Single photons by quenching the vacuum

Heisenberg's uncertainty principle implies that the quantum vacuum is not empty but fluctuates. These fluctuations can be converted into radiation through nonadiabatic changes in the Hamiltonian. Here, we discuss how to control this vacuum radiation, engineering a single-photon emitter out of a two-level system (2LS) ultrastrongly coupled to a finite-band waveguide in a vacuum state. More precisely, we show the 2LS nonlinearity shapes the vacuum radiation into a nonGaussian superposition of even and odd cat states. When the 2LS bare frequency lays within the band gaps, this emission can be well approximated by individual photons. This picture is confirmed by a characterization of the ground and bound states, and a study of the dynamics with matrix product states and polaron Hamiltonian methods.Comment: 9 pages, 10 figure

One- and two-photon scattering from generalized V-type atoms

The one- and two-photon scattering matrix S is obtained analytically for a one-dimensional waveguide and a point-like scatterer with N excited levels (generalized V -type atom). We argue that the two-photon scattering matrix contains sufficient information to distinguish between different level structures which are equivalent for single-photon scattering, such as a V -atom with N = 2 excited levels and two two-level systems. In particular, we show that the scattering with the V -type atom exhibits a destructive interference effect leading to two-photon Coupled-Resonator-Induced Transparency, where the nonlinear part of the two-photon scattering matrix vanishes when each incident photon fulfills a single-photon condition for transparency

Revisión sobre fusión nuclear y diseño del sistema de control de posición de FILD mediante PID y GPC

Debido a la actual demanda energética, nos vemos en la necesidad de utilizar fuentes de energía poco limpias (en el caso de combustibles fósiles) que son sensibles a cambios en las ondiciones ambientales (en el caso de las renovables). Para solventar el problema se ha acudido a la fusión nuclear, la cual es capaz de generar enormes cantidades de energía con un costo en combustible ínfimo, siendo insensible a cambios atmosféricos y generando productos que, aunque radiactivos, se vuelven seguros en periodos de tiempo muy cortos. Los reactores utilizados para dichos procesos nucleares son del tipo Tokamak y del tipo Stellarator. El panorama actual, en cuanto a fusión nuclear, se basa en mantener una reacción estable para la generación continua de electricidad. Para ello, uno de los campos abiertos de investigación se centra en el estudio de las pérdidas de iones rápidos. Para medir dichas pérdidas se utiliza un diagnóstico denominado FILD ,, por sus siglas en inglés Fast –Ion. Loss Detector. Un avance en su estudio ayudaría a comprender dichas pérdidas y en la medida de lo posible evitarlas o incluso controlarlas. En el Tokamak ASDEX Up grade del Instituto Max Planck se encuentran instalados dos tipos de FILD , uno dirigido con un actuador mecánico y otro dirigido magnéticamente. La diferencia entre ambos se basa en el mecanismo que los inserta dentro del reactor. Mientras que el primero se basa en el movimiento de un tornillo sin fin, el segundo se basa el giro producido en una bobina. El diseño de control se realizará al mecanismo dirigido magnéticamente. El objetivo principal de este trabajo es la comprensión y diseño de un controlador que inserte el FILD lo más rápido posible y lo inmunice ante perturbaciones y ruidos de instrumentación. Se barajarán dos tipos de controladores, un PID (Proportional - Integral -Derivative) y un GPC (Generalized Predictive Control). El primero es el más clásico en la ingeniería y el más simple, su diseño se realizará mediante métodos frecuenciales y posteriormente se ampliará añadiéndole un controlador anticipativo para la absorción de perturbaciones. El segundo es un control predictivo basado en modelo que integra el control anticipativo de una forma más natural. El GPC consigue integrar mediante una función de coste el tipo de control que queremos y que tenga en cuenta desde la agresividad del control, hasta otros parámetros, como los esfuerzos realizados en los cojinetes del mecanismo. También es posible incluir restricciones al controlador para que nunca sobrepase un rango en la referencia y, por tanto, no sobreoscile. Para la absorción del ruido se pretende diseñar un filtro de Kalman el cual consiga rechazar todo lo posible el ruido generado por la instrumentación y los posibles errores de modelado. Dicho filtro será colocado a la entrada de cualquiera de los controladores para suministrar una versión filtrada de las variables de control. Este trabajo concluirá con un resumen y análisis de ventajas e Inconvenientes de cada controlador y los estudios futuros a realizar en el diseño de control de FILD y las posibles mejoras y modificaciones que se pretenden realizar.Due to the current energy demand, we are in the need of us ing less clean energy sources (in the case of fossil fuels ) or are sensitive to environmental changes (in the case of newables). Nuclear fusion, which is capable to generat e huge amounts of energy with a tiny fuel cost, be ing insensitive to atmospheric changes and generating products that, although radioactive, become safe in very shorts periods , is a promissing alternative to solve this problem . The reactors used for this nuclear process are the Tokamak type and the Stellarator type. The current scenario, in terms of nuclear fusion, is based on sustaining a stable reaction for the continuous electricity generation. For this, one of .the open fields for research focuses on the study of fast ion losses detector or FILD by its acronym. An advance in its study would help to understand these losses and as far as possible avoid or even control them. In the ASDEX Upgrade tokamak two types of FILDs are installed , one mechanical and other magnetically driven. The difference between both is based on the mechanism that inserts them inside .the reactor chamber. While the first one is based on the movement of a worm, the second one is based on the rotation induced by a coil. The control system of the magnetically driven FILD will be the sco pe of this work. The main objective of this work is the understanding and design of a controller that inserts the FILD as fast as possible and immunizes it against disturbances and instrumentation noise. Two types of controllers are considered, a Proportional -Integral -Derivative (PID) and a Generalized Predictive Control (GPC) . The first one is the most classic in engineering and the simplest, its design will be done by frequency methods and later it will be expanded by adding a feedforward controller to ab sorbdisturbances. The second one is a predictive control based on a model that integrates the feedforward controller in a more naturally way. The GPC manages to integrate through a cost function the way that we want to perform the control and takes into a ccount its aggressiveness and other parameters such as the forces in the mechanism. It is also possible to include restrictions on the controller so that the response never exceeds a range in the reference and, therefore, is not overdamped For the absorpti on of noise, it is intended to design a Kalman filter, which will reject as much as possible the noise generated by the instrumentation and possible modelling errors. The filter will be placed at the entrance of any of the controllers to supply a filtered version of the control variables. This work will conclude with a summary,analysis of advantages and disadvantages of each controller and future studies to be carried out in the design of FILD control along with the possible improvements and modifications that are intended to be made.Universidad de Sevilla. Grado en Ingeniería de las Tecnologías Industriale

