9,693 research outputs found
Proving More Observational Equivalences with ProVerif
This paper presents an extension of the automatic protocol verifier ProVerif in order to prove more observational equivalences. ProVerif can prove observational equivalence between processes that have the same structure but differ by the messages they contain. In order to extend the class of equivalences that ProVerif handles, we extend the language of terms by defining more functions (destructors) by rewrite rules. In particular, we allow rewrite rules with inequalities as side-conditions, so that we can express tests ''if then else'' inside terms. Finally, we provide an automatic procedure that translates a process into an equivalent process that performs as many actions as possible in- side terms, to allow ProVerif to prove the desired equivalence. These extensions have been implemented in ProVerif and allow us to au- tomatically prove anonymity in the private authentication protocol by Abadi and Fournet
Public expenditure and consumption volatility
Recent estimates of the welfare cost of consumption volatility find that it is significant in developing nations, where it may reach an equivalent of reducing consumption by 10 percent per year. Hence, examining the determinants of consumption volatility is of utmost relevance. Based on cross-country data for the period 1960-2005, the paper explains consumption volatility using three sets of variables: one refers to the volatility of income and the persistence of income shocks; the second set of variables refers to policy volatility, considering the volatility of public spending and the size of government; while the third set captures the ability of agents to smooth shocks, and includes the depth of the domestic financial markets as well as the degree of integration to international capital markets. To allow for potential endogenous regressors, in particular the volatility of fiscal policy and the size of government, the system is estimated using the instrumental variables method. The results indicate that, besides income volatility, the variables with the largest and most robust impact on consumption volatility are government size and the volatility of public spending. Results also show that deeper and more stable domestic financial markets reduce the volatility of consumption, and that more integrated financial markets to the international capital markets are associated with lower volatility of consumption.Economic Conditions and Volatility,Emerging Markets,Economic Stabilization,Economic Theory&Research,Currencies and Exchange Rates
On the second cohomology of K\"ahler groups
Carlson and Toledo conjectured that any infinite fundamental group
of a compact K\"ahler manifold satisfies . We assume
that admits an unbounded reductive rigid linear representation. This
representation necessarily comes from a complex variation of Hodge structure
(\C-VHS) on the K\"ahler manifold. We prove the conjecture under some
assumption on the \C-VHS. We also study some related geometric/topological
properties of period domains associated to such \C-VHS.Comment: 21 pages. Exposition improved. Final versio
Optical gratings induced by field-free alignment of molecules
We analyze the alignment of molecules generated by a pair of crossed
ultra-short pump pulses of different polarizations by a technique based on the
induced time-dependent gratings. Parallel polarizations yield an intensity
grating, while perpendicular polarizations induce a polarization grating. We
show that both configurations can be interpreted at moderate intensity as an
alignment induced by a single polarized pump pulse. The advantage of the
perpendicular polarizations is to give a signal of alignment that is free from
the plasma contribution. Experiments on femtosecond transient gratings with
aligned molecules were performed in CO2 at room temperature in a static cell
and at 30 K in a molecular expansion jet.Comment: 10 pages, 5 figures, submitted to PR
Les espaces périurbains non bùtis en France : entre publicisation "urbaine" et privatisation "rurale" ?
International audienceCet article propose d'apprĂ©hender les sociabilitĂ©s en construction au sein des Espaces PĂ©riurbains Non BĂątis (EPNB) Ă partir d'une grille d'interprĂ©tation problĂ©matisĂ©e en termes de processus croisĂ©s de publicisation et de privatisation. AprĂšs avoir posĂ© les enjeux actuels de ces EPNB, morphologiquement ruraux mais soumis Ă l'influence urbaine, les auteurs explicitent les rouages de ces deux mouvements antagonistes qui renforcent l'incertitude du jeu social et conduisent les acteurs ordinaires Ă inventer leurs propres rĂšgles de coexistence. Or, en accentuant le rĂŽle des accommodements quotidiens, cette tension interroge Ă©galement le caractĂšre opĂ©ratoire du clivage rural-urbain. Alors que, depuis quelques annĂ©es, des approches thĂ©oriques prĂŽnent l'Ă©mergence de nouvelles catĂ©gories de connaissance pour penser le pĂ©riurbain, cet article invite Ă considĂ©rer que les relations sociales Ă l'Ćuvre dans les EPNB demeurent encore de l'ordre d'une hybridation entre rural et urbain. Cette perspective ouvre des pistes pour envisager les modalitĂ©s concrĂštes d'une rĂ©gulation publique de ces espaces en France
Sida et développement : un enjeu mondial
Lâarticle propose une revue des dĂ©bats Ă©conomiques que suscite la pandĂ©mie de SIDA en Afrique, notamment les dĂ©bats portant sur lâaccĂšs restreint aux thĂ©rapeutiques brevetĂ©es et sur le droit international en matiĂšre de propriĂ©tĂ© intellectuelle (OMC, accords TRIPs). AprĂšs une rapide description de la maladie, de son Ă©pidĂ©miologie, et des traitements existants, il Ă©nonce les diffĂ©rentes formes dâimpact de
la maladie sur lâĂ©conomie et examine les Ă©tudes macroĂ©conomiques disponibles pour les pays africains. La mĂ©connaissance des aspects diffĂ©rĂ©s du choc, sur lâaccumulation de capital et sur lâĂ©ducation, peut avoir conduit les Ă©tudes Ă sous-estimer lâeffet de la maladie sur les mĂ©canismes de dĂ©veloppement de ces pays trĂšs pauvres. Ce constat, la gravitĂ© de la maladie, ainsi que lâobservation des formes concrĂštes de lâĂ©change international, plaident pour une intervention publique mondiale Ă deux niveaux : dâune part une rĂ©Ă©valuation critique de la lĂ©gislation sur la protection des droits de propriĂ©tĂ© intellectuelle, mise en place sous lâĂ©gide de lâOrganisation mondiale du commerce ; dâautre part la constitution dâun « fonds global » de connaissances et de moyens financiers, dans lequel les pays pauvres pourraient trouver les traductions
concrĂštes des solidaritĂ©s et dâune vĂ©ritable gouvernance mondiales
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