Perturbations in the Ekpyrotic Scenarios

With the new cosmological data gathered over the last few years, the inflationary paradigm has seen its predictions largely unchallenged. A recent proposal, called the ekpyrotic scenario, was argued to be a viable competitor as it was claimed that the spectrum of primordial perturbations it produces is scale invariant. By investigating closely this scenario, we show that the corresponding spectrum depends explicitly on an arbitrary function of wavenumber and is therefore itself arbitrary. It can at will be set scale invariant. We conclude that the scenario is not predictive at this stage.Comment: 4 pages, no figure, uses moriond.sty, to appear in the proceeding of the Moriond cosmology meeting held at Les Arcs, France (March 16-23, 2002

Convergence of a linearly transformed particle method for aggregation equations

We study a linearly transformed particle method for the aggregation equation with smooth or singular interaction forces. For the smooth interaction forces, we provide convergence estimates in $L^1$ and $L^\infty$ norms depending on the regularity of the initial data. Moreover, we give convergence estimates in bounded Lipschitz distance for measure valued solutions. For singular interaction forces, we establish the convergence of the error between the approximated and exact flows up to the existence time of the solutions in $L^1 \cap L^p$ norm

Water permits and concessions for irrigation in Argentina. Status quaestionis and trends in comparative perspective

The article analyzes permits and concession granting water rights for irrigation in the various provincial legal frameworks of Argentina. The study was structured in the light of four dimensions concerning the conditions for the access and subsistence of water rights for irrigation granted by permits and concessions; 1) ownership of the property to be irrigated; 2) the term; 3) rights forfeiture for the lack of use; and 4) the water right attachment to the property. From a comparative analysis of the regulation some trends and findings arise. Highlights Most of the provinces provide for granting the water right to person other than the landowner, showing a trend towards flexibility in this variable. Establishing reasonable terms to water rights is valued as very positive or positive, while excessive terms –long or short- are considered negative very negative. Short term forfeiture for lack of use entails a strong promotion of production, something that prevent from keeping idle flows of water and speculation. Appurtenance is considered a positive element, but it is more positive when developed together with mechanisms that allow flexibility so as to allow authorities to assess due rights reallocation.The article analyzes permits and concession granting water rights for irrigation in the various provincial legal frameworks of Argentina. The study was structured in the light of four dimensions concerning the conditions for the access and subsistence of water rights for irrigation granted by permits and concessions; 1) ownership of the property to be irrigated; 2) the term; 3) rights forfeiture for the lack of use; and 4) the water right attachment to the property. From a comparative analysis of the regulation some trends and findings arise. Highlights Most of the provinces provide for granting the water right to person other than the landowner, showing a trend towards flexibility in this variable. Establishing reasonable terms to water rights is valued as very positive or positive, while excessive terms –long or short- are considered negative very negative. Short term forfeiture for lack of use entails a strong promotion of production, something that prevent from keeping idle flows of water and speculation. Appurtenance is considered a positive element, but it is more positive when developed together with mechanisms that allow flexibility so as to allow authorities to assess due rights reallocation

Glacial environment protection

Se presenta una revisión sintética del desarrollo de la regulación argentina en materia de preservación de glaciares y medio ambiente periglacial, incluyendo i) el marco jurídico general de protección de las aguas en Argentina; ii) los antecedentes de la Ley N° 26.639 de 2010 sobre protección de glaciares y medio ambiente periglacial; iii) la conflictividad generada entre la protección glacial y la minería, y vi) las principales cuestiones controvertidas de la aplicación de la Ley N° 26.639 de 2010.A synthetic review of the development of Argentina’s regulation concerning the preservation of glaciers and periglacial environment is presented, including: i) the general legal framework for water protection in Argentina; ii) the history of Law Nº 26.639 of 2010, on the protection of glaciers and periglacial environment; iii) the confl ict generated between glacial protection and mining protection; and iv) the main controversial issues of the implementation of Law No 26,639 of 2010.Fil: Martin, Liber Alexis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo; ArgentinaFil: Pinto, Martín. Universidad Nacional de Cuyo; Argentina. Universidad de Mendoza; Argentina. Universidad del Aconcagua; Argentin

