Friction in Gravitational Waves: a test for early-time modified gravity

Modified gravity theories predict in general a non standard equation for the propagation of gravitational waves. Here we discuss the impact of modified friction and speed of tensor modes on cosmic microwave polarization B modes. We show that the non standard friction term, parametrized by $\alpha_{M}$, is degenerate with the tensor-to-scalar ratio $r$, so that small values of $r$ can be compensated by negative constant values of $\alpha_M$. We quantify this degeneracy and its dependence on the epoch at which $\alpha_{M}$ is different from the standard, zero, value and on the speed of gravitational waves $c_{T}$. In the particular case of scalar-tensor theories, $\alpha_{M}$ is constant and strongly constrained by background and scalar perturbations, $0\le \alpha_{M}< 0.01$ and the degeneracy with $r$ is removed. In more general cases however such tight bounds are weakened and the B modes can provide useful constraints on early-time modified gravity.Comment: Minor changes after published version. One new figur

Le figural entre imagination et perception

International audienceWhereas in semiotics we have tried to account for the activity of the figurative dimension of meaning as a coherent text deformation, in other knowledge fields, the study of figures of speech and of images, have led to an original design of " figural " as a full dimension of cultures. Whether it was a matter of the relationship between saying and seeing or of the nature and power of images, the " figural " has been designed as a device able to move the boundaries between: speech and desire, rhetoric and esthesia, reality and reference, between the subjectal constitution and the phenomenal donation, between the singular expression as semiotic praxis and stabilization of values over time. 1. Sémiotique et méthode phénoménologique: l'épreuve figurale Si l'on se tourne vers l'histoire de la sémiotique de ces dernières vingt années, entendue autant comme discipline qu'en tant que méthode ou, en les termes d'Umberto Eco (1985), soit comme un ensemble des sémiotiques spécifiques, soit comme sémiotique générale, on a assisté, d'une part, à un véritable élargissement des champs ou domaines d'analyse, allant des passions et du corps aux pratiques sociales ayant engendré une pléthore de sémiotiques : de la photographie, du corps, des pratiques, etc. D'autre part, cette prolifération s'est partiellement rebattue sur une sémiotique plus générale, une voie d'investigation du sens du sens, un procédé d'interrogation de son faire ; par conséquent, au fur et à mesure que des « nouveaux » phénomènes réclamaient une description adéquate, sinon une explication, les modèles théoriques d'antan ont été soumis à une révision profonde, en constituant la sémiotique même comme une pratique (cf. Fontanille 2008). Le modèle génératif de la sémiotique greimasienne a notamment été modifié par l'intégration et la complexification des dimensions figurative et sensorielle-percpetive

Parametric and semiparametric estimation of ordered response models with sample selection and individual-specific thresholds

This paper provides a set of new Stata commands for parametric and semiparametric estimation of an extended version of ordered response models that accounts for both sample selection problems and heterogeneity in the thresholds for the latent variable. The standard estimator of ordered response models is therefore generalized along three directions. First, we account for the presence of endogenous selectivity effects that may lead to inconsistent estimates of the model parameters. Second, we control for both observed and unobserved heterogeneity in response scales by allowing the thresholds to depend on a set of covariates and a random individual effect. Finally, we consider two alternative specifications of the model, one parametric and one semiparametric. In the former, the error terms are assumed to follow a multivariate Gaussian distribution and the model parameters are estimated via maximum likelihood. In the latter, the distribution function of the error terms is instead approximated by following Gallant and Nychka (1997), and the model parameters are estimated via pseudo–maximum likelihood. After discussing identification and estimation issues, we present an empirical application using the second wave of the Survey on Health, Ageing and Retirement in Europe (SHARE). Specifically, we estimate an ordered response model for self-reported health on different domains by accounting for both sample selection bias due to survey nonresponse and reporting bias in the self-assessments of health.

La matière et la technique comme dispositifs de médiation. Le cas des Cartes-Tapisseries d'Alighiero Boetti

