226 research outputs found
Wer ist der beste Formel 1 Fahrer? Eine ökonometrische Talentbewertung
Who is the best Formula 1 driver? Until today it was impossible to answer this question because the observable performance of a driver depends both on his talent and the quality of his cars. In this article we separate for the first time driver talent from car quality by econometrically analyzing data for 57 years of Formula 1 racing. Our estimates also control for the number of drivers finishing, technical breakdowns and many other variables that influence race results. While Michael Schumacher is often believed to be the best driver, he is overtaken by Juan Manuel Fangio and Jim Clar
How Federalism Protects Future Generations from Today's Public Debts
From the politico-economic perspective, federalism is a protector of the present generation. But what about future generations? In federal states, Ricardian equivalence cannot be assumed to work properly, as migration between local jurisdictions undermines intergenerational redistribution based on parental altruism. However, we argue that there exists another equivalence mechanism which also works with purely selfish individuals: Public debts capitalize into property values. Jurisdictions with larger net debts exhibit, ceteris paribus, lower property prices. Debt capitalization in property values is the more pronounced the less elastic land supply is and the more mobile the other factors of production are. Therefore, capitalization is more relevant for local than for national debts, i.e. it is more pronounced in a federal than in a centralized state. Thus, federalism also becomes a protector of future generation
Superconductivity and antiferromagnetism in the two-dimensional Hubbard model: a variational study
A variational ground state of the repulsive Hubbard model on a square lattice is investigated numerically for an intermediate coupling strength (U=8t) and for moderate sizes (from 6Ă6 to 10Ă10). Our ansatz is superior to other widely used variational wave functions. The results for order parameters and correlation functions provide insight into the antiferromagnetic state at half-filling as well as strong evidence for a superconducting phase away from half-filling
Superconductivity and antiferromagnetism in the two-dimensional Hubbard model
En dĂ©pit de son apparente simplicitĂ© et bien quâil ait dĂ©jĂ Ă©tĂ© intensivement Ă©tudiĂ© dans des contextes trĂšs variĂ©s, le modĂšle de Hubbard bidimensionnel est encore trĂšs loin dâavoir livrĂ© tous ses mystĂšres. En particulier lorsquâil dĂ©crit une interaction moyenne Ă fortement rĂ©pulsive, câest-Ă -dire un rĂ©gime mal adaptĂ© aux mĂ©thodes perturbatives, son Ă©tat fondamental est encore mĂ©connu. La dĂ©couverte en 1986 dâune phase supraconductrice chez les oxydes de cuivre (cuprates), apparaissant Ă relativement haute tempĂ©rature, a encore avivĂ© lâintĂ©rĂȘt pour ce modĂšle puisquâil pourrait dĂ©crire les propriĂ©tĂ©s Ă©tonnantes de ces matĂ©riaux Ă structures planaires. Lorsque la densitĂ© Ă©lectronique correspond Ă une bande de valence demi remplie, le modĂšle de Hubbard est en effet connu pour rendre parfaitement compte de la phase antiferromagnĂ©tique obtenue expĂ©rimentalement chez les cuprates et il est probable quâil en soit de mĂȘme pour la phase supraconductive observĂ©e au-dessous dâune tempĂ©rature critique, lorsque la densitĂ© Ă©lectronique est modĂ©rĂ©ment rĂ©duite en modifiant la composition du matĂ©riau (dopage). Si tel est le cas, cela signifie que seules les interactions Ă©lectronique sont Ă lâorigine de la supraconductivitĂ©, contrairement aux supraconducteurs conventionnels oĂč lâinteraction entre les Ă©lectrons et les vibrations du rĂ©seau (phonons) est impliquĂ©e. Malheureusement, il existe pour lâheure peu de rĂ©sultats indiscutables venant Ă©tayer cette hypothĂšse et la question est encore largement dĂ©battue. Dans cette thĂšse, la mĂ©thode variationelle est mise Ă profit pour tenter dâapporter une rĂ©ponse claire concernant la possibilitĂ© dâun Ă©tat fondamental supraconducteur pour le modĂšle de Hubbard rĂ©pulsif. Bien que la fiabilitĂ© de ses rĂ©sultats soit conditionnĂ©e par le choix dâune fonction variationelle adĂ©quate, cette mĂ©thode est tout spĂ©cialement adaptĂ©e au rĂ©gime appropriĂ© pour les cuprates, câest-Ă -dire Ă une interaction intermĂ©diaire. Lâoptimisation dâune fonction variationelle Ă©laborĂ©e permet dâapprocher de trĂšs prĂšs lâĂ©tat fondamental exact, ce qui nâĂ©tait pas le cas des fonctions variationelles connues jusquâici. En fait, la considĂ©ration de petits systĂšmes rend accessible une solution exacte, qui indique que lâerreur commise dans notre calcul est trop faible pour influencer qualitativement nos rĂ©sultats. Ceux-ci montrent quâune phase antiferromagnĂ©tique est favorable au demi remplissage et dâune phase supraconductrice Ă©merge lorsque la densitĂ© Ă©lectronique diminue, avec un paramĂštre dâordre possĂ©dant une symĂ©trie onde-d. Toutes les caractĂ©ristiques principales propres aux oxydes de cuivre sont donc retrouvĂ©es pour lâĂ©tat fondamental variationel du modĂšle de Hubbard rĂ©pulsif. Des similitudes remarquables sont aussi observĂ©es au niveau quantitatif lorsque les propriĂ©tĂ©s de cet Ă©tat fondamental sont comparĂ©es aux donnĂ©es expĂ©rimentales obtenues pour les cuprates.Despite its apparent simplicity and even if it has been studied intensively in various contexts, the two-dimensional Hubbard model is not yet completely understood. In particular when it describes a system with an intermediate interaction, out of range for perturbative methods, its ground state is still not well known. The discovery in 1986 of a superconducting phase in the copper oxides (cuprates), which appears at rather high temperature, has further enhanced the interest for this model, as it may describe the amazing poperties of these layered materials. Indeed, when the electronic density corresponds to a half-filled band, the Hubbard model is known to nicely account for the antiferromagnetic phase obtained experimentally for the cuprates and it is possible, as first proposed by P. W. Anderson, that it describes equally well the superconducting phase observed below a critical temperature, when the electronic density is moderatly reduced by modifying the compound composition (doping). In this case, the superconductivity originates