14,050 research outputs found
Three-body problem in 3D space: ground state, (quasi)-exact-solvability
We study aspects of the quantum and classical dynamics of a -body system
in 3D space with interaction depending only on mutual distances. The study is
restricted to solutions in the space of relative motion which are functions of
mutual distances only. It is shown that the ground state (and some other
states) in the quantum case and the planar trajectories in the classical case
are of this type. The quantum (and classical) system for which these states are
eigenstates is found and its Hamiltonian is constructed. It corresponds to a
three-dimensional quantum particle moving in a curved space with special
metric. The kinetic energy of the system has a hidden Lie (Poisson)
algebra structure, alternatively, the hidden algebra typical for the
Calogero model. We find an exactly solvable three-body generalized
harmonic oscillator-type potential as well as a quasi-exactly-solvable
three-body sextic polynomial type potential; both models have an extra
integral.Comment: 24 pages, Appendix about non-equal masses adde
¿Qué contiene una escuela? sobre el sentido ético-político de la convivencia escolar
¿Qué contiene una escuela? no es, precisamente, una pregunta simple. Una forma casi ingenua de dar respuesta a la misma nos puede conducir a un proceso de enumeración, por ejemplo, decir que contiene estudiantes, maestros, pupitres, pizarrones, libros. Si, libros y una vez más estaríamos frente a la cuestión anterior. Pero en este caso avocados solamente a uno de los sentidos del término “contener”, esto es, comprender, abarcar. ¿Qué contiene una escuela? implica, también, entre otras acciones sujetar, aguantar, apoyar, acompañar. El interés en este escrito no es el de presentar una serie de prescripciones en torno a lo que debe contener la escuela y qué modelo de convivencia se puede deducir de dichas preceptos. Se ha optado por buscar apoyo en relatos de experiencias de estudiantes y maestros para construir con ellos una mirada comprensiva del sentido político de la convivencia escolar. Muchas de las cosas que aquí se expresan son tan corrientes que pasan por inadvertidas, otras lo son mucho menos. Desde unas y otras, el objetivo principal de este escrito es mostrar que lo que una escuela orientada a la formación de valores ciudadanos contiene no va más allá de lo que sus actores están dispuestos a reconocerle, la manera como dotan de sentido de sus experiencias cotidianas, sus formas de participación, sus decisiones vitales, el apoyo que cada quien recibe y está dispuesto a darle a los otros
a spatial analysis
The cultivation of coca (Erythroxylon coca) in Colombia represents the first
step of the largest illegal agribusiness that exists in the world, namely
Cocaine. In this production chain, the small local cultivators consists of the
first step, followed by the step, where most of the money profit is made. This
sphase correspond to the elaboration of cocaine and its commercialization at a
global scale which is in the hands of illegal armed groups and drug dealers.
Most of the literature related to illicit crops considers the national and
global factors that influence the expansion of these products. However, only
little is written in the scientific literature concerning the local conditions
where the social-environmental impacts due to these activities are
concentrated. This study analyses for the first time the local factors
(social, economic, environmental and institutional) associated to the
expansion of cocaine during the last decade and how these activities have
provided the favourable settings for the increase of deforestation in zones of
high environmental importance. For the proposed analysis a social-ecological
conceptual framework was made, based on literature reviews which were
confirmed by statistical analysis of data at a municipal level and the use of
bivariate Local Indicators of Spatial Association (LISA) during the two year
period of this study. This has allowed an improved comprehension of the
complexity between the coca cultivations and its association with the
emergence of social-environmental conflicts. It is shown that an relationship
exists between deforestation of primary forest in low-laying areas and the
increase of cultivated areas of coca with an intensification of land-use
conflicts. This study demonstrates the environmental, institutional and
social-economical resemblances that determine the establishment of coca
cultivations at a local level and its relationship with increase of coca
cultivations towards the north and southwest of Colombia and as such the
expansion of the social-environmental conflicts
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