On Probability and Cosmology: Inference Beyond Data?

Modern scientific cosmology pushes the boundaries of knowledge and the knowable. This is prompting questions on the nature of scientific knowledge. A central issue is what defines a 'good' model. When addressing global properties of the Universe or its initial state this becomes a particularly pressing issue. How to assess the probability of the Universe as a whole is empirically ambiguous, since we can examine only part of a single realisation of the system under investigation: at some point, data will run out. We review the basics of applying Bayesian statistical explanation to the Universe as a whole. We argue that a conventional Bayesian approach to model inference generally fails in such circumstances, and cannot resolve, e.g., the so-called 'measure problem' in inflationary cosmology. Implicit and non-empirical valuations inevitably enter model assessment in these cases. This undermines the possibility to perform Bayesian model comparison. One must therefore either stay silent, or pursue a more general form of systematic and rational model assessment. We outline a generalised axiological Bayesian model inference framework, based on mathematical lattices. This extends inference based on empirical data (evidence) to additionally consider the properties of model structure (elegance) and model possibility space (beneficence). We propose this as a natural and theoretically well-motivated framework for introducing an explicit, rational approach to theoretical model prejudice and inference beyond data

The economic impact of climate change in Namibia. How climate change will affect the contribution of Namibia’s natural resources to its economy

The IPCC recognises Africa as a whole to be “one of the most vulnerable continents to climate variability and change because of multiple stresses and low adaptive capacity. Climate change is likely to exacerbate the dry conditions already experienced in southern Africa. And when rainfall does come, it is likely to be more intense, leading to erosion and flood damage. This will affect the poor most, with resulting constraints on employment opportunities and declining wages. But at present these predictions gain little policy traction in southern African countries. The multilateral climate change process is complicated and slow, and policymakers often see serious action on climate change as a domestic ‘vote loser’. One way to raise climate change concerns further up the policymakers’ agenda is to try to put an economic value on the environmental impacts of climate change. Figures that provide a clear message about the expected impact of climate change will be powerful motivators for policymakers in developing countries to start considering climate change as a part of their national development policies. This study is a first attempt to provide some economic indicators of how climate change will affect Namibia – one of the most vulnerable countries in sub-Saharan Africa. Focusing on natural resources, the study aims to assess the likely economic values of some of the most important environmental and socio-economic impacts of climate change in Namibia, and also to capture how some of the most important impacts might affect the overall structure of the economy.Climate change, Economics, Namibia, Environmental Economics and Policy,

A Nearly Model-Independent Characterization of Dark Energy Properties as a Function of Redshift

Understanding the acceleration of the universe and its cause is one of the key problems in physics and cosmology today, and is best studied using a variety of mutually complementary approaches. Daly and Djorgovski (2003, 2004) proposed a model independent approach to determine the expansion and acceleration history of the universe and a number of important physical parameters of the dark energy as functions of redshift directly from the data. Here, we apply the method to explicitly determine the first and second derivatives of the coordinate distance with respect to redshift and combine them to solve for the acceleration of the universe and the kinetic and potential energy density of the dark energy as functions of redshift. A data set of 228 supernova and 20 radio galaxy measurements with redshifts from zero to 1.79 is used for this study. The values we obtain are shown to be consistent with the values expected in a standard Lambda Cold Dark Matter model.Comment: 5 pages, 8 figure

Peak systolic velocity using color-coded tissue Doppler imaging, a strong and independent predictor of outcome in acute coronary syndrome patients

BACKGROUND: Traditional echocardiographic methods like left ventricular ejection fraction(EF) and wall motion scoring (WMS) and new methods like speckle tracking (ST) based 2D strain carry important prognostic information in acute coronary syndrome (ACS) patients. Parameters from tissue Doppler imaging (TDI), with its high time resolution, may further increase the prognostic value. Peak systolic velocity (PSV) of the basal segments of the left ventricle from TDI is a robust and user independent parameter. The aim was to investigate the prognostic value of PSV compared to EF, WMS, 2D strain and E/e'. METHODS: Echocardiographic images were collected and post processed in 227 ACS patients. Additional clinical data was prospectively gathered and patients were followed for 3-5 years regarding the combined endpoint of death or re-admission due to ACS or heart failure. RESULTS: The combined endpoint occurred in 85 (37%) patients. Those with an event had lower median PSV than those without (4,4 cm/s) vs. (5,3 cm/s), (p<0.001). In a ROC analysis, the AUC was larger for PSV (0.75) than for EF (0.68), WMS (0.63), 2D strain (0.67) and E/e'(0.70). The combined endpoint increased with decreasing PSV. When adjusting for differences in baseline characteristics in a COX-regression model, PSV remained independently associated with outcome where the others did not. PSV was also less sensitive to image quality with fewer values missing or unacceptable for analysis. CONCLUSION: Peak systolic velocity (PSV) is a robust measurement that seems to have a strong and independent association with outcome compared to traditional echocardiographic measurements in ACS patients

