10,759 research outputs found
Isovector properties of the Gogny interaction
We analyse the properties of the Gogny interaction in homogeneous matter,
with special emphasis on the isovector sector. We provide analytical
expressions for both the single-particle and the bulk properties of symmetric
and asymmetric nuclear matter. We perform an extensive analysis of these
properties using 11 parametrizations extracted from the literature. We find
that most Gogny interactions have low values for the slope of the symmetry
energy, outside the range of empirically extracted values. As a test of extreme
isospin dependence, we also study the mass-radius relations implied by the
different Gogny equations of state. Our results call for a more careful fitting
procedure of the isovector properties of Gogny functionals.Comment: 23 pages, 14 figures, 1 table. Final published version, typos
correcte
Linkages between Market Participation and Productivity: Results from a Multi-Country Farm Household Sample
We build upon international trade literature to analyze the direction of causality between market participation and productivity. Cross-country household data from Tanzania, Vietnam and Guatemala are used in a 2SLS approach with market participation and productivity as endogenous variables. Results indicate that households with higher productivity tend to participate in agricultural markets regardless of market access factors. In contrast, having better market access does not necessarily lead to higher productivity. This finding suggests that investments in market access infrastructure provide minimal, if any, improvements in agricultural productivity; whereas programs targeted at enhancements in farm structure and capital have the potential to increase both productivity and market participation.International Relations/Trade, Marketing, Productivity Analysis,
Agricultural Prices and Income Distribution among Farmers: A Whole-Household, Multi-Country, Multi-Year Analysis
Recent studies have emphasized that the poorest farmers are often net buyers of key commodities and therefore harmed by rising prices. We use LSMS data from Tanzania, Vietnam and Guatemala to test the degree of net purchases or sales by income level. We find that poorer farmers may be net buyers of individual crops, but only the poorest are net buyers of all crops. More generally, net sales among poor farmers are low. We conclude that agricultural price changes have a diverse but limited influence on poor farmers’ welfare, because their farm sales tend to be offset by food purchases.market participation, poverty, inequality, multi-continent multicountry, Agricultural Finance,
Invariant manifolds and equilibrium states for non-uniformly hyperbolic horseshoes
In this paper we consider horseshoes containing an orbit of homoclinic
tangency accumulated by periodic points. We prove a version of the Invariant
Manifolds Theorem, construct finite Markov partitions and use them to prove the
existence and uniqueness of equilibrium states associated to H\"older
continuous potentials.Comment: 33 pages, 6 figure
The role of the Berry Phase in Dynamical Jahn-Teller Systems
The presence/absence of a Berry phase depends on the topology of the manifold
of dynamical Jahn-Teller potential minima. We describe in detail the relation
between these topological properties and the way the lowest two adiabatic
potential surfaces get locally degenerate. We illustrate our arguments through
spherical generalizations of the linear T x h and H x h cases, relevant for the
physics of fullerene ions. Our analysis allows us to classify all the spherical
Jahn-Teller systems with respect to the Berry phase. Its absence can, but does
not necessarily, lead to a nondegenerate ground state.Comment: revtex 7 pages, 2 eps figures include
Quantum Monte Carlo study of the Ne atom and the Ne+ ion
We report all-electron and pseudopotential calculations of the
ground-stateenergies of the neutral Ne atom and the Ne+ ion using the
variational and diffusion quantum Monte Carlo (DMC) methods. We investigate
different levels of Slater-Jastrow trial wave function: (i) using Hartree-Fock
orbitals, (ii) using orbitals optimized within a Monte Carlo procedure in the
presence of a Jastrow factor, and (iii) including backflow correlations in the
wave function. Small reductions in the total energy are obtained by optimizing
the orbitals, while more significant reductions are obtained by incorporating
backflow correlations. We study the finite-time-step and fixed-node biases in
the DMC energy and show that there is a strong tendency for these errors to
cancel when the first ionization potential (IP) is calculated. DMC gives highly
accurate values for the IP of Ne at all the levels of trial wave function that
we have considered
Historias de vida e historias lingĂĽĂsticas : una aproximaciĂłn a las identidades
Este texto se presentĂł como comunicaciĂłn al II Congreso Internacional de EtnografĂa y EducaciĂłn: Migraciones y CiudadanĂas. Universidad AutĂłnoma de Barcelona, Barcelona, 5-8 Septiembre 2008Desde una perspectiva etnográfica, a travĂ©s de las historias de vida e historias lingĂĽĂsticas de niños inmigrados, realizamos una aproximaciĂłn a sus identidades, como parte constitutiva de la realidad escolar actual. Pretendemos conocer las situaciones de multiculturalidad y plurilingĂĽismo, para formar identidades y contribuir al desarrollo de la convivencia en las escuelas, mediante una metodologĂa interdisciplinar que combina las aportaciones de las Ciencias Sociales, Educativas y LingĂĽĂsticas. La aplicaciĂłn de este estudio es principalmente de tipo educativo, para mejorar la formaciĂłn inicial de los maestros. Esta comunicaciĂłn forma parte de una investigaciĂłn que se realiza en nuestro Departamento en la que, con un enfoque interdisciplinar, participan las áreas de conocimiento de Didáctica y OrganizaciĂłn Escolar, Didáctica de la Lengua y Didáctica de las Ciencias Sociales. Adoptamos unas estrategias comunes para construir conocimiento, a fin de integrar las aportaciones procedentes de diversos ámbitos cientĂficos, de manera globalizada y relacional (ALTAVA et al.,1999). Puesto que la realidad es compleja (MORIN, 1994) y que tambiĂ©n lo es su conocimiento, asumimos que su aprendizaje requiere la convergencia de distintos clases de saberes procedentes de diferentes ámbitos cientĂficos. En nuestro caso, realizamos aportaciones desde los campos disciplinares de la LingĂĽĂstica, la PedagogĂa y la Didáctica, y desde el conjunto de las Ciencias Sociales (Historia, AntropologĂa, etc.). Nuestro objeto de estudio general es la situaciĂłn escolar de los niños inmigrantes en la provincia de CastellĂłn, las estrategias didácticas y organizativas que existen en la escuela respecto a la educaciĂłn intercultural y al multilingĂĽismo.Para lograrlo, en una perspectiva de indagaciĂłn y acciĂłn, dicha investigaciĂłn pretende dar respuesta a las situaciones de multiculturalidad y plurilingĂĽismo en las escuelas actuales, dentro de la formaciĂłn (inicial y permanente) de los maestros; todo ello bajo un planteamiento didáctico y acadĂ©mico de una mayor adaptaciĂłn a la realidad y al proceso de armonizaciĂłn europeas en los programas y metodologĂa docentes
Levy-Nearest-Neighbors Bak-Sneppen Model
We study a random neighbor version of the Bak-Sneppen model, where "nearest
neighbors" are chosen according to a probability distribution decaying as a
power-law of the distance from the active site, P(x) \sim |x-x_{ac
}|^{-\omega}. All the exponents characterizing the self-organized critical
state of this model depend on the exponent \omega. As \omega tends to 1 we
recover the usual random nearest neighbor version of the model. The pattern of
results obtained for a range of values of \omega is also compatible with the
results of simulations of the original BS model in high dimensions. Moreover,
our results suggest a critical dimension d_c=6 for the Bak-Sneppen model, in
contrast with previous claims.Comment: To appear on Phys. Rev. E, Rapid Communication
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