The Chemical Evolution of the Solar Neighbourhood: the Effect of Binaries

In this paper we compute the time evolution of the elements (4He, 12C, 14N, 16O, 20Ne, 24Mg, 28Si, 32S, 40Ca and 56Fe) and of the supernova rates in the solar neighbourhood by means of a galactic chemical evolutionary code that includes in detail the evolution of both single and binary stars. Special attention is payed to the formation of black holes. Our main conclusions: in order to predict the galactic time evolution of the different types of supernovae, it is essential to compute in detail the evolution of the binary population, the observed time evolution of carbon is better reproduced by a galactic model where the effect is included of a significant fraction of intermediate mass binaries, massive binary mass exchange provides a possible solution for the production of primary nitrogen during the very early phases of galactic evolution, chemical evolutionary models with binaries or without binaries but with a detailed treatment of the SN Ia progenitors predict very similar age-metallicity relations and very similar G-dwarf distributions whereas the evolution of the yields as function of time of the elements 4He, 16O, 20Ne, 24Mg, 28Si, 32S and 40Ca differ by no more than a factor of two or three, the observed time evolution of oxygen is best reproduced when most of the oxygen produced during core helium burning in ALL massive stars serves to enrich the interstellar medium. This can be used as indirect evidence that (massive) black hole formation in single stars and binary components is always preceded by a supernova explosion.Comment: 59 page

The Politics of Progressive Income Taxation with Incentive Effects

This paper studies majority voting over non-linear income taxes when individuals respond to taxation by substituting untaxable leisure to taxable labor (incentive effects). We first show that voting cycle over progressive and regressive taxes is inevitable. This is because the middle-class can always lower its tax burden at the expense of the rich by imposing progressive taxes (convex tax function) while the rich and the poor can reduce their tax burden by imposing regressive taxes (concave tax function). We then investigate three solutions to this cycling problem: (i) reducing the policy space to the policies that are ideal for some voter; (ii) weakening the voting equilibrium concept; (iii) assuming parties also care about the size of their majority. The main results is that progressivity emerges as a voting equilibrium if there is a lack of polarization at the extremes of the income distribution. Interestingly the poor would prefer regressive taxes.Majority voting, Income taxation, Tax progressivity

Voting under the Threat of Secession: Accommodation vs. Repression

We build a model of secession crises where voters may wish to accommodate the minority to prevent secession. We show the existence of a majority voting equilibrium with a government’s type biased in favor of the minority. We propose a measure of secession risk and perform the comparative static analysis of the equilibrium policy location and of the secession risk with respect to the cultural distinctiveness of the two regions, the relative weight attached by voters to economic factors, the relative size of the minority region, the probability that a secession attempt is successful, and the intra-regional heterogeneity of preferences.majority voting, secession risk, cultural distinctiveness, conflict, overlapping regional preferences

Equilibrium Social Insurance with Policy-Motivated Parties

We study the political economy of social insurance with double heterogeneity of voters (i.e., different income and risk levels). Social insurance is financed through distortionary taxation and redistributes across income and risks. Individuals vote over the extent of social insurance, which they can complement on the private market. Private insurance suffers from adverse selection which results into insurance rationing. We model political competition a la Wittman, with two parties maximizing the utility of their members. Party membership is endogenously determined. We show that although individuals differ in two dimensions, their preference for social insurance can be aggregated into a single dimensional type function. We then resort to numerical simulations to solve the political equilibrium resort to numerical simulations to solve the political equilibrium outcome as a function of the distribution of income and risk. We obtain equilibrium policy differentiation with the Left party proposing more social insurance than the Right party. The Left party’s equilibrium membership is made of low risk and high income individuals, with high risk and low income individuals forming the Right party’s constituency. In equilibrium, each party is tying for winning. Unlike the median voter outcome, our equilibrium outcome depends on the whole income and risks distribution, and increasing income polarization leads both parties to propose less social insurance. We also compare the political equilibrium outcome with the Rawlsian and utilitarian outcomes.electoral competition, endogenous parties, Wittman equilibrium, social insurance, adverse selection