Two-level interacting boson models beyond the mean field

The phase diagram of two-level boson Hamiltonians, including the Interacting Boson Model (IBM), is studied beyond the standard mean field approximation using the Holstein-Primakoff mapping. The limitations of the usual intrinsic state (mean field) formalism concerning finite-size effects are pointed out. The analytic results are compared to numerics obtained from exact diagonalizations. Excitation energies and occupation numbers are studied in different model space regions (Casten triangle for IBM) and especially at the critical points.Comment: 14 pages, 13 figure

Economy and Environmental Problems in the Mexican Coastal States

A canonical correspondence analysis (CCA) for environmental and economic variables was performed for 17 Mexican coastal states. The ordination method allowed us to identify three groups, namely hydroelectric energy generation (I), pollution (II) and harbours (III), which were associated to different human activities. Furthermore, CCA is efficient to help us generate hypotheses for future research. It is therefore advised that CCA should be used for routine analyses into economics.Coastal States of Mexico, Canonical Correspondence Analysis, Diversity Index, Economic Development, Environmental Variables.

Finite-size scaling exponents in the interacting boson model

We investigate the finite-size scaling exponents for the critical point at the shape phase transition from U(5) (spherical) to O(6) (deformed $\gamma$-unstable) dynamical symmetries of the Interacting Boson Model, making use of the Holstein-Primakoff boson expansion and the continuous unitary transformation technique. We compute exactly the leading order correction to the ground state energy, the gap, the expectation value of the $d$-boson number in the ground state and the $E2$ transition probability from the ground state to the first excited state, and determine the corresponding finite-size scaling exponents.Comment: 4 pages, 3 figures, published versio

Shaping an Itinerant Quantum Field by Dissipation

We show that inducing sidebands in the emission of a single emitter into a one dimensional waveguide, together with a dissipative re-pumping process, a photon field is cooled down to a squeezed vacuum. Our method does not require to be in the strong coupling regime, works with a continuum of propagating field modes and it may lead to sources of tunable multimode squeezed light in circuit QED systems.Comment: 4 pages, 3 figure

¿Comprenden los estudiantes las gráficas cartesianas usadas en los textos de ciencias?

Este artículo presenta los resultados de una investigación acerca del desempeño de los estudiantes de bachillerato y de licenciatura en química, en nueve tareas de interpretación de gráficas cartesianas incluidas en los libros de texto de química usados en el bachillerato. El estudio muestra que los participantes en el estudio no tienen dificultad para llevar a cabo las tareas de identificación de variables, lectura de datos y clasificación de la relación entre las variables. Sin embargo, los participantes presentan dificultad en tareas como la identificación de la relación entre las variables, el reconocimiento de los términos incluidos en la gráfica o la elaboración de conclusiones, explicaciones y predicciones a partir de la información gráfica. Así mismo, el estudio muestra que el aumento de complejidad de las tareas y algunas características de las gráficas (v.g. las líneas curvas o su uso instrumental en trabajos prácticos) hacen más difícil la ejecución de las tareas para los participantes en el estudio.This paper presents the findings of a research study on high school and B.Sc (Chemistry) students' performance in nine interpreting tasks of Cartesian graphs in high school Chemistry books. The study shows that participants did not find it difficult to perform tasks involving identification of variables, data reading, and classifi cation of relationships between variables. Nonetheless, participants encountered greater difficulty while carrying out tasks such as identification of variable relationships, recognition of terms in the graph, and elaboration of conclusions, explanations and predictions from graphical information. In addition, the study also found that increased task complexity and some characteristics of the graphs (e.g. curved lines or their instrumental use in practical assignments), made the execution of tasks more difficult to participants

¿Influye la formación académica de los estudiantes en su comprensión de las representaciones gráficas cartesianas?

RESUMEN: Este trabajo presenta los resultados de un estudio sobre la influencia de la formación académica de los estudiantes en su comprensión de la información gráfica, cuando interpretan una representación gráfica cartesiana referida a la Química e incluida en un libro de texto de Bachillerato.ABSTARCT: This paper presents the results of a study on the influence of the academic education of students in their understanding of graphic information , when interpreting a Cartesian graph referring to chemistry and included in a textbook of School

Cultura escolar e novos modelos culturais : duas realidades incompatíveis?

este texto apresenta resultados de debates promovido numa rede de discussão pela Internet, com a participação de investigadores de didática da Universidade de Sevilha, Espanha, e professores de escolas públicas e privadas. O tema dos debates esteve centrado na relação entre a escola e as novas opções culturais que permeiam a sociedade. Os autores partem da constatação de que vem aumentando consideravelmente a “brecha” entre a cultura em que estão imersas crianças e jovens e a cultura escolar tradicional para, em seguida, propor formas de superação desse desajuste cultural entre o dentro e o fora da escola

Yra1-bound RNA–DNA hybrids cause orientation-independent transcription– replication collisions and telomere instability

R loops are an important source of genome instability, largely due to their negative impact on replication progression. Yra1/ALY is an abundant RNA-binding factor conserved from yeast to humans and required for mRNA export, but its excess causes lethality and genome instability. Here, we show that, in addition to ssDNA and ssRNA, Yra1 binds RNA–DNA hybrids in vitro and, when artificially overexpressed, can be recruited to chromatin in an RNA– DNA hybrid-dependent manner, stabilizing R loops and converting them into replication obstacles in vivo. Importantly, an excess of Yra1 increases R-loop-mediated genome instability caused by transcription–replication collisions regardless of whether they are codirectional or head-on. It also induces telomere shortening in telomerase-negative cells and accelerates senescence, consistent with a defect in telomere replication. Our results indicate that RNA–DNA hybrids form transiently in cells regardless of replication and, after stabilization by excess Yra1, compromise genome integrity, in agreement with a two-step model of R-loop-mediated genome instability. This work opens new perspectives to understand transcription-associated genome instability in repair-deficient cells, including tumoral cells.European Research Council ERC2014 AdG669898 TARLOOPMinisterio de Economía y Competitividad BFU2016-75058-PJunta de Andalucía PA12- BIO123

Relationship between X(5)-models and the interacting boson model

The connections between the X(5)-models (the original X(5) using an infinite square well, X(5)-$\beta^8$, X(5)-$\beta^6$, X(5)-$\beta^4$, and X(5)-$\beta^2$), based on particular solutions of the geometrical Bohr Hamiltonian with harmonic potential in the $\gamma$ degree of freedom, and the interacting boson model (IBM) are explored. This work is the natural extension of the work presented in [1] for the E(5)-models. For that purpose, a quite general one- and two-body IBM Hamiltonian is used and a numerical fit to the different X(5)-models energies is performed, later on the obtained wave functions are used to calculate B(E2) transition rates. It is shown that within the IBM one can reproduce well the results for energies and B(E2) transition rates obtained with all these X(5)-models, although the agreement is not so impressive as for the E(5)-models. From the fitted IBM parameters the corresponding energy surface can be extracted and it is obtained that, surprisingly, only the X(5) case corresponds in the moderate large N limit to an energy surface very close to the one expected for a critical point, while the rest of models seat a little farther.Comment: Accepted in Physical Review