra dimensions are studied. In particular, in the case of models with one universal extra dimension their phenomenology is investigated and used to extract bounds on the size of the extra dimension. In addition, the phenomenology of their latticized counterparts is also investigated. The running of the gauge coupling constants in models with an arbitrary number of universal extra dimensions is revisited. The possible reliable determination of the power corrections that appear is studied. Finally, a model with one non-universal extra dimension is presented to compare the results in these kind of scenarios with the universal ones.Comment: Ph.D. Thesis, 94 page

Lensing in the McVittie metric

We investigate the effect of the cosmological expansion on the bending of light due to an isolated point-like mass. We adopt McVittie metric as the model for the geometry of the lens. Assuming a constant Hubble factor we find an analytic expression involving the bending angle, which turns out to be unaffected by the cosmological expansion at the leading order.Comment: 4 pages, 3 figures. Mistakes corrected. Conclusions completely change

On the effect of the cosmological expansion on the gravitational lensing by a point mass

We analyze the effect of the cosmological expansion on the deflection of light caused by a point mass, adopting the McVittie metric as the geometrical description of a pointlike lens embedded in an expanding universe. In the case of a generic, non-constant Hubble parameter $H$ we derive and approximately solve the null geodesic equations, finding an expression for the bending angle $\delta$, which we expand in powers of the mass-to-closest approach distance ratio and of the impact parameter-to-lens distance ratio. It turns out that the leading order of the aforementioned expansion is the same as the one calculated for the Schawarzschild metric and that cosmological corrections contribute to $\delta$ only at sub-dominant orders. We explicitly calculate these cosmological corrections for the case of $H$ constant and find that they provide a correction of order $10^{-11}$ on the lens mass estimate.Comment: 10 pages, 7 figures (created with tikz

Legume Pick ‘n’ Mix

In Spring 2009, ORC set up a legume trial on an organic farm, Barrington Park in Gloucestershire, as part of a large research project called Legume LINK. One of its aims is to compare the performance of several legume and grass species for use in fertility building leys. ORC researchers Thomas Döring and Oliver Crowley report that the trial shows the advantage of mixing species grows over time

Gravitational potential evolution in Unified Dark Matter Scalar Field Cosmologies: an analytical approach

We investigate the time evolution of the gravitational potential Phi for a special class of non-adiabatic Unified Dark matter Models described by scalar field lagrangians. These models predict the same background evolution as in the LambdaCDM and possess a non-vanishing speed of sound. We provide a very accurate approximation of Phi, valid after the recombination epoch, in the form of a Bessel function of the first kind. This approximation may be useful for a future deeper analysis of Unified Dark Matter scalar field models.Comment: 5 pages, 6 figure