Frustrated collisions and unconventional pairing on a quantum superlattice

We solve the problem of scattering and binding of two spin-1/2 fermions on a one-dimensional superlattice with a period of twice the lattice spacing analytically. We find the exact bound states and the scattering states, consisting of a generalized Bethe ansatz augmented with an extra scattering product due to "asymptotic" degeneracy. If a Bloch band is doubly occupied, the extra wave can be a bound state in the continuum corresponding to a single-particle interband transition. In all other cases, it corresponds to a quasi-momentum changing, frustrated collision.Comment: 4 pages, 2 figure

Endoscopic third ventriculostomy for the management of children with cerebrospinal fluid disorders, ventriculomegaly, and associated Chiari I malformation

OBJECTIVE: Our objective was to review the outcomes of children with CIM and associated cerebrospinal fluid (CSF) disorders and ventriculomegaly undergoing endoscopic third ventriculostomy (ETV) as a primary intervention. MATERIALS AND METHODS: A retrospective, single-center, observational cohort study was conducted of consecutive children with CIM with associated CSF disorders and ventriculomegaly treated first by ETV between January 2014 and December 2020. RESULTS: Raised intracranial pressure symptoms were the most frequent in ten patients, followed by posterior fossa and syrinx symptoms in three cases. One patient had a later stoma closure and required a shunt insertion. The success rate of the ETV in the cohort was 92% (11/12). There was no surgical mortality in our series. No other complications were reported. The median herniation of the tonsils was not statistically different in the pre vs. post-operative MRI (1.14 vs. 0.94, p=0.1). However, the median Evan’s index (0.4 vs. 0.36, p<0.01) and the median diameter of the third ventricle (1.35 vs. 0.76, p<0.01) were statistically different between the two measurements. The preoperative length of the syrinx did not change significantly compared with the postoperative (5 vs. 1; p=0.052); nevertheless, the median transverse diameter of the syrinx did improve significantly after the surgery (0.75 vs. 0.32, p=0.03). CONCLUSIONS: Our study supports ETV's safety and effectiveness for managing children with CSF disorders, ventriculomegaly, and associated CIM

Photoassociative spectroscopy at long range in ultracold strontium

We report photoassociative spectroscopy of $^{88}$Sr$_2$ in a magneto-optical trap operating on the ${^1S_0}\to{^3P_1}$ intercombination line at 689 nm. Photoassociative transitions are driven with a laser red-detuned by 600-2400 MHz from the ${^1S_0}\to{^1P_1}$ atomic resonance at 461 nm. Photoassociation takes place at extremely large internuclear separation, and the photoassociative spectrum is strongly affected by relativistic retardation. A fit of the transition frequencies determines the ${^1P_1}$ atomic lifetime ($\tau=5.22 \pm 0.03$ ns) and resolves a discrepancy between experiment and recent theoretical calculations.Comment: 4 pages, 4 figures, submitte

Gravitational lensing by gravitational waves

Gravitational lensing by gravitational wave is considered. We notice that although final and initial direction of photons coincide, displacement between final and initial trajectories occurs. This displacement is calculated analytically for the plane gravitational wave pulse. Estimations for observations are discussed.Comment: 9 pages, 3 figure

On the Definition of Effective Permittivity and Permeability For Thin Composite Layers

The problem of definition of effective material parameters (permittivity and permeability) for composite layers containing only one-two parallel arrays of complex-shaped inclusions is discussed. Such structures are of high importance for the design of novel metamaterials, where the realizable layers quite often have only one or two layers of particles across the sample thickness. Effective parameters which describe the averaged induced polarizations are introduced. As an explicit example, we develop an analytical model suitable for calculation of the effective material parameters $\epsilon_{\rm{eff}}$ and $\mu_{\rm{eff}}$ for double arrays of electrically small electrically polarizable scatterers. Electric and magnetic dipole moments induced in the structure and the corresponding reflection and transmission coefficients are calculated using the local field approach for the normal plane-wave incidence, and effective parameters are introduced through the averaged fields and polarizations. In the absence of losses both material parameters are purely real and satisfy the Kramers-Kronig relations and the second law of thermodynamics. We compare the analytical results to the simulated and experimental results available in the literature. The physical meaning of the introduced parameters is discussed in detail.Comment: 6 pages, 5 figure

Quantum Chessboards in the Deuterium Molecular Ion

We present a new algorithm for vibrational control in deuterium molecules that is feasible with current experimental technology. A pump mechanism is used to create a coherent superposition of the D2+ vibrations. A short, intense infrared control pulse is applied after a chosen delay time to create selective interferences. A `chessboard' pattern of states can be realized in which a set of even- or odd-numbered vibrational states can be selectively annihilated or enhanced. A technique is proposed for experimental realization and observation of this effect using 5 fs pulses of 790 nm radiation, with intermediate intensity (5e13 W/cm2)Comment: 12 pages, 5 figure

