1,720,974 research outputs found
Probing the ΛCDM Universe and beyond with present and future 21cm Intensity Mapping surveys
Full text linkThe measurement of the large-scale distribution of neutral hydrogen in the late Universe, obtained with radio telescopes through the hydrogen 21cm line emission, has the potential to become a pivotal cosmological probe in the upcoming years. This thesis presents a comprehensive analysis focused on forecasting the constraining power of 21cm intensity mapping observations, exploring a wide set of cosmological models, from standard \lcdm to modified gravity, dark energy, and massive neutrinos. We developed a pipeline to construct mock data sets for a variety of present and future 21cm observations, with an emphasis on the SKA Observatory and its precursor MeerKAT planned and ongoing surveys. We investigated the interplay between intensity mapping and other cosmological probes, such as the cosmic microwave background, galaxy clustering, and gravitational waves, providing valuable insights into the potential synergies between these different observables. To assess the constraining power of such observations we conducted a Bayesian analysis implementing a likelihood code to work with different 21cm probes and exploring the posterior with Monte Carlo Markov Chain methods. The numerical tools we develop are integrated with widely used codes and prepared to be exploited for upcoming observations and their cosmological analyses. As a proof of concept, the analysis pipeline is validated with the recent MeerKAT intensity mapping measurements in cross-correlation with galaxy clustering data, yielding encouraging results consistent with forecasted outcomes.
The main findings of this thesis suggest a promising constraining power of 21{\small cm} observations when considered both alone and combined with other probes. The joint analysis with cosmic microwave background observations significantly narrows the parameter constraints, leading to precise estimates of pivotal cosmological parameters like and . The tomographic nature of 21cm intensity mapping measurements further improves the estimated errors, potentially offering a powerful new probe to constrain beyond-CDM scenarios.
In conclusion, this thesis extensively tests the value of 21cm intensity mapping as a cosmological probe in the standard model scenario and beyond. It delivers tools for the preparation and analysis of current and future cosmological observations, taking part in the scientific community's effort to pave the way for future groundbreaking observations in cosmology that will potentially provide a deeper understanding of the fundamental properties of our Universe
Multipole expansion for 21cm Intensity Mapping power spectrum: forecasted cosmological parameters estimation for the SKA Observatory
Full text linkThe measurement of the large scale distribution of neutral hydrogen in the
late Universe, obtained with radio telescopes through the hydrogen 21cm line
emission, has the potential to become a key cosmological probe in the upcoming
years. We explore the constraining power of 21cm intensity mapping observations
on the full set of cosmological parameters that describe the CDM
model. We assume a single-dish survey for the SKA Observatory and simulate the
21cm linear power spectrum monopole and quadrupole within six redshift bins in
the range . Forecasted constraints are computed numerically through
Markov Chain Monte Carlo techniques. We extend the sampler \texttt{CosmoMC} by
implementing the likelihood function for the 21cm power spectrum multipoles. We
assess the constraining power of the mock data set alone and combined with
Planck 2018 CMB observations. We include a discussion on the impact of
extending measurements to non-linear scales in our analysis. We find that 21cm
multipoles observations alone are enough to obtain constraints on the
cosmological parameters comparable with other probes. Combining the 21cm data
set with CMB observations results in significantly reduced errors on all the
cosmological parameters. The strongest effect is on and ,
for which the error is reduced by almost a factor four. The percentage errors
we estimate are and , to
be compared with the Planck only results and
. We conclude that 21cm SKAO observations will provide a
competitive cosmological probe, complementary to CMB and, thus, pivotal for
gaining statistical significance on the cosmological parameters constraints,
allowing a stress test for the current cosmological model.Comment: 16 pages, 9 figure
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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