Non-relativistic Lee Model on two Dimensional Riemannian Manifolds

This work is a continuation of our previous work (JMP, Vol. 48, 12, pp. 122103-1-122103-20, 2007), where we constructed the non-relativistic Lee model in three dimensional Riemannian manifolds. Here we renormalize the two dimensional version by using the same methods and the results are shortly given since the calculations are basically the same as in the three dimensional model. We also show that the ground state energy is bounded from below due to the upper bound of the heat kernel for compact and Cartan-Hadamard manifolds. In contrast to the construction of the model and the proof of the lower bound of the ground state energy, the mean field approximation to the two dimensional model is not similar to the one in three dimensions and it requires a deeper analysis, which is the main result of this paper.Comment: 18 pages, no figure

Intraband and interband spin-orbit torques in non-centrosymmetric ferromagnets

Intraband and interband contributions to the current-driven spin-orbit torque in magnetic materials lacking inversion symmetry are theoretically studied using Kubo formula. In addition to the current-driven field-like torque ${\bf T}_{\rm FL}= \tau_{\rm FL}{\bf m}\times{\bf u}_{\rm so}$ (${\bf u}_{\rm so}$ being a unit vector determined by the symmetry of the spin-orbit coupling), we explore the intrinsic contribution arising from impurity-independent interband transitions and producing an anti-damping-like torque of the form ${\bf T}_{\rm DL}= \tau_{\rm DL}{\bf m}\times({\bf u}_{\rm so}\times{\bf m})$. Analytical expressions are obtained in the model case of a magnetic Rashba two-dimensional electron gas, while numerical calculations have been performed on a dilute magnetic semiconductor (Ga,Mn)As modeled by the Kohn-Luttinger Hamiltonian exchanged coupled to the Mn moments. Parametric dependences of the different torque components and similarities to the analytical results of the Rashba two-dimensional electron gas in the weak disorder limit are described.Comment: 10 pages, 5 figure

Membangun Modal Sosial Pada Gabungan Kelompok Tani

Sumber Makmur farmer's association (Gapoktan) have been changed structurally due to village enlargement processes. Differences of opinion, interest conflict, truth and norm, the decreasing the participation and cooperation were regarded as threat to Gapoktan performance. This study aims to explore members of Gapoktan's perspective toward social capital values. This article also explores social capital mechanism to realize Gapoktan good performance. This study conducted in Pekon Adiluwih, Adiluwih sub-district, Pringsewu District in 2013. Respondents were Gapoktan management board and members (33 person). Data collected by in-depth interviews. Qualitative description method used to analyze the data. Based on the discussion, the research concludes that: (1) the main social capital elements patch in Sumber Makmur farmer's group are: identity (X1, X2, X3), vision and goal (X4, X5), truth (X6, X7), smash anxiety (X8, X9), dan openness (X10). Positive value of social capital is considered as intrinsic value which create bonds between Gapoktan members. Mechanism to built solidarity of member was developed by strengthen trust to every members, and uniting identity, cooperation, and openness in a synergetic networks

A Hybrid Achromatic Metalens

Metamaterials and metasurfaces are widely used to manipulate electromagnetic waves over a broad range of wavelengths. Several recent efforts have focused on metalenses, ultra-thin optical elements that focus light using subwavelength structures. Compared to their refractive counterparts, metalenses offer reduced size and weight, improved manufacturability, and new functionality such as polarization control. However, metalenses that correct chromatic aberration also suffer from markedly reduced focusing efficiency. Here we introduce a Hybrid Achromatic Metalens (HAML), that overcomes this trade-off and offers improved focusing efficiency over a broad wavelength range from 1000 - 1800 nm. Fabricated HAMLs demonstrated diffraction limited performance for numerical apertures (NA) of 0.27, 0.11, and 0.06 with average focusing efficiencies $> 60\%$ and maximum efficiencies ~ $80\%$. HAMLs can be designed by combining recursive ray-tracing and simulated phase libraries rather than computational intensive global search algorithms. Moreover, HAMLs can be fabricated in low-refractive index materials using multi-photon lithography for customization or using molding for mass production.Comment: 20 pages, 7 figure

