Line-of-sight velocity distributions of elliptical galaxies from collisionless mergers

We analyse the skewness of the line-of-sight velocity distributions in model elliptical galaxies built through collisionless galaxy mergers. We build the models using large N-body simulations of mergers between either two spiral or two elliptical galaxies. Our aim is to investigate whether the observed ranges of skewness coefficient (h3) and the rotational support (V/sigma), as well as the anticorrelation between h3 and V, may be reproduced through collisionless mergers. Previous attempts using N-body simulations failed to reach V/sigma ~ 1-2 and corresponding high h3 values, which suggested that gas dynamics and ensuing star formation might be needed in order to explain the skewness properties of ellipticals through mergers. Here we show that high V/sigma and high h3 are reproduced in collisionless spiral-spiral mergers whenever a central bulge allows the discs to retain some of their original angular momentum during the merger. We also show that elliptical-elliptical mergers, unless merging from a high-angular momentum orbit, reproduce the strong skewness observed in non-rotating, giant, boxy ellipticals. The behaviour of the h3 coefficient therefore associates rapidly-rotating disky ellipticals to disc-disc mergers, and associates boxy, slowly-rotating giant ellipticals to elliptical-elliptical mergers, a framework generally consistent with the expectations of hierarchical galaxy formation.Comment: 5 pages, 4 figures, MNRAS Letters, in pres

Multi-GPU Acceleration of the iPIC3D Implicit Particle-in-Cell Code

iPIC3D is a widely used massively parallel Particle-in-Cell code for the simulation of space plasmas. However, its current implementation does not support execution on multiple GPUs. In this paper, we describe the porting of iPIC3D particle mover to GPUs and the optimization steps to increase the performance and parallel scaling on multiple GPUs. We analyze the strong scaling of the mover on two GPU clusters and evaluate its performance and acceleration. The optimized GPU version which uses pinned memory and asynchronous data prefetching outperform their corresponding CPU versions by 5-10x on two different systems equipped with NVIDIA K80 and V100 GPUs.Comment: Accepted for publication in ICCS 201

Информационные модели сельскохозяйственных объектов

The role of information technologies as interindustry direction of science is presented. The hypothesis of possibility of their uniform information description on the basis of the law on substance circulation in the nature and dialectic interrelation of objects of agricultural production is formulated: earth, plants, animals, machines, environment and society. The interrelation of these resources and its optimality (rationality) is possible on the basis of use of information technologies that in many respects defines efficiency of agrarian production. These postulates unite using a paradigm of information support of technological processes of agricultural production. It is represented by set of objective information (devices, measuring computer systems, information and measuring systems, bases and knowledge data) and subjective one, used at creation of devices, information, expert, and artificial intelligence systems. The authors worked out blocks of information models, calculated and justificated size of the converted word and the size of data stream of the universal block. Their technique of creation of «virtual laboratory» of engine 4Ch10.5/12 (D-144) research with use of the device of data collection of NI PCI-6251 is presented. A special software application is developed to realize interpolating of data of 4-factorial experiment at research of an internal combustion engine.Показана роль информационных технологий как межотраслевого направления науки. Сформулирована гипотеза о возможности единого их информационного описания на основе закона о круговороте вещества в природе и диалектической взаимосвязи объектов сельскохозяйственного производства: земли, растений, животных, машин, окружающей среды и социума. Взаимосвязь этих ресурсов и ее оптимальность (рациональность) возможна на основе использования информационных технологий, что во многом определяет эффективность аграрного производства. Эти положения объединяются парадигмой информационного обеспечения технологических процессов сельскохозяйственного производства. Она представлена совокупностью объективной информации (приборы, измерительно-вычислительные комплексы, информационно-измерительные системы, базы данных и знаний) и субъективной, используемой при создании приборов, информационных, экспертных систем и систем искусственного интеллекта. Представлены разработанные авторами блоки информационных моделей. Приведены расчет и обоснование величины обменного слова и размер информационного потока универсального блока информационных моделей. Предложена методика создания «виртуальной лаборатории» исследования двигателя 4Ч10,5/12 (Д-144) с использованием устройства сбора данных NI PCI-6251. Для этого разработан специальный программный комплекс, позволяющим вести интерполирование данных 4-факторного эксперимента при исследовании двигателя внутреннего сгорания. Ключевые слова: диалектическая общность, парадигма информационного обеспечения, информационные модели, потоки информации, интерполирование данных, «виртуальная лаборатория»