Emergent Causality and the N-photon Scattering Matrix in Waveguide QED

In this work we discuss the emergence of approximate causality in a general setup from waveguide QED -i.e. a one-dimensional propagating field interacting with a scatterer. We prove that this emergent causality translates into a structure for the N-photon scattering matrix. Our work builds on the derivation of a Lieb-Robinson-type bound for continuous models and for all coupling strengths, as well as on several intermediate results, of which we highlight (i) the asymptotic independence of space-like separated wave packets, (ii) the proper definition of input and output scattering states, and (iii) the characterization of the ground state and correlations in the model. We illustrate our formal results by analyzing the two-photon scattering from a quantum impurity in the ultrastrong coupling regime, verifying the cluster decomposition and ground-state nature. Besides, we generalize the cluster decomposition if inelastic or Raman scattering occurs, finding the structure of the S-matrix in momentum space for linear dispersion relations. In this case, we compute the decay of the fluorescence (photon-photon correlations) caused by this S-matrix

Evanescent waves and deaf bands in sonic crystals

The properties of sonic crystals (SC) are theoretically investigated in this work by solving the inverse problem k(¿) using the extended plane wave expansion (EPWE). The solution of the resulting eigenvalue problem gives the complex band structure which takes into account both the propagating and the evanescent modes. In this work we show the complete mathematical formulation of the EPWE for SC and the supercell approximation for its use in both a complete SC and a SC with defects. As an example we show a novel interpretation of the deaf bands in a complete SC in good agreement with multiple scattering simulations. © 2011 Copyright 2011 Author(s).This work was supported by MCI-Secretaria de Estado de Investigacion (Spanish government) and the FEDER funds, under grant MAT2009-09438. LMGR would like to thank the UPV for the grant PAID-00-11. VRG is grateful for the support of "Programa de Contratos Post-Doctorales con Movilidad UPV (CEI-01-11)."Romero García, V.; García Raffi, LM.; Sánchez Pérez, JV. (2011). Evanescent waves and deaf bands in sonic crystals. AIP Advances. 1(4):416011-416019. doi:10.1063/1.3675801S4160114160191

