Hard thermal loops in the real-time formalism

We present a systematic discussion of Braaten and Pisarski's hard thermal loop (HTL) effective theory within the framework of the real-time (Schwinger-Keldysh) formalism. As is well known, the standard imaginary-time HTL amplitudes for hot gauge theory express the polarization of a medium made out of nonabelian charged point-particles; we show that the complete real-time HTL theory includes, in addition, a second set of amplitudes which account for Gaussian fluctuations in the charge distributions, but nothing else. We give a concise set of graphical rules which generate both set of functions, and discuss its relation to classical plasma physics.Comment: 14 pages, 6 figure

The Earth as an extrasolar planet: The vegetation spectral signature today and during the last Quaternary climatic extrema

The so-called Vegetation Red-Edge (VRE), a sharp increase in the reflectance around $700 nm$, is a characteristic of vegetation spectra, and can therefore be used as a biomarker if it can be detected in an unresolved extrasolar Earth-like planet integrated reflectance spectrum. Here we investigate the potential for detection of vegetation spectra during the last Quaternary climatic extrema, the Last Glacial Maximum (LGM) and the Holocene optimum, for which past climatic simulations have been made. By testing the VRE detectability during these extrema when Earth's climate and biomes maps were different from today, we are able to test the vegetation detectability on a terrestrial planet different from our modern Earth. Data from the Biome3.5 model have been associated to visible GOME spectra for each biome and cloud cover to derive Earth's integrated spectra for given Earth phases and observer positions. The VRE is then measured. Results show that the vegetation remains detectable during the last climatic extrema. Compared to current Earth, the Holocene optimum with a greener Sahara slightly increases the mean VRE on one hand, while on the other hand, the large ice cap over the northern Hemisphere during the LGM decreases vegetation detectability. We finally discuss the detectability of the VRE in the context of recently proposed space missions.Comment: 31-page manuscript, 12 figures, accepted for publication in Int. J. of Astrobiolog

Verification of Linear Optical Quantum Computing using Quantum Process Calculus

We explain the use of quantum process calculus to describe and analyse linear optical quantum computing (LOQC). The main idea is to define two processes, one modelling a linear optical system and the other expressing a specification, and prove that they are behaviourally equivalent. We extend the theory of behavioural equivalence in the process calculus Communicating Quantum Processes (CQP) to include multiple particles (namely photons) as information carriers, described by Fock states or number states. We summarise the theory in this paper, including the crucial result that equivalence is a congruence, meaning that it is preserved by embedding in any context. In previous work, we have used quantum process calculus to model LOQC but without verifying models against specifications. In this paper, for the first time, we are able to carry out verification. We illustrate this approach by describing and verifying two models of an LOQC CNOT gate.Comment: In Proceedings EXPRESS/SOS 2014, arXiv:1408.127

High momentum lepton pairs from jet-plasma interactions

We discuss the emission of high momentum lepton pairs (p_T>4 GeV) with low invariant masses (M << p_T) in central Au+Au collisions at RHIC (\sqrt{s_{NN}}=200 GeV). The spectra of dileptons produced through interactions of quark and antiquark jets with the quark-gluon plasma (QGP) have been calculated. Annihilation and Compton scattering processes, as well as processes benefitting from collinear enhancement, including Landau-Pomeranchuk-Migdal (LPM) effects, are calculated and convolved with a one dimensional hydrodynamic expansion. The jet-induced contributions are compared to thermal dilepton emission and Drell-Yan processes, and are found to dominate around p_T=4 GeV.Comment: Parallel talk given at QM2006, Shanghai November 2006. 4 pages, 3 figure

Supporting public availability and accessibility with Elvin: experiences and reflections.

