Evolution Operators for Linearly Polarized Two-Killing Cosmological Models

We give a general procedure to obtain non perturbative evolution operators in closed form for quantized linearly polarized two Killing vector reductions of general relativity with a cosmological interpretation. We study the representation of these operators in Fock spaces and discuss in detail the conditions leading to unitary evolutions.Comment: Accepted for publication in Physical Review

Groupoïdes riemanniens

We propose a definition of a riemannian groupoid, and we show that the Stefan foliation that it induces is a riemannian (singular) foliation. We also prove that the homotopy groupoid of a riemannian (regular) foliation is a riemannian groupoid

Layer-by-Layer Materials for the Fabrication of Devices with Electrochemical Applications

The construction of nanostructured materials for their application in electrochemical processes, e.g., energy storage and conversion, or sensing, has undergone a spectacular development over the last decades as a consequence of their unique properties in comparison to those of their bulk counterparts, e.g., large surface area and facilitated charge/mass transport pathways. This has driven strong research on the optimization of nanostructured materials for the fabrication of electrochemical devices, which demands techniques allowing the assembly of hybrid materials with well-controlled structures and properties. The Layer-by-Layer (LbL) method is well suited for fulfilling the requirements associated with the fabrication of devices for electrochemical applications, enabling the fabrication of nanomaterials with tunable properties that can be exploited as candidates for their application in fuel cells, batteries, electrochromic devices, solar cells, and sensors. This review provides an updated discussion of some of the most recent advances on the application of the LbL method for the fabrication of nanomaterials that can be exploited in the design of novel electrochemical devices.Depto. de Química FísicaFac. de Ciencias QuímicasTRUEUnión Europea. Horizonte 2020Ministerio de Ciencia e Innovación (MICINN)pu

Quantum unitary evolution of linearly polarized S^1\times S^2 and S^3 Gowdy models coupled to massless scalar fields

The purpose of this paper is to study in detail the problem of defining unitary evolution for linearly polarized S^1 x S^2 and S^3 Gowdy models (in vacuum or coupled to massless scalar fields). We show that in the Fock quantizations of these systems no choice of acceptable complex structure leads to a unitary evolution for the original variables. Nonetheless, unitarity can be recovered by suitable redefinitions of the basic fields. These are dictated by the time dependent conformal factors that appear in the description of the standard deparameterized form of these models as field theories in certain curved backgrounds. We also show the unitary equivalence of the Fock quantizations obtained from the SO(3)-symmetric complex structures for which the dynamics is unitarily implemented.Comment: Final version to appear in Classical and Quantum Gravit

Geomorfología y dinámica del Canal San Blas, provincia de Buenos Aires (Argentina)

Se estudió la geomorfología submarina y se efectuaron mediciones de corrientes de marea en el canal San Blas para determinar la dinámica sedimentaria actual. Se relevó un sector del fondo del canal con el sistema batimétrico GeoSwath para describir exhaustivamente la morfología de un campo de dunas. Su asimetría permite inferir un transporte residual del material del fondo hacia el interior de la Bahía Anegada sobre el veril NE del canal. Se realizó un estudio de la dinámica de las corrientes de marea, determinándose sus velocidades y direcciones durante un ciclo completo de marea en toda la columna de agua y a lo largo de un perfil transversal a la costa mediante un ADCP. A pesar que el ambiente corresponde a un régimen micromareal (rango de marea alrededor de 2 m), en el canal San Blas existen fuertes corrientes de marea que desde el sector medio transportan todo el material inconsolidado del fondo, formando un delta de reflujo en la boca externa del canal y un delta de flujo en la Bahía Anegada. Se reconocieron diferentes geoformas costeras que permiten inferir un transporte litoral hacia el exterior del canal sobre la costa sur del mismo. Basándose en sus características morfodinámicas, es posible definir el canal San Blas como una entrada de marea que conecta el mar abierto con la Bahía Anegada

Hamiltonian Dynamics of Linearly Polarized Gowdy Models Coupled to Massless Scalar Fields

The purpose of this paper is to analyze in detail the Hamiltonian formulation for the compact Gowdy models coupled to massless scalar fields as a necessary first step towards their quantization. We will pay special attention to the coupling of matter and those features that arise for the three-handle and three-sphere topologies that are not present in the well studied three torus case -in particular the polar constraints that come from the regularity conditions on the metric. As a byproduct of our analysis we will get an alternative understanding, within the Hamiltonian framework, of the appearance of initial and final singularities for these models.Comment: Final version to appear in Classical and Quantum Gravit

