On the Non-Lorentz Invariance of M.W. Evans O(3)-Symmetry Law

Correcting a former proof of M.W. Evans it is shown that his O(3) hypothesis is not Lorentz invariant and hence no law of Physics.Comment: 5 page

Matroid and Tutte-connectivity in infinite graphs

We relate matroid connectivity to Tutte-connectivity in an infinite graph. Moreover, we show that the two cycle matroids, the finite-cycle matroid and the cycle matroid, in which also infinite cycles are taken into account, have the same connectivity function. As an application we re-prove that, also for infinite graphs, Tutte-connectivity is invariant under taking dual graphs.Comment: 11 page

A tale of two species : revisiting the effect of registration reform on informal business owners in Mexico

Different views have been put forward to explain why most firms in developing countries operate informally. One view argues that informal-business owners are entrepreneurs who do not register their firm because the regulation process is too complex. Another argues that informal-business owners are people trying to make a living while searching for a wage job. This paper contributes to recent literature that argues that both factors are at work. The author uses discriminant analysis to separate informal business owners into two groups: those with personal characteristics similar to wage workers, and those with traits similar to formal-business owners. The paper then examines how the two groups were affected by a business registration reform in Mexico. Informal-business owners from the second group were more likely to register their business after the reform. By contrast, informal-business owners from the first group were less likely to register but more likely to become wage workers after the reform. This is consistent with the finding in Bruhn (2008 and 2011) that the reform led to job creation. It also explains why the earlier papers find that the reform didn’t affect the number of new registrations by all informal business owners.Competitiveness and Competition Policy,Business in Development,Business Environment,E-Business,Access to Finance

Female-owned firms in Latin America : characteristics, performance, and obstacles to growth

This paper examines the characteristics and performance of female-owned firms in Latin America. Data from firm surveys show that female-owned firms tend to be smaller than male-owned firms in terms of employees, sales, costs, and physical capital. Female-owned firms also have lower profits than male-owned firms, but for larger firms this difference disappears after controlling for labor and capital inputs. Medium-size and large female-owned firms are as productive as male-owned firms of the same size, although micro and small female-owned firms are less productive than male-owned firms. There is no evidence that the differences between female and male-owned firms are due to differences in access to finance or regulatory burdens. However, this paper finds a negative correlation between child care and household obligations and female-owned firm size and performance.