Large scale environmental bias of the QSO line of sight proximity effect

We analyse the proximity zone of the intergalactic matter around high-redshift quasars in a cosmological environment. In a box of 64 h-1 Mpc base length we employ dark matter only simulations. For estimating the hydrogen temperature and density distribution we use the effective equation of state. Hydrogen is assumed to be in photoionisation equilibrium with a model background flux which is fit to recent observations of the mean optical depth and transmission flux statistics. At redshifts z = 3, 4, and 4.8, we select model quasar positions at the centre of the 20 most massive halos and 100 less massive halos identified in the simulation. From each assumed quasar position we cast 100 random lines of sight for two box length including the changes in the ionisation fractions by the QSO flux field and derive mock Ly{\alpha} spectra. The proximity effect describes the dependence of the mean normalised optical depth {\xi} = {\tau}eff, QSO/{\tau}eff, Ly{\alpha} as a function of the ratio of the ionisation rate by the QSO and the background field, {\omega} = {\Gamma}QSO/{\Gamma}UVB, i.e. the profile {\xi} = (1 + {\omega}/a)-0.5, where a strength parameter a is introduced. The strength parameter measures the deviation from the theoretical background model and is used to quantify any influence of the environmental density field. We reproduce an unbiased measurement of the proximity effect which is not affected by the host halo mass. The scatter between different lines of sight and different quasar host positions increases with decreasing redshift. Around the host halos, we find only a slight average overdensity in the proximity zone at comoving radii of 1 < rc < 10h-1 Mpc. However, a clear power-law correlation of the strength parameter with the average overdensity in rc is found, showing an overestimation of the ionising background in overdense regions and an underestimation in underdense regions.Comment: Accepted by Monthly Notices of the Royal Astronomical Society. 15 pages, 12 figure

Mario Telò, Globalisation, Multilateralism, Europe: Towards a Better Global Governance? (Globalisation, Europe, Multilateralism)

Book Revie

Mario Telò, Globalisation, Multilateralism, Europe: Towards a Better Global Governance? (Globalisation, Europe, Multilateralism)

Book Revie

Thermodynamic formalism for jump processes and diffusions

Neste trabalho, generalizamos alguns conceitos de formalismo termodinâmico já conhecidos em casos mais simples, para dois tipos de processos de Markov a tempo contínuo: processos de salto e difusões, ambos com espaço de estados compacto. Para embasar esses estudos, foi necessário reorganizar e desenvolver alguns pontos da teoria de processos de Markov, o que fizemos no primeiro capítulo desta tese, com foco nos processos de salto. Para estes dois tipos de processos de Markov, utilizando um potencial V fixado, definimos o operador de Ruelle e o normalizamos, de modo a obter o processo de Gibbs e a respectiva probabilidade de Gibbs associada. Finalmente, fomos capazes de mostrar que o processo de Gibbs é o estado de equilíbrio que maximiza um problema variacional para a pressão.In this work, we generalize some concepts of thermodynamic formalism already known for simpler cases, for two types of continuous-time Markov processes: jump processes and diffusions, both with compact state space. To support these studies, it was necessary to reorganize and develop some points of the Markov process theory, which we made in the first chapter of this thesis, focusing on jump processes. For this two types of Markov processes, using a fixed potential V , we define the Ruelle operator and normalize it, getting the Gibbs process and its respective Gibbs probability associated. Finally, we were able to show that the Gibbs process is the equilibrium state that maximizes a variational problem for the pressure

Rumble: Data Independence for Large Messy Data Sets

This paper introduces Rumble, an engine that executes JSONiq queries on large, heterogeneous and nested collections of JSON objects, leveraging the parallel capabilities of Spark so as to provide a high degree of data independence. The design is based on two key insights: (i) how to map JSONiq expressions to Spark transformations on RDDs and (ii) how to map JSONiq FLWOR clauses to Spark SQL on DataFrames. We have developed a working implementation of these mappings showing that JSONiq can efficiently run on Spark to query billions of objects into, at least, the TB range. The JSONiq code is concise in comparison to Spark's host languages while seamlessly supporting the nested, heterogeneous data sets that Spark SQL does not. The ability to process this kind of input, commonly found, is paramount for data cleaning and curation. The experimental analysis indicates that there is no excessive performance loss, occasionally even a gain, over Spark SQL for structured data, and a performance gain over PySpark. This demonstrates that a language such as JSONiq is a simple and viable approach to large-scale querying of denormalized, heterogeneous, arborescent data sets, in the same way as SQL can be leveraged for structured data sets. The results also illustrate that Codd's concept of data independence makes as much sense for heterogeneous, nested data sets as it does on highly structured tables.Comment: Preprint, 9 page

