Rydberg rings

Atoms in highly excited Rydberg states exhibit remarkable properties and constitute a powerful tool for studying quantum phenomena in strongly interacting many-particle systems. We investigate alkali atoms that are held in a ring lattice and excited to Rydberg states. The system constitutes an ideal model system to study thermalization of a coherently evolving quantum many-particle system in the absence of a thermal bath. Moreover, it offers exciting perspective to create entangled many-body quantum states which can serve as a resource for the generation of single photons.Comment: invited PCCP Perspectiv

Out-of-equilibrium evolution of kinetically constrained many-body quantum systems under purely dissipative dynamics

We explore the relaxation dynamics of quantum many-body systems that undergo purely dissipative dynamics through non-classical jump operators that can establish quantum coherence. Our goal is to shed light on the differences in the relaxation dynamics that arise in comparison to systems evolving via classical rate equations. In particular, we focus on a scenario where both quantum and classical dissipative evolution lead to a stationary state with the same values of diagonal or "classical" observables. As a basis for illustrating our ideas we use spin systems whose dynamics becomes correlated and complex due to dynamical constraints, inspired by kinetically constrained models (KCMs) of classical glasses. We show that in the quantum case the relaxation can be orders of magnitude slower than the classical one due to the presence of quantum coherences. Aspects of these idealized quantum KCMs become manifest in a strongly interacting Rydberg gas under electromagnetically induced transparency (EIT) conditions in an appropriate limit. Beyond revealing a link between this Rydberg gas and the rather abstract dissipative KCMs of quantum glassy systems, our study sheds light on the limitations of the use of classical rate equations for capturing the non-equilibrium behavior of this many-body system.Comment: 7 pages, 4 figure

Lived and taught interculturality: Reflections on conviviality relations and integration in educational environments in Spain (Granada) and Portugal (Lisbon)

The researches are ‘Culturas de Convivência e Super-diversidade’ (PTDC / CS-SOC / 101693/2008), funded by the Fundação para a Ciência e a Tecnologia de Portugal and directed by Beatriz Padilla; ‘Multiculturality and integration of the foreign immigrant population in Andalusian schools’ (Junta de Andalucía, Projects of Excellence, 2007–10), and ‘Building differences in the school. Studies of the trajectories of ATAL in Andalusia, its teachers and its students’ (Ministry of Science and Innovation, National Plan of I+D+i, 2014–16), directed by F. Javier García Castaño (University of Granada)Granada and Lisbon, cities defined as ‘super-diverse’, host dynamics of exchange and interactions among sociocultural groups that go beyond mere coexistence. Educational environments (both formal and informal) host these aforementioned relationships especially among teenagers. Adolescents represent a significant social group as the ‘subjects/objects’ of public interventions through intercultural programmes and are protagonists of daily intercultural dialogues. In this article, we approach these ideas through the concept of conviviality. We comparatively analyse the indicators from the Migrant Integration Policy Index (MIPEX), a policy instrument-tool, applied in the education field and the data obtained through ethnographic research carried out in educational environments in Granada and Lisbon in specific programmes targeting adolescents and youth. Through this analysis we unveil the gaps of migration integration indexes such as MIPEX in the field of integration in education, compared with an ethnographic assessment of intercultural relations on how youngsters live and learn interculturality.Fundação para a Ciência e a Tecnologia de Portugal PTDC / CS-SOC / 101693/2008Junta de Andalucía, Projects of Excellence, 2007–10Ministry of Science and Innovation, National Plan of I+D+i, 2014–1

Rapid estimation of gamma number of viscose by UV Spectrophotometry

Viscose process is the most important method for industrial cellulose dissolution. The degree of substitution (DS) is an important parameter in cellulose derivatives, and it is usually expressed as a gamma number (γ No.). In this work, viscose was prepared from eucalyptus and cotton linter dissolving pulps. Two methods were used for by-product separation: coagulation method (CM, reference) and ion exchange method (IEM). Similar γ Nos. were obtained with both methods for viscoses from cotton linters. The molar absorptivity of cellulose xanthate at 303 nm (e303nm) was determined by, firstly, measuring the absorbance of different purified viscoses and, subsequently, drawing a linear regression with the values obtained. The purification efficacy of IEM was analyzed from the UV peaks obtained in the range of 220-380 nm of the original and purified viscoses. The disappearance of the absorption of the main byproduct, sodium trithiocarbonate, was observed. Finally, with the e303nm mentioned above and the absorbance measurement of the purified viscoses, their γ Nos. were determined using a spectrophotometric method (SM). This would indicate that UV spectrophotometry could be used to estimate this parameter in a quick and easy way, which is decisive for the use of viscose in regenerated cellulose products.Fil: Lanieri, Diana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Olmos, Graciela Viviana. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Instituto de Tecnología Celulósica; ArgentinaFil: Alberini, Ivana Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Instituto de Tecnología Celulósica; ArgentinaFil: Maximino, Mirta Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Instituto de Tecnología Celulósica; Argentin

