11 research outputs found
A measure of the impact of future dark energy experiments based on discriminating power among quintessence models
We evaluate the ability of future data sets to discriminate among different
quintessence dark energy models. This approach gives an alternative measure for
assessing the impact of future experiments, as compared with the large body of
literature that compares experiments in abstract parameter spaces and more
recent work that evaluates the constraining power of experiments on individual
parameter spaces of specific quintessence models. We use the Dark Energy Task
Force (DETF) models of future data sets, and compare the discriminative power
of experiments designated by the DETF as Stages 2, 3, and 4. Our work reveals a
minimal increase in discriminating power when comparing Stage 3 to Stage 2, but
a very striking increase in discriminating power when going to Stage 4. We also
see evidence that even modest improvements over DETF Stage 4 could result in
even more dramatic discriminating power among quintessence dark energy models.
We develop and demonstrate the technique of using the independently measured
modes of the equation of state as a common parameter space in which to compare
the different quintessence models, and we argue that this technique is a
powerful one. We use the PNGB, Exponential, Albrecht-Skordis, and Inverse
Tracker (or Inverse Power Law) quintessence models for this work. One of our
main results is that the goal of discriminating among these models sets a
concrete measure on the capabilities of future dark energy experiments.
Experiments have to be somewhat better than DETF Stage 4 simulated experiments
to fully meet this goal.Comment: 11 pages,10 figures, 4 labels V2: Figure resolution improved, typos
corrected V3: conclusions supplemented, submitted to PRD V4: Technical error
corrected (see footnote 26). No change to our main points and conclusion
Exploring Parameter Constraints on Quintessential Dark Energy: The Exponential Model
We present an analysis of a scalar field model of dark energy with an
exponential potential using the Dark Energy Task Force (DETF) simulated data
models. Using Markov Chain Monte Carlo sampling techniques we examine the
ability of each simulated data set to constrain the parameter space of the
exponential potential for data sets based on a cosmological constant and a
specific exponential scalar field model. We compare our results with the
constraining power calculated by the DETF using their ``''
parametrization of the dark energy. We find that respective increases in
constraining power from one stage to the next produced by our analysis give
results consistent with DETF results. To further investigate the potential
impact of future experiments, we also generate simulated data for an
exponential model background cosmology which can not be distinguished from a
cosmological constant at DETF ``Stage 2'', and show that for this cosmology
good DETF Stage 4 data would exclude a cosmological constant by better than
3.Comment: 11 pages including 10 figure
Exploring Parameter Constraints on Quintessential Dark Energy: the Albrecht-Skordis model
We consider the effect of future dark energy experiments on
``Albrecht-Skordis'' (AS) models of scalar field dark energy using the
Monte-Carlo Markov chain method. We deal with the issues of parameterization of
these models, and have included spatial curvature as a parameter, finding it to
be important. We use the Dark Energy Task Force (DETF) simulated data to
represent future experiments and report our results in the form of likelihood
contours in the chosen parameter space. Simulated data is produced for cases
where the background cosmology has a cosmological constant, as well as cases
where the dark energy is provided by the AS model. The latter helps us
demonstrate the power of DETF Stage 4 data in the context of this specific
model. Though the AS model can produce equations of state functions very
different from what is possible with the parametrization used by the
DETF, our results are consistent with those reported by the DETF.Comment: 7 pages, including 9 figure
Exploring Parameter Constraints on Quintessential Dark Energy: the Inverse Power Law Model
We report on the results of a Markov Chain Monte Carlo (MCMC) analysis of an
inverse power law (IPL) quintessence model using the Dark Energy Task Force
(DETF) simulated data sets as a representation of future dark energy
experiments. We generate simulated data sets for a Lambda-CDM background
cosmology as well as a case where the dark energy is provided by a specific IPL
fiducial model and present our results in the form of likelihood contours
generated by these two background cosmologies. We find that the relative
constraining power of the various DETF data sets on the IPL model parameters is
broadly equivalent to the DETF results for the w_{0}-w_{a} parameterization of
dark energy. Finally, we gauge the power of DETF "Stage 4" data by
demonstrating a specific IPL model which, if realized in the universe, would
allow Stage 4 data to exclude a cosmological constant at better than the
3-sigma level.Comment: 15 pages, including 13 figure
Characterizing and Propagating Modeling Uncertainties in Photometrically-Derived Redshift Distributions
The uncertainty in the redshift distributions of galaxies has a significant
potential impact on the cosmological parameter values inferred from multi-band
imaging surveys. The accuracy of the photometric redshifts measured in these
surveys depends not only on the quality of the flux data, but also on a number
of modeling assumptions that enter into both the training set and SED fitting
methods of photometric redshift estimation. In this work we focus on the
latter, considering two types of modeling uncertainties: uncertainties in the
SED template set and uncertainties in the magnitude and type priors used in a
Bayesian photometric redshift estimation method. We find that SED template
