Channel Blockade in a Two-Path Triple-Quantum-Dot System

Electronic transport through a two-path triple-quantum-dot system with two source leads and one drain is studied. By separating the conductance of the two double dot paths, we are able to observe double dot and triple dot physics in transport and study the interaction between the paths. We observe channel blockade as a result of inter-channel Coulomb interaction. The experimental results are understood with the help of a theoretical model which calculates the parameters of the system, the stability regions of each state and the full dynamical transport in the triple dot resonances.Comment: 6 pages, 6 figure

What if the Masses of the First Two Quark Families are not Generated by the Standard Higgs?

We point out that, in the context of the SM, $|V^2_{13}| + | V^2_{23}|$ is expected to be large, of order one. The fact that $|V^2_{13}| + |V^2_{23}| \approx 1.6 \times 10^{-3}$ motivates the introduction of a symmetry S which leads to $V_{CKM} ={1\>\!\!\!\mathrm{I}}$, with only the third generation of quarks acquiring mass. We consider two scenarios for generating the mass of the first two quark generations and full quark mixing. One consists of the introduction of a second Higgs doublet which is neutral under S. The second scenario consists of assuming New Physics at a high energy scale , contributing to the masses of light quark generations, in an effective field theory approach. This last scenario leads to couplings of the Higgs particle to $s\overline s$ and $c \overline c$ which are significantly enhanced with respect to those of the SM. In both schemes, one has scalar-mediated flavour- changing neutral currents which are naturally suppressed. Flavour violating top decays are predicted in the second scenario at the level \mbox{Br} (t \rightarrow h c ) \geq 5\times 10^{-5}.Comment: 11 pages, 1 figur

Curvature-driven coarsening in the two dimensional Potts model

We study the geometric properties of polymixtures after a sudden quench in temperature. We mimic these systems with the $q$-states Potts model on a square lattice with and without weak quenched disorder, and their evolution with Monte Carlo simulations with non-conserved order parameter. We analyze the distribution of hull enclosed areas for different initial conditions and compare our results with recent exact and numerical findings for $q=2$ (Ising) case. Our results demonstrate the memory of the presence or absence of long-range correlations in the initial state during the coarsening regime and exhibit super-universality properties.Comment: 12 pages, 16 figure

Strong superadditivity and monogamy of the Renyi measure of entanglement

Employing the quantum R\'enyi $\alpha$-entropies as a measure of entanglement, we numerically find the violation of the strong superadditivity inequality for a system composed of four qubits and $\alpha>1$. This violation gets smaller as $\alpha\rightarrow 1$ and vanishes for $\alpha=1$ when the measure corresponds to the Entanglement of Formation (EoF). We show that the R\'enyi measure aways satisfies the standard monogamy of entanglement for $\alpha = 2$, and only violates a high order monogamy inequality, in the rare cases in which the strong superadditivity is also violated. The sates numerically found where the violation occurs have special symmetries where both inequalities are equivalent. We also show that every measure satisfing monogamy for high dimensional systems also satisfies the strong superadditivity inequality. For the case of R\'enyi measure, we provide strong numerical evidences that these two properties are equivalent.Comment: replaced with final published versio

Geometrical properties of Potts model during the coarsening regime

We study the dynamic evolution of geometric structures in a poly-degenerate system represented by a $q$-state Potts model with non-conserved order parameter that is quenched from its disordered into its ordered phase. The numerical results obtained with Monte Carlo simulations show a strong relation between the statistical properties of hull perimeters in the initial state and during coarsening: the statistics and morphology of the structures that are larger than the averaged ones are those of the initial state while the ones of small structures are determined by the curvature driven dynamic process. We link the hull properties to the ones of the areas they enclose. We analyze the linear von-Neumann--Mullins law, both for individual domains and on the average, concluding that its validity, for the later case, is limited to domains with number of sides around 6, while presenting stronger violations in the former case.Comment: 12 page

Sobre el tiempo: primeras aproximaciones entre el pensamiento físico y el pensamiento sociológico de Norbert Elias

