Triplet-Singlet Spin Relaxation in Quantum Dots with Spin-Orbit Coupling

We estimate the triplet-singlet relaxation rate due to spin-orbit coupling assisted by phonon emission in weakly-confined quantum dots. Our results for two and four electrons show that the different triplet-singlet relaxation trends observed in recent experiments under magnetic fields can be understood within a unified theoretical description, as the result of the competition between spin-orbit coupling and phonon emission efficiency. Moreover, we show that both effects are greatly affected by the strength of the confinement and the external magnetic field, which may give access to very long-lived triplet states as well as to selective population of the triplet Zeeman sublevels.Comment: 5 pages, 3 figures. Closely related to recent experiments in cond-mat/060972

Effect of the Coulomb interaction on the electron relaxation of weakly-confined quantum dot systems

We study acoustic-phonon-induced relaxation of charge excitations in single and tunnel-coupled quantum dots containing few confined interacting electrons. The Full Configuration Interaction approach is used to account for the electron-electron repulsion. Electron-phonon interaction is accounted for through both deformation potential and piezoelectric field mechanisms. We show that electronic correlations generally reduce intradot and interdot transition rates with respect to corresponding single-electron transitions, but this effect is lessened by external magnetic fields. On the other hand, piezoelectric field scattering is found to become the dominant relaxation mechanism as the number of confined electrons increases. Previous proposals to strongly suppress electron-phonon coupling in properly designed single-electron quantum dots are shown to hold also in multi-electron devices. Our results indicate that few-electron orbital degrees of freedom are more stable than single-electron ones.Comment: 20 pages (preprint format), 7 figures, submitted to Phys. Rev.

Phonon-induced electron relaxation in weakly-confined single and coupled quantum dots

We investigate charge relaxation rates due to acoustic phonons in weakly-confined quantum dot systems, including both deformation potential and piezoelectric field interactions. Single-electron excited states lifetimes are calculated for single and coupled quantum dot structures, both in homonuclear and heteronuclear devices. Piezoelectric field scattering is shown to be the dominant relaxation mechanism in many experimentally relevant situations. On the other hand, we show that appropriate structure design allows to minimize separately deformation potential and piezolectric field interactions, and may bring electron lifetimes in the range of microseconds.Comment: 20 pages (preprint format), 7 figures, submitted to Physical Review

Intra-family links in the analysis of marital networks

Marriage networks, which represent the matrimonial connections between different families in a given historical and geographical milieu, rarely take into account one aspect of internal family dynamics, namely the existence of intra-family marriages. The inclusion of such marriages, represented in the graph by self-loops, is essential in order to compute more accurate measures of centrality. In this paper, we discuss various procedures for incorporating these links into the analysis, with the requirement that they be compatible with the use of already available social network analysis software. We then apply them to two historical marriage networks, one from the Republic of Venice and the other from Taiwan. By comparing centrality measures for the baseline and modified networks, we found that the most satisfactory of the proposed methods is the one that duplicates nodes of families with intra-family marriages and adds new edges that link these duplicated nodes to all the families to which the original node was connected. This procedure is computationally simple and conceptually sound, making it a useful tool for analysing marital networks.PID2020-115570GB-C22 (DemocratAI::UGR) Acceso abierto financiado por Universidad de Granada/CBU

Effect of electron-electron interaction on the phonon-mediated spin relaxation in quantum dots

We estimate the spin relaxation rate due to spin-orbit coupling and acoustic phonon scattering in weakly-confined quantum dots with up to five interacting electrons. The Full Configuration Interaction approach is used to account for the inter-electron repulsion, and Rashba and Dresselhaus spin-orbit couplings are exactly diagonalized. We show that electron-electron interaction strongly affects spin-orbit admixture in the sample. Consequently, relaxation rates strongly depend on the number of carriers confined in the dot. We identify the mechanisms which may lead to improved spin stability in few electron (>2) quantum dots as compared to the usual one and two electron devices. Finally, we discuss recent experiments on triplet-singlet transitions in GaAs dots subject to external magnetic fields. Our simulations are in good agreement with the experimental findings, and support the interpretation of the observed spin relaxation as being due to spin-orbit coupling assisted by acoustic phonon emission.Comment: 12 pages, 10 figures. Revised version. Changes in section V (simulation of PRL 98, 126601 experiment

Diferencias en la predicción afectiva entre población normal y clínica: un estudio preliminar.

