Fermion localization on thick branes

We consider chiral fermion confinement in scalar thick branes, which are known to localize gravity, coupled through a Yukawa term. The conditions for the confinement and their behavior in the thin-wall limit are found for various different BPS branes, including double walls and branes interpolating between different AdS_5 spacetimes. We show that only one massless chiral mode is localized in all these walls, whenever the wall thickness is keep finite. We also show that, independently of wall's thickness, chiral fermionic modes cannot be localized in dS_4 walls embedded in a M_5 spacetime. Finally, massive fermions in double wall spacetimes are also investigated. We find that, besides the massless chiral mode localization, these double walls support quasi-localized massive modes of both chiralities.Comment: 8 pages, 3 figure

Close to the edge: hierarchy in a double braneworld

We show that the hierarchy between the Planck and the weak scales can follow from the tendency of gravitons and fermions to localize at different edges of a thick double wall embedded in an $AdS_5$ spacetime without reflection symmetry. This double wall is a stable BPS thick-wall solution with two sub-walls located at its edges; fermions are coupled to the scalar field through Yukawa interactions, but the the lack of reflection symmetry forces them to be localized in one of the sub-walls. We show that the graviton zero-mode wavefunction is suppressed in the fermion edge by an exponential function of the distance between the sub-walls, and that the massive modes decouple so that Newtonian gravity is recuperated.Comment: Some typos corrected, references adde

Gauge field localization on brane worlds

We consider the effects of spacetime curvature and brane thickness on the localization of gauge fields on a brane via kinetic terms induced by localized fermions. We find that in a warped geometry with and infinitely thin brane, both the infrared and the ultraviolet behavior of the electromagnetic propagator are affected, providing a more stringent bound on the brane's tension than that coming from the requirement of four-dimensional gravity on the brane. On the other hand, for a thick wall in a flat spacetime, where the fermions are localized by means of a Yukawa coupling, we find that 4-dimensional electromagnetism is recovered in a region bounded from above by the same critical distance appearing in the thin case, but also from below by a new scale related to the brane's thickness and the electromagnetic couplings.Comment: 7 page

Symmetries of distributional domain wall geometries

Generalizing the Lie derivative of smooth tensor fields to distribution-valued tensors, we examine the Killing symmetries and the collineations of the curvature tensors of some distributional domain wall geometries. The chosen geometries are rigorously the distributional thin wall limit of self gravitating scalar field configurations representing thick domain walls and the permanence and/or the rising of symmetries in the limit process is studied. We show that, for all the thin wall spacetimes considered, the symmetries of the distributional curvature tensors turns out to be the Killing symmetries of the pullback of the metric tensor to the surface where the singular part of these tensors is supported. Remarkably enough, for the non-reflection symmetric domain wall studied, these Killing symmetries are not necessarily symmetries of the ambient spacetime on both sides of the wall

Variability In The Accuracy Of Self-Assessments Among Low, Moderate, And High Performing Students In University Education

The present work empirically examines the validity of Student Self-Assessment (SSA) as an educational assessment in higher education. We briefly review the principle methodological factors that could affect SSA validity, as well as the main findings identified in the literature. One empirical study is presented that compares student-self evaluations on a test with the evaluation made by the course instructor while controlling for students\u27 experience with SSA, criteria, rubric, and scales used by the student and teacher, and that the teacher was blind. Results show a strong correlation overall between the SSA and the instructor’s evaluation and show that lower-performing students tend to over-estimate their performance while higher-performing students under-estimate their performance. The results support that SSA is valid for the average student, but less so for those that deviate above and below average in the absence of measurements of potentially mediating variables. The need to consider metacognitive factors in SSA is proposed

Estudio de alternativas para almacenar aceites lubricantes en los talleres y lubricadoras automotrices de la ciudad de Riobamba

El objetivo del proyecto de investigación fue proponer un manejo de aceites lubricantes usados de los diferentes centros automotrices del cantón Riobamba para la reducción del impacto ambiental de los cuales atraen efectos negativos para la salud de la población. Para el proceso de la investigación se necesitó el grado de la contaminación que generan estos talleres y mediante encuestas se logró obtener resultados estadísticos y conocer si se están cumpliendo las normativas locales. En la inspección se encontró que los recipientes se encontraban muy deteriorados ya que el 87.73% de talleres utilizan recipientes de metal sin ninguna protección causando derrames en el suelo y además con el 85.71% mencionaron que no clasifican los aceites y que todo es almacenado en un mismo contenedor. Con la información obtenida diseñó un contenedor para almacenar aceites clasificados teniendo en cuenta que tipos de aceites son los más recolectados que son aceites multigrados, monogrados y aceites de transmisión. Además, en este contenedor se agregó un etiquetado normalizado de residuos tóxicos. Para el análisis estadístico se utilizó el software Excel para obtener la información dando como resultado el grado de contaminación de los aceites y así se logró diseñar el contenedor ecológico para su construcción con los elementos adicionales como un embudo giratorio para cada sección y niveladores de aceites que evita el derrame los residuos tóxicos. Se concluye, que mediante las encuestas a los diferentes talleres se tuvo información de estado de contaminación de la ciudad y se planteó una solución de cómo podríamos mejorar el manejo de los aceites usados por medio del contenedor ecológico. Se recomienda realizar un análisis más profundo de los aceites contaminados para saber con exactitud el grado de contaminación y hacer conocer a las autoridades para que apliquen medidas reglamentarias sobre el almacenaje de los cites usados.The objective of this research project was to propose a management of used lubricating oils from the different automotive centers of the Riobamba canton to reduce the environmental impact of which they attract negative effects on the health of the population. For this, the degree of contamination generated by these workshops was investigated and through surveys it was possible to obtain statistical results and know if local regulations are being met. In the inspection it was found that the containers were very deteriorated since 87.73% of workshops use metal containers without any protection causing spills on the ground, also 85.71% mentioned that they do not classify the oils and that everything is stored in the same container. With the information obtained, a container was designed to store oils classified into multigrade, monograde and transmission oils; In addition, a standard toxic waste labeling was added to this container. For the statistical analysis, the Excel software was used to obtain the information resulting in the degree of contamination of the oils and thus it was possible to design the ecological container for its construction with additional elements such as a rotating funnel for each section and oil levelers that avoid spillage of toxic waste. It is concluded that by means of the surveys to the different workshops, information was obtained on the state of pollution of the city and a solution was proposed on how to improve the management of used oils through the ecological container. It is recommended to carry out a more in-depth analysis of the contaminated oil to know exactly the degree of contamination and to inform the authorities so that they can apply regulatory measures on the storage of used containers

Localizing gravity on exotic thick 3-branes

We consider localization of gravity on thick branes with a non trivial structure. Double walls that generalize the thick Randall-Sundrum solution, and asymmetric walls that arise from a Z_2-symmetric scalar potential, are considered. We present a new asymmetric solution: a thick brane interpolating between two AdS_5 spacetimes with different cosmological constants, which can be derived from a ``fake supergravity'' superpotential, and show that it is possible to confine gravity on such branes.Comment: Final version, minor changes, references adde