The fundamental concept of time used by Physics was built by Galileo, through the observation of the apparent pendulum isochronism and establishing the possibility of using an instrument as a generator of temporal intervals to investigate natural phenomena occurring around them. At that time, a religious conception of time was dominant: according to this, the celestial objects, infallible and without the imperfections of the common world, dictated the temporal evolution of every phenomena. Thanks to Galileo, we are able to measure time and, consequently, we started to measure the world. With Newton, we return to a divine conception of time: evolution is an absolute space and time which can be understood as a divine sensation. The absolute time permeates everything that happens in our universe; it does not matter where the clock is because it is always capable of measuring uniformly time intervals. The three-dimensional space is Euclidean, meanwhile time is completely independent. For Elias, beyond the three physical and classical dimensions, it is needed to add are two other dimensions which are built in the context of human interdependency, namely, time and symbol. Time is an relevant dimension of Elias thought, time as an experience of duration, reference, and as a measurable change; time, simultaneously, as a physical and social entity. Clocks play a key role in the way we investigate the world and as instruments of time measurement produce a new time dimensions. But they are not built just for this purpose; their accuracy is closely related to the great voyages. Accuracy in time measurement provides a more exact position of a ship's longitude on the globe. With Einstein, this absolute synchronicity of two clocks loses its meaning: from this moment, clocks measure different time intervals according to their location and spatial movement. The time is "spatialized" and space-time is now a locating system of any event in our universe. The purpose of this article is to explore the possibilities of a dialogue on concepts of time, between a natural science, Physics, and the multiple faces offered by figurational approach.La concepción fundamental del tiempo en la Física es aquella construida por Galileo,  al observar el aparente isocronismo de un péndulo,  instrumento empleado como generador de intervalos temporales para investigar los fenómenos naturales que ocurrían en la órbita de los satélites de Júpiter. En aquel momento prevalecía una concepción divina del tiempo, en la que los objetos celestes, infalibles y sin las imperfecciones del mundo cotidiano, regían  la evolución temporal de todos los fenómenos: con Galileo medimos el tiempo y a partir de él comenzamos a medir el mundo. Con Newton se produce un retorno a la concepción divina del tiempo: toda evolución es un espacio y tiempo absolutos entendidos en última instancia como sensación divina. El tiempo absoluto permea todo lo que ocurre en nuestro universo. No importa donde se encuentre el reloj ya que éste es capaz de medir los intervalos de tiempo de forma uniforme. El espacio tridimensional es euclidiano, y el tiempo totalmente independiente. Para Elias, a las tres dimensiones físicas, se le añaden otras dos construidas con base en las relaciones interdependientes entre los seres humanos: tiempo y símbolo. El tiempo es una dimensión relevante en el pensamiento de Elias, tiempo como experiencia de duración, con referencia mensurable y perspectiva de cambio que se bifurca en tiempo físico y tiempo social. El perfeccionamiento de los relojes desempeña un papel fundamental en nuestro conocimiento del mundo: en tanto instrumentos de medición, ellos mismos son productores de una dimensión del  tiempo. Sin embargo no se construyeron con ese único propósito pues su precisión esta también íntimamente relacionada con las grandes navegaciones. La exactitud en la medición del tiempo ofrece mayor precisión a la hora de determinar la posición  de un barco en el globo terráqueo. Con Einstein la sincronía absoluta de los relojes pierde significado: éstos medirán a partir de ahora intervalos de tiempo diferentes de acuerdo con su localización y su movimiento en el espacio. El tiempo se ha “especializado” y disponemos de un espacio como tiempo encargado de la localización de cualquier evento en nuestro universo. El propósito de este artículo es explorar las posibilidades de diálogo pertinentes en las concepciones del tiempo que maneja una ciencia natural, la Física, y las que derivan de un abordaje sociológico figuracional

Insights into the room temperature magnetism of ZnO/Co3O4 mixtures

The origin of room temperature (RT) ferromagneticlike behavior in ZnO-based diluted magnetic semiconductors is still an unclear topic. The present work concentrates on the appearance of RT magnetic moments in just mixed ZnO/Co3O4 mixtures without thermal treatment. In this study, it is shown that the magnetism seems to be related to surface reduction of the Co3O4 nanoparticles, in which, an antiferromagnetic Co3O4 nanoparticle (core) is surrounded by a CoO-like shell. This singular superficial magnetism has also been found in other mixtures with semiconductors such as TiO2 and insulators such as Al2O3

Air gap influence on the vibro-acoustic response of Solar Arrays during launch

One of the primary elements on the space missions is the electrical power subsystem, for which the critical component is the solar array. The behaviour of these elements during the ascent phase of the launch is critical for avoiding damages on the solar panels, which are the primary source of energy for the satellite in its final configuration. The vibro-acoustic response to the sound pressure depends on the solar array size, mass, stiffness and gap thickness. The stowed configuration of the solar array consists of a multiple system composed of structural elements and the air layers between panels. The effect of the air between panels on the behaviour of the system affects the frequency response of the system not only modifying the natural frequencies of the wings but also as interaction path between the wings of the array. The usual methods to analyze the vibro-acoustic response of structures are the FE and BE methods for the low frequency range and the SEA formulation for the high frequency range. The main issue in the latter method is, on one hand, selecting the appropriate subsystems, and, on the other, identifying the parameters of the energetic system: the internal and coupling loss factors. From the experimental point of view, the subsystems parameters can be identified by exciting each subsystem and measuring the energy of all the subsystems composing the Solar Array. Although theoretically possible, in practice it is difficult to apply loads on the air gaps. To analyse this situation, two different approaches can be studied depending on whether the air gaps between the panels are included explicitly in the problem or not. For a particular case of a solar array of three wings in stowed configuration both modelling philosophies are compared. This stowed configuration of a three wing solar arrays in stowed configuration has been tested in an acoustic chamber. The measured data on the solar wings allows, in general, determining the loss factors of the configuration. The paper presents a test description and measurements on the structure, in terms of the acceleration power spectral density. Finally, the performance of each modelling technique has been evaluated by comparison between simulations with experimental results on a spacecraft solar array and the influence on the apparent properties of the system in terms of the SEA loss factors has been analyse

Satellite accelerometer measurements of neutral density and winds during geomagnetic storms

A new thermospheric wind measurement technique is reported which is based on a Satellite Electrostatic Triaxial Accelerometer (SETA) system capable of accurately measuring accelerations in the satellite's in-track, cross-track and radial directions. Data obtained during two time periods are presented. The first data set describes cross-track winds measured between 170 and 210 km during a 5-day period (25 to 29 March 1979) of mostly high geomagnetic activity. In the second data set, cross-track winds and neutral densities from SETA and exospheric temperatures from the Millstone Hill incoherent scatter radar are examined during an isolated magnetic substorm occurring on 21 March 1979. A polar thermospheric wind circulation consisting of a two cell horizontal convection pattern is reflected in both sets of cross-track acceleration measurements. The density response is highly asymmetric with respect to its day/night behavior. Latitude structures of the density response at successive times following the substorm peak suggest the equatorward propagation of a disturbance with a phase speed between 300 and 600 m/s. A deep depression in the density at high latitudes (less than 70 deg) is evident in conjunction with this phenomenon. The more efficient propagation of the disturbance to lower latitudes during the night is probably due to the midnight surge effect