Variability and nature of the binary in the Red Rectangle Nebula

We present new observations of the central binary inside the Red Rectangle nebula. The detection of zinc in the optical spectrum confirms that the peculiar photospheric abundances are due to accretion of circumstellar gas. Grey brightness variations with the orbital period are observed. They are interpreted as being due to the variation of the scattering angle with orbital phase. The small orbital separation of the system is not compatible with previous normal evolution of the primary on the AGB. We point out the similarity of the orbital history of this and other similar systems with those of some close Barium stars and suggest that the nonzero eccentricity of the orbit is the result of tidal interaction with the circumbinary disk.Comment: 4 pages, 3 figures, A&A Letters accepte

Infrared High-Resolution Spectroscopy of Post-AGB Circumstellar Disks. I. HR 4049 - The Winnowing Flow Observed?

High-resolution infrared spectroscopy in the 2.3-4.6 micron region is reported for the peculiar A supergiant, single-lined spectroscopic binary HR 4049. Lines from the CO fundamental and first overtone, OH fundamental, and several H2O vibration-rotation transitions have been observed in the near-infrared spectrum. The spectrum of HR 4049 appears principally in emission through the 3 and 4.6 micron region and in absorption in the 2 micron region. The 4.6 micron spectrum shows a rich 'forest' of emission lines. All the spectral lines observed in the 2.3-4.6 micron spectrum are shown to be circumbinary in origin. The presence of OH and H2O lines confirm the oxygen-rich nature of the circumbinary gas which is in contrast to the previously detected carbon-rich material. The emission and absorption line profiles show that the circumbinary gas is located in a thin, rotating layer near the dust disk. The properties of the dust and gas circumbinary disk and the spectroscopic orbit yield masses for the individual stars, M_AI~0.58 Msolar and M_MV~0.34 Msolar. Gas in the disk also has an outward flow with a velocity of $\gtrsim$ 1 km/s. The severe depletion of refractory elements but near-solar abundances of volatile elements observed in HR 4049 results from abundance winnowing. The separation of the volatiles from the grains in the disk and the subsequent accretion by the star are discussed. Contrary to prior reports, the HR 4049 carbon and oxygen isotopic abundances are typical AGB values: 12C/13C=6^{+9}_{-4} and 16O/17O>200.Comment: 42 pages, 14 figures, Accepted by Ap

Hamilton-Jacobi formalism for Linearized Gravity

In this work we study the theory of linearized gravity via the Hamilton-Jacobi formalism. We make a brief review of this theory and its Lagrangian description, as well as a review of the Hamilton-Jacobi approach for singular systems. Then we apply this formalism to analyze the constraint structure of the linearized gravity in instant and front-form dynamics.Comment: To be published in Classical and Quantum Gravit

Equivalence of renormalized covariant and light-front perturbation theory: I. Longitudinal divergences in the Yukawa model

Light-front perturbation theory has been proposed as an alternative to covariant perturbation theory. Light-front perturbation theory is only acceptable if it produces invariant S-matrix elements. Doubts have been raised concerning the equivalence of light-front and covariant perturbation theory. One of the obstacles to a rigorous proof of equivalence is the occurrence of longitudinal divergences not present in covariant perturbation theory. We show in the case of the Yukawa model of fermions interacting with scalar bosons at the one-loop level how to deal with the longitudinal divergences. Invariant S-matrix elements are obtained using our method.Comment: 11 pages, epsf, revtex, contains more elaborate explanation of Forced Instantaneous Loops (FILs

The canonical structure of Podolsky's generalized electrodynamics on the Null-Plane

In this work we will develop the canonical structure of Podolsky's generalized electrodynamics on the null-plane. This theory has second-order derivatives in the Lagrangian function and requires a closer study for the definition of the momenta and canonical Hamiltonian of the system. On the null-plane the field equations also demand a different analysis of the initial-boundary value problem and proper conditions must be chosen on the null-planes. We will show that the constraint structure, based on Dirac formalism, presents a set of second-class constraints, which are exclusive of the analysis on the null-plane, and an expected set of first-class constraints that are generators of a U(1) group of gauge transformations. An inspection on the field equations will lead us to the generalized radiation gauge on the null-plane, and Dirac Brackets will be introduced considering the problem of uniqueness of these brackets under the chosen initial-boundary condition of the theory

Interplay of Peltier and Seebeck effects in nanoscale nonlocal spin valves

We have experimentally studied the role of thermoelectric effects in nanoscale nonlocal spin valve devices. A finite element thermoelectric model is developed to calculate the generated Seebeck voltages due to Peltier and Joule heating in the devices. By measuring the first, second and third harmonic voltage response non locally, the model is experimentally examined. The results indicate that the combination of Peltier and Seebeck effects contributes significantly to the nonlocal baseline resistance. Moreover, we found that the second and third harmonic response signals can be attributed to Joule heating and temperature dependencies of both Seebeck coefficient and resistivity.Comment: 4 pages, 4 figure

Electromagnetic properties of ground and excited state pseudoscalar mesons

The axial-vector Ward-Takahashi identity places constraints on particular properties of every pseudoscalar meson. For example, in the chiral limit all pseudoscalar mesons, except the Goldstone mode, decouple from the axial-vector current. Nevertheless, all neutral pseudoscalar mesons couple to two photons. The strength of the \pi_n^0 \gamma \gamma coupling, where n=0 denotes the Goldstone mode, is affected by the Abelian anomaly's continuum contribution. The effect is material for n \neq 0. The \gamma* \pi_n \gamma* transition form factor, T_{\pi_n}(Q^2), is nonzero for all n, and T_{\pi_n}(Q^2) \approx (4\pi^2/3) (f_{\pi_n}/Q^2) at large Q^2. For all pseudoscalars but the Goldstone mode, this leading contribution vanishes in the chiral limit. In this instance the ultraviolet power-law behaviour is 1/Q^4 for n \neq 0, and we find numerically T_{\pi_1}(Q^2) \simeq (4\pi^2/3) (-/Q^4). This subleading power-law behaviour is always present. In general its coefficient is not simply related to f_{\pi_n}. The properties of n \neq 0 pseudoscalar mesons are sensitive to the pointwise behaviour of the long-range piece of the interaction between light-quarks.Comment: 13 pages, 5 figure

Product design and business model strategies for a circular economy

© 2016 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. The transition within business from a linear to a circular economy brings with it a range of practical challenges for companies. The following question is addressed: What are the product design and business model strategies for companies that want to move to a circular economy model? This paper develops a framework of strategies to guide designers and business strategists in the move from a linear to a circular economy. Building on Stahel, the terminology of slowing, closing, and narrowing resource loops is introduced. A list of product design strategies, business model strategies, and examples for key decision-makers in businesses is introduced, to facilitate the move to a circular economy. This framework also opens up a future research agenda for the circular economy.Part of this work was supported by ResCoM, which is co-funded by the European Union under EU Seventh Framework Programme (FP7), Grant agreement number: 603843. We would like to thank the ResCoM team for their support and encouraging discussions on the topic of the circular economy