A supersymmetric exotic field theory in (1+1) dimensions. One loop soliton quantum mass corrections

We consider one loop quantum corrections to soliton mass for the ${\cal N}=1$ supersymmetric extension of the (1+1)-dimensional scalar field theory with the potential $U(\phi) = \phi^2 \cos^2\left(\ln \phi^2\right)$. First, we compute the one loop quantum soliton mass correction of the bosonic sector. To do that, we regularize implicitly such quantity by subtracting and adding its corresponding tadpole graph contribution, and use the renormalization prescription that the added term vanishes with the corresponding counterterms. As a result we get a finite unambiguous formula for the soliton quantum mass corrections up to one loop order. Afterwards, the computation for the supersymmetric case is extended straightforwardly and we obtain for the one loop quantum correction of the SUSY kink mass the expected value previously derived for the SUSY sine-Gordon and $\phi^4$ models. However, we also have found that for a particular value of the parameters, contrary to what was expected, the introduction of supersymmetry in this model worsens ultraviolet divergences rather than improving them.Comment: 16 pages, 8 figures; Major modifications included to match version published in JHE

Suspension flow: do particles act as mixers?

Recently, Roht et al. [J. Contam. Hydrol. 145, 10-16 (2013)] observed that the presence of suspended non-Brownian macroscopic particles decreased the dispersivity of a passive solute, for a pressure-driven flow in a narrow parallel-plates channel at low Reynolds number. This result contradicts the idea that the streamline distortion caused by the random diffusive motion of the particles increases the dispersion and mixing of the solute. Therefore, to estimate the influence of this motion on the dispersivity of the solute, and investigate the origin of the reported decrease, we experimentally studied the probability density functions (pdf) of the particle velocities, and spatio-temporal correlations, in the same experimental configuration. We observed that, as the mean suspension velocity exceeds a critical value, the pdf of the streamwise velocities of the particles markedly changes from a symmetric distribution to an asymmetric one strongly skewed to high velocities and with a peak of most probable velocity close to the maximum velocity. The latter observations and the analysis of suspension microstructure indicate that the observed decrease in the dispersivity of the solute is due to particle migration to the mid-plane of the channel, and consequent flattening of the velocity profile. Moreover, we estimated the contribution of particle diffusive motion to the solute dispersivity to be three orders of magnitude smaller than the reported decrease, and thus negligible. Solute dispersion is then much more affected by how particles modify the flow velocity profile across the channel, than by their diffusive random motion

Globally stable control of a dynamic bipedal walker using adaptive frequency oscillators

We present a control method for a simple limit-cycle bipedal walker that uses adaptive frequency oscillators (AFOs) to generate stable gaits. Existence of stable limit cycles is demonstrated with an inverted-pendulum model. This model predicts a proportional relationship between hip torque amplitude and stride frequency. The closed-loop walking control incorporates adaptive Fourier analysis to generate a uniform oscillator phase. Gait solutions (fixed points) are predicted via linearization of the walker model, and employed as initial conditions to generate exact solutions via simulation. Global stability is determined via a recursive algorithm that generates the approximate basin of attraction of a fixed point. We also present an initial study on the implementation of AFO-based control on a bipedal walker with realistic mass distribution and articulated knee joint

Generation of maximally entangled states of qudits using twin photons

We report an experiment to generate maximally entangled states of D-dimensional quantum systems, qudits, by using transverse spatial correlations of two parametric down-converted photons. Apertures with D-slits in the arms of the twin fotons define the qudit space. By manipulating the pump beam correctly the twin photons will pass only by symmetrically opposite slits, generating entangled states between these differents paths. Experimental results for qudits with D=4 and D=8 are shown. We demonstrate that the generated states are entangled states.Comment: 04 pages, 04 figure

Financiamiento del servicio de educación al turista en áreas protegidas: concesión u operación estatal

The conflicts between public and private consumption are as old as mankind itself and can be observed in the permanent fight between the private individual and the collective its belongs. Specially in the use of certain goods and services, that by its nature has solely private consumption, with characteristics of purely collective consumption lik education. The study was conducted n August 2006, between 315 domestic and foreigners visitors to Volcán Poas National Park, in order to identify the preferred option and the essential conditions to reopen according to desire, and the visitors interests, the auditorium facilities of the park. The results would suggest that the sociodemographic characteristics of the visitors do not seem to have much influence in their desire of using the service or his willingness to pay an additional amount for the services. The preferred time of duration for the conferences was around 15 minutes. The presence and the audience's use must be negotiated with the tour operators. The way of collection of payment preferred was Internet, followed by tour operator. The additional average amounts to be pay for the service was three dollars. The reopening must contemplate four things: clear objectives, transparent procedures, separating the rent for the premises from the one to cover maintenance, since the auditorium is a public good product of a donation's product, and a periodic supervision mechanism for service's being provided. The data collected indicates that base on the additional amount to be pay by the service and the potential volume of visitors is possible to concession the auditorium to a private supplier or for the park to supply the service by itself if they so desire

Modelamiento y simulación de algoritmos adaptivos de alocación de bits para sistemas multiuser

Este proyecto se enfoca en el análisis y desarrollo de un algoritmo que nos permitirá entender con mayor facilidad lo que es la alocación adaptiva de bit en un sistema multiuser OFDM.La solución que hemos planteado para el desarrollo de este proyecto es de tipo “Multi-userdiscrete bit-loading”, la cual podremos ver desarrollada más adelante {3.3}, pero que con una sencilla explicación podemos decir que esta solución trata de encontrar la forma más optima de transmitir una cierta cantidad de bits, con el único propósito de minimizar la potencia total de transmisión.la solución planteada será desarrollada en un escenario específico con valores determinados con la finalidad de que cumpla con las condiciones necesarias para trabajar en un medio VDSL2. Gracias a análisis realizado se pudo verificar la eficiencia del algoritmo y la gran utilidad al momento de realizar la alocación ya que permite minimizar al máximo la potencia total de transmición. El algoritmo planteado en este proyecto fue desarrollado en el software MATLAB, ya que consideramos que es un software nos permite recopilar datos de una manera más real, con el propósito de brindar la explicación más clara a lector

Landau parameters for isospin asymmetric nuclear matter based on a relativistic model of composite and finite extension nucleons

We study the properties of cold asymmetric nuclear matter at high density, applying the quark meson coupling model with excluded volume corrections in the framework of the Landau theory of relativistic Fermi liquids. We discuss the role of the finite spatial extension of composite baryons on dynamical and statistical properties such as the Landau parameters, the compressibility, and the symmetry energy. We have also calculated the low lying collective eigenfrequencies arising from the collisionless quasiparticle transport equation, considering both unstable and stable modes. An overall analysis of the excluded volume correlations on the collective properties is performed.Comment: 24 pages, 6 figure

A Critique of Personas as representations of "the other" in Cross-Cultural Technology Design

A literature review on cross-cultural personas reveals both, a trend in projects lacking accomplishment and personas reinforcing previous biases. We first suggest why failures or incompleteness may have ensued, while then we entice a thoughtful alteration of the design process by creating and validating personas together with those that they embody. Personas created in people's own terms support the design of technologies by truly satisfying users' needs and drives. Examining the experiences of those working "out there", and our practises, we conclude persona is a vital designerly artefact to empowering people in representing themselves. A persona-based study on User-Created Persona in Namibia contrasts the current persona status-quo via an ongoing co-design effort with urban and rural non-designers. However we argue persona as a design device must ease its implicit colonial tendency to and impulses in depicting "the other". Instead we endorse serenity, mindfulness and local enabling in design at large and in the African context in particular