Introducción: Las predicciones emocionales que hacemos frente a acontecimientos futuros son conocidas como predicciones afectivas (Wilson y Gilbert, 2003). Diversos estudios han identificado que tendemos a sobreestimar la intensidad de nuestras emociones (e.g., Loewenstein, 2011; Wilson y Gilbert, 2003); esto es definido como sesgo de intensidad (Loewenstein, 2011). Objetivo: someter a prueba la predicción afectiva de población normal y clínica ante futuros eventos positivos. Método: Participaron 20 voluntarios de los cuales 11 concluyeron el estudio (80 % mujeres). Los participantes realizaron una tarea en la que imaginaron y visualizaron su futuro de la mejor forma posible (best self). Posteriormente, se les pidió que estimaran la intensidad de varias emociones (felicidad, tristeza, ansiedad y enfado) en caso de que ocurriera alguno de los eventos que habían imaginado. Seis meses después, y en caso de que hubiera ocurrido lo que imaginaron, se evaluó la intensidad real de sus emociones. Resultados: Fueron identificadas diferencias significativas solo entre la predicción y la emoción real en felicidad y en la población normal, lo cual sugiere que solo se ha generado el «sesgo de intensidad» en esa emoción, y que la población normal pudo haber sobreestimado su intensidad. Conclusiones: La presencia del «sesgo de intensidad» en la población normal sugiere que la sobreestimación de la emoción de felicidad podría estar asociada con padecer o no un problema de salud físico o psicológico. Por otro lado, los resultados sugieren que las emociones negativas podrían presentar un mejor ajuste entre la predicción y la emoción real, respecto a las emociones positivas.Introduction: The forecast that we do about the emotions in the face of future events are known as «affective forecasting» (Wilson & Gilbert, 2003). Several studies have found that we tend to overestimate the intensity of our emotions (e.g., Loewenstein, 2011; Wilson & Gilbert, 2003); this is defined as «intensity bias» (Loewenstein, 2011). Objective: To test the affective forecasting in normal and clinic population in the face of positive future events. Method: Twenty volunteers participated of which only eleven completed the study (80 % female). The participants carried out a task in which they imagined and visualized their future in the best possible way (best self). Later, they were asked to forecast the intensity of various emotions (happiness, sadness, anxiety, and anger) in case of any of the events they imagined would happen. Six months later, and in case that the event they imagined happened, the real intensity of their emotions was assessed. Results: Significant differences were found between the predicted emotion and the real emotion in happiness and in the normal population; this suggests that only was generated the «intensity bias» in that emotion and that the normal population could have overestimated its intensity. Conclusions: The presence of the «intensity bias» in the normal population suggests that the overestimation of happiness could be associated with suffering or not a physical or psychological health problem. Furthermore, the results suggest that the negative emotions could present a better fit between the predicted emotion and the real emotion compared to positive emotions

Implementación del Modelo de Red Causal en un texto narrativo en español

The Causal Network Model suggests that the causal structure of a story and its representation in the episodic memory resemble a network, where the events are a combination of causal antecedent and have multiple consequences. The purpose of this article was to present the application of the Causal Network Model in a Spanish natural narrative text. Given that studies in text comprehension have tended to use experimental texts written in English, the purpose was to describe the application of the Model in a Spanish natural text, in order to advocate for the relevance of this model to study the cognitive processes involved in the comprehension of texts.El Modelo de Red Causal propone que la estructura causal de una historia y su representación en la memoria episódica se asemejan a una red, en la que los acontecimientos resultan de una combinación de antecedentes causales, que a su vez tienen múltiples consecuencias. El estudio de la comprensión de textos según este modelo ha tendido a llevarse a cabo utilizando textos experimentales en inglés. En razón de ello, el objetivo de este trabajo consistió en presentar la aplicación del Modelo de Red Causal a un texto narrativo natural en español, a fin de abogar por su utilidad para examinar los procesos cognitivos involucrados en la comprensión textual

