Hearing Delzant polytopes from the equivariant spectrum

Let M^{2n} be a symplectic toric manifold with a fixed T^n-action and with a toric K\"ahler metric g. Abreu asked whether the spectrum of the Laplace operator $\Delta_g$ on $\mathcal{C}^\infty(M)$ determines the moment polytope of M, and hence by Delzant's theorem determines M up to symplectomorphism. We report on some progress made on an equivariant version of this conjecture. If the moment polygon of M^4 is generic and does not have too many pairs of parallel sides, the so-called equivariant spectrum of M and the spectrum of its associated real manifold M_R determine its polygon, up to translation and a small number of choices. For M of arbitrary even dimension and with integer cohomology class, the equivariant spectrum of the Laplacian acting on sections of a naturally associated line bundle determines the moment polytope of M.Comment: 23 pages, 9 figures; v2 is published versio

Recovering S1S^1-invariant metrics on S2S^2 from the equivariant spectrum

We prove an inverse spectral result for $S^1$-invariant metrics on $S^2$ based on the so-called asymptotic equivariant spectrum. This is roughly the spectrum together with large weights of the $S^1$ action on the eigenspaces. Our result generalizes an inverse spectral result of the first and last named authors, together with Victor Guillemin, concerning $S^1$-invariant metrics on $S^2$ which are invariant under the antipodal map. We use higher order terms in the asymptotic expansion of a natural spectral measure associated with the Laplacian and the $S^1$ action.Comment: 16 pages; minor revisions throughout following comments from referee

Electric properties of granitic rocks

The objective of this work is to clarify the role of water content on the charge trans- port mechanisms of different granitic rocks. The mineralogical content of the rocks will also be taken into account. From the electrical point of view these materials are rather insulating porous media where charge injection creates different phenomena like build-up charges, space charge limited currents, surface effects and other behav- iors that resemble much a variety of oxides, like AlO

Massive vector fields on the Schwarzschild spacetime: quasinormal modes and bound states

We study the propagation of a massive vector or Proca field on the Schwarzschild spacetime. The field equations are reduced to a one-dimensional wave equation for the odd-parity part of the field and two coupled equations for the even-parity part of the field. We use numerical techniques based on solving (scalar or matrix-valued) three-term recurrence relations to compute the spectra of both quasi-normal modes and quasi-bound states, which have no massless analogue, complemented in the latter case by a forward-integration method. We study the radial equations analytically in both the near-horizon and far-field regions and use a matching procedure to compute the associated spectra in the small-mass limit. Finally, we comment on extending our results to the Kerr geometry and its phenomenological relevance for hidden photons arising e.g. in string theory compactifications.Comment: 15 pages, 8 figures; minor corrections, to be published in Phys. Rev.

Increasing U.S. Hard Red Winter Wheat Competitiveness in Latin American Markets

The United States wheat sector leadership in world markets is facing serious challenges. Canada, Australia, Argentina, the European Union (EU), and the Former Soviet Union (FSU) are growing contenders for international wheat markets. Wheat buyers´ concerns about quality specifications and its consistency have intensified without precedents in the last years. The study focuses on identifying the attributes that wheat buyers most value at the moment of purchase. The study will be done in two stages. The first stage will focus in estimating preferences from actual wheat transactions from different grain-sheds in the HRW growing area. The second stage will focus on the demand from Latin American millers and will estimate their attribute preference and elicit willingness to pay. The second stage will start with Mexican millers, given their importance for the HRW exports. A hedonic price model will be used for the first stage. The second part of the study will attempt to elicit miller´s preferences by using a self explicated approach. Expected results are that the "easy-to-measure attributes": test weight, and protein levels; and all functionality characteristics such as bake absorption, farinograph peak time, farinograph stability, alveograph p/l ratio will be the most valued by the wheat customers. We hypothesize that millers will be willing to pay a premium if those attributes are present in desirable levels. The information should provide insight into the efforts being made by wheat marketing agencies and the U.S. Wheat Associates to promote quality-based marketing of wheat to domestic and foreign millers. Discussion may also include the impacts of quality-based marketing on U.S. share of the world wheat market.International Relations/Trade,