Radiation from the impact of broad-line region clouds onto AGN accretion disks

Context. Active galactic nuclei are supermassive black holes surrounded by an accretion disk, two populations of clouds, bipolar jets, and a dusty torus. The clouds move in Keplerian orbits at high velocities. In particular, the broad-line region (BLR) clouds have velocities ranging from 1000 to 10 000 km s-1. Given the extreme proximity of these clouds to the supermassive black hole, frequent collisions with the accretion disk should occur. Aims. The impact of BLR clouds onto the accretion disk can produce strong shock waves where particles might be accelerated. The goal of this work is to investigate the production of relativistic particles, and the associated non-thermal radiation in these events. In particular, we apply the model we develop to the Seyfert galaxy NGC 1068. Methods. We analyze the efficiency of diffusive shock acceleration in the shock of colliding clouds of the BLR with the accretion disk. We calculate the spectral energy distribution of photons generated by the relativistic particles and estimate the number of simultaneous impacts needed to explain the gamma radiation observed by Fermi in Seyfert galaxies. Results. We find that is possible to understand the measured gamma emission in terms of the interaction of clouds with the disk if the hard X-ray emission of the source is at least obscured between 20% and 40%. The total number of clouds contained in the BLR region might be between 3 × 108 and 6 × 108, which are values in good agreement with the observational evidence. The maximum energy achieved by the protons (∼PeV) in this context allows the production of neutrinos in the observing range of IceCube.Fil: Müller, Ana Laura. Universidad Nacional de San Martín; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; Argentina. Karlsruhe Institute Of Technology; AlemaniaFil: Romero, Gustavo Esteban. Universidad Nacional de La Plata; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; Argentin

Gamma-Rays From Large-Scale Outflows In Starburst Galaxies

The combined effects of supernova explosions and stellar winds produce a hot bubble in thecentral regions of starburst galaxies. As the bubble expands, it can outbreak into the galactichalo driving a superwind that transports hot gas and fields to the intergalactic space. We presentestimates of cosmic ray generation and gamma-ray emission in both this large-scale wind and thebow shocks created around the embedded clouds.Fil: Romero, Gustavo Esteban. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Müller, Ana Laura. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaHigh Energy Phenomena in Relativistic Outflows VII (HEPRO VII)BarcelonaEspañaUniversitat de Barcelona. Facultat de Físic

Reproducible Floating-Point Aggregation in RDBMSs

Industry-grade database systems are expected to produce the same result if the same query is repeatedly run on the same input. However, the numerous sources of non-determinism in modern systems make reproducible results difficult to achieve. This is particularly true if floating-point numbers are involved, where the order of the operations affects the final result. As part of a larger effort to extend database engines with data representations more suitable for machine learning and scientific applications, in this paper we explore the problem of making relational GroupBy over floating-point formats bit-reproducible, i.e., ensuring any execution of the operator produces the same result up to every single bit. To that aim, we first propose a numeric data type that can be used as drop-in replacement for other number formats and is---unlike standard floating-point formats---associative. We use this data type to make state-of-the-art GroupBy operators reproducible, but this approach incurs a slowdown between 4x and 12x compared to the same operator using conventional database number formats. We thus explore how to modify existing GroupBy algorithms to make them bit-reproducible and efficient. By using vectorized summation on batches and carefully balancing batch size, cache footprint, and preprocessing costs, we are able to reduce the slowdown due to reproducibility to a factor between 1.9x and 2.4x of aggregation in isolation and to a mere 2.7% of end-to-end query performance even on aggregation-intensive queries in MonetDB. We thereby provide a solid basis for supporting more reproducible operations directly in relational engines. This document is an extended version of an article currently in print for the proceedings of ICDE'18 with the same title and by the same authors. The main additions are more implementation details and experiments.Comment: This document is the extended version of an article in the Proceedings of the 34th IEEE International Conference on Data Engineering (ICDE) 201

High-energy processes in starburst-driven winds

Starburst galaxies generate large-scale winds powered by the activity in the starforming regions located in the galactic disks. Fragmentation of the disk produced bythe outbreak of the wind results in the formation of clouds. Bowshocks caused by thesupersonic outflow appear around such clouds. In this paper we discuss the accelerationof relativistic particles and the production of non-thermal radiation in such scenario.Cosmic rays accelerated at the bowshocks do not reach the highest energies, althoughthe high-energy luminosity generated is significant. We show that up to ∼ 10% of thegamma-ray emission in starbursts might come from these sources outside the galacticdisks. Discrete X-ray sources with a power-law component are also expected.Fil: Müller, Ana Laura. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; Argentina. Karlsruher Institut fur Technologie; AlemaniaFil: Romero, Gustavo Esteban. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Roth, Markus. Karlsruher Institut fur Technologie; Alemani