We provide a retrospective account of how a generic event notification service called Elvin and a suite of simple client applications: CoffeeBiff, Tickertape and Tickerchat, came to be used within our organisation to support awareness and interaction. After overviewing Elvin and its clients, we outline various experiences from data collated across two studies where Elvin and its clients have been used to augment the workaday world to support interaction, to make digital actions visible, to make physical actions available beyond the location of action, and to support content and socially based information filtering. We suggest there are both functional and technical reasons for why Elvin works for enabling awareness and interaction. Functionally, it provides a way to produce, gather and redistribute information from everyday activities (via Elvin) and to give that information a perceptible form (via the various clients) that can be publicly available and accessible as a resource for awareness. The integration of lightweight chat facilities with these information sources enables awareness to easily flow into interaction, starting to re-connect bodies to actions, and starting to approximate the easy flow of interaction that happens when we are co-located. Technically, the conceptual simplicity of the Elvin notification, the wide availability of its APIs, and the generic functionality of its clients, especially Tickertape, have made the use of the service appealing to developers and users for a wide range of uses

The GICHD Regional Support Centre: An Approach to Regional Information Management

Ask most people in mine action what is meant by regional information management and they will talk to you about the consolidation of country-specific mine action information at centralized regional locations. They may talk about the need for data aggregation, the reluctance of programmes to provide data and the generally slow pace of the work. In almost all cases, they will mention data analysis and comparisons between the work completed in different programmes as key elements in regional systems. Most of the examples given will focus on efforts that fell short of expectations and failed to deliver on the promise of increased efficiency and improved resource allocation so often touted as reasons for regional or global data management. In short, for many people, regional information management is a concept that has seldom managed to maintain the constant flow of unconsolidated and standardized data required to achieve its real potential over the long term

It just doesn't ADD Up: ADHD/ADD, the Workplace and Discrimination

Standard workplace conditions that are commonly perceived as neutral and reasonable can discriminate against people who find conforming to them difficult or impossible because of innate differences in neuronal and cognitive functioning. We use the example of Attention Deficit/Hyperactivity Disorder to show that, for people with cognitive differences, it is necessary to seek legal protection from discrimination within a disability framework. This approach can be problematic because of the stigma that attaches to disability and because of the way that provisions of the Disability Discrimination Act 1992 (Cth) are interpreted. An alternative approach is to treat cognitive and behavioural attributes within a framework that recognises different abilities, rather than starting from a presumptive position of disability, in much the same way that gender or religious beliefs are treated

Neutral and Ionized Hydrides in Star-forming Regions -- Observations with Herschel/HIFI

The cosmic abundance of hydrides depends critically on high-energy UV, X-ray, and particle irradiation. Here we study hydrides in star-forming regions where irradiation by the young stellar object can be substantial, and density and temperature can be much enhanced over interstellar values. Lines of OH, CH, NH, SH and their ions OH+, CH+, NH+, SH+, H2O+, and H3O+ were observed in star-forming regions by the HIFI spectrometer onboard the Herschel Space Observatory. Molecular column densities are derived from observed ground-state lines, models, or rotational diagrams. We report here on two prototypical high-mass regions, AFGL 2591 and W3 IRS5, and compare them to chemical calculations making assumptions on the high-energy irradiation. A model assuming no ionizing protostellar emission is compared with (i) a model assuming strong protostellar X-ray emission and (ii) a two-dimensional (2D) model including emission in the far UV (FUV, 6 -- 13.6 eV) irradiating the outflow walls that separate the outflowing gas and infalling envelope material. We confirm that the effect of FUV in two dimensional models with enlarged irradiated surfaces is clearly noticeable. A molecule that is very sensitive to FUV irradiation is CH+, enhanced in abundance by more than 5 orders of magnitude. The HIFI observations of CH+ lines agree with the two-dimensional FUV model by Bruderer et al. which computes abundances, non-LTE excitation and line radiative transfer.{Ref 20} It is concluded that CH+ is a good FUV tracer in star-forming regions. The effect of potential X-ray irradiation is not excluded, but cannot be demonstrated by the present data.Comment: 8 pages, 4 figures, Journal of Physical Chemistry in pres