Reducing sample variance: halo biasing, non-linearity and stochasticity

Comparing clustering of differently biased tracers of the dark matter distribution offers the opportunity to reduce the cosmic variance error in the measurement of certain cosmological parameters. We develop a formalism that includes bias non-linearities and stochasticity. Our formalism is general enough that can be used to optimise survey design and tracers selection and optimally split (or combine) tracers to minimise the error on the cosmologically interesting quantities. Our approach generalises the one presented by McDonald & Seljak (2009) of circumventing sample variance in the measurement of $f\equiv d \ln D/d\ln a$. We analyse how the bias, the noise, the non-linearity and stochasticity affect the measurements of $Df$ and explore in which signal-to-noise regime it is significantly advantageous to split a galaxy sample in two differently-biased tracers. We use N-body simulations to find realistic values for the parameters describing the bias properties of dark matter haloes of different masses and their number density. We find that, even if dark matter haloes could be used as tracers and selected in an idealised way, for realistic haloes, the sample variance limit can be reduced only by up to a factor $\sigma_{2tr}/\sigma_{1tr}\simeq 0.6$. This would still correspond to the gain from a three times larger survey volume if the two tracers were not to be split. Before any practical application one should bear in mind that these findings apply to dark matter haloes as tracers, while realistic surveys would select galaxies: the galaxy-host halo relation is likely to introduce extra stochasticity, which may reduce the gain further.Comment: 21 pages, 13 figures. Published version in MNRA

Una comparación de algoritmos basados en trayectoria granular para el problema de localización y ruteo con flota heterogénea (LRPH)

Indexación: Scopus.We consider the Location-Routing Problem with Heterogeneous Fleet (LRPH) in which the goal is to determine the depots to be opened, the customers to be assigned to each open depot, and the corresponding routes fulfilling the demand of the customers and by considering a heterogeneous fleet. We propose a comparison of granular approaches of Simulated Annealing (GSA), of Variable Neighborhood Search (GVNS) and of a probabilistic Tabu Search (pGTS) for the LRPH. Thus, the proposed approaches consider a subset of the search space in which non-favorable movements are discarded regarding a granularity factor. The proposed algorithms are experimentally compared for the solution of the LRPH, by taking into account the CPU time and the quality of the solutions obtained on the instances adapted from the literature. The computational results show that algorithm GSA is able to obtain high quality solutions within short CPU times, improving the results obtained by the other proposed approaches.https://revistas.unal.edu.co/index.php/dyna/article/view/55533/5896

Singular Lagrangian Systems on Jet Bundles

The jet bundle description of time-dependent mechanics is revisited. The constraint algorithm for singular Lagrangians is discussed and an exhaustive description of the constraint functions is given. By means of auxiliary connections we give a basis of constraint functions in the Lagrangian and Hamiltonian sides. An additional description of constraints is also given considering at the same time compatibility, stability and second-order condition problems. Finally, a classification of the constraints in first and second class is obtained using a cosymplectic geometry setting. Using the second class constraints, a Dirac bracket is introduced, extending the well-known construction by Dirac.Comment: 65 pages. LaTeX fil

Geología del valle del río Piedra en Llumes (Zaragoza)

Se publica una zona reducida del mapa geológico perteneciente al curso medio del río Piedra en vías de estudio. El área cartografiada está compuesta por terrenos comprendidos entre el Keuper y el Cretácico superior, aparte de los mantos y tobas cuaternarios. Los niveles cenomanenses están bien datados por su fauna, atribuyéndose sus infrapuestos por litologías bastante inequívocas. Existe una laguna estratigráfica entre el Infralías y el Albense que afecta a un área extensa de la que se exceptúa el Jurásico de Cimballa (fuera ya de los predios considerados). Se presenta una relación de fósiles liásicos de dicha localidad

Condromatosis sinovial en localizaciones atípicas

La condromatosis sinovial es una metaplasia cartilaginosa del tejido sinovial de las articulaciones. Es una enfermedad de etiología desconocida y poco frecuente. Puede definirse como un proceso benigno sinovial caracterizado por la formación de nódulos cartilaginosos (cuerpos libres intraarticulares). Afecta principalmente a grandes articulaciones sinoviales, siendo la sintomatología predominante dolor e inflamación articular. El diagnóstico de presunción se basa en el estudio radiológico de la articulación. El tratamiento de elección es la extirpación completa de los cuerpos libres y de la sinovial afecta. Presentamos dos casos clínicos de CS situadas en localizaciones poco frecuentes: a nivel esternoclavicular y en la articulación temporomandibular, con la particularidad de esta última de presentar extensión a base de cráneo. Realizamos asimismo una revisión de los datos bibliográficos existentes sobre la CS.Synovial chondromatosis is a cartilaginous metaplasia of the synovial tissue of joints. It is an uncommon disease whose etiology is unknown. This benign synovial process involves the formation of cartilaginous nodules (loose bodies) in the synovium and within the articular space. Synovial chondromatosis mainly affects large synovial joints and the main symptoms are pain and swelling. Diagnosis can be made by panoramic radiograph, computed tomography scan and magnetic resonance imaging of the joint. The main treatment includes complete removal of the loose bodies in conjunction with excision of the affected synovium. We report two cases of synovial chondromatosis located in an uncommon regions: in the esternoclavicular joint and in the temporomandibular joint. We also make a literature review about synovial chondromatosis

Reconocimiento y evaluación para riegos de los suelos de la comarca de Andujar (Jaén) (Escala 1:50.000)

67 páginas.-- 14 perfiles de suelos.-- Memoria presenta en el V Curso Internacional de Edafología y Biología VegetalEste estudio resume las características morfológicas y analíticas de los suelos que constituyen el área del proyecto, principalmente para evaluar su actitud parar riegos. Se ha indicado también el método de trabajo seguido para llegar a dicha evaluación. Anteriormente se ha expresado que el proyecto tiene una aptitud mediana para regadío. Debe hacerse notar que dicha aptitud obedece sólo a las posibilidades del suelo natural o en estado actual para su utilización directa, sin considerar los efectos de mejora que puedan introducirse por medio de trabajos, cuyo fin es el de disminuir o eliminar alguno de los factores limitantes. Algunos de ellos, como la textura por ejemplo, no puede ser modificados en absoluto o son de difícil corrección. Otros como el drenaje, con la realización de ciertas obras, se vería reducidos al mínimo. Dejando aparte el factor climático, para el adecuado manejo y transformación de los suelos que integras el proyecto, sería de gran utilidad el mapa de suelos, de posiciones fisiográficas y clases para riegos que acompañar al estudio.Patrocinado por la UNESCO, OEA, Instituto de Cultura Hispánica, Consejo Superior de Investigaciones Científicas y Universidad de Sevilla y GranadaPeer reviewe

Attractors for The Stochastic 3D Navier-Stokes Equations

In a 1997 paper, Ball defined a generalised semiflow as a means to consider the solutions of equations without (or not known to possess) the property of uniqueness. In particular he used this to show that the 3D Navier–Stokes equations have a global attractor provided that all weak solutions are continuous from (0, ∞) into L2. In this paper we adapt his framework to treat stochastic equations: we introduce a notion of a stochastic generalised semiflow, and then show a similar result to Ball's concerning the attractor of the stochastic 3D Navier–Stokes equations with additive white noise