G-biliaison of ladder Pfaffian varieties

The ideals generated by pfaffians of mixed size contained in a subladder of a skew-symmetric matrix of indeterminates define arithmetically Cohen-Macaulay, projectively normal, reduced and irreducible projective varieties. We show that these varieties belong to the G-biliaison class of a complete intersection. In particular, they are glicci.Comment: 15 page

The influence of capital origin on Brazilian foreign trade patterns

This article aims to determine whether the geographical pattern of the external trade of foreign-owned enterprises in Brazil differs from that of domestic enterprises and whether, in the case of foreign enterprises, the region of origin of their capital is an important factor in determining that pattern, both in terms of the origin and destination of their imports and exports and with regard to the technological content. The methodology employed was panel analysis, applied to a representative set of enterprises, using trade data broken down by region for 1989, 1997 and 2000.Multinational Firm Intra-Firm Trade

Koszul algebras and regularity

This is a survey paper on commutative Koszul algebras and Castelnuovo-Mumford regularity. We describe several techniques to establish the Koszulness of algebras. We discuss variants of the Koszul property such as strongly Koszul, absolutely Koszul and universally Koszul. We present several open problems related with these notions and their local variants

Knowledge production and firm growth in Brazil

The aim of this study is to gauge the impact of the production of knowledge on the accumulation of fixed capital in Brazil. The hypothesis is that investment in R&D causes investment in fixed capital in Brazilian industrial firms. The empirical estimates rest on an IPEA database for information on firms and the workers linked to these firms during the period 1996-2003 and on the National Innovation Survey (PINTEC) for information on technological development. In the article, various estimates are made using three empirical procedures. First, the firms that grew most and invested most are described. Second, econometric models relating R&D expenditures, technological innovation and the accumulation of fixed capital are estimated. A model having five equations and a structure similar to that of CDM models is estimated. The system employs instrumental variables to correct for endogeneity and solves the selection problem by including a firm-survival equation. Third, the causal relations between R&D and investment in fixed capital are sought through contrafactual analysis and a difference model. The results support the initial hypothesis, indicating that investments in R&D lead to an average 17% increase in investments in fixed capital among Brazilian firms.firm growth, knowledge production, R&D, innovation, simultaneous equation models