99 research outputs found
Blondel, Colbert et lâorigine de lâAcadĂ©mie royale dâarchitecture
Je tiens Ă remercier Olivier Morteau pour lâaide apportĂ©e dans la traduction de cet article. Cette contribution examine le contexte politique qui entoure la crĂ©ation de lâAcadĂ©mie royale dâarchitecture en 1671, et en particulier le rĂŽle jouĂ© par François Blondel et le ministre Jean-Baptiste Colbert dans la dĂ©finition de son rĂšglement et dans lâĂ©laboration de son programme de confĂ©rences. Une telle enquĂȘte sâinscrit parfaitement dans la problĂ©matique du colloque â lâhĂ©ritage de la Renaissance ..
Architecture et thĂ©orie. LâhĂ©ritage de la Renaissance
Ce colloque sâinsĂšre dans un ensemble de manifestations consacrĂ©es Ă la thĂ©orie de lâart : une table ronde introductive en avril 2009 sur la problĂ©matique organisĂ©e Ă Paris par Milovan Stanic (universitĂ© Paris IV) au Centre allemand dâhistoire de lâart Ă Paris, et un colloque sur la thĂ©orie des arts figuratifs Ă Saint-PĂ©tersbourg (direction Milovan Stanic) en 2010. Il est exclusivement dĂ©volu Ă lâarchitecture de la Renaissance Ă nos jours, dans le prolongement du programme de recherche Architectura du CESR, dont lâune des bases est consacrĂ©e aux livres dâarchitecture (XVIe-XVIIe siĂšcle). En mĂȘme temps que lâarchitecture « Ă lâantique », la Renaissance voit renaĂźtre la thĂ©orie de lâarchitecture. Quâil sâagisse de gloses du traitĂ© de Vitruve ou dâentreprises autonomes, les traitĂ©s fleurissent, du De re ĂŠdificatoria dâAlberti (Florence, 1485) Ă lâIdea della architettura universale de Scamozzi (Venise, 1615), en passant par lâĆuvre de Serlio, la plus vaste entreprise Ă©ditoriale du Cinquecento, la Regola de Vignole (Rome, 1562) maintes fois rĂ©Ă©ditĂ©e et les Quattro libri dâarchitettura de Palladio (Venise, 1570). Tous ces ouvrages formalisent une pratique de lâart de bĂątir dont les reprĂ©sentations mentales restaient implicites au Moyen Ăge, limitĂ©es aux transmissions traditionnelles des savoir-faire au sein des corporations. Ils ont Ă©tĂ© souvent rĂ©Ă©ditĂ©s, lus et mĂ©ditĂ©s tout au long des XVIIe et XVIIIe siĂšcles ; et ils marquaient encore lâenseignement de lâĂcole des beaux-arts au dĂ©but du XXe siĂšcle. Comment la thĂ©orie dĂ©veloppĂ©e dans les traitĂ©s de la Renaissance a-t-elle contribuĂ© Ă former la pensĂ©e architecturale des architectes des siĂšcles suivants ? Telle est la question Ă laquelle les intervenants, historiens de lâarchitecture, architectes et critiques contemporains, tenteront de fournir des Ă©lĂ©ments de rĂ©ponse
Exploring Cosmic Origins with CORE: Cosmological Parameters
We forecast the main cosmological parameter constraints achievable with theCORE space mission which is dedicated to mapping the polarisation of the CosmicMicrowave Background (CMB). CORE was recently submitted in response to ESA'sfifth call for medium-sized mission proposals (M5). Here we report the resultsfrom our pre-submission study of the impact of various instrumental options, inparticular the telescope size and sensitivity level, and review the great,transformative potential of the mission as proposed. Specifically, we assessthe impact on a broad range of fundamental parameters of our Universe as afunction of the expected CMB characteristics, with other papers in the seriesfocusing on controlling astrophysical and instrumental residual systematics. Inthis paper, we assume that only a few central CORE frequency channels areusable for our purpose, all others being devoted to the cleaning ofastrophysical contaminants. On the theoretical side, we assume LCDM as ourgeneral framework and quantify the improvement provided by CORE over thecurrent constraints from the Planck 2015 release. We also study the jointsensitivity of CORE and of future Baryon Acoustic Oscillation and Large ScaleStructure experiments like DESI and Euclid. Specific constraints on the physicsof inflation are presented in another paper of the series. In addition to thesix parameters of the base LCDM, which describe the matter content of aspatially flat universe with adiabatic and scalar primordial fluctuations frominflation, we derive the precision achievable on parameters like thosedescribing curvature, neutrino physics, extra light relics, primordial heliumabundance, dark matter annihilation, recombination physics, variation offundamental constants, dark energy, modified gravity, reionization and cosmicbirefringence. (ABRIDGED
L. Evidence of spatial variation of the polarized thermal dust spectral energy distribution and implications for CMB B-mode analysis
Planck Collaboration.The characterization of the Galactic foregrounds has been shown to be the main obstacle in thechallenging quest to detect primordial B-modes in the polarized microwave sky. We make use of the Planck-HFI 2015 data release at high frequencies to place new constraints on the properties of the polarized thermal dust emission at high Galactic latitudes. Here, we specifically study the spatial variability of the dust polarized spectral energy distribution (SED), and its potential impact on the determination of the tensor-to-scalar ratio, r. We use the correlation ratio of the angular power spectra between the 217 and 353 GHz channels as a tracer of these potential variations, computed on different high Galactic latitude regions, ranging from 80% to 20% of the sky. The new insight from Planck data is a departure of the correlation ratio from unity that