A Model of Dark Energy and Dark Matter

A dynamical model for the dark energy is presented in which the ``quintessence'' field is the axion, $a_Z$, of a spontaneously broken global $U(1)_{A}^{(Z)}$ symmetry whose potential is induced by the instantons of a new gauge group $SU(2)_Z$. The $SU(2)_Z$ coupling becomes large at a scale $\Lambda_Z \sim 10^{-3} eV$ starting from an initial value $M$ at high energy which is of the order of the Standard Model (SM) couplings at the same scale $M$. A perspective on a possible unification of $SU(2)_Z$ with the SM will be briefly discussed. We present a scenario in which $a_Z$ is trapped in a false vacuum characterized by an energy density $\sim (10^{-3} eV)^4$. The lifetime of this false vacuum is estimated to be extremely large. Other estimates relevant to the ``coincidence issue'' include the ages of the universe when the $a_Z$ potential became effective, when the acceleration ``began'' and when the energy density of the false vacuum became comparable to that of (baryonic and non-baryonic) matter. Other cosmological consequences include a possible candidate for the weakly interacting (WIMP) Cold Dark Matter as well as a scenario for leptogenesis. A brief discussion on possible laboratory detections of some of the particles contained in the model will also be presented.Comment: 24 double-column pages, 14 figures; Added references; Corrected Typo

The XMM Cluster Survey: Evidence for energy injection at high redshift from evolution of the X-ray luminosity-temperature relation

We measure the evolution of the X-ray luminosity-temperature (L_X-T) relation since z~1.5 using a sample of 211 serendipitously detected galaxy clusters with spectroscopic redshifts drawn from the XMM Cluster Survey first data release (XCS-DR1). This is the first study spanning this redshift range using a single, large, homogeneous cluster sample. Using an orthogonal regression technique, we find no evidence for evolution in the slope or intrinsic scatter of the relation since z~1.5, finding both to be consistent with previous measurements at z~0.1. However, the normalisation is seen to evolve negatively with respect to the self-similar expectation: we find E(z)^{-1} L_X = 10^{44.67 +/- 0.09} (T/5)^{3.04 +/- 0.16} (1+z)^{-1.5 +/- 0.5}, which is within 2 sigma of the zero evolution case. We see milder, but still negative, evolution with respect to self-similar when using a bisector regression technique. We compare our results to numerical simulations, where we fit simulated cluster samples using the same methods used on the XCS data. Our data favour models in which the majority of the excess entropy required to explain the slope of the L_X-T relation is injected at high redshift. Simulations in which AGN feedback is implemented using prescriptions from current semi-analytic galaxy formation models predict positive evolution of the normalisation, and differ from our data at more than 5 sigma. This suggests that more efficient feedback at high redshift may be needed in these models.Comment: Accepted for publication in MNRAS; 12 pages, 6 figures; added references to match published versio

Synergy between the Large Synoptic Survey Telescope and the Square Kilometre Array

We provide an overview of the science benefits of combining information from the Square Kilometre Array (SKA) and the Large Synoptic Survey Telescope (LSST). We first summarise the capabilities and timeline of the LSST and overview its science goals. We then discuss the science questions in common between the two projects, and how they can be best addressed by combining the data from both telescopes. We describe how weak gravitational lensing and galaxy clustering studies with LSST and SKA can provide improved constraints on the causes of the cosmological acceleration. We summarise the benefits to galaxy evolution studies of combining deep optical multi-band imaging with radio observations. Finally, we discuss the excellent match between one of the most unique features of the LSST, its temporal cadence in the optical waveband, and the time resolution of the SKA

Building Dynamic Capabilities in Web Startups: An Empirical Study of Norwegian Web Startups

Purpose: This thesis explores how web startups operating in a crowded, fast-moving and highly competitive marketplace can gain competitive advantage through building dynamic capabilities and what these capabilities consist of. Design/methodology/approach: Firstly, insight was obtained through reviewing key themes within classic resource based theory and entrepreneurship theory. Newer empirical research on entrepreneurial success factors, as well as popular science and advice given by expert web entrepreneurs was then reviewed. Combining this, a framework of dynamic capabilities in web startups was synthesized. Qualitative empirical data was collected from interviewing founders and key people in four active Norwegian web startups. From the empirical findings in these interviews, the synthesized framework was iterated to account for important factors that were found to apply specifically for web startups. Lastly, a set of propositions was derived from the combination of the synthesized framework and the empirical findings.Findings: It was found that many of the contributions both from established contributors, newer contributors and popular science build on the same principles, albeit with a different degree of practical versus theoretical approach. By bridging different literature and approaches, this thesis contributes to clarify many of the invented terms found in the literature and operationalize them in practice for what they actually mean for web startups, and much of this is probably applicable for startups in general. From the empirical data it was found that web startups have important differences from other types of companies and startups. This was e.g. planning on very short time spans (most planned on a weekly basis or shorter), the ability of employees to do work outside of their expertise areas and the ability to learn or acquire new skills fast according to continuously changing market needs.Research limitations/implications: The propositions have both empirical and theoretical backing, but the empirical backing is limited to four cases, all in Norway. It would be useful to test the propositions on larger sample sizes, and preferably also to include cases from other contexts and cultures than Norway.Practical implications: Entrepreneurs in web startups should focus on building a great team and company culture. Policy makers should consider introducing programmin

The phenomenological approach to modeling the dark energy

In this mini-review we discuss first why we should investigate cosmological models beyond LCDM. We then show how to describe dark energy or modified gravity models in a fluid language with the help of one background and two perturbation quantities. We review a range of dark energy models and study how they fit into the phenomenological framework, including generalizations like phantom crossing, sound speeds different from c and non-zero anisotropic stress, and how these effective quantities are linked to the underlying physical models. We also discuss the limits of what can be measured with cosmological data, and some challenges for the framework.Comment: 44 pages, 5 figures; accepted review article to appear in a special volume of the "Comptes Rendus de l'Academie des Sciences" about Dark Energy and Dark Matte