Constraints on spin observables

Positivity constrains the allowed domain for sets of spin observables in exclusive or inclusive reactions. Examples are given for strangeness-echange reactions and photoproduction.Comment: 4 pages, to appear in the Proc. QCD08, MOntpellier, France, July 2008, ed. S. Nariso

The Core of a coalitional exchange economy

In pure exchange economies, a poor attention has been given to how the individual consumption possibilities of the members of a coalition should be represented. It seems economically reasonable that our knowledge and our possibility to make decisions depend on the coalition we belong to. We define a coalitional exchange economy by considering a pure exchange economy in which the individual consumption sets of consumers within a coalition depend on the membership of the coalition. Our definition includes as a particular case the classical definition of pure exchange economy. We adapt the core concept to a coalitional exchange economy, and we show the non-emptiness of the core. Finally, we discuss more general setting where individual preferences are also depending on the coalitions.Cooperative game, core, exchange economy, consumption possibility.

Les monnaies sociales : un outil et ses limites. Introduction générale

Introduction générale de livre collectifMonnaies sociales. Pratiques monétaires. Echange.

A probability-conserving cross-section biasing mechanism for variance reduction in Monte Carlo particle transport calculations

In Monte Carlo particle transport codes, it is often important to adjust reaction cross sections to reduce the variance of calculations of relatively rare events, in a technique known as non-analogous Monte Carlo. We present the theory and sample code for a Geant4 process which allows the cross section of a G4VDiscreteProcess to be scaled, while adjusting track weights so as to mitigate the effects of altered primary beam depletion induced by the cross section change. This makes it possible to increase the cross section of nuclear reactions by factors exceeding 10^4 (in appropriate cases), without distorting the results of energy deposition calculations or coincidence rates. The procedure is also valid for bias factors less than unity, which is useful, for example, in problems that involve computation of particle penetration deep into a target, such as occurs in atmospheric showers or in shielding

"A New Approach to Modeling Early Warning Systems for Currency Crises : can a machine-learning fuzzy expert system predict the currency crises effectively?"

This paper presents a hybrid model for predicting the occurrence of currency crises by using the neuro fuzzy modeling approach. The model integrates the learning ability of neural network with the inference mechanism of fuzzy logic. The empirical results show that the proposed neuro fuzzy model leads to a better prediction of crisis. Significantly, the model can also construct a reliable causal relationship among the variables through the obtained knowledge base. Compared to the traditionally used techniques such as logit, the proposed model can thus lead to a somewhat more prescriptive modeling approach towards finding ways to prevent currency crises.

French Exchange Rate Management in the mid-1920\'s lessons drawn from new evidence

This paper challenges the conventional view of the existence of a pure floating regime in France during the mid-1920’s. Our study of the archives of the Bank of France and the French Ministry of Finance, as well as a thourough examination of the exchange rates (FRF/USD) and (FRF/GBP) during the 1920\'s reveal that the French authorities did intervene on several occasions. How ever from these first direct actions, as well as some over abortive attempts, several lessons can be drawn about the effectiveness of interventions on a ‘modern’ echange rate market.Exchange rate Expectations Speculation Bank of France French Treasury Intervention Dirty floating Signalling effect, Credibility

Le concept de confiance à l'épreuve des faits : le cas de la relation entre l'enseigne Auchan et ses fournisseurs.

Relations clients-fournisseurs; Grande distribution; Echange vertical; Confiance;

Vers la constitution de la confiance optimale : réconcilier l'économique et le social.

Echange intra-organisationnel; Confiance;

A magnetic tight-binding model : the origin and the effects of the exchange-correlation hole in transition metals

The accuracy of a method solving an electronic many-body problem lies in the estimation of the exact exchange-correlation term. Many approximations are formulated for some special situations and how to tackle the correlations, leading to overestimated or underestimated physical properties. It is possible to understand and evaluate the exact exchange-correlation in a semi-empirical model by understanding the charge distribution and a screening effect of a delocalized s state. A quantitative calculation in a simple tight-binding + U model is performed, which describes quite accurately some physical properties as the magnetism and the gap in transition metal oxides. Unifying several approaches of the band structure theory, explaining some disagreements in theoretical physics and some experimental results. We found 1.3 eV in the Iron BCC, 1.55 eV in the Cobalt FCC and 2.2 eV in the Nickel for the exchange-correlation energies per orbital and a good estimation of the Curie temperature

Public regulatory reform and management earnings forecasts in a low private litigation environment

We examine the impact of continuous disclosure regulatory reform on the likelihood, frequency and qualitative characteristics of management earnings forecasts issued in New Zealand’s low private litigation environment. Using a sample of 720 earnings forecasts issued by 94 firms listed on the New Zealand Exchange before and after the reform (1999–2005), we provide strong evidence of significant changes in forecasting behaviour in the post-reform period. Specifically, firms were more likely to issue earnings forecasts to pre-empt earnings announcements and, in contrast to findings in other legal settings, those earnings forecasts exhibited higher frequency and improved qualitative characteristics (better precision and accuracy). An important implication of our findings is that public regulatory reforms may have a greater benefit in a low private litigation environment and thus add to the global debate about the effectiveness of alternative public regulatory reforms of corporate requirements