DANSSino: a pilot version of the DANSS neutrino detector

DANSSino is a reduced pilot version of a solid-state detector of reactor antineutrinos (to be created within the DANSS project and installed under the industrial 3 GW(th) reactor of the Kalinin Nuclear Power Plant -- KNPP). Numerous tests performed at a distance of 11 m from the reactor core demonstrate operability of the chosen design and reveal the main sources of the background. In spite of its small size (20x20x100 ccm), the pilot detector turned out to be quite sensitive to reactor antineutrinos, detecting about 70 IBD events per day with the signal-to-background ratio about unity.Comment: 16 pages, 11 figures, 3 tables. arXiv admin note: substantial text overlap with arXiv:1304.369

Search for sterile neutrinos at the DANSS experiment

DANSS is a highly segmented 1~m${}^3$ plastic scintillator detector. Its 2500 one meter long scintillator strips have a Gd-loaded reflective cover. The DANSS detector is placed under an industrial 3.1~$\mathrm{GW_{th}}$ reactor of the Kalinin Nuclear Power Plant 350~km NW from Moscow. The distance to the core is varied on-line from 10.7~m to 12.7~m. The reactor building provides about 50~m water-equivalent shielding against the cosmic background. DANSS detects almost 5000 $\widetilde\nu_e$ per day at the closest position with the cosmic background less than 3$\%$. The inverse beta decay process is used to detect $\widetilde\nu_e$. Sterile neutrinos are searched for assuming the $4\nu$ model (3 active and 1 sterile $\nu$). The exclusion area in the $\Delta m_{14}^2,\sin^22\theta_{14}$ plane is obtained using a ratio of positron energy spectra collected at different distances. Therefore results do not depend on the shape and normalization of the reactor $\widetilde\nu_e$ spectrum, as well as on the detector efficiency. Results are based on 966 thousand antineutrino events collected at 3 distances from the reactor core. The excluded area covers a wide range of the sterile neutrino parameters up to $\sin^22\theta_{14}<0.01$ in the most sensitive region.Comment: 10 pages, 13 figures, version accepted for publicatio

Effects of fieldline topology on energy propagation in the corona

We study the effect of photospheric footpoint motions on magnetic field structures containing magnetic nulls. The footpoint motions are prescribed on the photospheric boundary as a velocity field which entangles the magnetic field. We investigate the propagation of the injected energy, the conversion of energy, emergence of current layers and other consequences of the non-trivial magnetic field topology in this situation. These boundary motions lead initially to an increase in magnetic and kinetic energy. Following this, the energy input from the photosphere is partially dissipated and partially transported out of the domain through the Poynting flux. The presence of separatrix layers and magnetic null-points fundamentally alters the propagation behavior of disturbances from the photosphere into the corona. Depending on the field line topology close to the photosphere, the energy is either trapped or free to propagate into the corona.Comment: 14 pages, 15 figure

Four-Fermion Production in Electron-Positron Collisions

This report summarises the results of the four-fermion working group of the LEP2-MC workshop, held at CERN from 1999 to 2000. Recent developments in the calculation of four-fermion processes in electron-positron collisions at LEP-2 centre-of-mass energies are presented, concentrating on predictions for four main reactions: W-pair production, visible photons in four-fermion events, single-W production and Z-pair production. Based on a comparison of results derived within different approaches, theoretical uncertainties on these predictions are established.Comment: 150 pages, 73 figures, 45 table