Quasifolds, Diffeology and Noncommutative Geometry

After embedding the objects quasifolds into the category {Diffeology}, we associate a C*-agebra with every atlas of any quasifold, and show how different atlases give Morita equivalent algebras. This builds a new bridge between diffeology and noncommutative geometry (beginning with the today classical example of the irrational torus) which associates a Morita class of C*-algebras with a diffeomorphic class of quasifolds.Comment: 21 pages, 3 figures, final version to appear in J. Noncommut. Geom., notes added in introductio

Primary Spaces, Mackey's Obstruction, and the Generalized Barycentric Decomposition

We call a hamiltonian N-space \emph{primary} if its moment map is onto a single coadjoint orbit. The question has long been open whether such spaces always split as (homogeneous) x (trivial), as an analogy with representation theory might suggest. For instance, Souriau's \emph{barycentric decomposition theorem} asserts just this when N is a Heisenberg group. For general N, we give explicit examples which do not split, and show instead that primary spaces are always flat bundles over the coadjoint orbit. This provides the missing piece for a full "Mackey theory" of hamiltonian G-spaces, where G is an overgroup in which N is normal.Comment: 23 pages, 1 figure. Final preprint version, to appear in Journal of Symplectic Geometr

Tolkien in the Land of Arthur: the Old Forest Episode from \u3ci\u3eThe Lord of the Rings\u3c/i\u3e

A study of Arthurian and other medieval romance motifs in the Old Forest episode, relying heavily on the linguistic features of this chapter

Diffeological, Fr\"{o}licher, and Differential Spaces

Differential calculus on Euclidean spaces has many generalisations. In particular, on a set $X$, a diffeological structure is given by maps from open subsets of Euclidean spaces to $X$, a differential structure is given by maps from $X$ to $\mathbb{R}$, and a Fr\"{o}licher structure is given by maps from $\mathbb{R}$ to $X$ as well as maps from $X$ to $\mathbb{R}$. We illustrate the relations between these structures through examples.Comment: 21 page

What shapes the generosity of short- and long-term benefits? A political economy approach

URL des Documents de travail : http://ces.univ-paris1.fr/cesdp/cesdp2013.htmlDocuments de travail du Centre d'Economie de la Sorbonne 2013.27 - ISSN : 1955-611XDegressivity of unemployment benefits is a major feature of social protection in most industrialised countries: the replacement rate (the ratio between the level of welfare benefits and the previous income) typically declines with the length of the unemployment spell. Moreover degressivity of unemployment benefits has significant distributive effects as the risk of long-term unemployment varies from one individual to another. This paper proposes a formal model of political support for unemployment insurance that takes into account the decrease in the level of benefits over time. A discount factor is introduced that diminishes the level of benefits for long-term unemployed. The main predictions of our model are the following: i) Unemployment insurance size negatively depends on both the average level and the heterogeneity of unemployment risk ii) The degressivity increases with the average level and the heterogeneity in the individual level of employability defined as the probability of finding a job when unemployed. These predictions are then tested using a dataset of 24 OECD countries. Empirical results are consistent with the model.Le caractère dégressif de l'assurance chômage est un trait commun de nombreux pays industrialisés : le taux de remplacement décline au cours de la période de chômage. De plus, le degré de dégressivité a des conséquences distributives importantes dans la mesure où le risque de chômage de longue durée n'est pas uniforme. Cet article propose un modèle d'économie politique dans lequel la demande d'assurance chômage prend en compte la distinction entre chômage de courte et de longue durée et la possibilité de prestations dégressives. Les principales prédictions du modèle sont les suivantes : i) le taux de remplacement moyen des prestations chômage dépend négativement du chômage moyen et de l'hétérogénéité du risque de chômage dans la population. ii) la dégressivité des prestations est d'autant plus forte que l'employabilité moyenne est plus faible et que le niveau d'employabilité des salariés est hétérogène. Ces prédictions sont testées sur des données OCDE concernant 24 pays. Les résultats obtenus sont cohérents avec le modèle

Four levers of redistribution: The impact of tax and transfer systems on inequality reduction

Using observational micro data from the Luxembourg Income Study (LIS), we assess the redistributive impact of tax and transfer configurations across 22 OECD countries for the period 1999-2013. After recovering new tax data (employer social contributions), we measure the reduction of income inequality due to the four structural dimensions of tax and transfer systems: the average tax rate, tax progressivity, the average transfer rate, and transfer targeting. Among the most remarkable results, we notice (i) the diverse combinations of taxation and transfers that achieve the same reduction in inequality; (ii) the absence of configurations that match strongly progressive taxation with a high rate of taxation; and (iii) the decisive impact of the rate of transfers relative to targeting

Primary Spaces, Mackey\u27s Obstruction, and the Generalized Barycentric Decomposition

We call a hamiltonian N-space primary if its moment map is onto a single coadjoint orbit. The question has long been open whether such spaces always split as (homogeneous) x (trivial), as an analogy with representation theory might suggest. For instance, Souriau\u27s barycentric decomposition theorem asserts just this when N is a Heisenberg group. For general N, we give explicit examples which do not split, and show instead that primary spaces are always flat bundles over the coadjoint orbit. This provides the missing piece for a full Mackey theory of hamiltonian G-spaces, where G is an overgroup in which N is normal

Les quatre leviers de la redistribution

Les systèmes de taxes et transferts permettent de réduire les inégalités de revenus à travers quatre leviers : taux d'imposition, progressivité de l'impôt, taux de transferts sociaux et degré de ciblage des transferts. Nous étudions les différentes configurations combinant ces quatre leviers dans 22 pays de l'OCDE. La progressivité de l'impôt est mesurée par un indice de Kakwani qui évalue la surconcentration de la fiscalité sur les revenus élevés; le ciblage des transferts est mesuré par un indice symétrique; la réduction des inégalités de revenu est mesurée par la variation des indices de Gini avant et après redistribution. Nous utilisons les micro-données du Luxembourg Income Study sur le revenu des ménages, que nous complétons par l'imputation de données fiscales non observées (en particulier les cotisations employeur). L'étude porte sur 67 observations entre 1999 et 2013. Nous montrons que la plupart des pays utilisent davantage les prélèvements obligatoires que les prestations en espèces (hors pensions de retraite) afin de redistribuer les revenus. Par ailleurs, l'effet plus ou moins redistributif des transferts sociaux dépend davantage de leur niveau moyen que d'une différence dans leur degré de ciblage. En revanche, c'est à la fois le taux de prélèvements et la progressivité qui expliquent l'effet redistributif du système fiscal. Enfin, nous observons une incompatibilité entre forte progressivité et haut niveau de prélèvements obligatoires