La enseñanza de las ciencias a través del enfoque CTS

En este trabajo se recogen las reflexiones más interesantes sobre el Máster de Profesorado y la labor docente. También se discuten desde un punto de vista de la didáctica de las ciencias dos trabajos realizados durante el curso desde un enfoque CTS. Estos trabajos son proyectos didácticos sobre el cambio climático y las pseudociencias. Ambos buscan abogan por la alfabetización científica y la promoción de la cultura científica.<br /

Ultradiscrete kinks with supersonic speed in a layered crystal with realistic potentials

We develop a dynamical model of the propagating nonlinear localized excitations, supersonic kinks, in the cation layer in a silicate mica crystal. We start from purely electrostatic Coulomb interaction and add the Ziegler-Biersack-Littmark short-range repulsive potential and the periodic potential produced by other atoms of the lattice. This approach allows the construction of supersonic kinks which can propagate in the lattice within a large range of energies and velocities. The interparticle distances in the lattice kinks with high energy are physically reasonable values. The introduction of the periodic lattice potential results in the important feature that the kinks propagate with a single velocity and a single energy which are independent on the excitation conditions. The found kinks are ultra-discrete and can be described with the "magic wave number" $q\simeq 2\pi/3a$, which was previously revealed in the nonlinear sinusoidal waves and supersonic kinks in the Fermi-Pasta-Ulam lattice. The extreme discreteness of the supersonic kinks, with basically two particles moving at the same time, allows the interpretation of their double-kink structure. The energy of the supersonic kinks is between the possible source of $^{40}$K recoil in beta decay and the energy necessary for the ejection of an atom at the border as has been found experimentally.Comment: 14 pages, 15 figure

Nonlinear waves in a chain of magnetically coupled pendula

A motivation for the study of reduced models like one-dimensional systems in Solid State Physics is the complexity of the full problem. In recent years our group has studied theoretically, numerically and experimentally wave propagation in lattices of nonlinearly coupled oscillators. Here, we present the dynamics of magnetically coupled pendula lattices. These macroscopic systems can model the dynamical processes of matter or layered systems. We report the results obtained for harmonic wave propagation in these media, and the different regimes of mode conversion into higher harmonics strongly influenced by dispersion and discreteness, including the phenomenon of acoustic dilatation of the chain, as well as some results on the propagation of localized waves i.e., solitons and kinks.Generalitat Valenciana APOSTD/2017/042Umiversitat Politècnica de València PAID-01-14Ministerio de Economía y Competitividad (MINECO), Spain FIS2015-65998-C2-2-PJunta de Andalucía 2017/FQM-28

On pp-Frobenius of affine semigroups

The aim of this paper is to study the $p$-Frobenius vector of affine semigroups $S\subset \mathbb N^q$; that is, the maximum element, with respect to a graded monomial order, with at most $p$ factorizations in $S$. We produce several algorithms to compute these vectors. Finally, we study how the $p$-Frobenius vectors behave when considering gluings of $S$ with $\mathbb N^q$

Hunger and sustainability

This paper examines the problem of world hunger and discusses potential solutions to it. It reflects on the debate about whether transgenic foods should be used, which is more of a social controversy than a scientific one. Sustainability is considered a key driver for innovation that can be used as a basis for assessing the problem of hunger in the world, and the question is inseparable from its ethical aspects. Given that economic growth does not directly equate to human development, this paper states that it is necessary to address the problem of poverty and hunger from the capacity development framework according to human rights. Poverty causes disability by limiting human development; it creates the conditions for the violation of human rights; therefore, an institutional framework and social initiatives aimed at protecting the poor should be established. Finally, the main lines of research in the field of biotechnology are outlined, such as the development of genetically modified organisms and the need to continue defining methods, based on the development of capabilities. Such capabilities should be embedded in educational programmes, to establish guidelines that are incorporated into curricula as transversal orientations to be able to make sustainability a social reality