Far-field resonance fluorescence from a dipole-interacting laser-driven cold atomic gas

We analyze the temporal response of the fluorescence light that is emitted from a dense gas of cold atoms driven by a laser. When the average interatomic distance is comparable to the wavelength of the photons scattered by the atoms, the system exhibits strong dipolar interactions and collective dissipation. We solve the exact dynamics of small systems with different geometries and show how these collective features are manifest in the scattered light properties such as the photon emission rate, the power spectrum and the second-order correlation function. By calculating these quantities beyond the weak (linear) driving limit, we make progress in understanding the signatures of collective behavior in these many-body systems. Furthermore, we shed light on the role of disorder and averaging on the resonance fluorescence, of direct relevance for recent experimental efforts that aim at the exploration of many-body effects in dipole–dipole interacting gases of atoms

Dispersionless subradiant photon storage in one-dimensional emitter chains

Atomic emitter ensembles couple collectively to the radiation field. Although an excitation on a single emitter may be short-lived, a collection of them can contain a photon several orders of magnitude longer than the single emitter lifetime. We provide the exact conditions for optimal absorption, long-lived and dispersionless storage, and release, of a single photon in a sub-wavelength one-dimensional lattice of two-level emitters. In particular, we detail two storage schemes. The first is based on the uncovering of approximate flat sections in the single-photon spectrum, such that a single photon can be stored as a wave packet with effective zero group velocity. For the second scheme we exploit the angular dependence of the interactions induced between the emitters and mediated via exchange of virtual photons, which on a ring gives rise to an effective trapping potential for the photon. In both cases, we are able to obtain, within current experimentally accessible parameters, high-fidelity photon storage for times hundreds of times longer than the single emitter lifetime.Comment: 8 pages, 7 figures, comments welcom

Modified dipole-dipole interactions in the presence of a nanophotonic waveguide

When an emitter ensemble interacts with the electromagnetic field, dipole-dipole interactions are induced between the emitters. The magnitude and shape of these interactions are fully determined by the specific form of the electromagnetic field modes. If the emitters are placed in the vicinity of a nanophotonic waveguide, such as a cylindrical nanofiber, the complex functional form of these modes makes the analytical evaluation of the dipole-dipole interaction cumbersome and numerically costly. In this work, we provide a full detailed description of how to successfully calculate these interactions, outlining a method that can be easily extended to other environments and boundary conditions. Such exact evaluation is of importance as, due to the collective character of the interactions and dissipation in this kind of systems, any small modification of the interactions may lead to dramatic changes in experimental observables, particularly as the number of emitters increases. We illustrate this by calculating the transmission signal of the light guided by a cylindrical nanofiber in the presence of a nearby chain of emitters.Comment: 14 pages, 5 figures, comments welcom

Contabilidad... un viaje multimedia de 10! : estrategias didácticas mediadas por TIC para la enseñanza y el aprendizaje de la contabilidad inicial

Trabajo Final (Especialización en Tecnologías Multimedia para Desarrollos Educativos)--UNC- Facultad de Ciencias Agropecuarias, 2016.Tanto la sociedad como el sistema educativo, entre ellos, se encuentra transvasado por las tecnologías de la información y la comunicación (TIC). Esto propicia un paradigma educativo, donde los alumnos que ingresan a la universidad deben fortalecer la capacidad de construir sus conocimientos de manera permanente, afianzar la forma colaborativa de trabajo con la guía, indiscutida, del docente. El objetivo de este trabajo es presentar una propuesta de estrategias didácticas para la enseñanza y aprendizaje de la contabilidad inicial, a través del diseño de un sitio web: “Contabilidad... un viaje multimedia de 10!”; destinado a los alumnos ingresantes a la Facultad de Ciencias Económicas (UNC) para ser incorporado a la plataforma educativa virtual de la facultad. Esta propuesta está integrada por contenidos textuales, visuales, auditivos, gráficos. El uso de las TIC permite una llegada al alumno a distancia, asincrónica y ubicua alcanzado logros destacados en el aprendizaje significativo

Superdiversity and conviviality: exploring frameworks for doing ethnography in Southern European intercultural cities

International migration contributes to increasing cultural diversity in many European cities. Historically, migration studies have focused on the integration of immigrants foregrounding race/ethnicity and identity issues, limiting our understanding of intercultural diversity. A new paradigm focusing on relational patterns among groups is emerging, highlighting the importance of mutual relations, interactions and influences among residents of different origins and backgrounds, including the experience of both immigrants and autochthonous populations. The notions of superdiversity and conviviality have significantly contributed to this debate. This paper discusses how both were methodologically operationalized in multi-sited ethnographies carried out in Lisbon and Granada, during 2009–2012. Superdiversity and conviviality are the main theoretical frameworks used to understand how interculturality is lived and experienced at the local level. We reflect on their strengths and weaknesses, unpacking common assumptions about race, ethnicity and culture, specifically looking at the negotiation of difference in intercultural events