1,721,288 research outputs found
Testing discrete symmetries with the cosmic microwave background: current constraints and Planck forecasts
No full textAnisotropy and polarization of the CMB are probing cosmological models with unprecedented precision. The WMAP satellite data are largely consistent with concordance ACDM cosmology. However, intriguing flukes are known to exist that may pinpoint at physics beyond the standard model. Constraining the violations of discrete symmetries in the CMB pattern is a promising mean to investigate these discrepancies. In this paper we constrain the Parity and CPT symmetries through CMB datasets. We describe the basic formalism, the relevant estimators and the overall analysis strategy. We provide marginal evidence for large scale Parity anomaly in the WMAP data that may be soon confirmed or discarded by the Planck satellite. Planck is currently measuring CMB anisotropies and their polarization with a level of precision that will remain unparalleled for many years to come. We also show how the CMB can be used to constrain fundamental symmetry violations in the photon sector through the so-called cosmological birefringence phenomenon. Finally, we provide forecasts for Planck and we discuss how emission from a specific diffuse foreground component arising within the Solar System needs to be kept under strict control to avoid incurring into false positive detections
Seguendo le Tracce della Complessità/ Following the traces of Complexity
Full text linkQuesta raccolta di scritti nasce come omaggio ad Armando De Guio in occasione del ritiro dall'attività accademica. Il suo entusiasmo e la sua mente brillante hanno contribuito ad aprire la strada verso spazi e tempi inesplorati, anticipando talvolta di interi decenni le direzioni metodologiche applicative della ricerca archeologica a livello nazionale e internazionale. Sulle sue tracce - multiformi, a volte complesse, ma sempre illuminanti - gli autori di questo volume hanno costruito i loro contributi quali segno tangibile di stima, affetto e gratitudine a una figura che è stata, e continua a essere, un punto di riferimento del panorama archeologico italiano
Sulle tracce dei più antichi vetri dell'Altopiano dei Sette Comuni Vicentini
No full textThis contribution presents the first comprehensive survey of the protohistoric glasses found on the Altopiano dei Sette Comuni Vicentini in the sites of Monte Corgnon (Lusiana) and Bostel (Rotzo) during the excavations directed by Armando De Guio. Starting from the history of the studies, the work offers insights into the typo-chronology, stratigraphy, topography, and function of the finds considered. Also, the paper proposes and briefly discusses the preliminary results of the archaeometric analysis of the major, minor and trace elements carried out by LA-ICP-MS, as a means for understanding the raw materials, the coloring/ opacification technologies and the origin of the base glass
In-flight main beam reconstruction for Planck-LFI
No full textIn-flight measurements of the shape of the antenna main beam is a crucial input to the data analysis pipeline of each high resolution Cosmic Microwave Background (CMB) anisotropy experiment. We study the main beam reconstruction achievable by the PLANCK Low Frequency Instrument (LFI) through the observation of external planets. Although we restrict our analysis to the 30 GHz LFI channel, the method can be easily extended to all the PLANCK frequency channels and to other CMB anisotropy experiments. We show that it is possible to fit the time ordered data from the external planets (mainly Jupiter and Saturn) to obtain an accurate, robust, simple and fast reconstruction of the main beam properties under very general conditions, almost independently of the calibration accuracy. In addition, we find that a bivariate Gaussian approximation of main beam shapes represents a significant improvement with respect to a symmetric representation. The impact of the most relevant systematic effects is also addressed. We demonstrate that by combining the recovery of the maximum signal at the planet transit with accurate in-flight calibration, it is possible to measure the intrinsic planet temperatures at millimetric wavelengths with <1% accuracy. This work is based on PLANCK-LFI activities
The Planck Mission: Recent Results, Cosmological and Fundamental Physics Perspectives
No full textWe provide a description of the latest status and performance of the Planck satellite, focusing on the final predicted sensitivity of Planck. The optimization of the observational strategy for the additional surveys following the nominal 15 months of integration (about two surveys) originally allocated and the limitation represented by astrophysical foreground emissions are presented. An outline of early and intermediate astrophysical results from the Planck Collaboration is provided. A concise view of some fundamental cosmological results that will be achieved by exploiting Planck's full set of temperature and polarization data are presented. Finally, the perspectives opened by Planck in answering some key questions in fundamental physics, with particular attention to parity symmetry analyses, are described
Asteroid detection at millimetric wavelengths with the PLANCK survey
No full textThe PLANCK mission, originally devised for cosmological studies, offers the opportunity to observe Solar System objects at millimetric and submillimetric wavelengths. In this paper we concentrate on the asteroids of the Main Belt, a large class of minor bodies in the Solar System. At present, more that 40000 of these asteroids have been discovered and their detection rate is rapidly increasing. We intend to estimate the number of asteroids that can be detected during the mission and to evaluate the strength of their signal. We have rescaled the instrument sensitivities, calculated by the LFI and HFI teams for sources fixed in the sky, introducing some degradation factors to properly account for moving objects. In this way a detection threshold is derived for asteroidal detection that is related to the diameter of the asteroid and its geocentric distance. We have developed a numerical code that models the detection of asteroids in the LFI and HFI channels during the mission. This code performs a detailed integration of the orbits of the asteroids in the timespan of the mission and identifies those bodies that fall in the beams of PLANCK and their signal strength. According to our simulations, a total of 397 objects will be observed by PLANCK and an asteroidal body will be detected in some beam in 30% of the total sky scan-circles. A significant fraction (in the range from ~50 to 100 objects) of the 397 asteroids will be observed with a high /S/N ratio. Flux measurements of a large sample of asteroids in the submillimeter and millimeter range are relevant since they allow to analyze the thermal emission and its relation to the surface and regolith properties. Furthermore, it will be possible to check on a wider base, the two standard thermal models, based on a nonrotating or rapidly rotating sphere. Our method can also be used to separate Solar System sources from cosmological sources in the survey. This work is based on PLANCK LFI activities
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
Fortified Venice: the line of fortifications around Venice and its relation to the geomorphology of the lagoon and the mainland
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