Decaying Dark Energy in Higher-Dimensional Gravity

We use data from observational cosmology to put constraints on higher-dimensional extensions of general relativity in which the effective four-dimensional dark-energy density (or cosmological "constant") decays with time. In particular we study the implications of this decaying dark energy for the age of the universe, large-scale structure formation, big-bang nucleosynthesis and the magnitude-redshift relation for Type Ia supernovae. Two of these tests (age and the magnitude-redshift relation) place modest lower limits on the free parameter of the theory, a cosmological length scale L akin to the de Sitter radius. These limits will improve if experimental uncertainties on supernova magnitudes can be reduced around z=1.Comment: 11 pages, 5 figures, submitted to A&

The Second Law and Rivalrous Digital Information (Or Maxwell's Demon in an Information Age)

Over thirty years ago Nicholas Georgescu-Roegen, in an extraordinary book The Entropy Law and the Economic Process opened up a whole new branch of environmental economics, exploring the impact of a fundamental, though not widely known, law of nature, the second law of thermodynamics, on the economic process. The 2nd law of thermodynamics basically says that when energy gets transformed some of it always gets wasted. No matter how efficient we make any machine it will always waste energy to some degree. This has implications for the knowledge society. There is a widespread belief that once information is digitised it can be copied and distributed at zero marginal cost but digital information fundamentally depends on access to a source of energy. And it turns out that large data centres and servers use up a lot of energy. The big technology companies' energy bills can run into hundreds of millions of dollars. In a world facing an energy crisis that means digital information is a little more rivalrous than we originally thought..

Realising Value from Big Data Technology Adoption: Understanding the Role of Organisational Capabilities in the Affordance Actualization Process

The adoption of big data technologies presents organisations with many value creation opportunities that can transform and improve their business. Much of the research today focuses on big data value creation (what value big data technologies offer), whereas limited research focuses on big data value realisation (how big data value is realized). We aim to fill this research gap by addressing the following research question: how do organisations effectively realize value from the adoption of a new big data technology? We do so by adopting an affordance theory lens and empirically examine the adoption of smart meters (a big data technology) in the UK energy sector. We introduce the concept of actualization enablers, and our findings provide empirically grounded insights into the role of organisational capabilities and actualization enablers in the big data value realization process (affordance actualization). Furthermore, our findings provide important and relevant theoretical and managerial implications

Revisiting the Constraint on the Helium Abundance from CMB

We revisit the constraint on the primordial helium mass fraction Yp from observations of cosmic microwave background (CMB) alone. By minimizing chi square of recent CMB experiments over 6 other cosmological parameters, we obtained rather weak constraints as 0.17 < Yp < 0.52 at 1 sigma C.L. for a particular data set. We also study the future constraint on cosmological parameters when we take account of the prediction of the standard big bang nucleosynthesis (BBN) theory as a prior on the helium mass fraction where Yp can be fixed for a given energy density of baryon. We discuss the implications of the prediction of the standard BBN on the analysis of CMB.Comment: 15 pages, 5 figures, published versio

THE 2H(α, γ)6LI REACTION AT LUNA AND BIG BANG NUCLEOSYNTHETIS

The 2H(α, γ)6Li reaction is the leading process for the production of 6Li in standard Big Bang Nucleosynthesis. Recent observations of lithium abundance in metal-poor halo stars suggest that there might be a 6Li plateau, similar to the well-known Spite plateau of 7Li. This calls for a re-investigation of the standard production channel for 6Li. As the 2H(α, γ)6Li cross section drops steeply at low energy, it has never before been studied directly at Big Bang energies. For the first time the reaction has been studied directly at Big Bang energies at the LUNA accelerator. The preliminary data and their implications for Big Bang nucleosynthesis and the purported 6Li problem will be shown

The Cosmic Infrared Background: Measurements and Implications

The cosmic infrared background records much of the radiant energy released by processes of structure formation that have occurred since the decoupling of matter and radiation following the Big Bang. In the past few years, data from the Cosmic Background Explorer mission provided the first measurements of this background, with additional constraints coming from studies of the attenuation of TeV gamma-rays. At the same time there has been rapid progress in resolving a significant fraction of this background with the deep galaxy counts at infrared wavelengths from the Infrared Space Observatory instruments and at submillimeter wavelengths from the Submillimeter Common User Bolometer Array instrument. This article reviews the measurements of the infrared background and sources contributing to it, and discusses the implications for past and present cosmic processes.Comment: 61 pages, incl. 9 figures, to be published in Annual Reviews of Astronomy and Astrophysics, 2001, Vol. 3

THE 2H(α, γ)6LI REACTION AT LUNA AND BIG BANG NUCLEOSYNTHETIS

The 2H(α, γ)6Li reaction is the leading process for the production of 6Li in standard Big Bang Nucleosynthesis. Recent observations of lithium abundance in metal-poor halo stars suggest that there might be a 6Li plateau, similar to the well-known Spite plateau of 7Li. This calls for a re-investigation of the standard production channel for 6Li. As the 2H(α, γ)6Li cross section drops steeply at low energy, it has never before been studied directly at Big Bang energies. For the first time the reaction has been studied directly at Big Bang energies at the LUNA accelerator. The preliminary data and their implications for Big Bang nucleosynthesis and the purported 6Li problem will be shown