1,990 research outputs found

    Where Do the Buffalo Roam? Determining the Scope of American Indian Off-Reservation Hunting Rights in the Pacific Northwest

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    Courts have failed to develop a uniform test to determine the extent of Indian off-reservation hunting rights in the Pacific Northwest. Though the language guaranteeing these rights is consistent from treaty to treaty, analysis of this language varies widely from court to court. The United States Supreme Court employs three well-founded canons of construction in its interpretations of Indian treaties. These same principles should be applied by lower courts to determine the extent of off-reservation hunting rights. Consistent use of accepted canons of treaty construction would add much certainty to an area of law plagued by uncertainty and controversy

    The Variational Homoencoder: Learning to learn high capacity generative models from few examples

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    Hierarchical Bayesian methods can unify many related tasks (e.g. k-shot classification, conditional and unconditional generation) as inference within a single generative model. However, when this generative model is expressed as a powerful neural network such as a PixelCNN, we show that existing learning techniques typically fail to effectively use latent variables. To address this, we develop a modification of the Variational Autoencoder in which encoded observations are decoded to new elements from the same class. This technique, which we call a Variational Homoencoder (VHE), produces a hierarchical latent variable model which better utilises latent variables. We use the VHE framework to learn a hierarchical PixelCNN on the Omniglot dataset, which outperforms all existing models on test set likelihood and achieves strong performance on one-shot generation and classification tasks. We additionally validate the VHE on natural images from the YouTube Faces database. Finally, we develop extensions of the model that apply to richer dataset structures such as factorial and hierarchical categories.Comment: UAI 2018 oral presentatio

    Helicity, polarization, and Riemann-Silberstein vortices

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    Riemann-Silberstein (RS) vortices have been defined as surfaces in spacetime where the complex form of a free electromagnetic field given by F=E+iB is null (F.F=0), and they can indeed be interpreted as the collective history swept out by moving vortex lines of the field. Formally, the nullity condition is similar to the definition of "C-lines" associated with a monochromatic electric or magnetic field, which are curves in space where the polarization ellipses degenerate to circles. However, it was noted that RS vortices of monochromatic fields generally oscillate at optical frequencies and are therefore unobservable while electric and magnetic C-lines are steady. Here I show that under the additional assumption of having definite helicity, RS vortices are not only steady but they coincide with both sets of C-lines, electric and magnetic. The two concepts therefore become one for waves of definite frequency and helicity. Since the definition of RS vortices is relativistically invariant while that of C-lines is not, it may be useful to regard the vortices as a wideband generalization of C-lines for waves of definite helicity.Comment: 5 pages, no figures. Submitted to J of Optics A, special issue on Singular Optics; minor changes from v.

    Financial sector performance and economic growth in Nigeria

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    Towards the end of 2010, banking halls in Nigeria were crowded with people. Following the Central Bank of Nigeria’s advice, banks were updating records of their clients. The essence was for the banks to be better informed about their clients and their sources of funds with a view to eliminating or limiting the problem of money laundering in Nigeria. This is only one of several policies or reforms that the financial sector in Nigeria has gone through in recent times. The numbers of banks were pruned down through the recapitalization programme, non-performing microfinance banks were weeded out, and five bank chiefs were accused of mismanagement and replaced. The Nigerian Stock Exchange also experienced difficulties leading to the exit of its Chief Executive Officer. Practically, every aspect of the Nigerian financial system has in recent times experienced one form of reform or challenge but these are the sources of capital formation for the real sector in Nigeria. In view of these how well has the sector performed its role as a driver of economic growth? This work using data obtained from the Central Bank spanning 24 years was able to establish that there is a positive relationship between the performance of the sector and economic growth in Nigeria

    Quantum effects in the evolution of vortices in the electromagnetic field

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    We analyze the influence of electron-positron pairs creation on the motion of vortex lines in electromagnetic field. In our approach the electric and magnetic fields satisfy nonlinear equations derived from the Euler-Heisenberg effective Lagrangian. We show that these nonlinearities may change the evolution of vortices.Comment: REVTEX4 and 5 EPS figure

    Vortex lines of the electromagnetic field

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    Relativistic definition of the phase of the electromagnetic field, involving two Lorentz invariants, based on the Riemann-Silberstein vector is adopted to extend our previous study [I. Bialynicki-Birula, Z. Bialynicka-Birula and C. Sliwa, Phys. Rev. A 61, 032110 (2000)] of the motion of vortex lines embedded in the solutions of wave equations from Schroedinger wave mechanics to Maxwell theory. It is shown that time evolution of vortex lines has universal features; in Maxwell theory it is very similar to that in Schroedinger wave mechanics. Connection with some early work on geometrodynamics is established. Simple examples of solutions of Maxwell equations with embedded vortex lines are given. Vortex lines in Laguerre-Gaussian beams are treated in some detail.Comment: 11 pages, 6 figures, to be published in Phys. Rev.

    Towards a systematic design of isotropic bulk magnetic metamaterials using the cubic point groups of symmetry

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    In this paper a systematic approach to the design of bulk isotropic magnetic metamaterials is presented. The role of the symmetries of both the constitutive element and the lattice are analyzed. For this purpose it is assumed that the metamaterial is composed by cubic SRR resonators, arranged in a cubic lattice. The minimum symmetries needed to ensure an isotropic behavior are analyzed, and some particular configurations are proposed. Besides, an equivalent circuit model is proposed for the considered cubic SRR resonators. Experiments are carried out in order to validate the proposed theory. We hope that this analysis will pave the way to the design of bulk metamaterials with strong isotropic magnetic response, including negative permeability and left-handed metamaterials.Comment: Submitted to Physical Review B, 23 page

    Electronic band structure, Fermi surface, and elastic properties of new 4.2K superconductor SrPtAs from first-principles calculations

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    The hexagonal phase SrPtAs (s.g. P6/mmm; #194) with a honeycomb lattice structure very recently was declared as a new low-temperature (TC ~ 4.2K) superconductor. Here by means of first-principles calculations the optimized structural parameters, electronic bands, Fermi surface, total and partial densities of states, inter-atomic bonding picture, independent elastic constants, bulk and shear moduli for SrPtAs were obtained for the first time and analyzed in comparison with the related layered superconductor SrPt2As2.Comment: 8 pages, 4 figure

    1863-03-24 Mr. Nye recommends George Blake for promotion

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