Search results for "CALL"
showing 10 items of 2320 documents
Overionization in X-ray spectra: a new paradigm for Mixed-Morphology SNRs
2011
Mixed-morphology SNRs are characterized by a shell-like radio emission, a centrally peaked X-ray morphology, and by interaction with molecular clouds. Many models have been proposed to explain these peculiar remnants, but their physical origin is still unclear. The recent discovery of over-ionized (i. e. recombining) ejecta in 3 mixed-morphology SNRs has dramatically challenged all the previous models and opened up new, unexpected scenarios. I review the main properties of these remnants and their peculiar X-ray spectral properties. I also discuss the hydrodynamic model developed to explain the presence of over-ionized ejecta in W49B and present a list of open issues that still need to be c…
Wormholes and nonsingular spacetimes in Palatinif(R)gravity
2015
We reconsider the problem of $f(R)$ theories of gravity coupled to Born-Infeld theory of electrodynamics formulated in a Palatini approach, where metric and connection are independent fields. By studying electrovacuum configurations in a static and spherically symmetric space-time, we find solutions which reduce to their Reissner-Nordstr\"om counterparts at large distances but undergo important non-perturbative modifications close to the center. Our new analysis reveals that the point-like singularity is replaced by a finite-size wormhole structure, which provides a geodesically complete and thus nonsingular space-time, despite the existence of curvature divergences at the wormhole throat. …
Operator approach to the Gluing Theorem in String Field Theory
1999
An algebraic proof of the Gluing Theorem at tree level of perturbation theory in String Field Theory is given. Some applications of the theorem to closed string non-polynomial action are briefly discussed
High-contrast dark resonances on the D1 line in cesium nanocell: the advantages compared with the other alkali D lines
2015
Electromagnetically induced transparency (EIT) effect in a -system formed by Cs atoms line, enclosed in nanometric-thin cells, is studied both experimentally and theoretically for the first time. T...
Universities' Reporting on SDGs: Using THE Impact Rankings to Model and Measure Their Contribution to Sustainability
2021
Higher education institutions (HEIs) have voiced growing concerns about sustainability issues since Agenda 2030 was approved, but this is not enough for societal stakeholders seeking and delivering innovation and excellence. The 17 Sustainable Development Goals (SDGs) were adopted by all UN Member States in 2015 as a universal call to action, and pose a challenge for HEIs as for the efforts made to fulfill them and knowing how to assess their performance. However, the metric management system implemented by HEIs quickly led to rankings emerging, which compare HEIs to metrics not related to the sustainability dimensions of the 17 SDGs. The main aim of the paper is to assess the level of repo…
On the graded identities and cocharacters of the algebra of 3×3 matrices
2004
Abstract Let M2,1(F) be the algebra of 3×3 matrices over an algebraically closed field F of characteristic zero with non-trivial Z 2 -grading. We study the graded identities of this algebra through the representation theory of the hyperoctahedral group Z 2 ∼S n . After splitting the space of multilinear polynomial identities into the sum of irreducibles under the Z 2 ∼S n -action, we determine all the irreducible Z 2 ∼S n -characters appearing in this decomposition with non-zero multiplicity. We then apply this result in order to study the graded cocharacter of the Grassmann envelope of M2,1(F). Finally, using the representation theory of the general linear group, we determine all the grade…
Sophie Calle, Douleur exquise : le récit de l’intime comme objet de la démarche artistique
2012
Throughout her work, Sophie Calle has never ceased staging herself. Traces and testimonies of her life became the basis of her work that presents itself as a memoir of her existence. In Exquisite Pain, which can be read as a therapeutic move because its aim was to soothe the pain of the end of a love affair, Calle sets up an aesthetics of archives through multiple indications of place and time present in the visual documents as well as in written texts. The artist thus ensures the veracity of the facts exhibited before the spectators, who are voluntarily induced into wondering about how much fiction and seduction are present. This work also allows Calle to bring in the voice of other anonym…
Flat synchronizations in spherically symmetric space-times
2010
It is well known that the Schwarzschild space-time admits a spacelike slicing by flat instants and that the metric is regular at the horizon in the associated adapted coordinates (Painleve-Gullstrand metric form). We consider this type of flat slicings in an arbitrary spherically symmetric space-time. The condition ensuring its existence is analyzed, and then, we prove that, for any spherically symmetric flat slicing, the densities of the Weinberg momenta vanish. Finally, we deduce the Schwarzschild solution in the extended Painleve-Gullstrand-Lemaitre metric form by considering the coordinate decomposition of the vacuum Einstein equations with respect to a flat spacelike slicing.
Luminescence properties of AlN nanostructures revealed under UV light irradiation
2007
The luminescence properties of the AlN nanostructures – nanorods and nanotips -revealed under the UV irradiation are similar to those of the AlN ceramics. Presumably they are induced by the recombination processes in the oxygen-related centers. All the studied luminescence processes (photoluminescence, thermoluminescence and optically stimulated luminescence) in the nanostructures occur mainly through the host lattice excitation. That may be explained by the smaller concentration of the defect centers and more perfect structure of the host lattice of the nanostructures compared to the ceramics. The small mutual differences revealed in the spectra and TL curves of the AlN nanotips and nanoro…
Notas a la diacronía y la fraseología de andana y traque
2022
El estudio fraseológico del español carece todavía hoy de una obra lexicográfica en la que sus unidades se vean descritas en su historia. Aunque el DHISFRAES llena parcialmente ese vacío, no pocos trabajos han podido detallar la historia de un número importante de unidades fraseológicas. El presente estudio pretende adherirse a ellos, explorando desde los preceptos de la fraseología histórica las unidades fraseológicas que tienen como núcleo andana y traque, ambas palabras diacríticas.