Evaluation of the Sportsmanship-Aggression Continuum in Youth Football

Given the importance of sport in modern society, it is essential that appropriate instruments are available for the assessment of both fair play and unfair play in the sport of football, particularly in the context of youth football. This research study presents the findings from the implementation of a protocol intended to assess fair play during football matches across three seasons. The study included 64 teams, 1192 players, 64 coaches and 292 referees all of whom were involved in the First Cadet category of the Football Federation of Alava (FFA). The measurement instrument employed was the Record of Football Match Evaluations (RFME) developed by Gimeno, Saenz, Arino and Aznar (2007). The results revealed that there was a high level of fair play at this level of play which extended to referees, coaches and players across the seasons of interest; there was a greater frequency of fair play attitudes relative to unfair play attitudes; home teams that were victorious were judged to have the most favorable fair play attitudes; and there was a negative correlation between perceived fair play and the number of cards shown by referees. The instrument 1) allowed for the effective utilization of a tool to assess fair play in youth football; 2) was effective for use over the course of the season; and 3) provided knowledge about the social agents who initiate inappropriate and unsportsmanlike acts during football matches for of school age youth, which enables consideration of appropriate counter measures. Dada la trascendencia que tiene en nuestra sociedad el deporte, en especial el fútbol desde edades muy tempranas, se hace necesario que los gestores de las competiciones dispongan de herramientas que permitan evaluar los comportamientos de deportividad y no deportividad que se observan en contextos deportivos de fútbol. En la presente investigación, se muestra la implementación de un protocolo de evaluación continua de la deportividad en los partidos de fútbol, durante tres temporadas deportivas. Participaron 64 equipos; 1192 futbolistas, 64 entrenadores y 292 árbitros, de la categoría primera cadete de la Federación Alavesa de Fútbol (F.A.F.). El instrumento de recogida de información utilizado fue el “Registro de Evaluación de Partidos de Fútbol” (REPF) (Gimeno, Sáenz, Ariño y Aznar, 2007). Los resultados re"ejan: puntuaciones positivas, en relación a la deportividad de árbitros, entrenadores y jugadores en cada una de las temporadas evaluadas; una mayor frecuencia de actitudes y conductas deportivas en comparación con las no-deportivas; una mayor percepción de deportividad en aquellos partidos en los que el equipo local es el ganador; y una correlación negativa entre la percepción de deportividad de un partido y el número de tarjetas mostradas por los árbitros. Como conclusión, se puede afirmar que el instrumento que se presenta permite: 1. Utilizar una herramienta de evaluación específica de la deportividad para la disciplina del fútbol en edad escolar; 2. Evaluar la deportividad a lo largo de toda la temporada; 3. Identificar los agentes que presentan comportamientos inadecuados durante la práctica deportiva de los jóvenes deportistas, pudiendo proponer las mejores medidas de intervenció

Estimating Lorenz’s Reference State in an Ocean with a Nonlinear Equation of State for Seawater

The study of the mechanical energy budget of the oceans using the Lorenz available potential energy (APE) theory is based on knowledge of the adiabatically rearranged Lorenz reference state of minimum potential energy. The compressible and nonlinear character of the equation of state for seawater has been thought to cause the reference state to be ill defined, casting doubt on the usefulness of APE theory for investigating ocean energetics under realistic conditions. Using a method based on the volume frequency distribution of parcels as a function of temperature and salinity in the context of the seawater Boussinesq approximation, which is illustrated using climatological data, the authors show that compressibility effects are in fact minor. The reference state can be regarded as a well-defined one-dimensional function of depth, which forms a surface in temperature, salinity, and density space between the surface and the bottom of the ocean. For a very small proportion of water masses, this surface can be multivalued and water parcels can have up to two statically stable levels in the reference density profile, of which the shallowest is energetically more accessible. Classifying parcels from the surface to the bottom gives a different reference density profile than classifying in the opposite direction. However, this difference is negligible. This study shows that the reference state obtained by standard sorting methods is equivalent to, though computationally more expensive than, the volume frequency distribution approach. The approach that is presented can be applied systematically and in a computationally efficient manner to investigate the APE budget of the ocean circulation using models or climatological data

Spectroscopic determination of the s-wave scattering lengths of 86Sr and 88Sr

We report the use of photoassociative spectroscopy to determine the ground state s-wave scattering lengths for the main bosonic isotopes of strontium, 86Sr and 88Sr. Photoassociative transitions are driven with a laser red-detuned by up to 1400 GHz from the 1S0-1P1 atomic resonance at 461 nm. A minimum in the transition amplitude for 86Sr at -494+/-5 GHz allows us to determine the scattering lengths 610a0 < a86 < 2300a0 for 86Sr and a much smaller value of -1a0 < a88 < 13a0 for 88Sr.Comment: 4 pages, 3 figures, submitted to Physical Review Letter