Asymptotic symmetries of three-dimensional higher-spin gravity: the metric approach

The asymptotic structure of three-dimensional higher-spin anti-de Sitter gravity is analyzed in the metric approach, in which the fields are described by completely symmetric tensors and the dynamics is determined by the standard Einstein-Fronsdal action improved by higher order terms that secure gauge invariance. Precise boundary conditions are given on the fields. The asymptotic symmetries are computed and shown to form a non-linear W-algebra, in complete agreement with what was found in the Chern-Simons formulation. The W-symmetry generators are two-dimensional traceless and divergenceless rank-s symmetric tensor densities of weight s (s = 2, 3, ...), while asymptotic symmetries emerge at infinity through the conformal Killing vector and conformal Killing tensor equations on the two-dimensional boundary, the solution space of which is infinite-dimensional. For definiteness, only the spin 3 and spin 4 cases are considered, but these illustrate the features of the general case: emergence of the W-extended conformal structure, importance of the improvement terms in the action that maintain gauge invariance, necessity of the higher spin gauge transformations of the metric, role of field redefinitions.Comment: 74 pages. References amended and typos corrected. Version to appear in JHE

Revised instability domains of SPB and beta Cephei stars

The excitation of pulsation modes in beta Cephei and Slowly Pulsating B stars is known to be very sensitive to opacity changes in the stellar interior where T~2 10^5 K. In this region differences in opacity up to ~50% can be induced by the choice between OPAL and OP opacity tables, and between two different metal mixtures (Grevesse and Noels 1993 and Asplund et al. 2005). We have extended the non-adiabatic computations presented in Miglio et al. (2007) towards models of higher mass and pulsation modes of degree l=3, and we present here the instability domains in the HR- and log(P)-log(Teff) diagrams resulting from different choices of opacity tables, and for three different metallicities.Comment: 9 pages, 4 figures. Accepted for publication in Communications in Asteroseismolog

CAN EQIP BE EFFECTIVE IN HELPING FARMERS MEET MANURE MANAGEMENT GOALS?

A manure application cost model was used to examine the impact financial assistance from EQIP can have on reducing costs to confined hog operations from meeting a manure nutrient application standard. Sector costs are examined under alternative scenarios involving type of nutrient standard and landowner willingness to accept manure.Livestock Production/Industries,

Uncertainty and global warming : an option - pricing approach to policy

Uncertainty is inherent in the analysis of global warming issues. Not only is there considerable scientific uncertainty about the magnitude of global warming, but even if that problem were resolved, there is uncertainty about what monetary value to assign to the costs and benefits of various policies to reduce global warming. And yet the influence of uncertainty in policymaker's decisions is ignored in most studies of the issue. The authors try to explicitly incorporate the effect of uncertainty in the choice of global warming abatement policies. The approach they develop draws on the emerging literature on investment under uncertainty - in particular, that on the option-valuation approach. Their numerical applications focus on the Cline's (1992) analysis of global warming, but it may be applied to a range of global warming analyses. First, they assess whether it is optimal to implement Cline's strategy of limiting global warming today, or whether it should be postponed, and for how long. Then, they identify the optimal policy to be implemented today for different levels of uncertainty about the costs and benefits of policies to reduce global warming.Economic Theory&Research,Montreal Protocol,Decentralization,Climate Change,Environmental Economics&Policies,Economic Theory&Research,Climate Change,Montreal Protocol,Carbon Policy and Trading,Environmental Economics&Policies

Hybrid Scene Compression for Visual Localization

Localizing an image wrt. a 3D scene model represents a core task for many computer vision applications. An increasing number of real-world applications of visual localization on mobile devices, e.g., Augmented Reality or autonomous robots such as drones or self-driving cars, demand localization approaches to minimize storage and bandwidth requirements. Compressing the 3D models used for localization thus becomes a practical necessity. In this work, we introduce a new hybrid compression algorithm that uses a given memory limit in a more effective way. Rather than treating all 3D points equally, it represents a small set of points with full appearance information and an additional, larger set of points with compressed information. This enables our approach to obtain a more complete scene representation without increasing the memory requirements, leading to a superior performance compared to previous compression schemes. As part of our contribution, we show how to handle ambiguous matches arising from point compression during RANSAC. Besides outperforming previous compression techniques in terms of pose accuracy under the same memory constraints, our compression scheme itself is also more efficient. Furthermore, the localization rates and accuracy obtained with our approach are comparable to state-of-the-art feature-based methods, while using a small fraction of the memory.Comment: Published at CVPR 201

The influence of turbulence during magnetized core collapse and its consequences on low-mass star formation

[Abridged] Theoretical and numerical studies of star formation have shown that magnetic field (B) has a strong influence on both disk formation and fragmentation; even a relatively low B can prevent these processes. However, very few studies investigated the combined effects of B and turbulence. We study the effects of turbulence in magnetized core collapse, focusing on the magnetic diffusion, the orientation of the angular momentum (J) of the protostellar core, and on its consequences on disk formation, fragmentation and outflows. We perform 3D, AMR, MHD simulations of magnetically supercritical collapsing dense cores of 5 Msun using the MHD code RAMSES. A turbulent velocity field is imposed as initial conditions, characterised by a Kolmogorov power spectrum. Different levels of turbulence and magnetization are investigated, as well as 3 realisations for the turbulent velocity field. Magnetic diffusion, orientation of the rotation axis with respect to B, transport of J, disk formation, fragmentation and outflows formation are studied. The turbulent velocity field imposed as initial conditions contains a non-zero J, responsible for a misalignment of the rotation axis. Turbulence is also responsible for an effective turbulent diffusivity in the vicinity of the core. Both effects are responsible for a significant decrease of the magnetic braking, and facilitate the formation of early massive disks for not too high magnetization. Fragmentation can occur even with mu ~ 5 at late time in contrast with 1 Msun cores for which fragmentation is prevented for such values of mu. Slow asymmetric outflows are launched. They carry a mass which is comparable to the mass within the core. Because of misalignment and turbulent diffusion, massive disk formation is possible though their mass and size are still reduced compared to the hydrodynamical case. We find that for mu >= 5, fragmentation can happen.Comment: 15 pages, 21 figures, submitted in A&

The structure of Inter-Urban traffic: A weighted network analysis

We study the structure of the network representing the interurban commuting traffic of the Sardinia region, Italy, which amounts to 375 municipalities and 1,600,000 inhabitants. We use a weighted network representation where vertices correspond to towns and the edges to the actual commuting flows among those. We characterize quantitatively both the topological and weighted properties of the resulting network. Interestingly, the statistical properties of commuting traffic exhibit complex features and non-trivial relations with the underlying topology. We characterize quantitatively the traffic backbone among large cities and we give evidences for a very high heterogeneity of the commuter flows around large cities. We also discuss the interplay between the topological and dynamical properties of the network as well as their relation with socio-demographic variables such as population and monthly income. This analysis may be useful at various stages in environmental planning and provides analytical tools for a wide spectrum of applications ranging from impact evaluation to decision-making and planning support.Comment: 12 pages, 12 figures, 4 tables; 1 missing ref added and minor revision