Vlogs in University EFL Speaking: Student-Teachers' Perceptions

Vlogs increase significantly in the contexts of English learning especially in the context of English as a Foreign Language education. Yet, little has been reported how university EFL students perceive vlogs for their English learning, e.g. speaking activities. Thus, this paper is aimed at investigating student-teachers' perception toward vlog-mediated English speaking activities. From 99 EFL student-teachers, 49 students of English department of a private university were recruited and they willingly participated in this study. After a week classroom project of vloging in speaking activities was implemented, questionnaires were distributed. After the results of the questionnaire had been tabulated, a semi-structured interview was conducted to explore further students’ perception of vloging activities. The findings show that vlog-mediated EFL speaking successfully stimulates students for speaking English in the out-class activities. Students enjoyed vloging activities. Students’ learning motivation was also improved. Some implication of the vlog-mediated EFL speaking activities were presented and discussed. Students’ speaking engagement and challenges were also sought to elaborate.  Keywords: EFL speaking, learning motivation, self-directed learning, vlog-mediated speakin

A Many-body Problem with Point Interactions on Two Dimensional Manifolds

A non-perturbative renormalization of a many-body problem, where non-relativistic bosons living on a two dimensional Riemannian manifold interact with each other via the two-body Dirac delta potential, is given by the help of the heat kernel defined on the manifold. After this renormalization procedure, the resolvent becomes a well-defined operator expressed in terms of an operator (called principal operator) which includes all the information about the spectrum. Then, the ground state energy is found in the mean field approximation and we prove that it grows exponentially with the number of bosons. The renormalization group equation (or Callan-Symanzik equation) for the principal operator of the model is derived and the $\beta$ function is exactly calculated for the general case, which includes all particle numbers.Comment: 28 pages; typos are corrected, three figures are adde

3D thumbnails for 3D videos with depth

In this chapter, we present a new thumbnail format for 3D videos with depth, 3D thumbnail, which helps users to understand the content by preserving the recognizable features and qualities of 3D videos. The current thumbnail solutions do not give the general idea of the content and are not illustrative. In spite of the existence of 3D media content databases, there is no thumbnail representation for 3D contents. Thus, we propose a framework that generates 3D thumbnails from layered depth video (LDV) and video plus depth (V+D) by using two different methodologies on importance maps: Saliency-depth and layer based approaches. Finally, several experiments are presented that indicate 3D thumbnails are illustrative. © 2012, IGI Global

Composition Dependence of the In-Plane Cu-O Bond-stretching LO Phonon Mode in YBa₂Cu₃O₆₊ₓ

An inelastic pulsed neutron scattering study was performed on the dependence of the dispersion and spectral intensity of the in-plane Cu-O bond-stretching LO phonon mode on doped charge density. The measurements were made in the time-of-flight mode with the multiangle position sensitive spectrometer of the ISIS facility on single crystals of YBa2Cu3O6+x (x=0.15, 0.35, 0.6, 0.7, and 0.95). The focus of the study is the in-plane Cu-O bond-stretching LO phonon mode, which is known for strong electron-phonon coupling and unusual dependence on composition and temperature. It is shown that the dispersions for the samples with x=0.35, 0.6, and 0.7 are similar to the superposition of those for x=0.15 and 0.95 samples, and cannot be explained in terms of the structural anisotropy. It is suggested that the results are consistent with the model of nanoscale electronic phase separation, with the fraction of the phases being dependent on the doped charge density

Dengue fever and severe dengue in Barbados, 2008–2016

Analysis of the temporal, seasonal and demographic distribution of dengue virus (DENV) infections in Barbados was conducted using national surveillance data from a total of 3994 confirmed dengue cases. D