Ab-initio determination of Bose-Hubbard parameters for two ultracold atoms in an optical lattice using a three-well potential

We calculate numerically the exact energy spectrum of the six dimensional problem of two interacting Bosons in a three-well optical lattice. The particles interact via a full Born-Oppenheimer potential which can be adapted to model the behavior of the s-wave scattering length at Feshbach resonances. By adjusting the parameters of the corresponding Bose-Hubbard (BH) Hamiltonian the deviation between the numerical energy spectrum and the BH spectrum is minimized. This defines the optimal BH parameter set which we compare to the standard parameters of the BH model. The range of validity of the BH model with these parameter sets is examined, and an improved analytical prediction of the interaction parameter is introduced. Furthermore, an extended BH model and implications due to the energy dependence of the scattering length and couplings to higher Bloch bands at a Feshbach resonance are discussed.Comment: 14 pages, 11 figures; typos and minor errors corrected, five references added, next-to-nearest neighbor hopping included in extended Bose-Hubbard mode

Exact Keldysh theory of strong-field ionization: residue method vs saddle-point approximation

In recent articles [Mishima et al., Phys. Rev. A, 66, 033401(2002); Chao, Phys. Rev. A, 72, 053414 (2005)] it was proposed to use the residue theorem for the exact calculation of the transition amplitude describing strong-field ionization of atomic systems within Keldysh theory. This should avoid the necessity to apply the method of steepest descent (saddle-point approximation). Comparing the results of both approaches for atomic hydrogen a difference by a factor of 2 was found for the 1s, and an even more drastic deviation for the 2s state. Thus it was concluded that the use of the saddle-point approximation is problematic. In this work the deviations are explained and it is shown that the previous conclusion is based on an unjustified neglect of an important contribution occurring in the application of the residue theorem. Furthermore, the applicability of the method of steepest descent for the ionization of Rydberg states is discussed and an improvement of the standard result is suggested that successfully removes the otherwise drastic failure for large principal quantum numbers.Comment: 7 pages, 3 figures, 1 tabl

Influence of a tight isotropic harmonic trap on photoassociation in ultracold homonuclear alkali gases

The influence of a tight isotropic harmonic trap on photoassociation of two ultracold alkali atoms forming a homonuclear diatomic is investigated using realistic atomic interaction potentials. Confinement of the initial atom pair due to the trap leads to a uniform strong enhancement of the photoassociation rate to most, but also to a strongly suppressed rate for some final states. Thus tighter traps do not necessarily enhance the photoassociation rate. A further massive enhancement of the rate is found for strong interatomic interaction potentials. The details of this interaction play a minor role, except for large repulsive interactions for which a sharp window occurs in the photoassociation spectrum as is known from the trap-free case. A comparison with simplified models describing the atomic interaction like the pseudopotential approximation shows that they often provide reasonable estimates for the trap-induced enhancement of the photoassociation rate even if the predicted rates can be completely erroneous.Comment: 19 pages, 17 figure

Efficacy Beliefs of Beginning Hispanic Teachers and The Organizational Health of Schools in a South Texas School District

This quantitative study examined the relationship between teachers’ sense of efficacy and school organizational health. Teachers’ sense of efficacy was measured using three dimensions of teacher efficacy: efficacy in student engagement, efficacy in instructional strategies, and efficacy in classroom management. Organizational health was measured using dimensions of school health for elementary, middle, and high school including: academic emphasis, institutional integrity, collegial leadership, resource influence, teacher affiliation, morale, principal influence, resource support, consideration, and initiating structure. The sample consisted of 498 beginning Hispanic teachers with one to five years of teaching experience. The sample included, 255 elementary, 126 middle school, and 117 high school teachers from one school district with a student population that was 99% Hispanic and 96% economically disadvantaged. Regression analyses were used to examine relationships among variables. The study found that the organizational health of elementary, middle, and high schools predicted teachers’ sense of efficacy. Specifically, beginning Hispanic teachers in elementary, middle, and high schools felt efficacious in schools with a strong academic emphasis defined by a quest for academic excellence with high, but achievable academic goals

Coherent molecule formation in anharmonic potentials near confinement-induced resonances

We perform a theoretical and experimental study of a system of two ultracold atoms with tunable interaction in an elongated trapping potential. We show that the coupling of center-of-mass and relative motion due to an anharmonicity of the trapping potential leads to a coherent coupling of a state of an unbound atom pair and a molecule with a center of mass excitation. By performing the experiment with exactly two particles we exclude three-body losses and can therefore directly observe coherent molecule formation. We find quantitative agreement between our theory of inelastic confinement-induced resonances and the experimental results. This shows that the effects of center-of-mass to relative motion coupling can have a significant impact on the physics of quasi-1D quantum systems.Comment: 7 pages, 4 figure

Perspectiva bioética de la detención temprana de hipoacusias y el implante coclear en edad pediátrica en la Argentina

La hipoacusia se define como la disminución de la percepción auditiva, la cual constituye la vía habitual para la adquisición el lenguaje. Se trata de un problema relevante en la infancia temprana, dado que el logro de capacidades y habilidades intelectuales y sociales están ligados a un desarrollo adecuado de la audición como principal vía de aprendizaje. La audición, junto con el resto de los sentidos permite el establecer relaciones sociales y del individuo con su entorno. Es uno de los principales procesos fisiológicos que posibilita a los niños el aprendizaje, siendo de suma importancia para el desarrollo del pensamiento. Por ello es importante analizar las diferentes aristas que intervienen en la prevención, promoción y atención primaria y secundaria de dicha afección. A continuación analizaremos el Programa Nacional de Detección Temprana de Hipoacusias (su legislación, gestión y funcionalización), la importancia de una adecuada información a los padres o responsables del niño hipoacúsico, la perspectiva de la cultura sorda y la perspectiva de la oralización de pacientes sordos mediante el implante coclear en la infancia.Hearing loss is defined as the decrease in auditory perception, wich is the usual way to acquire language. This is a relevant problem in early childhood, as the achievement of skills and intellectual and social skills are linked to proper development of hearing as the main means of learning. The hearing, along with the rest of the senses allows social relationships and the individual with his environment. It is one of the key physiological processes that enables children learning to be of utmost importance for the development of thought. We considered important to analyze the different aspects involved in prevention, promotion and primary and secondary care of these condition. We will discuss the National Early Hearing Loss Screening (legislation, management and functionalization), the importance of adequate information to parents or guardians of children with hearing loss, the deaf culture perspective and the perspective of oralist deaf patients, through the cochlear implant in children.Fil: Saenz, A. Hospital Universitario (Mendoza, Argentina)Fil: Fazio, S.. Hospital Universitario (Mendoza, Argentina)Fil: Arreghini, M.. Hospital Pediátiro Humberto J. Notti (Mendoza, Argentina

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