International audienceLa réflexion globale autour des notions de sens et de médiation ainsi que de leurs relations réciproques fait émerger un champ sémantique et de problématiques s'articulant, à notre avis, sur trois axes principaux et imbriqués entre eux : i) la médiation et le milieu, en entendant par médiation l'opération ou le processus à même d'instaurer des environnements et des espaces de circulation de valeurs et d'ancrage des pratiques, ii) la médiation et les instances médiatrices – quelle que soit leur nature – par lesquelles l'action de la médiation peut prendre place et donner lieu à des configurations spécifiques d'articulation des différences et de persistance des horizons de valorisation, iii) la médiation et le médium, lorsque l'on conçoit ce dernier tantôt en sa déclinaison médiatique à proprement parler – les médias –, tantôt en celle de support comme lieu d'effectuation et de convergence de pratiques diverses. Cette perspective triple que la notion de médiation livre à la sémiotique permettrait à cette dernière, en suivant l'intérêt actuel envers la notion de forme de vie ainsi que le rapprochement et l'ouverture à certaines suggestions théoriques de l'anthropologie contemporaine, de se configurer comme discipline véritablement médiatrice à l'égard des sciences humaines. Elle serait en mesure d'observer et de décrire lesdites ontologies, en tant que grandes schématisations des modes d'articulation et d'identification des relations entre les êtres proposées par l'anthropologue Philippe Descola et reprises par Jacques Fontanille dans son dernier ouvrage (Fontanille 2015), et, à la fois, lesdites ontogénies en tant que chemins d'émergence et de développement des êtres et des sociétés, telles qu'elles se trouvent disséminées dans plusieurs contributions de l'anthropologue Tim Ingold. Dans ce cadre, la sémiotique, grâce à ses outils de détermination et d'articulation de différents plans d'immanence (Fontanille 2008), ainsi que par sa vocation première d'interrogation sur le sens du sens – sur l'être du sens et sur ses transformations –, s'avère non seulement une discipline permettant de déterminer des niveaux spécifiques et des moments de l'articulation entre expression et contenu ou de dégager des enchaînements syntagmatiques structurant des scènes et des cours d'action, mais elle se constitue également en tant que discipline permettant d'esquisser ou de préfigurer des trajectoires, des devenirs du valoir même des valorisations et, par conséquent, de penser les temps et les espaces mêmes où des sémioses à venir peuvent s'engendrer

Constraints on coupled dark energy using CMB data from WMAP and SPT

We consider the case of a coupling in the dark cosmological sector, where a dark energy scalar field modifies the gravitational attraction between dark matter particles. We find that the strength of the coupling {\beta} is constrained using current Cosmic Microwave Background (CMB) data, including WMAP7 and SPT, to be less than 0.063 (0.11) at 68% (95%) confidence level. Further, we consider the additional effect of the CMB-lensing amplitude, curvature, effective number of relativistic species and massive neutrinos and show that the bound from current data on {\beta} is already strong enough to be rather stable with respect to any of these variables. The strongest effect is obtained when we allow for massive neutrinos, in which case the bound becomes slightly weaker, {\beta} < 0.084(0.14). A larger value of the effective number of relativistic degrees of freedom favors larger couplings between dark matter and dark energy as well as values of the spectral index closer to 1. Adding the present constraints on the Hubble constant, as well as from baryon acoustic oscillations and supernovae Ia, we find {\beta} < 0.050(0.074). In this case we also find an interesting likelihood peak for {\beta} = 0.041 (still compatible with 0 at 1{\sigma}). This peak comes mostly from a slight difference between the Hubble parameter HST result and the WMAP7+SPT best fit. Finally, we show that forecasts of Planck+SPT mock data can pin down the coupling to a precision of better than 1% and detect whether the marginal peak we find at small non zero coupling is a real effect.Comment: 22 pages, 17 figure

Cooperative and non-cooperative solutions to carbon leakage

A modified version of the CGE GTAP-E model is developed for assessing the economic and carbon emissions effects related to alternative policy measures implemented with the aim of reducing carbon leakage. We explore a set of scenarios, comparing solutions where Annex I countries introduce exogenously or endogenously determined carbon border taxes in order to solve the carbon leakage problem unilaterally. Results provide evidence on the scarce effectiveness of carbon tariffs in reducing carbon leakage and enhancing economic competitiveness, while they have large negative welfare effects not only on the Non-Annex countries, but also on certain Annex I countriesCarbon Leakage, Carbon Border Tax, GTAP-E model

Bargaining Coalitions in the Agricultural Negotiations of the Doha Round: Similarity of Interests or Strategic Choices? An Empirical Assessment

The paper aims at understanding the structural features of the bargaining coalitions in the Doha Round of the WTO. We provide an empirical assessment of the preferences of each negotiating actor looking at general economics indicators, development levels, structure of the agricultural sectors, and trade policies for agricultural products. Bargaining coalitions are analyzed by grouping countries through a cluster analysis procedure. The clusters are compared with existing coalitions, in order to assess their degree of internal homogeneity as well as their common interests. Such a comparison allows the detection of possible “defectors”, i.e. countries that according to their economic conditions and policies seem to be relatively less committed to the positions of the coalition they join.Agricultural trade negotiations, Bargaining coalitions, WTO, Cluster analysis

Vita indipendente e sviluppo di abilità personali e sociali per l’indipendenza. Un percorso di consapevolezza verso la vita adulta per persone con disabilità

This paper presents data from nationwide research performed in Italy by the University of Bo-logna on developing Independent Lifestyles within residential services for adults with disabilities. These reflections concern residents’ self awareness and awareness of their own well-being, further investigating which basic relational, cognitive, and emotional skills have been acquired during the path to independent living.Il presente articolo presenta i dati emersi da una ricerca condotta in Italia dall’Uni-versità di Bologna sullo sviluppo degli stili di vita indipendente nell’ambito dei servizi residenziali per adulti con disabilità. Le riflessioni riportate riguardano in particolare gli aspetti legati alla consapevolezza di sé e del proprio benessere dei residenti. Ven-gono inoltre presentati i dati emersi dall’indagine su quali principali competenze re-lazionali, cognitive ed emotive sono state acquisite durante il percorso durante esperienze vita indipendente