Generalizing the Planck distribution

Along the lines of nonextensive statistical mechanics, based on the entropy $S_q = k(1- \sum_i p_i^q)/(q-1) (S_1=-k \sum_i p_i \ln p_i)$, and Beck-Cohen superstatistics, we heuristically generalize Planck's statistical law for the black-body radiation. The procedure is based on the discussion of the differential equation $dy/dx=-a_{1}y-(a_{q}-a_{1}) y^{q}$ (with $y(0)=1$), whose $q=2$ particular case leads to the celebrated law, as originally shown by Planck himself in his October 1900 paper. Although the present generalization is mathematically simple and elegant, we have unfortunately no physical application of it at the present moment. It opens nevertheless the door to a type of approach that might be of some interest in more complex, possibly out-of-equilibrium, phenomena.Comment: 6 pages, including 2 figures. To appear in {\it Complexity, Metastability and Nonextensivity}, Proc. 31st Workshop of the International School of Solid State Physics (20-26 July 2004, Erice-Italy), eds. C. Beck, A. Rapisarda and C. Tsallis (World Scientific, Singapore, 2005

Regional and demographic determinants of poverty in Brazil

The paper identifies the role of regional and demographic determinants of poverty in Brazil. We first estimate the probability of a household being classified as poor or indigent. We then apply decomposition techniques to identify the role of demographic variables (family size, parent’s education, etc.) and of regional variables in explaining those probabilities. We found out that parent’s education is the most important determinant, but regional aspects also play a role in determining poverty across states in Brazil.

The inter-generational persistence of child labor

The authors use the"Pesquisa Nacional por Amostragem a Domicilio"(PNAD) data for Brazil. Their paper asks two related questions. First, does the child labor status of parents impact the child labor incidence of their children? The authors find strong evidence that it does. Second, is this link only a function of permanent family income or is there a direct link between the child labor status of the parents, and their children? They find evidence that such a direct link exists. This complements their previous research (Emerson and Souza 2002) in which they went on to ask if a person works as a child, would this increase the probability of his, or her child working by more than what can be explained, by the fact that the person will be poor as an adult (by virtue of having been a child worker), and therefore compelled to send the child to work? The answer to this is also yes. Hence, the presence of social factors can cause the perpetuation of child labor through non-income channels. It is, for instance, possible that having been a child laborer oneself, affects one's social norms, and attitude to child labor (Basu 1999, Lopez-Calva 2002), such that one is more prone to send ones'own child to work.

Correlated electrons systems on the Apollonian network

Strongly correlated electrons on an Apollonian network are studied using the Hubbard model. Ground-state and thermodynamic properties, including specific heat, magnetic susceptibility, spin-spin correlation function, double occupancy and one-electron transfer, are evaluated applying direct diagonalization and quantum Monte Carlo. The results support several types of magnetic behavior. In the strong-coupling limit, the quantum anisotropic spin 1/2 Heisenberg model is used and the phase diagram is discussed using the renormalization group method. For ferromagnetic coupling, we always observe the existence of long-range order. For antiferromagnetic coupling, we find a paramagnetic phase for all finite temperatures.Comment: 7 pages, 8 figure