52 research outputs found
The global wave front set of tempered oscillatory integrals with inhomogeneous phase functions
We study certain families of oscillatory integrals ,
parametrised by phase functions and amplitude functions globally
defined on , which give rise to tempered distributions, avoiding
the standard homogeneity requirement on the phase function. The singularities
of are described both from the point of view of the lack of
smoothness as well as with respect to the decay at infinity. In particular, the
latter will depend on a version of the set of stationary points of ,
including elements lying at the boundary of the radial compactification of
. As applications, we consider some properties of the two-point
function of a free, massive, scalar relativistic field and of classes of global
Fourier integral operators on , with the latter defined in terms
of kernels of the form .Comment: 30 pages, 2 figures, mistakes and typos correctio
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Gaia Early Data Release 3: The celestial reference frame (Gaia-CRF3)
Context. Gaia-CRF3 is the celestial reference frame for positions and proper motions in the third release of data from the Gaia mission, Gaia DR3 (and for the early third release, Gaia EDR3, which contains identical astrometric results). The reference frame is defined by the positions and proper motions at epoch 2016.0 for a specific set of extragalactic sources in the (E)DR3 catalogue. Aims. We describe the construction of Gaia-CRF3 and its properties in terms of the distributions in magnitude, colour, and astrometric quality. Methods. Compact extragalactic sources in Gaia DR3 were identified by positional cross-matching with 17 external catalogues of quasi-stellar objects (QSO) and active galactic nuclei (AGN), followed by astrometric filtering designed to remove stellar contaminants. Selecting a clean sample was favoured over including a higher number of extragalactic sources. For the final sample, the random and systematic errors in the proper motions are analysed, as well as the radio-optical offsets in position for sources in the third realisation of the International Celestial Reference Frame (ICRF3). Results. Gaia-CRF3 comprises about 1.6 million QSO-like sources, of which 1.2 million have five-parameter astrometric solutions in Gaia DR3 and 0.4 million have six-parameter solutions. The sources span the magnitude range G = 13-21 with a peak density at 20.6 mag, at which the typical positional uncertainty is about 1 mas. The proper motions show systematic errors on the level of 12 ÎŒas yr-1 on angular scales greater than 15 deg. For the 3142 optical counterparts of ICRF3 sources in the S/X frequency bands, the median offset from the radio positions is about 0.5 mas, but it exceeds 4 mas in either coordinate for 127 sources. We outline the future of Gaia-CRF in the next Gaia data releases. Appendices give further details on the external catalogues used, how to extract information about the Gaia-CRF3 sources, potential (Galactic) confusion sources, and the estimation of the spin and orientation of an astrometric solution
A MODEST review
We present an account of the state of the art in the fields explored by the
research community invested in 'Modeling and Observing DEnse STellar systems'.
For this purpose, we take as a basis the activities of the MODEST-17
conference, which was held at Charles University, Prague, in September 2017.
Reviewed topics include recent advances in fundamental stellar dynamics,
numerical methods for the solution of the gravitational N-body problem,
formation and evolution of young and old star clusters and galactic nuclei,
their elusive stellar populations, planetary systems, and exotic compact
objects, with timely attention to black holes of different classes of mass and
their role as sources of gravitational waves.
Such a breadth of topics reflects the growing role played by collisional
stellar dynamics in numerous areas of modern astrophysics. Indeed, in the next
decade, many revolutionary instruments will enable the derivation of positions
and velocities of individual stars in the Milky Way and its satellites and will
detect signals from a range of astrophysical sources in different portions of
the electromagnetic and gravitational spectrum, with an unprecedented
sensitivity. On the one hand, this wealth of data will allow us to address a
number of long-standing open questions in star cluster studies; on the other
hand, many unexpected properties of these systems will come to light,
stimulating further progress of our understanding of their formation and
evolution.Comment: 42 pages; accepted for publication in 'Computational Astrophysics and
Cosmology'. We are much grateful to the organisers of the MODEST-17
conference (Charles University, Prague, September 2017). We acknowledge the
input provided by all MODEST-17 participants, and, more generally, by the
members of the MODEST communit
Highly-parallelized simulation of a pixelated LArTPC on a GPU
The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on 10^3 pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype
The DUNE far detector vertical drift technology. Technical design report
DUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals
Antimicrobial resistance genes aph(3âČ)-III, erm(B), sul2 and tet(W) abundance in animal faeces, meat, production environments and human faeces in Europe
Background: Real-Time quantitative PCR (qPCR) is an affordable method to quantify antimicrobial resistance gene (ARG) targets, allowing comparisons of ARG abundance along animal production chains. Objectives: We present a comparison of ARG abundance across various animal species, production environments and humans in Europe. AMR variation sources were quantified. The correlation of ARG abundance between qPCR data and previously published metagenomic data was assessed. Methods: A cross-sectional study was conducted in nine European countries, comprising 9572 samples. qPCR was used to quantify abundance of ARGs [aph(3âČ)-III, erm(B), sul2, tet(W)] and 16S rRNA. Variance component analysis was conducted to explore AMR variation sources. Spearman's rank correlation of ARG abundance values was evaluated between pooled qPCR data and earlier published pooled metagenomic data. Results: ARG abundance varied strongly among animal species, environments and humans. This variation was dominated by between-farm variation (pigs) or within-farm variation (broilers, veal calves and turkeys). A decrease in ARG abundance along pig and broiler production chains ('farm to fork') was observed. ARG abundance was higher in farmers than in slaughterhouse workers, and lowest in control subjects. ARG abundance showed a high correlation (Spearman's Ï>0.7) between qPCR data and metagenomic data of pooled samples. Conclusions: qPCR analysis is a valuable tool to assess ARG abundance in a large collection of livestock-Associated samples. The between-country and between-farm variation of ARG abundance could partially be explained by antimicrobial use and farm biosecurity levels. ARG abundance in human faeces was related to livestock antimicrobial resistance exposure
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