42,111 research outputs found
Modelling and interpreting the dependence of clustering on the spectral energy distributions of galaxies
We extend our previous physically-based halo occupation distribution models
to include the dependence of clustering on the spectral energy distributions of
galaxies. The high resolution Millennium Simulation is used to specify the
positions and the velocities of the model galaxies. The stellar mass of a
galaxy is assumed to depend only on M_{infall}, the halo mass when the galaxy
was last the central dominant object of its halo. Star formation histories are
parametrized using two additional quantities that are measured from the
simulation for each galaxy: its formation time (t_{form}), and the time when it
first becomes a satellite (t_{infall}). Central galaxies begin forming stars at
time t_{form} with an exponential time scale tau_c. If the galaxy becomes a
satellite, its star formation declines thereafter with a new time scale tau_s.
We compute 4000 \AA break strengths for our model galaxies using stellar
population synthesis models. By fitting these models to the observed abundances
and projected correlations of galaxies as a function of break strength in the
Sloan Digital Sky Survey, we constrain tau_c and tau_s as functions of galaxy
stellar mass. We find that central galaxies with large stellar masses have
ceased forming stars. At low stellar masses, central galaxies display a wide
range of different star formation histories, with a significant fraction
experiencing recent starbursts. Satellite galaxies of all masses have declining
star formation rates, with similar e-folding times, tau_s ~ 2.5Gyr. One
consequence of this long e-folding time is that the colour-density relation is
predicted to flatten at redshifts > 1.5, because star formation in the majority
of satellites has not yet declined by a significant factor. This is consistent
with recent observational results from the DEEP and VVDS surveys.Comment: 14 pages, 11 figures, submitted to MNRA
TrIMS: Transparent and Isolated Model Sharing for Low Latency Deep LearningInference in Function as a Service Environments
Deep neural networks (DNNs) have become core computation components within
low latency Function as a Service (FaaS) prediction pipelines: including image
recognition, object detection, natural language processing, speech synthesis,
and personalized recommendation pipelines. Cloud computing, as the de-facto
backbone of modern computing infrastructure for both enterprise and consumer
applications, has to be able to handle user-defined pipelines of diverse DNN
inference workloads while maintaining isolation and latency guarantees, and
minimizing resource waste. The current solution for guaranteeing isolation
within FaaS is suboptimal -- suffering from "cold start" latency. A major cause
of such inefficiency is the need to move large amount of model data within and
across servers. We propose TrIMS as a novel solution to address these issues.
Our proposed solution consists of a persistent model store across the GPU, CPU,
local storage, and cloud storage hierarchy, an efficient resource management
layer that provides isolation, and a succinct set of application APIs and
container technologies for easy and transparent integration with FaaS, Deep
Learning (DL) frameworks, and user code. We demonstrate our solution by
interfacing TrIMS with the Apache MXNet framework and demonstrate up to 24x
speedup in latency for image classification models and up to 210x speedup for
large models. We achieve up to 8x system throughput improvement.Comment: In Proceedings CLOUD 201
A new species of Archaeoryctes from the Middle Paleocene of China and the phylogenetic diversification of Didymoconidae
Didymoconidae are an enigmatic group of Asian endemic insectivorous mammals. We describe the new didymoconid species Archaeoryctes wangi sp. nov. from the Upper Member of the Wanghudun Formation (Middle Paleocene). This new species from the Qianshan Basin (Anhui Province, China) forms an interesting geographical intermediate between A. notialis from South China and A. borealis and A. euryalis from the Mongolian Plateau. To better understand the origin and evolutionary diversification of Didymoconidae, we performed a cladistic and stratocladistic study of the Didymoconidae and various outgroups. This study of dental material did not resolve the higher level affinities of Didymoconidae, but confirms the validity of the family and its distinctiveness from the morphologically similar Sarcodontidae. Moreover, our results corroborate the current didymoconid classification with the distinction of three subfamilies: “Ardynictinae”, Kennatheriinae and Didymoconinae; “Ardynictinae” are a paraphyletic stemgroup for the two other subfamilies. Our results suggest three distinct didymoconid radiations: (1) primitive ardynictines appeared in South China from the start of the Nongshanian; their evolution continues on the Mongolian Plateau with (2) the radiation of more evolved ardynictines and kennatheriines at the start of the Middle Eocene Arshantan and (3) the origin of didymoconines at the start of the Late Eocene Ergilian
Light Propagation in Nonlinear Waveguide and Classical Two-Dimensional Oscillator
The quantum optical problem of the propagation of electromagnetic waves in a
nonlinear waveguide is related to the solutions of the classical nonstationary
harmonic oscillator using the method of linear integrals of motion [ Malkin
et.al., Phys Rev. 2D (1970) p.1371 ]. An explicit solution of the classical
oscillator with a varying frequency, corresponding to the light propagation in
an anisotropic waveguide is obtained using the expressions for the quantum
field fluctuations. Substitutions have been found which allow to establish
connections of the linear and quadratic invariants of Malkin et.al. to several
types of invariants of quadratic systems, considered in later papers. These
substitutions give the opportunity to relate the corresponding quantum problem
to that of the classical two-dimensional nonstationary oscillator, which is
physically more informative.Comment: 14 pages, including one Table, 29 bibliographic references; E-mail:
[email protected]
The evolution of circular loops of a cosmic string with periodic tension
In this paper the equation of circular loops of cosmic string with periodic
tension is investigated in the Minkowski spacetime and Robertson-Walker
universe respectively. We find that the cosmic string loops possessing this
kind of time-varying tension will evolve to oscillate instead of collapsing to
form a black hole if their initial radii are not small enough.Comment: 9 pages, 3 figure
GeV detection of HESS J0632+057
HESS J0632+057 is the only gamma-ray binary that has been detected at TeV
energies, but not at GeV energies yet. Based on nearly nine years of Fermi
Large Area Telescope (LAT) Pass 8 data, we report here on a deep search for the
gamma-ray emission from HESS J0632+057 in the 0.1-300 GeV energy range. We find
a previously unknown gamma-ray source, Fermi J0632.6+0548, spatially coincident
with HESS J0632+057. The measured flux of Fermi J0632.6+0548 is consistent with
the previous flux upper limit on HESS J0632+057 and shows variability that can
be related to the HESS J0632+057 orbital phase. We propose that Fermi
J0632.6+0548 is the GeV counterpart of HESS J0632+057. Considering the Very
High Energy (VHE) spectrum of HESS J0632+057, a possible spectral turnover
above 10 GeV may exist in Fermi J0632.6+0548, as appears to be common in other
established gamma-ray binaries.Comment: 17 pages, 4 figures, 1 table; Accepted for publication in Ap
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