Bound states on the lattice with partially twisted boundary conditions

We propose a method to study the nature of exotic hadrons by determining the wave function renormalization constant $Z$ from lattice simulations. It is shown that, instead of studying the volume-dependence of the spectrum, one may investigate the dependence of the spectrum on the twisting angle, imposing twisted boundary conditions on the fermion fields on the lattice. In certain cases, e.g., the case of the $DK$ bound state which is addressed in detail, it is demonstrated that the partial twisting is equivalent to the full twisting up to exponentially small corrections

Epidemiology of sports injuries in european union countries

La práctica deportiva es una actividad que se recomienda para mantener y promocionar la salud y los buenos hábitos. Sin embargo puede acarrear un riesgo importante de lesiones. Este estudio presenta, mediante técnicas de análisis multivariante, la relación que existe entre la tipo de lesiones, lugares del cuerpo donde se producen, los deportes más populares; fútbol, baloncesto, voleibol, y gimnasia, edad y países donde se practica, tomando datos de cinco países de la Unión Europea. Si relacionamos estas características entre sí, podemos elaborar estrategias específicas al tipo de deporte y país donde se practica, con el objeto de mejorar la prevención y poder disminuir la cantidad de lesiones que se producen.Participation in sports is a health promotion activity and maintains good habits that entail an important injury risk. The present article is a study using Multivariatye Analysis, the relationship between type of injury, location of injury, the most popular sports; soccer, basketball, volleyball, gymnastics, county where it has been practiced and age, in five European Union countries. With these relationships, we can develop specific strategies to improve prevention and to reduce the injuries that occur

Continuum variational and diffusion quantum Monte Carlo calculations

This topical review describes the methodology of continuum variational and diffusion quantum Monte Carlo calculations. These stochastic methods are based on many-body wave functions and are capable of achieving very high accuracy. The algorithms are intrinsically parallel and well-suited to petascale computers, and the computational cost scales as a polynomial of the number of particles. A guide to the systems and topics which have been investigated using these methods is given. The bulk of the article is devoted to an overview of the basic quantum Monte Carlo methods, the forms and optimisation of wave functions, performing calculations within periodic boundary conditions, using pseudopotentials, excited-state calculations, sources of calculational inaccuracy, and calculating energy differences and forces

The Inverse Amplitude Method and Adler Zeros

The Inverse Amplitude Method is a powerful unitarization technique to enlarge the energy applicability region of Effective Lagrangians. It has been widely used to describe resonances from Chiral Perturbation Theory as well as for the Strongly Interacting Symmetry Breaking Sector. In this work we show how it can be slightly modified to account also for the sub-threshold region, incorporating correctly the Adler zeros required by chiral symmetry and eliminating spurious poles. These improvements produce negligible effects on the physical region.Comment: 17 pages, 4 figure

Social practices in the public space. Uses beyond social norms and the design of space.

En este artículo pretendemos describir las prácticas sociales y urbanas de las personas en un espacio público, concretamente en la ciudad de Barcelona. Las personas, cuando usan el espacio público lo transforman en lugar, es decir, generan ciertas relaciones y vínculos entre ellas y el espacio urbano, de tal forma que éste se modifica paulatinamente. Para la descripción de esas prácticas sociales y urbanas utilizamos una metodología cualitativa, específicamente una etnografía. Se identificaron y se eligieron tres tipos básicos de prácticas asociadas al espacio urbano: un tipo de esas prácticas se relaciona con el concepto de trabajo, otro con la idea de transitar (movimiento) y el último tipo con la práctica turística. Dichas prácticas sociales y urbanas evidenciaron el uso que llega a hacerse de los espacios públicos, uso que, la mayoría de las veces, es distinto al concebido en su diseño, bien por cuestiones estéticas o debido a las normas de uso. Las prácticas sociales descritas se relacionan con procesos psicosociales tales como: la identidad, la cohesión social, las normas sociales y la movilidad. Así mismo, dichas prácticas tienen la peculiaridad de sobrepasar los lineamientos de las normas sociales y urbanas y las finalidades de las estructuras existentes en el espacio

Two-photon exchange and normal spin asymmetries in the A4 experiment

The A4 Collaboration at the MAMI facility has measured, at backward angles and at Q2 = 0.23 (GeV/c)2 and Q2 = 0.35 (GeV/c)2, the asymmetry in the elastic and quasielastic scattering of normally polarized electrons on hydrogen and deuterium, respectively. Some preliminary results will be presented

Energetics of intrinsic point defects in ZrSiO4_4

Using first principles calculations we have studied the formation energies, electron and hole affinities, and electronic levels of intrinsic point defects in zircon. The atomic structures of charged interstitials, vacancies, Frenkel pairs and anti-site defects are obtained. The limit of high concentration of point defects, relevant for the use of this material in nuclear waste immobilization, was studied with a variable lattice relaxation that can simulate the swelling induced by radiation damage. The limit of low concentration of defects is simulated with larger cells and fixed lattice parameters. Using known band offset values at the interface of zircon with silicon, we analyze the foreseeable effect of the defects on the electronic properties of zircon used as gate in metal-oxide-semiconductor devices.Comment: preprint 16 pages, 4 figures, and 5 table

Efficient excitation of cavity resonances of subwavelength metallic gratings

One dimensional rectangular metallic gratings enable enhanced transmission of light for specific resonance frequencies. Two kinds of modes participating to enhanced transmission have already been demonstrated : (i) waveguide modes and (ii) surface plasmon polaritons (SPP). Since the original paper of Hessel and Oliner \cite{hessel} pointing out the existence of (i), no progress was made in their understanding. We present here a carefull analysis, and show that the coupling between the light and such resonances can be tremendously improved using an {\it evanescent} wave. This leads to enhanced localisation of light in cavities, yielding, in particular, to a very selective light transmission through these gratings.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let

Quantum Monte Carlo study of a positron in an electron gas

Quantum Monte Carlo calculations of the relaxation energy, pair-correlation function, and annihilating-pair momentum density are presented for a positron immersed in a homogeneous electron gas. We find smaller relaxation energies and contact pair-correlation functions in the important low-density regime than predicted by earlier studies. Our annihilating-pair momentum densities have almost zero weight above the Fermi momentum due to the cancellation of electron-electron and electron-positron correlation effects

Nuevas aberraciones de plumaje en aves paraguayas no passeriformes y la definición de una nueva aberración de plumaje única a Psittacidae

Anomalous plumage colourations are reported for three species of non-passerine birds from Paraguay, Limpkin (Aramaus guarauna; Aramidae), Nanday Parakeet (Nandayus nenday; Psittacidae), and the Little Woodpecker (Veniliornis passerinus; Picidae). A leucistic Limpkin is the first published report of a colour anomaly for the family Aramidae. The colour aberration in N. nenday is hypothesised to be a result of an excess of red psittacofulvin pigments, which are unique to the Psittacidae. Although the mechanisms causing this colour aberration remain unknown, we suggest the term psittacofulvism for the phenotypic effect observed.Se reportan anomalías en la coloración de tres aves no passeriformes del Paraguay, caraú Aramus guarauna (Aramidae), ñanday Nandayus nenday (Psittacidae) y carpinterito oliváceo Veniliornis passerinus (Picidae). Un caraú leucístico es el primer reporte publicado de coloración anómala en Aramidae. La presencia de coloración aberrante en Nandayus se hipotetiza como resultado de un exceso de pigmentos psittacofulvinos rojos, únicos a los Psittacidae. Aunque el mecanismo causante de esta aberración de color sigue siendo desconocido, sugerimos el término psittacofulvismo para el efecto fenotípico observado