679 research outputs found
Separate Constraints on Early and Late Cosmology
Since the public release of Planck data, several attempts have been made to
explain the observed small tensions with other data-sets, most of them
involving an extension of the {\Lambda}CDM Model. We try here an alternative
approach to the data analysis, based on separating the constraints coming from
the different epochs in cosmology, in order to assess which part of the
Standard Model generates the tension with the data. To this end, we perform a
particular analysis of Planck data probing only the early cosmological
evolution, until the time of photon decoupling. Then, we utilise this result to
see if the {\Lambda}CDM model can fit all observational constraints probing
only the late cosmological background evolution, discarding any information
concerning the late perturbation evolution. We find that all tensions between
the datasets are removed, suggesting that our standard assumptions on the
perturbed late-time history, as well as on reionisation, could sufficiently
bias our parameter extraction and be the source of the alleged tensions.Comment: 6 pages, 3 figure
Les professeurs de droit, la RĂ©publique et le nouvel esprit juridique : Introduction
En mettant en perspective les contributions de ce dossier, une interprĂ©tation globale des transformations affectant le rĂŽle des professeurs de droit Ă la Belle Ăpoque est ici proposĂ©e. RattrapĂ©s par une rĂ©alitĂ© sociale quâils ont longuement ignorĂ©e, ces enseignants se prĂ©sentent alors, autour de 1900, comme les nouveaux experts du social. Souvent hostiles Ă la RĂ©publique, ils se posent Ă©galement en dĂ©fenseurs du droit contre un parlementarisme quâils jugent despotique. Mobilisant outils de la science et ressources politiques et sociales, les professeurs de droit feront de la crise de leurs facultĂ©s un « Ăąge dâor » de la pensĂ©e juridique.This article is an introduction to the contributions of this volume. It suggests a new interpretation of the role of Law Professors in the Belle Ăpoque era (1870-1914). In order to protect society from the dangers of parliamentarism, Law Professors presented themselves as the new experts of the Social and supported the emergence of the Ătat de droit in France. As a consequence, Law Professors have transformed the crisis of their faculties into a golden age of legal science
Cosmological constraints on Lorentz violating dark energy
The role of Lorentz invariance as a fundamental symmetry of nature has been
lately reconsidered in different approaches to quantum gravity. It is thus
natural to study whether other puzzles of physics may be solved within these
proposals. This may be the case for the cosmological constant problem. Indeed,
it has been shown that breaking Lorentz invariance provides Lagrangians that
can drive the current acceleration of the universe without experiencing large
corrections from ultraviolet physics. In this work, we focus on the simplest
model of this type, called ThetaCDM, and study its cosmological implications in
detail. At the background level, this model cannot be distinguished from
LambdaCDM. The differences appear at the level of perturbations. We show that
in ThetaCDM, the spectrum of CMB anisotropies and matter fluctuations may be
affected by a rescaling of the gravitational constant in the Poisson equation,
by the presence of extra contributions to the anisotropic stress, and finally
by the existence of extra clustering degrees of freedom. To explore these
modifications accurately, we modify the Boltzmann code CLASS. We then use the
parameter inference code Monte Python to confront ThetaCDM with data from
WMAP-7, SPT and WiggleZ. We obtain strong bounds on the parameters accounting
for deviations from LambdaCDM. In particular, we find that the discrepancy
between the gravitational constants appearing in the Poisson and Friedmann
equations is constrained at the level 1.8%.Comment: 17 pages, 5 figure
Figures des sciences sociales (XIXe-XXe siĂšcles)
