Operator Mixing in Large NN Superconformal Field Theories on S4\mathbb{S}^4 and Correlators with Wilson loops

We find a general formula for the operator mixing on the $\mathbb{S}^4$ of chiral primary operators (CPO) for the ${\cal N}=4$ theory at large $N$ in terms of Chebyshev polynomials. As an application, we compute the correlator of a CPO and a Wilson loop, reproducing an earlier result by Giombi and Pestun obtained from a two-matrix model proposal. Finally, we discuss a simple method to obtain correlators in general ${\cal N}=2$ superconformal field theories in perturbation theory in terms of correlators of the ${\cal N}=4$ theory.Comment: 15 pages, no figure

Measuring the interaction force between a high temperature superconductor and a permanent magnet

Repulsive and attractive forces are both possible between a superconducting sample and a permanent magnet, and they can give place to magnetic levitation or free-suspension phenomena, respectively. We show experiments to quantify this magnetic interaction which represents a promising field regarding to short-term technological applications of high temperature superconductors. The measuring technique employs an electronic balance and a rare-earth magnet that induces a magnetic moment in a melt-textured YBa2Cu3O7 superconductor immersed in liquid nitrogen. The simple design of the experiments allows a fast and easy implementation in the advanced physics laboratory with a minimum cost. Actual levitation and suspension demonstrations can be done simultaneously as a help to interpret magnetic force measurements.Comment: 12 pages and 3 figures in postscrip

El origen de los estudios modernos sobre Periodismo y Literatura en España: el aporte fundacional de la Gaceta de la Prensa Española (1942-1972) .

Este artículo demuestra que, de 1942 a 1972, los principales aportes sobre las conexiones periodístico-literarias se plasmaron en la Gaceta de la Prensa Española, una revista corporativa editada por la franquista Delegación Nacional de Prensa, donde colaboraron periodistas, escritores y académicos interesados en reflexionar sobre la actividad informativa. El presente trabajo intenta llenar un vacío en los estudios relacionados con la mixtura entre el Periodismo y la Literatura en España, pues, de los años cuarenta a los setenta del siglo XX, poco o nada se publicó sobre ese maridaje en los manuales de Redacción Periodística. Se rescatan así esos aportes aún no documentados por la tradición

Boundary Conformal Anomalies on Hyperbolic Spaces and Euclidean Balls

We compute conformal anomalies for conformal field theories with free conformal scalars and massless spin $1/2$ fields in hyperbolic space $\mathbb{H}^d$ and in the ball $\mathbb{B}^d$, for $2\leq d\leq 7$. These spaces are related by a conformal transformation. In even dimensional spaces, the conformal anomalies on $\mathbb{H}^{2n}$ and $\mathbb{B}^{2n}$ are shown to be identical. In odd dimensional spaces, the conformal anomaly on $\mathbb{B}^{2n+1}$ comes from a boundary contribution, which exactly coincides with that of $\mathbb{H}^{2n+1}$ provided one identifies the UV short-distance cutoff on $\mathbb{B}^{2n+1}$ with the inverse large distance IR cutoff on $\mathbb{H}^{2n+1}$, just as prescribed by the conformal map. As an application, we determine, for the first time, the conformal anomaly coefficients multiplying the Euler characteristic of the boundary for scalars and half-spin fields with various boundary conditions in $d=5$ and $d=7$.Comment: 16 pages. V3: small correction