Scalar field dark energy and Cosmic Microwave Background

A dynamical scalar field represents the simplest generalization of a pure Cosmological Constant as a candidate to explain the recent evidence in favour of the accelerated cosmic expansion. We review the dynamical properties of such a component, and argue that, even if the background expectation value of this field is fixed and the equation of state is the same as a Cosmological Constant, scalar field fluctuations can still be used to distinguish the two components. We compare predicted spectra of Cosmic Microvave Background (CMB) anisotropies in tracking scalar field cosmologies with the present CMB data, in order to get constraints on the amount and equation of state of dark energy. High precision experiments like SNAP, {\sc Planck} and {\sc SNfactory}, together with the data on Large Scale Structure, are needed to probe this issue with the necessary accuracy. Here we show the intriguing result that, with a strong prior on the value of the Hubble constant today, the assumption of a flat universe, and consistency relations between amplitude and spectral index of primordial gravitational waves, the present CMB data at $1\sigma$ give indication of a dark energy equation of state larger than -1, while the ordinary Cosmological Constant is recovered at $2\sigma$.Comment: 4 pages including 2 figures, Dark Matter 2002 proceedings, Nucl.Phys.B in pres

Assessment, technology and democratic education in the age of data

This paper contends that powerful techniques to manipulate data, enabled by technological and economic developments, can be easily co-opted to serve the restrictive frameworks of hyper-controlling, managerial accountability that characterise current cultures of summative assessment in education. In response to these challenges, research is urgently needed to increase our understanding of the impact that assessments have on individuals and society. The paper concludes that social research ought to contribute to the identification of responses – educational, technological and political – that can minimise inequalities and potential abuses through the encouragement of data literacy across society

Implications for quintessence models from MAXIMA-1 and BOOMERANG-98

Prompted by the recent MAXIMA-1 and BOOMERANG-98 measurements of the cosmic microwave background (CMB) anisotropy power spectrum, and motivated by the results from the observation of high-redshift Type Ia supernovae, we investigate CMB anisotropies in quintessence models in order to characterize the nature of the dark energy today. We perform a Bayesian likelihood analysis, using the MAXIMA-1 and BOOMERANG-98 published bandpowers, in combination with COBE/DMR, to explore the space of quintessence parameters: the quintessence energy density \Omega_\phi and equation of state w_\phi. We restrict our analysis to flat, scale-invariant, inflationary adiabatic models. We find that this simple class of inflationary models, with a quintessence component \Omega_\phi < ~0.7, -1 < = w_\phi < ~-0.5, is in good agreement with the data. Within the assumptions of our analysis, pure quintessence models seem to be slightly favored, although the simple cosmological constant scenario is consistent with the data.Comment: 4 pages, 3 figures. Reflects version accepted for publication by ApJ Letter

What's Behind Acoustic Peaks in the Cosmic Microwave Background Anisotropies

We give a brief review of the physics of acoustic oscillations in Cosmic Microwave Background (CMB) anisotropies. As an example of the impact of their detection in cosmology, we show how the present data on CMB angular power spectrum on sub-degree scales can be used to constrain dark energy cosmological models.Comment: 6 pages, proceedings to the TAUP2001 conference, LNGS, Italy, Sept. 200

Design of a Highly Portable Data Logging Embedded System for Naturalistic Motorcycle Study

According to Motorcycle Industrial Council (MIC), in USA the number of owned motorcycle increased during last few years and most likely will keep increasing. However, the number of the deadly crash accidents associated with motorcycles is on the rise. Although MIC doesn\u27t explain why the accident rate has increased, the unprotected motorcyclist gear can be one of the reasons. The most recent National Highway Traffic Safety Administration (NHTSA) annual report stated that its data analyses are based on their experiences and the best judgment is not based on solid scientific experiment [3]. Thus, building a framework for the data acquisition about the motorcyclist environment is a first step towards decreasing motorcyclist crashes. There are a few naturalistic motorcycle studies reported in the literature. The naturalistic motorcycle study also identifies the behaviors and environmental crash hazards. The primary objective of this thesis work is to design a highly portable data logging embedded system for naturalistic motorcycle study with capability of collecting many types of data such as images, speed, acceleration, time, location, distance approximation, etc. This thesis work is the first phase (of three phases) of a naturalistic motorcycle study project. The second phase is to optimize system area, form factor, and power consumption. The third phase will be concerned with aggressive low power design and energy harvesting. The proposed embedded system design is based on an Arduino microcontroller. A whole suite of Arduino based prototype boards, sensor boards, support software, and user forum is available. The system is high portable with capability to store up to eight (8) hours of text/image data during a one month study period. We have successfully designed and implemented the system and performed three trial runs. The data acquired has been validated and found to be accurate

Probing dark energy with the CMB: projected constraints from WMAP and Planck

We investigate the accuracy attainable by forthcoming space-based observations of the cosmic microwave background (CMB) temperature and polarization anisotropy in constraining the dark energy density parameter \Oq and equation of state \wq=p_{\rm Q}/\rho_{\rm Q}. Despite degeneracies among parameters, it is possible for high precision observations such as those from WMAP and Planck to provide interesting information on the nature of the dark energy. Furthermore, we show that imposing a flat universe constraint makes it possible to obtain tight limits in the space of dark energy parameters even from the CMB alone.Comment: 4 pages, 3 figures. Matches version accepted by ApJL. Figures may also be downloaded at http://www.sissa.it/~bacci/de

A Geant4 simulation code for simulating optical photons in SPECT scintillation detectors

Geant4 is an object oriented toolkit created for the simulation of High-Energy Physics detectors. Geant4 allows an accurate modeling of radiation sources and detector devices, with easy configuration and friendly interface and at the same time with great accuracy in the simulation of physical processes. While most Monte Carlo codes do not allow the simulation of the transport and boundary characteristics for optical photons transport generated by scintillating crystal, Geant4 allows the simulation of the optical photons. In this paper we present an application of the Geant4 program for simulating optical photons in SPECT cameras. We aim to study the light transport within scintillators, photomultiplier tubes and coupling devices. To this end, we simulated a detector based on a scintillator, coupled to a photomultiplier tube through a glass window. We compared simulated results with experimental data and theoretical models, in order to verify the good matching with our simulations. We simulated a pencil beam of 140 keV photons impinging the crystal at different locations. For each condition, we calculated the value of the Pulse Height Centroid and the spread of the charge distribution, as read out by the anode array of the photomultiplier. Finally, the spatial and the energy resolutions of the camera have been estimated by simulated data. In all cases, we found that simulations agree very well with experimental data

Neither predator nor prey:What trafficking discourses miss about masculinities, mobility and work

Within trafficking discourses, men appear as predatory and exploitative, while boys appear as victims. This flattens the complexities of social life and obscures the ways that constructs of masculinity frame the trajectories of labour migrants and their brokers. This article challenges those discourses, drawing on research with two groups of labour migrants characterized as ‘victims of trafficking’, as well as with ‘traffickers’ who help them to move and work. The first are adolescents moving from Benin to the gravel quarries of Abeokuta, Nigeria. The second are adults from across West Africa who have made the illegal journey to Italy, where they live in ‘ghettos’ and work as gang labourers on harvests. In each case, migrants and their brokers come from the same or similar communities; (shared) ideals of masculinity structure their mobility and labour. Gendered transitions towards adulthood, the pressure to attain riches and status and a duty of responsibility to those younger and less successful are important. A focus on their masculinities takes us beyond ‘victim-perpetrator’ dyads.</p