selection effects dominate over magnitude prior errors. We introduce a method
for parameterizing the resulting ignorance of the redshift distributions, and
for propagating these uncertainties to uncertainties in cosmological
parameters.Comment: 13 pages, 12 figures, version published in Ap
TRAZADOR DE CURVAS I-V DE CÓDIGO ABIERTO PARA MONITOREO DE RENDIMIENTO DE PANELES FOTOVOLTAICOS EN BOLIVIA
Se presenta el desarrollo de un trazador de curva I-V de código abierto para el monitoreo de potencia producida por un panel solar en Bolivia, y los resultados obtenidos por éste. El dispositivo está elaborado con componentes de bajo costo y es posible adaptar su diseño para monitorear paneles de diferentes potencias. El dispositivo toma muestras de corriente y voltaje para un elemento fotovoltaico utilizando una carga variable para obtener los diferentes puntos que conforman una curva corriente-voltaje. El dispositivo también tiene un régimen de control, el cual desconecta y reconecta el panel de su carga en intervalos de tiempo fijos para la toma de datos, permitiendo el monitoreo del panel aun cuando está siendo  utilizado en un sistema de energÃa solar
INTERCAMBIO EDUCATIVO VIRTUAL: UNA CLASE VIRTUAL COMPARTIDA NORTE – SUD SOBRE DESARROLLO SOSTENIBLE
Las competencias globales son, cada vez más, habilidades importantes que se deben adquirir desde pregrado. Un intercambio internacional representa un reto y es inviable para muchos estudiantes, por tanto, existe la necesidad de desarrollar e implementar medios alternativos para introducir experiencias internacionales e interculturales en las aulas de pregrado. En este trabajo se presenta un programa basado en intercambios virtuales, en el que se creó una materia virtual de un semestre, entre la Universidad Privada Boliviana en Bolivia y la Universidad de Siena en los Estados Unidos de Norte América, sobre desarrollo sostenible. La clase proveyó una experiencia multidisciplinaria e intercultural relevante tanto para los estudiantes de las carreras de ciencias puras e ingenierÃa como para los de ciencias sociales, sin la necesidad de viajar. Además, el proceso de aprendizaje, basado en la investigación y en la resolución de problemas, se fortaleció a través de la incorporación del servicio social que se realizó en colaboración con una organización rural boliviana, Unidad Académica Campesina Carmen Pampa. Los resultados de este emprendimiento muestran que los cursos virtuales compartidos pueden proveer experiencias internacionales a estudiantes de pregrado
A Virtual Educational Exchange: A North–South Virtually Shared Class on Sustainable Development
Increasingly, international competence is considered an important skill to be acquired from an undergraduate education. Because international exchange presents a challenge to many students, there is a need to develop and implement alternative means for incorporating international and cross-cultural experiences into the undergraduate classroom. We report on the implementation of a semester-long, virtually shared course offering between a U.S. and a Bolivian university. As STEM (science, technology, engineering, and mathematics) majors tend to be under-represented in study-abroad programs, this class sought to provide a multidisciplinary experience that could be relevant to both hard and social science majors. Furthermore, the relevance and learning impact of this class was enhanced through the incorporation of a service-learning component in conjunction with a rural Bolivian partner organization. The results of this experience show that virtually shared classroom experiences can successfully facilitate international experiences for undergraduate students
DESARROLLO DE UN SISTEMA DE MONITOREO DE RADIACIÓN SOLAR BASADO EN UN ESPECTRÓMETRO DE AMPLIO ESPECTRO
La eficiencia cuántica de materiales fotovoltaicos depende de la longitud de onda de la radiación incidente, el espectro solar influye en la producción de energÃa producida por estos sistemas. En el presente trabajo, se diseñó y construyó un prototipo funcional de un sistema de medición de radiación solar (global y difusa) basado en un espectrómetro de amplio espectro para el monitoreo solar en Cochabamba, Bolivia, conjuntamente con un sistema similar instalado en Kingston, Ontario. Los datos obtenidos en dos regiones con caracterÃsticas geográficas muy distintas ayudarán en el estudio y optimización de materiales fotovoltaicos, para su implementación en diferentes partes del mundo, con caracterÃsticas particulares de radiación incidente. Los resultados obtenidos serán publicados para que otras regiones también se beneficien de sistemas fotovoltaicos con materiales optimizados según las caracterÃsticas geográficas.
Para la construcción mecánica del sistema, se utilizaron perfiles de aluminio de 60x30 mm. Esta estructura metálica sujeta a una fibra óptica de cuarzo lleva la radiación solar al espectrómetro Ocean Optics USB4000 (200-900 nm). La electrónica del sistema de control, está gobernada por un microcontrolador Arduino UNO, el cual se encarga de sincronizar el movimiento de dos motores PAP bipolares y la toma de datos en el espectrómetro que se activa con un trigger externo. La caracterÃstica principal del sistema es permitir la medición del espectro de los componentes global y difuso de la radiación solar en diferentes ángulos de incidencia. El sistema mecánico ajusta un extremo de una fibra óptica de 0 a 90 grados en dirección norte, cada nueve grados, midiendo la radiación global y mediante una banda mecánica que produce sombra sobre la fibra óptica, mide la radiación difusa. Las medidas son tomadas cada hora y el rango espectral abarcado es del UVA, VIS y parte del IR cercano. Se realizaron pruebas preliminares en dos ciudades de Bolivia y se demostró que la cantidad de radiación UVA es mayor en el El Alto (4062 msnm), la ciudad con mayor elevación, en comparación con Cochabamba que se encuentra a 2570 msnm