Dynamical Mass Generation for Non-Abelian Gauge Fields without the Higgs

We present an alternative to the Higgs mechanism to generate masses for non-abelian gauge fields in (3+1)-dimensions. The initial Lagrangian is composed of a fermion with current-current and dipole-dipole type self-interactions minimally coupled to non-abelian gauge fields. The mass generation occurs upon the fermionic functional integration. We show that by fine-tuning the coupling constants the effective theory contains massive non-abelian gauge fields without any residual scalars or other degrees of freedom.Comment: 14 pages, UdeM-LPN-TH-94-194, CRM-216

Common and Fundamental Factors in Stock Returns of Canadian Oil and Gas Companies

In this paper, we assess the determinants of Canadian oil and gas stocks returns. We find that the stock return of Canadian energy stock is positively associated with returns on the Canadian stock market, appreciations of crude oil and natural gas prices, growth in internal cash flows and proven reserves, and negatively with interest rates. Surprisingly, however, production volume and a weakening of the Canadian dollar against the U.S. dollar have a negative impact. This latter impact is more pronounced for oil producers than for integrated energy companies. Finally, we find that the influence of the exchange rate, the market return and prices of natural gas on Canadian oil and gas stocks changes significantly over the years 1995-1998 and 2000-2002. Le but de cet article est de mesurer ce qui influence le rendement des actions d'entreprises pétrolières et gazières canadiennes. Nous trouvons que le rendement des actions de ces entreprises énergétiques est influencé positivement par le rendement du marché canadien dans son ensemble, par une appréciation du prix du pétrole et du gaz naturel, par une croissance dans les flux monétaires discrétionnaires de l'entreprise, par la quantité de réserves prouvées de l'entreprise. Nous trouvons également que le volume de production et une dépréciation du dollar canadien par rapport à la devise américaine réduit sensiblement le rendement des titres énergétiques, ce qui va à l'encontre de notre hypothèse initiale. L'impact du taux de change est encore plus marqué pour les producteurs indépendants que pour les entreprises intégrées. En dernier lieu, nous montrons que le marché a subi une cassure significative entre les années 1995-1998 et 2000-2002, spécialement pour ce qui est de l'impact du taux de change, du rendement de marché et du pris du gaz naturel.stock return valuation, panel data analysis, oil and gas industry, rendement des actions, analyse de données transversales, industrie pétrolière et gazière

Moment and SDP relaxation techniques for smooth approximations of problems involving nonlinear differential equations

Combining recent moment and sparse semidefinite programming (SDP) relaxation techniques, we propose an approach to find smooth approximations for solutions of problems involving nonlinear differential equations. Given a system of nonlinear differential equations, we apply a technique based on finite differences and sparse SDP relaxations for polynomial optimization problems (POP) to obtain a discrete approximation of its solution. In a second step we apply maximum entropy estimation (using moments of a Borel measure associated with the discrete solution) to obtain a smooth closed-form approximation. The approach is illustrated on a variety of linear and nonlinear ordinary differential equations (ODE), partial differential equations (PDE) and optimal control problems (OCP), and preliminary numerical results are reported