Ce numĂ©ro propose une galerie de portraits. Les personnalitĂ©s croquĂ©es ici n'avaient, jusqu'Ă prĂ©sent, que rarement retenu l'attention des historiens. Certaines d'entre elles ont participĂ© aux activitĂ©s du mouvement leplaysien, voire exercĂ© quelques responsabilitĂ©s en son sein. Ainsi Jacques Bardoux et RenĂ© de Kerallain interviennent devant la SociĂ©tĂ© d'Ă©conomie sociale ou dans les CongrĂšs qu'elle organise de concert avec les Unions de la paix sociale et publient dans La RĂ©forme sociale, tandis que le magistrat Jules Lacointa est, lui, un dirigeant majeur du mouvement leplaysien, siĂšgeant au conseil d'administration de la SociĂ©tĂ© d'Ă©conomie sociale dĂšs 1882. Les influences leplaysiennes dans l'Ă©chantillon de personnalitĂ©s ici Ă©tudiĂ©es sont parfois plus diffuses et indirectes comme dans le cas du juriste belge Arthur Levoz, hĂ©rault de la protection de l'enfance, qui fut un disciple du pĂ©naliste Adolphe Prins, membre de la SociĂ©tĂ© belge d'Ă©conomie sociale. Par cette forte prĂ©sence des juristes, ce numĂ©ro prolonge l'enquĂȘte, inaugurĂ©e dans le numĂ©ro 135-136 (2002), sur les liens entre les professionnels du droit et le mouvement de FrĂ©dĂ©ric Le Play. L'action et la rĂ©flexion de ces figures font pleinement Ă©cho Ă plusieurs thĂšmes rĂ©currents de la science sociale leplaysienne. Qu'il soit monarchiste ou libĂ©ral, chaque auteur ici Ă©tudiĂ© appelle de ses vĆux une rĂ©forme des mĆurs adaptĂ©e aux besoins du temps prĂ©sent. Adossant ces ambitions rĂ©formatrices sur des compĂ©tences intellectuelles attestĂ©es et des expertises raisonnĂ©es, il leur donne, le plus souvent, une orientation fonciĂšrement conservatrice mais non exempte d'un esprit de nouveautĂ© et d'ouverture. [PremiĂšres lignes
Potential of power recovery of a subsonic axial fan in windmilling operation
During the last decades, efforts to find efficient green energy solutions have been widely increased in response to environmental concerns. Among all renewable energies, this paper is focused on wind power generation. To this end, a windmilling axial fan in turbine operation is experimentally and numerically investigated. Under specific conditions, the studied fan is naturally freewheeling. Consequently, the main objective of this analysis is to determine whether or not this intrinsic windmilling behavior can be optimized for power generation. A preliminary study of the fan is dedicated to the knowledge of the fan characteristics in normal operating conditions. Then, two windmilling configurations (direct and reverse flow direction) are tested and compared on the basis of the output power. An analysis of the velocity triangle gives the opportunity to evaluate the energy recovery potential of both solutions. Of the two, the reversed configuration showed a higher level of output power than the direct one
La Belle eÌpoque des juristes catholiques (1870-1914)
Cet article dresse le portrait du groupe, aux contours et aux activitĂ©s mal connus, des professeurs de droit catholiques, qu'ils appartiennent aux facultĂ©s libres ou aux facultĂ©s d'Ătat. Constatant l'absence de relations rĂ©guliĂšres entre ces deux milieux, il souligne l'importance de la culture catholique dans la construction de leur position scientifique respective dans la France de la Belle Ă©poque. Il montre Ă©galement l'importance de ce rĂ©seau non seulement dans le dĂ©veloppement du droit des cultes mais Ă©galement dans l'Ă©mergence d'une Ăcole scientifique.This paper portrays the group, whose limits and activities remain poorly known, of the catholic professors of Law in public or in private faculties. The study reveals the absence of regular relations between these two environments but emphasizes the part played by the catholic culture in the construction of theses jurists' scientific stance in late nineteenth-century France. It shows also how this network of scholars contributed significantly to the development of Cult Law as well as to the rise of a Scientific School
Paul Huvelin (1873-1924) : juriste et durkheimien
Pour lâhistoire des sciences humaines, Paul Huvelin est lâhomme dâune controverse : avec Marcel Mauss, Ă propos des rapports quâentretiennent le droit, la religion et la magie. Câest naturellement un peu court pour rĂ©sumer une carriĂšre. CarriĂšre brĂšve, il est vrai, car Paul Huvelin est dĂ©cĂ©dĂ©, en pleine activitĂ©, Ă lâĂąge de 51 ans, le 2 juin 1924. Il enseignait alors le droit romain Ă la facultĂ© de droit de Lyon. La Revue historique de droit français et Ă©tranger, vitrine de la discipline histoire du droit, lui consacre en hommage une assez brĂšve nĂ©crologie. Elle vante lâesprit et la culture du juriste mais ne mentionne Ă aucun moment ses prĂ©occupations sociologiques. Pourtant, actif collaborateur Ă LâAnnĂ©e sociologique Ă partir du sixiĂšme volume (1901-1902), il confie Ă la revue un mĂ©moire original et plus dâune quarantaine de comptes rendus. Les annĂ©es 1910 marquent une incontestable Ă©volution de la carriĂšre. Sans abandonner son enseignement, il se tourne alors vers la diplomatie et la politique (...)
