1,720,968 research outputs found
How to measure the curvature of space-time
No full textWe propose a new method of measuring the curvature of space-time using test particles. We show that to determine the curvature of space-time in vacuum it is necessary to use at least four test particles and in general at least six
Approximate angular diameter distance in a locally inhomogeneous universe with nonzero cosmological constant
No full textApproximate angular diameter distance in a locally inhomogeneous universe with nonzero cosmological constant
No full textAccelerating universe in scalar tensor models - comparison of theoretical predictions with observations
No full textApproximate angular diameter distance in a locally inhomogeneous universe with nonzero cosmological constant
No full textTwo viable quintessence models of the Universe: Confrontation of theoretical predictions with observational data
No full textWe use some of the recently released observational data
to test the viability of two classes of minimally coupled scalar
field models of quintessence with exponential potentials for which
exact solutions of the Einstein equations are known. These models
are very sturdy, depending on only one parameter – the Hubble
constant. To compare predictions of our models with observations
we concentrate on the following data: the power spectrum of the
CMBR anisotropy as measured by WMAP, the publicly available data
on type Ia supernovae, and the parameters of large scale structure
determined by the 2-degree Field Galaxy Redshift Survey (2dFGRS).
We use the WMAP data on the age of the universe and the Hubble
constant to fix the free parameters in our models. We then show
that the predictions of our models are consistent with the
observed positions and relative heights of the first 3 peaks in
the CMB power spectrum, with the energy density of dark energy as
deduced from observations of distant type Ia supernovae, and with parameters of the large scale structure as determined by
2dFGRS, in particular with the average density of dark matter. Our
models are also consistent with the results of the Sloan Digital
Sky Survey (SDSS). Moreover, we investigate the evolution of
matter density perturbations in our quintessential models, solve
exactly the evolution equation for the density perturbations, and
obtain an analytical expression for the growth index f. We
verify that the approximate relation also holds in our models
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
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