cannot be attributed to a spurious decorrelation due to the cosmic microwave background, instrumental noise, or instrumental systematics. The effect is marginally detected on each region, but the statistical combination of all the regions gives more than 99% confidence for this variation in polarized dust properties. In addition, we show that the decorrelation increases when there is a decrease in the mean column density of the region of the sky being considered, and we propose a simple power-law empirical model for this dependence, which matches what is seen in the Planck data. We explore the effect that this measured decorrelation has on simulations of the BICEP2-Keck Array/Planck analysis and show that the 2015 constraints from these data still allow a decorrelation between the dust at 150 and 353 GHz that is compatible with our measured value. Finally, using simplified models, we show that either spatial variation of the dust SED or of the dust polarization angle are able to produce decorrelations between 217 and 353 GHz data similar to the values we observe in the data.The Planck Collaboration acknowledges the support of: ESA; CNES, and CNRS/INSU-IN2P3-INP (France); ASI, CNR, and INAF (Italy); NASA and DoE (USA); STFC and UKSA (UK); CSIC, MINECO, J.A., and RES (Spain); Tekes, AoF, and CSC (Finland); DLR and MPG
(Germany); CSA (Canada); DTU Space (Denmark); SER/SSO (Switzerland); RCN (Norway); SFI (Ireland); FCT/MCTES (Portugal); ERC and PRACE (EU). The research leading to these results has received funding from the European Research Council under the European Unionâs Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement No. 267934.Peer Reviewe
CMB-S4: Forecasting Constraints on Primordial Gravitational Waves
CMB-S4---the next-generation ground-based cosmic microwave background (CMB)
experiment---is set to significantly advance the sensitivity of CMB
measurements and enhance our understanding of the origin and evolution of the
Universe, from the highest energies at the dawn of time through the growth of
structure to the present day. Among the science cases pursued with CMB-S4, the
quest for detecting primordial gravitational waves is a central driver of the
experimental design. This work details the development of a forecasting
framework that includes a power-spectrum-based semi-analytic projection tool,
targeted explicitly towards optimizing constraints on the tensor-to-scalar
ratio, , in the presence of Galactic foregrounds and gravitational lensing
of the CMB. This framework is unique in its direct use of information from the
achieved performance of current Stage 2--3 CMB experiments to robustly forecast
the science reach of upcoming CMB-polarization endeavors. The methodology
allows for rapid iteration over experimental configurations and offers a
flexible way to optimize the design of future experiments given a desired
scientific goal. To form a closed-loop process, we couple this semi-analytic
tool with map-based validation studies, which allow for the injection of
additional complexity and verification of our forecasts with several
independent analysis methods. We document multiple rounds of forecasts for
CMB-S4 using this process and the resulting establishment of the current
reference design of the primordial gravitational-wave component of the Stage-4
experiment, optimized to achieve our science goals of detecting primordial
gravitational waves for at greater than , or, in the
absence of a detection, of reaching an upper limit of at CL.Comment: 24 pages, 8 figures, 9 tables, submitted to ApJ. arXiv admin note:
text overlap with arXiv:1907.0447
CMB-S4: Forecasting Constraints on Primordial Gravitational Waves
Abstract: CMB-S4âthe next-generation ground-based cosmic microwave background (CMB) experimentâis set to significantly advance the sensitivity of CMB measurements and enhance our understanding of the origin and evolution of the universe. Among the science cases pursued with CMB-S4, the quest for detecting primordial gravitational waves is a central driver of the experimental design. This work details the development of a forecasting framework that includes a power-spectrum-based semianalytic projection tool, targeted explicitly toward optimizing constraints on the tensor-to-scalar ratio, r, in the presence of Galactic foregrounds and gravitational lensing of the CMB. This framework is unique in its direct use of information from the achieved performance of current Stage 2â3 CMB experiments to robustly forecast the science reach of upcoming CMB-polarization endeavors. The methodology allows for rapid iteration over experimental configurations and offers a flexible way to optimize the design of future experiments, given a desired scientific goal. To form a closed-loop process, we couple this semianalytic tool with map-based validation studies, which allow for the injection of additional complexity and verification of our forecasts with several independent analysis methods. We document multiple rounds of forecasts for CMB-S4 using this process and the resulting establishment of the current reference design of the primordial gravitational-wave component of the Stage-4 experiment, optimized to achieve our science goals of detecting primordial gravitational waves for r > 0.003 at greater than 5Ï, or in the absence of a detection, of reaching an upper limit of r < 0.001 at 95% CL
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