La sociologie de René Worms
Qui connaĂźt RenĂ© Worms ? Lâhistoire de la sociologie nâa conservĂ© de lui quâun assez vague souvenir, comme peut en tĂ©moigner une historiographie le concernant fort modeste. Sa contribution scientifique et institutionnelle est le plus souvent jugĂ©e sĂ©vĂšrement par une tradition sociologique qui nâa dâĂ©gard que pour le durkheimisme. De sorte que, aujourdâhui encore, lâopinion communĂ©ment admise sur R. Worms nâest autre que celle, formulĂ©e il y a plus dâun siĂšcle, par Durkheim et ses Ă©lĂšves : R. Worms ne serait quâun « farceur » dont lâĂ©clectisme stĂ©rile nâaurait rien produit de sĂ©rieux et dâintĂ©ressant pour une discipline en pleine construction. La puĂ©rilitĂ© de son « organicisme » est raillĂ©e et vilipendĂ©e. Une telle disqualification nâen finit pas de faire sentir ses effets de telle sorte que, Ă quelques exceptions prĂšs, lâitinĂ©raire et le projet de R. Worms nâont guĂšre Ă©tĂ© pris au sĂ©rieux et nâont jamais donnĂ© lieu Ă une enquĂȘte collective et approfondie. Avec ce dossier « La sociologie de RenĂ© Worms », Les Ătudes sociales souhaitent contribuer Ă combler cette lacune. [PremiĂšres lignes
Strongest model-independent bound on the lifetime of Dark Matter
Dark Matter is essential for structure formation in the late Universe so it
must be stable on cosmological time scales. But how stable exactly? Only
assuming decays into relativistic particles, we report an otherwise model
independent bound on the lifetime of Dark Matter using current cosmological
data. Since these decays affect only the low- multipoles of the CMB, the
Dark Matter lifetime is expected to correlate with the tensor-to-scalar ratio
as well as curvature . We consider two models, including and
respectively, versus data from Planck, WMAP, WiggleZ and Baryon
Acoustic Oscillations, with or without the BICEP2 data (if interpreted in terms
of primordial gravitational waves). This results in a lower bound on the
lifetime of CDM given by 160Gyr (without BICEP2) or 200Gyr (with BICEP2) at 95%
confidence level.Comment: 15 pages, 5 figures. Prepared for submission to JCA
Cosmological constraints on deviations from Lorentz invariance in gravity and dark matter
We consider a scenario where local Lorentz invariance is violated by the
existence of a preferred time direction at every space-time point. This
scenario can arise in the context of quantum gravity and its description at low
energies contains a unit time-like vector field which parameterizes the
preferred direction. The particle physics tests of Lorentz invariance preclude
a direct coupling of this vector to the fields of the Standard Model, but do
not bear implications for dark matter. We discuss how the presence of this
vector and its possible coupling to dark matter affect the evolution of the
Universe. At the level of homogeneous cosmology the only effect of Lorentz
invariance violation is a rescaling of the expansion rate. The physics is
richer at the level of perturbations. We identify three effects crucial for
observations: the rescaling of the matter contribution to the Poisson equation,
the appearance of an extra contribution to the anisotropic stress and the
scale-dependent enhancement of dark matter clustering. These effects result in
distinctive features in the power spectra of the CMB and density fluctuations.
Making use of the data from Planck and WiggleZ we obtain the most stringent
cosmological constraints to date on departures from Lorentz symmetry. Our
analysis provides the first direct bounds on deviations from Lorentz invariance
in the dark matter sector.Comment: 10 pages, 3 figures, revtex; footnote on isocurvature modes added,
discussion on the decoupling of the Standard Model fields from the aether
extended, a reference added; version to be published in JCA
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