Uniform convergence of a linearly transformed particle method for the Vlasov-Poisson system

International audienceA particle method with linear transformation of the particle shape functions is studied for the 1d-1v Vlasov-Poisson equation, and a priori error estimates are proven which show that the approximated densities converge in the uniform norm. When compared to standard fixed-shape particle methods, the present approach can be seen as a way to gain one order in the convergence rate of the particle trajectories at the cost of linearly transforming each particle shape. It also allows to compute strongly convergent densities with particles that overlap in a bounded way

Tracking defect-induced ferromagnetism in GaN:Gd

We report on the magnetic properties of GaN:Gd layers grown by molecular beam epitaxy (MBE). A poor reproducibility with respect to the magnetic properties is found in these samples. Our results show strong indications that defects with a concentration of the order of 10^19 cm^-3 might play an important role for the magnetic properties. Positron annihilation spectroscopy does not support the suggested connection between the ferromagnetism and the Ga vacancy in GaN:Gd. Oxygen co-doping of GaN:Gd promotes ferromagnetism at room temperature and points to a role of oxygen for mediating ferromagnetic interactions in Gd doped GaN

Bounded commuting projections for multipatch spaces with non-matching interfaces

We present commuting projection operators on de Rham sequences of two-dimensional multipatch spaces with local tensor-product parametrization and non-matching interfaces. Our construction yields projection operators which are local and stable in any $L^p$ norm with $p \in [1,\infty]$: it applies to shape-regular spline patches with different mappings and local refinements, under the assumption that neighboring patches have nested resolutions and that interior vertices are shared by exactly four patches. It also applies to de Rham sequences with homogeneous boundary conditions. Following a broken-FEEC approach, we first consider tensor-product commuting projections on the single-patch de Rham sequences, and modify the resulting patch-wise operators so as to enforce their conformity and commutation with the global derivatives, while preserving their projection and stability properties with constants independent of both the diameter and inner resolution of the patches

First Chemical Analysis of Stars in The Triangulum-Andromeda Star Cloud

We undertake the first high resolution spectroscopic study of the Triangulum-Andromeda (TriAnd) star cloud --- an extended, mid-latitude Milky Way halo substructure about 20 kpc away in the second Galactic quadrant --- through six M giant star candidates selected to be both spatially and dynamically associated with this system. The abundance patterns of [Ti/Fe], [Y/Fe] and [La/Fe] as a function of [Fe/H] for these stars support TriAnd as having an origin in a dwarf galaxy with a chemical enrichment history somewhat similar to that of the Sagittarius dwarf spheroidal (dSph) galaxy. We also investigate the previously proposed hypothesis that TriAnd is an outlying, dynamically older piece of the Monoceros Stream (also known as the Galactic Anticenter Stellar Structure, "GASS") under the assumption that both features come from the tidal disruption of the same accreted Milky Way satellite and find that net differences in the above abundance patterns between the TriAnd and GASS stars studied suggest that these two systems are independent and unrelated.Comment: Accepted for publication in ApJ Letter

Digital acoustics: processing wave fields in space and time using DSP tools

Systems with hundreds of microphones for acoustic field acquisition, or hundreds of loudspeakers for rendering, have been proposed and built. To analyze, design, and apply such systems requires a framework that allows us to leverage the vast set of tools available in digital signal processing in order to achieve intuitive and efficient algorithms. We thus propose a discrete space-time framework, grounded in classical acoustics, which addresses the discrete nature of the spatial and temporal sampling. In particular, a short-space/time Fourier transform is introduced, which is the natural extension of the localized or short-time Fourier transform. Processing in this intuitive domain allows us to easily devise algorithms for beam-forming, source separation, and multi-channel compression, among other useful tasks. The essential space band-limitedness of the Fourier spectrum is also used to solve the spatial equalization task required for sound field rendering in a region of interest. Examples of applications are show