1,720,962 research outputs found
Modified gravity and alternatives to single field inflation
Full text linkMotivated by the need to understand the origin of inflation and address theoretical
limitations of general relativity, this thesis investigates four complementary directions
beyond standard single-field inflation. Each approach is rooted in well-motivated extensions of gravity and multifield inflationary dynamics, aiming to bridge fundamental
theory and cosmological observations. After introducing the theoretical foundations of
modified gravity and inflation, the thesis presents original research across four main
themes: multifield inflation with kinetic couplings, scale-invariant models, non-local
gravity, and cyclic cosmologies.
First, multifield models with non-trivial kinetic couplings are analysed. Arising from
conformal transformations in non-minimally coupled theories, these models exhibit rich
dynamics including adiabatic and isocurvature perturbations. Using our sampling algorithm, the thesis explores their predictions and compares them with cosmological data. Second, the R-squared scale-invariant inflationary model is studied, where mass scales emerge dynamically via spontaneous symmetry breaking. This model addresses the hierarchy problem and yields predictions consistent with current observations, offering an interesting alternative to Starobinsky and alpha-attractor scenarios.
Third, the thesis examines inflation in non-local hybrid metric-Palatini gravity, inspired by attempts to include quantum corrections through non-local operators. Reformulating the theory with auxiliary fields, we identify stable configurations and investigate how non-local terms deform the inflationary potential in observable ways.
Finally, a non-inflationary alternative is explored: the cyclic universe. A general
framework is developed to study the evolution of primordial gravitational waves across
cosmological cycles. The impact of initial conditions and vacuum choice is assessed,
with implications for the robustness of gravitational wave predictions.
Together, these results offer novel insight into early-universe cosmology, proposing
viable alternatives to standard inflation, and guiding future observational and theoretical
research
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
Tracing cosmic stretch marks: probing scale invariance in the early Universe
Full text linkThis paper investigates a scale-invariant inflationary model characterized by a scalar field non-minimally coupled to gravity and a curvature term quadratic in the Ricci scalar. The model\u27s dynamic is analyzed using a full numerical solution of the two-field system, going beyond previous analytical studies. We derive robust constraints on the model parameters using the latest Cosmic Microwave Background (CMB) data from Planck and BICEP/Keck. The study confirms that scale-invariance effectively reduces the system to single-field dynamics, eliminating entropy perturbations and ensuring stability. Key predictions include a minimal level of primordial gravitational waves with a tensor-to-scalar ratio r > 0.003, which upcoming CMB experiments are well-positioned to test. The model is compared to Starobinsky and - attractor inflation, with future observations of tensor modes offering a potential discriminator between them. Overall, the results suggest that scale-invariant inflation is a viable and competitive framework for explaining early universe dynamics and predicting cosmological observables.Contribution to the Seventeenth Marcel Grossmann Meeting, see https://indico.icranet.org/event/8/page/53-proceeding
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
- …