from purely electronic interactions, contrary to conventional superconductivity where the interaction between electrons and lattice vibrations (phonons) is involved. Unfortunately, very few stringent results are available in order to support this statement and this question is still largely debated. In this thesis, the variational method is used in order to scrutinize the possibility of a superconducting ground state for the repulsive Hubbard model. Although its reliability is based on the adequate choice of the variational wave function, this method is especially suited for treating intermediate interactions, which is the appropriate regime of the cuprates. The optimization of a refined wave function allows us to obtain a variational ground state which is much closer to the exact ground state than those obtained so far using less elaborate wave functions. Actually, the exact study of small systems indicates that the error of our calculation is too small to allow for a qualitatively different behavior. Our results show that an antiferromagnetic phase is dominant at half-filling, while a superconducting phase with a d-wave symmetry of the order parameter emerges at moderate doping. The key features of the copper oxides are therefore found in the variational ground state of the repulsive Hubbard model. Some amazing similarities are also observed at the quantitative level when the properties of this ground state are compared to the experimental data obtained for the cuprates
Superconducting ground state of the two-dimensional Hubbard model: a variational study
A trial wave function is proposed for studying the instability of the
two-dimensional Hubbard model with respect to d-wave superconductivity. Double
occupancy is reduced in a similar way as in previous variational studies, but
in addition our wave function both enhances the delocalization of holes and
induces a kinetic exchange between the electron spins. These refinements lead
to a large energy gain, while the pairing appears to be weakly affected by the
additional term in the variational wave function.Comment: 2 pages, 1 figure, Proceedings of the M2S-HTSC-VII
District magnitude and representation of the majority's preferencesâa reply and new perspectives
We reply to the comment of John Carey and Simon Hix on our original contribution entitled "District Magnitude and Representation of the Majority's Preferences: Quasi-Experimental Evidence from Popular and Parliamentary Votesâ in Public Choice 151:585-610 (2012). District magnitude does not necessarily affect deviations between political representatives and their district voters in a strictly monotonic way but monotonicity is upheld for deviations between representatives and the national majority. We provide new perspectives and caution against evaluating electoral systems by focusing on individual politicians' behavior but neglecting aggregation effect
District magnitude and representation of the majority's preferences: Evidence from popular and parliamentary votes
Representatives have more effective incentives to cater to the preferences of the majority of citizens when they are elected in districts with few rather than many seats. We investigate this hypothesis empirically by matching Swiss members of parliament's voting behavior on legislative proposals with real referendum outcomes on the same issues for the years 1996 to 2008. We thus identify the impact of district magnitude on representatives' incentives to adhere to citizens' revealed preferences. We find systematic, statistically significant and economically relevant evidence that individual representatives from districts with few seats vote more often in line with majority preference
A comparative analysis of the voting behavior of constituents and their representatives for public debts
We explore the quality of political representation of constituents' preferences for budgetary decisions within a quasi-experimental setting. In the Swiss referendum process, constituents reveal their preferences for budgetary proposals which are either expected to increase or decrease public debts. We match individual politicians' voting behavior on debt increasing and debt reducing legislative proposals with eight real referendum decisions on exactly the same issues from 2008 to 2011. Thereby, we directly explore deviations of politicians from constituents' preferences with respect to budgetary policie
Full Transparency of Politicians' Actions Does Not Increase the Quality of Political Representation
We identify the impact of transparency in political decision-making on the quality of political representation with a difference-in-difference strategy. The quality of political representation is measured by the observed divergence of parliamentary decisions from revealed voter preferences on identical issues. We show that full transparency of votes of individual politicians does not decrease divergence from voter preference
âIn the interest of your bank and our countryâ: two encounters between China and the International Chamber of Commerce
This article examines Chinaâs path to joining the International Chamber of Commerce (ICC), a private international organization founded in Paris in 1920, of which China was a member from 1931â1949 and from 1994 onwards. The article charts the actors and debates behind two meaningful encounters. The first took place while the Nanjing government was raising funds for economic reconstruction, and the ICC aimed to mediate Chinaâs fundraising efforts through private multilateral channels. The second was in the 1980s, when the Peopleâs Republic was seeking to enter the world trade system. ICC members acted as educators and facilitators of world trade practicalities for the Peopleâs Republic, which eventually rejoined the ICC in 1994. The article draws on Chinese, European, and American source material collected from governments, chambers of commerce, and private businessmen to make a twofold contribution. First, it adds nuance to the narrative of Chinaâs economic internationalization by identifying an important non-governmental diplomatic channel. Second, it questions the ICCâs self-proclaimed identity as a non-political economic organization by showing how the political was indissociable from the economic when it came to Chinaâs membership
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