La responsabilidad social empresarial en las estrategias de desarrollo del gobierno peruano: propuestas de la Carta de Navegación y el sector privado

Presenta las exposiciones de expertos acerca de la responsabilidad social en las empresas peruanas, en el marco de la XLVII Reunión de Intercampus

The construction of authority on the first peronism: understandinf the current crisis of authority at school

El propósito de este artículo es aportar a la comprensión de la crisis actual de la autoridad escolar a través del estudio de las representaciones de la autoridad durante el primer peronismo (1945 – 1955). La crisis de la autoridad es definida como una ruptura de los mecanismos, que aseguran la constitución de la subjetividad en el marco de los dispositivos institucionales. Se justifica la pertinencia de realizar un análisis histórico, y se plantea la posibilidad de explorar las apelaciones que, durante el período del primer peronismo, el Estado formuló a la escuela y a la familia. Se propone que la cultura política del peronismo es el contexto discursivo en el que surgió la metáfora de la nación – familia, que sustentará el par de identificaciones gobierno de la Nación – gobierno de la familia y educación familiar – educación escolar. A través del análisis de textos escolares del nivel primario, se estudiará la emergencia de un conjunto de representaciones de la autoridad, que conforman sentidos comunes a los dispositivos estatal, escolar, y familiar.The aim of this paper is to provide some suggestions about the current crisis of authority that takes place at school. This will be done through the analysis of the authority representations constructed during the stage of first peronism (1945 – 1955). The crisis of authority is defined as a breakdown of the mechanisms that allows subjectivity to be constituted within institutions. The adequacy of an historical analysis is stated, and the posibility of exploring the interpellations that the peronist State addressed to school and family is suggested. It is proposed that the political culture of peronism configures a frame in which the nation – family metaphor arose. This metaphor gave birth to two identifications: the identification between govern of State and govern of family, and the identification between school education and family education. Through the analysis of school texts, the emergence of a set of authority representations that conforms a shared meaning will be discussed.Fil: Molinari, Juan Martín. Universidad Nacional de Mar del Plata. Facultad de Humanidades. Centro de Investigaciones Multidisciplinarias en Educación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Porta Vazquez, Luis Gabriel. Universidad Nacional de Mar del Plata. Facultad de Humanidades. Centro de Investigaciones Multidisciplinarias en Educación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Humanidades y Ciencias Sociales. Universidad Nacional de Mar del Plata. Instituto de Humanidades y Ciencias Sociales; Argentin

La construcción del sentido de la autoridad en el primer peronismo: elementos para la comprensión de la crisis actual de la autoridad escolar - The construction of authority on the first peronism: understandinf the current crisis of authority at school

El propósito de este artículo es aportar a la comprensión de la crisis actual de la autoridad escolar a través del estudio de las representaciones de la autoridad durante el primer peronismo (1945 – 1955). La crisis de la autoridad es definida como una ruptura de los mecanismos, que aseguran la constitución de la subjetividad en el marco de los dispositivos institucionales. Se justifica la pertinencia de realizar un análisis histórico, y se plantea la posibilidad de explorar las apelaciones que, durante el período del primer peronismo, el Estado formuló a la escuela y a la familia. Se propone que la cultura política del peronismo es el contexto discursivo en el que surgió la metáfora de la nación – familia, que sustentará el par de identificaciones gobierno de la Nación – gobierno de la familia y educación familiar – educación escolar. A través del análisis de textos escolares del nivel primario, se estudiará la emergencia de un conjunto de representaciones de la autoridad, que conforman sentidos comunes a los dispositivos estatal, escolar, y familiar