Three-loop HTL gluon thermodynamics at intermediate coupling

We calculate the thermodynamic functions of pure-glue QCD to three-loop order using the hard-thermal-loop perturbation theory (HTLpt) reorganization of finite temperature quantum field theory. We show that at three-loop order hard-thermal-loop perturbation theory is compatible with lattice results for the pressure, energy density, and entropy down to temperatures $T\simeq3\;T_c$. Our results suggest that HTLpt provides a systematic framework that can used to calculate static and dynamic quantities for temperatures relevant at LHC.Comment: 24 pages, 13 figs. 2nd version: improved discussion and fixing typos. Published in JHE

Measuring the Hidden Aspects of Solar Magnetism

2008 marks the 100th anniversary of the discovery of astrophysical magnetic fields, when George Ellery Hale recorded the Zeeman splitting of spectral lines in sunspots. With the introduction of Babcock's photoelectric magnetograph it soon became clear that the Sun's magnetic field outside sunspots is extremely structured. The field strengths that were measured were found to get larger when the spatial resolution was improved. It was therefore necessary to come up with methods to go beyond the spatial resolution limit and diagnose the intrinsic magnetic-field properties without dependence on the quality of the telescope used. The line-ratio technique that was developed in the early 1970s revealed a picture where most flux that we see in magnetograms originates in highly bundled, kG fields with a tiny volume filling factor. This led to interpretations in terms of discrete, strong-field magnetic flux tubes embedded in a rather field-free medium, and a whole industry of flux tube models at increasing levels of sophistication. This magnetic-field paradigm has now been shattered with the advent of high-precision imaging polarimeters that allow us to apply the so-called "Second Solar Spectrum" to diagnose aspects of solar magnetism that have been hidden to Zeeman diagnostics. It is found that the bulk of the photospheric volume is seething with intermediately strong, tangled fields. In the new paradigm the field behaves like a fractal with a high degree of self-similarity, spanning about 8 orders of magnitude in scale size, down to scales of order 10 m.Comment: To appear in "Magnetic Coupling between the Interior and the Atmosphere of the Sun", eds. S.S. Hasan and R.J. Rutten, Astrophysics and Space Science Proceedings, Springer-Verlag, Heidelberg, Berlin, 200

Three-loop HTL QCD thermodynamics

The hard-thermal-loop perturbation theory (HTLpt) framework is used to calculate the thermodynamic functions of a quark-gluon plasma to three-loop order. This is the highest order accessible by finite temperature perturbation theory applied to a non-Abelian gauge theory before the high-temperature infrared catastrophe. All ultraviolet divergences are eliminated by renormalization of the vacuum, the HTL mass parameters, and the strong coupling constant. After choosing a prescription for the mass parameters, the three-loop results for the pressure and trace anomaly are found to be in very good agreement with recent lattice data down to $T \sim 2-3\,T_c$, which are temperatures accessible by current and forthcoming heavy-ion collision experiments.Comment: 27 pages, 11 figures; corresponds with published version in JHE

Note on Moufang-Noether currents

The derivative Noether currents generated by continuous Moufang tranformations are constructed and their equal-time commutators are found. The corresponding charge algebra turns out to be a birepresentation of the tangent Mal'ltsev algebra of an analytic Moufang loop.Comment: LaTeX2e, 6 pages, no figures, presented on "The XVth International Colloquium on Integrable Systems and Quantum Symmetries, Prague, 15-17 June, 2006

Improving Monolithic Perovskite Silicon Tandem Solar Cells From an Optical Viewpoint

Perovskite silicon tandem solar cells are the most promising concept for a future photovoltaic technology. We report on recent progress from an optical viewpoint and disucss how we achieved more than 25 device efficienc

Tackling Ageing Continence through Theory, Tools & Technology

Originally presented at ‘Aging and Society: An Interdisciplinary Conference’, University of California, Berkeley (2011), this article was double-blind peer reviewed, receiving scores of 96% and 73%. It outlines the interdisciplinary research of the cross-Research-Council-funded New Dynamics of Ageing Tackling Ageing Continence through Theory Tools & Technology (TACT3) project (2008–12), which brought together designers, social scientists, bio-engineers, chemists and care-management services to understand the challenges faced by an ageing population in the management of continence. Bichard’s Work Package, ‘Challenging Environmental Barriers to Continence’, explored the need for public toilet provision as essential for quality of life, health and well-being. It developed a life-course methodology that considered ageing from birth through to advanced age (0–101 years), and involved inclusive design research with members of the public and providers of facilities to assess public expectations and provider limitations in service provision. As co-investigator on TACT3, this research built on Bichard’s previous work for the VivaCity2020 consortium (Bichard REF Output 2). Whereas the VivaCity2020 work focused on architectural barriers in toilet provision, the TACT3 project examined the problem in service provision, and how, through inclusive design research, service-design solutions might be explored and implemented. Bichard’s contribution to the TACT3 project produced The Great British Public Toilet Map (http://greatbritishpublictoiletmap.rca.ac.uk/), a public participation website that provides information and locations of public toilets, encouraging members of the public to contact relevant local authorities that have not released information in the format of Open Data. Secondary analysis of TACT3 data for references to issues of personal safety and community initiative in toilet provision was used for the ESRC-funded Robust Accessible Toilets (RATs) project (2011) and produced Publicly Accessible Toilets: An Inclusive Design Guide (2011). Related published conference papers include those in ‘Cumulus 2010’ (China) and ‘Include 2011’ (UK)