Dark photon searches with atomic transitions

Dark matter could be made up of dark photons, massive but very light particles whose interactions with matter resemble those of usual photons but suppressed by a small mixing parameter. We analyze the main approaches to dark photon interactions and how they can be applied to direct detection experiments which test different ranges of masses and mixings. A new experiment based on counting dark photons from induced atomic transitions in a target material is proposed. This approach appears to be particularly appropriate for dark photon detection in the meV mass range, extending the constraints in the mixing parameter by up to eight orders of magnitude with respect to previous experiments.Comment: 16 pages, 3 figure

The effects of magnetic-field geometry on longitudinal oscillations of solar prominences: Cross-sectional area variation for thin tubes

Solar prominences are subject to both field-aligned (longitudinal) and transverse oscillatory motions, as evidenced by an increasing number of observations. Large-amplitude longitudinal motions provide valuable information on the geometry of the filament-channel magnetic structure that supports the cool prominence plasma against gravity. Our pendulum model, in which the restoring force is the gravity projected along the dipped field lines of the magnetic structure, best explains these oscillations. However, several factors can influence the longitudinal oscillations, potentially invalidating the pendulum model. The aim of this work is to study the influence of large-scale variations in the magnetic field strength along the field lines, i.e., variations of the cross-sectional area along the flux tubes supporting prominence threads. We studied the normal modes of several flux tube configurations, using linear perturbation analysis, to assess the influence of different geometrical parameters on the oscillation properties. We found that the influence of the symmetric and asymmetric expansion factors on longitudinal oscillations is small.}{We conclude that the longitudinal oscillations are not significantly influenced by variations of the cross-section of the flux tubes, validating the pendulum model in this context.Comment: Accepted for publication in Astronomy & Astrophysic

Teaching and learning in information retrieval

A literature review of pedagogical methods for teaching and learning information retrieval is presented. From the analysis of the literature a taxonomy was built and it is used to structure the paper. Information Retrieval (IR) is presented from different points of view: technical levels, educational goals, teaching and learning methods, assessment and curricula. The review is organized around two levels of abstraction which form a taxonomy that deals with the different aspects of pedagogy as applied to information retrieval. The first level looks at the technical level of delivering information retrieval concepts, and at the educational goals as articulated by the two main subject domains where IR is delivered: computer science (CS) and library and information science (LIS). The second level focuses on pedagogical issues, such as teaching and learning methods, delivery modes (classroom, online or e-learning), use of IR systems for teaching, assessment and feedback, and curricula design. The survey, and its bibliography, provides an overview of the pedagogical research carried out in the field of IR. It also provides a guide for educators on approaches that can be applied to improving the student learning experiences

Adsorption Characteristics of Refrigerants for Thermochemical Energy Storage in Metal-Organic Frameworks

The adsorption of fluorocarbons has gained significant importance as its use as refrigerants in energy storage applications. In this context, the adsorption behavior of two low global warming potential refrigerants, R125 fluorocarbon and its hydrocarbon analog, R170, within four nanoporous materials, namely MIL-101, Cu-BTC, ZIF-8, and UiO-66 has been investigated. By analyzing the validity of our models against experimental observations, we ensure the reliability of our molecular simulations. Our analysis encompasses a range of crucial parameters, including adsorption isotherms, enthalpy of adsorption, and energy storage densities, all under varying operating conditions.We find remarkable agreement between computed and observed adsorption isotherms for R125 within MIL-101. However, to obtain similar success for the rest of the adsorbents, we need to take into account a few considerations, such as the presence of inaccessible cages in Cu-BTC, the flexibility of ZIF-8, or the defects in UiO-66. Transitioning to energy storage properties, we investigated various scenarios, including processes with varying adsorption and desorption conditions. Our findings underscore the dominance of MIL-101 in terms of storage densities, with R125 exhibiting superior affinity over R170. Complex mechanisms governed by changes in pressure, temperature, and desorption behavior make for complicated patterns, demanding a case-specific approach. In summary, this study navigates the complex landscape of refrigerant adsorption in diverse nanoporous materials. It highlights the significance of operating conditions, model selection, and refrigerant and adsorbent choices for energy storage applications