Plan de clase de la unidad de óptica reflexión y refracción

Debido a los altos índices de estudiantes que reprueban la materia Física D, se ha decidido realizar un plan piloto para implementar un plan de estudio que incluya el cambio de metodología para el dictado de esta materia. La metodología a seguir está basada en el método de Gagne, ya que este pone énfasis en el aprendizaje para lograr el desarrollo individual y promueve el desarrollo de habilidades más complejas en el individuo. El método de Gagne se fundamenta en la teoría del procesamiento de la información, que se refiere a la secuencia de procesos y operaciones mentales que se realizan para llegar a un conocimiento organizado de grandes cantidades de información. Las variables que interfieren en la aplicación de este método son: 1. Los procesos de aprendizaje 2. Las fases del aprendizaje 3. Los resultados del aprendizaje 4. Las condiciones del aprendizaj

Willingness-to-Pay for Attribute Level and Variability: The Case of Mexican Millers’ Demand for Hard Red Winter Wheat

In-person interviews were carried out with Mexican millers who were administered a conjoint-type survey designed to incorporate uncertainty in attribute levels. Two methods were used to model millers’ risk preferences: a modified mean-variance approach and an explicit expected utility approach. Controlling for variability, Mexican millers are willing to pay premiums for increases in quality factors such as test weight, protein content, falling number, and dough strength/extensibility. We find millers are not particularly sensitive to changes in the variability of quality characteristics. Out-of-sample forecasts suggest the mean-variance model provides an accurate depiction of actual Mexican imports.mean-variance, Mexican wheat market, moment generating function, preference elicitation, wheat quality, Agribusiness, Farm Management, Food Consumption/Nutrition/Food Safety, International Relations/Trade, Marketing, Production Economics, Risk and Uncertainty, C35, C42, Q13,

CONSCIÊNCIA DE CLASSE E LUTA POR DIREITOS NAS REDES DE FAST FOOD

Esse artigo, fruto de um projeto de tese em desenvolvimento, tem como objetivo apresentar algumas questões que perpassam a discussão do trabalho em redes de fast food. A partir da compreensão de que os trabalhadores inseridos nesses espaços sofrem intensa exploração, são apontados elementos que contribuirão para o entendimento da forma como a ideologia opera em suas lutas por direitos. Apresentase, portanto, uma breve discussão sobre o trabalho nesses espaços, considerando o perfil etário predominante desses trabalhadores – jovens – e uma breve discussão acerca de ideologia e consciência de classe, que irá subsidiar as pesquisas a serem desenvolvidas

Crystal structure and physical properties of EuPtIn4_{4} intermetallic antiferromagnet

We report the synthesis of EuPtIn$_{4}$ single crystalline platelets by the In-flux technique. This compound crystallizes in the orthorhombic Cmcm structure with lattice parameters $a=4.542(1)$ \AA, $b=16.955(2)$ \AA$\,$ and $c=7.389(1)$ \AA. Measurements of magnetic susceptibility, heat capacity, electrical resistivity, and electron spin resonance (ESR) reveal that EuPtIn$_{4}$ is a metallic Curie-Weiss paramagnet at high temperatures and presents antiferromagnetic (AFM) ordering below $T_{N}=13.3$ K. In addition, we observe a successive anomaly at $T^{*} = 12.6$ K and a spin-flop transition at $H_{c} \sim 2.5$ T applied along the $ac$-plane. In the paramagnetic state, a single Eu$^{2+}$ Dysonian ESR line with a Korringa relaxation rate of $b = 4.1(2)$ Oe/K is observed. Interestingly, even at high temperatures, both ESR linewidth and electrical resistivity reveal a similar anisotropy. We discuss a possible common microscopic origin for the observed anisotropy in these physical quantities likely associated with an anisotropic magnetic interaction between Eu$^{2+}$ 4$f$ electrons mediated by conduction electrons.Comment: 5 pages, 5 figure

Unexpected effect of Ru-substitution in lightly doped manganites

In this Communication we report about the unexpected effect of ruthenium doping in sodium ligthly-doped manganites. This effect seems to be in contrast with the usual model applied to describe the effect of this magnetic ion into the manganite structure. We propose a possible compensation mechanism which seems also able to describe other peculiar features encountered in these materials.Comment: 3 pages, 2 Figures to appear in ChemCom