1,720,968 research outputs found
Localized non-relativistic quantum systems in curved spacetimes: a general characterization of particle detector models
Get PDFIn this manuscript we provide a consistent way of describing a localized
non-relativistic quantum system undergoing a timelike trajectory in a
background curved spacetime. Namely, using Fermi normal coordinates, we
identify an inner product and canonically conjugate position and momentum
operators defined in the rest space of the trajectory for each value of its
proper time. This framework then naturally provides a recipe for mapping a
quantum theory defined in a non-relativistic background to a theory around a
timelike trajectory in curved spacetimes. This is done by reinterpreting the
position and momentum operators and by introducing a local redshift factor to
the Hamiltonian, which gives rise to new dynamics due to the curvature of
spacetime and the acceleration of the trajectory. We then apply our formalism
to particle detector models, that is, to the case where the non-relativistic
quantum system is coupled to a quantum field in a curved background. This
allows one to write a general definition for particle detector models which is
able to recover the previous models in the literature. Our framework also
allows one to estimate the regime of validity of these models, characterizing
the situations where particle detectors can be used to accurately probe quantum
fields.Comment: 16 pages, 3 figures, v3 added clarification after Eq. (41
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Spacetime curvature from ultra rapid measurements of quantum fields
Get PDFWe write the curvature of spacetime in terms of the excitation probability of
particle detectors ultra-rapidly coupled to a quantum field. More precisely, we
provide an expansion for the excitation probability of a smeared UDW detector
delta-coupled to a real scalar quantum field in a curved background. Using a
short distance expansion for the Wightman function, we express the excitation
probability of a detector as the transition probability in Minkowski spacetime
plus correction terms written as a function of the curvature tensors and the
detector size. Comparing the excitation probability in curved spacetimes with
its flat analog, we are able to express the components of the Ricci and Riemann
curvature tensors as a function of physically measurable excitation
probabilities of different shaped detectors.Comment: 7 pages + 3 appendice
A Wavefunction Description for a Localized Quantum Particle in Curved Spacetimes
Get PDFWe reduce Dirac's spinor formalism for a spin 1/2 particle to a complex
wavefunction description in curved spacetimes. We consider a localized
fermionic particle in curved spacetimes and perform an expansion in terms of
the acceleration and curvature around the center of mass of the system,
generalizing the results of [Phys. Rev. D 22, 1922]. Under a non-relativistic
approximation, one obtains a quantum description in a Hilbert space of complex
wavefunctions defined in the rest space of the system. The wavefunction of the
particle then evolves according to a modified Schr\"odinger equation associated
with a symmetric Hamiltonian. When compared to the standard Schr\"odinger
equation for a wavefunction, we obtain corrections in terms of the acceleration
of the system's center of mass and curvature of spacetime along its trajectory.
In summary, we provide a formalism for the use of a complex wavefunction to
describe a localized quantum particle in curved spacetimes.Comment: 26 pages, 1 figure. RevTeX 4.1. V4. Added a more detailed explanation
in Appendix C and fixed minor typo
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
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