Perspectives of regional paleoclimate modeling

Regional climate modeling bridges the gap between the coarse resolution of current global climate models and the regional‐to‐local scales, where the impacts of climate change are of primary interest. Here, we present a review of the added value of the regional climate modeling approach within the scope of paleoclimate research and discuss the current major challenges and perspectives. Two time periods serve as an example: the Holocene, including the Last Millennium, and the Last Glacial Maximum. Reviewing the existing literature reveals the benefits of regional paleo climate modeling, particularly over areas with complex terrain. However, this depends largely on the variable of interest, as the added value of regional modeling arises from a more realistic representation of physical processes and climate feedbacks compared to global climate models, and this affects different climate variables in various ways. In particular, hydrological processes have been shown to be better represented in regional models, and they can deliver more realistic meteorological data to drive ice sheet and glacier modeling. Thus, regional climate models provide a clear benefit to answer fundamental paleoclimate research questions and may be key to advance a meaningful joint interpretation of climate model and proxy data

Procesos hidrosedimentológicos y meteorológicos relacionados con la sedimentación de un puerto

Se estudian los procesos que intervienen en la generación de una tasa de sedimentación muy alta en Puerto Rosales. Para ello se analiza la distribución de la concentración de sedimentos en suspensión en la columna de agua, velocidad y dirección de las corrientes, así como también las condiciones meteorológicas correspondientes a un ciclo de marea completo. Se identifica la importancia de los vientos del sector SE, los que al coincidir con la dirección de mayor fetch, generan olas que actúan sobre las planicies de marea aledañas al puerto, aumentando notablemente la concentración de sedimento en suspensión. Se concluye que la resuspensión del sedimento en suspensión, producto de la acción de las olas sobre las planicies, es la responsable de la alta tasa de sedimentación que históricamente ha presentado Puerto Rosales. Para disminuir la velocidad de sedimentación del puerto se propone evitar el ingreso de agua con concentraciones muy altas de sedimento en suspensión mediante la construcción de una barrera que atraviese la planicie de marea. Al mismo tiempo se propone proteger y una manera de propiciar el desarrollo de la Spartina alterniflora sobre la marisma con el objeto de disminuir la generación de sedimento en suspensión.Processes involved in the generation of an abnormally high siltation rate in Rosales harbor are studied. The vertical distribution of suspended sediment concentration related to tidal currents and meteorological conditions during a complete tidal cycle is analyzed. The importance of the southeastern winds is identified. Because the coincidence with the maximum available fetch, winds from this sector are responsible to generate waves that act over the tidal flats near the harbor and notably increase the suspended sediment concentration of the area. It is concluded that the excess in suspended sediment generated by this way is responsible for the high siltation rate that Rosales harbor has historically presented. In order to diminish the harbor siltation rate, the income of water with high suspended sediment concentrations can be arrested constructing a barrier across the entire intertidal area. To protect and propitiate the development of a Spartina alterniflora marsh to diminish the suspended sediment excessive generation it is also proposed.Asociación Argentina de Geofísicos y Geodesta

Procesos hidrosedimentológicos y meteorológicos relacionados con la sedimentación de un puerto

Se estudian los procesos que intervienen en la generación de una tasa de sedimentación muy alta en Puerto Rosales. Para ello se analiza la distribución de la concentración de sedimentos en suspensión en la columna de agua, velocidad y dirección de las corrientes, así como también las condiciones meteorológicas correspondientes a un ciclo de marea completo. Se identifica la importancia de los vientos del sector SE, los que al coincidir con la dirección de mayor fetch, generan olas que actúan sobre las planicies de marea aledañas al puerto, aumentando notablemente la concentración de sedimento en suspensión. Se concluye que la resuspensión del sedimento en suspensión, producto de la acción de las olas sobre las planicies, es la responsable de la alta tasa de sedimentación que históricamente ha presentado Puerto Rosales. Para disminuir la velocidad de sedimentación del puerto se propone evitar el ingreso de agua con concentraciones muy altas de sedimento en suspensión mediante la construcción de una barrera que atraviese la planicie de marea. Al mismo tiempo se propone proteger y una manera de propiciar el desarrollo de la Spartina alterniflora sobre la marisma con el objeto de disminuir la generación de sedimento en suspensión.Processes involved in the generation of an abnormally high siltation rate in Rosales harbor are studied. The vertical distribution of suspended sediment concentration related to tidal currents and meteorological conditions during a complete tidal cycle is analyzed. The importance of the southeastern winds is identified. Because the coincidence with the maximum available fetch, winds from this sector are responsible to generate waves that act over the tidal flats near the harbor and notably increase the suspended sediment concentration of the area. It is concluded that the excess in suspended sediment generated by this way is responsible for the high siltation rate that Rosales harbor has historically presented. In order to diminish the harbor siltation rate, the income of water with high suspended sediment concentrations can be arrested constructing a barrier across the entire intertidal area. To protect and propitiate the development of a Spartina alterniflora marsh to diminish the suspended sediment excessive generation it is also proposed.Asociación Argentina de Geofísicos y Geodesta