Smooth geometries with four charges in four dimensions

A class of axially symmetric, rotating four-dimensional geometries carrying D1, D5, KK monopole and momentum charges is constructed. The geometries are found to be free of horizons and singulaties, and are candidates to be the gravity duals of microstates of the (0,4) CFT. These geometries are constructed by performing singularity analysis on a suitably chosen class of solutions of six-dimensional minimal supergravity written over a Gibbons-Hawking base metric. The properties of the solutions raise some interesting questions regarding the CFT.Comment: 1+32 pages, LaTeX, v2: references added, typographical errors correcte

Anisotropic flow

Recent experimental results on directed and elliptic flow, theoretical developments, and new techniques for anisotropic flow analysis are reviewed.Comment: 10 pages, review talk at Quark Matter 2002 conference, Nantes, France, July 2002 Corrected typographical errors in the reference section. No other change

Quantifying tensions in cosmological parameters: Interpreting the DES evidence ratio

We provide a new interpretation for the Bayes factor combination used in the Dark Energy Survey (DES) first year analysis to quantify the tension between the DES and Planck datasets. The ratio quantifies a Bayesian confidence in our ability to combine the datasets. This interpretation is prior-dependent, with wider prior widths boosting the confidence. We therefore propose that if there are any reasonable priors which reduce the confidence to below unity, then we cannot assert that the datasets are compatible. Computing the evidence ratios for the DES first year analysis and Planck, given that narrower priors drop the confidence to below unity, we conclude that DES and Planck are, in a Bayesian sense, incompatible under LCDM. Additionally we compute ratios which confirm the consensus that measurements of the acoustic scale by the Baryon Oscillation Spectroscopic Survey (SDSS) are compatible with Planck, whilst direct measurements of the acceleration rate of the Universe by the SHOES collaboration are not. We propose a modification to the Bayes ratio which removes the prior dependency using Kullback-Leibler divergences, and using this statistical test find Planck in strong tension with SHOES, in moderate tension with DES, and in no tension with SDSS. We propose this statistic as the optimal way to compare datasets, ahead of the next DES data releases, as well as future surveys. Finally, as an element of these calculations, we introduce in a cosmological setting the Bayesian model dimensionality, which is a parameterisation-independent measure of the number of parameters that a given dataset constrains.Comment: 16 pages, 9 figures. v2 & v3: updates post peer-review. v4: typographical correction to the reported errors in the log S column of Table II. v5: typographical correction to equation 2

Testing General Relativity with Current Cosmological Data

Deviations from general relativity, such as could be responsible for the cosmic acceleration, would influence the growth of large scale structure and the deflection of light by that structure. We clarify the relations between several different model independent approaches to deviations from general relativity appearing in the literature, devising a translation table. We examine current constraints on such deviations, using weak gravitational lensing data of the CFHTLS and COSMOS surveys, cosmic microwave background radiation data of WMAP5, and supernova distance data of Union2. Markov Chain Monte Carlo likelihood analysis of the parameters over various redshift ranges yields consistency with general relativity at the 95% confidence level.Comment: 11 pages; 7 figures; typographical errors corrected; this is the published versio

On the non-vanishing of the Collins mechanism for single spin asymmetries

The Collins mechanism provides a non-perturbative explanation for the large single spin asymmetries found in hard semi-inclusive reactions involving a transversely polarized nucleon. However, there are seemingly convincing reasons to suspect that the mechanism vanishes, and indeed it does vanish in the naive parton model where a quark is regarded as an essentially 'free' particle. We give an intuitive analysis which highlights the difference between the naive picture and the realistic one, and shows how the Collins mechanism arises when the quark is described as an off-shell particle by a field in interaction. A typographical error is corrected in this version.Comment: 15 pages, 2 figure