515 research outputs found
Neural network time-series classifiers for gravitational-wave searches in single-detector periods
The search for gravitational-wave signals is limited by non-Gaussian
transient noises that mimic astrophysical signals. Temporal coincidence between
two or more detectors is used to mitigate contamination by these instrumental
glitches. However, when a single detector is in operation, coincidence is
impossible, and other strategies have to be used. We explore the possibility of
using neural network classifiers and present the results obtained with three
types of architectures: convolutional neural network, temporal convolutional
network, and inception time. The last two architectures are specifically
designed to process time-series data. The classifiers are trained on a month of
data from the LIGO Livingston detector during the first observing run (O1) to
identify data segments that include the signature of a binary black hole
merger. Their performances are assessed and compared. We then apply trained
classifiers to the remaining three months of O1 data, focusing specifically on
single-detector times. The most promising candidate from our search is
2016-01-04 12:24:17 UTC. Although we are not able to constrain the significance
of this event to the level conventionally followed in gravitational-wave
searches, we show that the signal is compatible with the merger of two black
holes with masses and at the luminosity distance of .Comment: 29 pages, 11 figures, submitted to CQ
Quantum Noise in Multipixel Image Processing
We consider the general problem of the quantum noise in a multipixel
measurement of an optical image. We first give a precise criterium in order to
characterize intrinsic single mode and multimode light. Then, using a
transverse mode decomposition, for each type of possible linear combination of
the pixels' outputs we give the exact expression of the detection mode, i.e.
the mode carrying the noise. We give also the only way to reduce the noise in
one or several simultaneous measurements.Comment: 8 pages and 1 figur
Direct Measurement of the Photon Statistics of a Triggered Single Photon Source
We studied intensity fluctuations of a single photon source relying on the
pulsed excitation of the fluorescence of a single molecule at room temperature.
We directly measured the Mandel parameter Q(T) over 4 orders of magnitude of
observation timescale T, by recording every photocount. On timescale of a few
excitation periods, subpoissonian statistics is clearly observed and the
probablility of two-photons events is 10 times smaller than Poissonian pulses.
On longer times, blinking in the fluorescence, due to the molecular triplet
state, produces an excess of noise.Comment: 4 pages, 3 figures, 1 table submitted to Physical Review Letter
Squeezed light at sideband frequencies below 100 kHz from a single OPA
Quantum noise of the electromagnetic field is one of the limiting noise
sources in interferometric gravitational wave detectors. Shifting the spectrum
of squeezed vacuum states downwards into the acoustic band of gravitational
wave detectors is therefore of challenging demand to quantum optics
experiments. We demonstrate a system that produces nonclassical continuous
variable states of light that are squeezed at sideband frequencies below 100
kHz. A single optical parametric amplifier (OPA) is used in an optical noise
cancellation scheme providing squeezed vacuum states with coherent bright phase
modulation sidebands at higher frequencies. The system has been stably locked
for half an hour limited by thermal stability of our laboratory.Comment: 3 pages, 3 figure
Optimum Small Optical Beam Displacement Measurement
We derive the quantum noise limit for the optical beam displacement of a
TEM00 mode. Using a multimodal analysis, we show that the conventional split
detection scheme for measuring beam displacement is non-optimal with 80%
efficiency. We propose a new displacement measurement scheme that is optimal
for small beam displacement. This scheme utilises a homodyne detection setup
that has a TEM10 mode local oscillator. We show that although the quantum noise
limit to displacement measurement can be surpassed using squeezed light in
appropriate spatial modes for both schemes, the TEM10 homodyning scheme
out-performs split detection for all values of squeezing.Comment: 13 pages, 7 figure
Oxide nanotemplates for self-assembling "solid" building blocks
It is widely accepted that self-assembling building blocks is one of the
promising ways for engineering new materials. Recent years reveal substantial
progress in fabricating colloidal particles, polymer blocks and supramolecular
aggregates of organic molecules. Despite of substantial progress in molecular
self-assembly there is still a lack of simple blocks made of "solid matter"
(e.g. metals, oxides etc.) with well-defined crystal structure and spatial
order. Here we demonstrate that ordered arrays of metal nanoclusters can be
fabricated by self-assembly on a wide range of oxide templates. These
nano-templates are produced either by depositing an alien oxide film or by
oxidizing a metal/metal oxide substrate.Comment: 11 pages, 2 figures added DFT calculations and Fig.
Host galaxies of long gamma-ray bursts in the Millennium Simulation
(abridged) In this work, we investigate the nature of the host galaxies of
long Gamma-Ray bursts (LGRBs) using a galaxy catalogue constructed from the
Millennium Simulation. We developed an LGRB synthetic model based on the
hypothesis that these events originate at the end of the life of massive stars
following the collapsar model, with the possibility of including a constraint
on the metallicity of the progenitor star. A complete observability pipeline
was designed to calculate a probability estimation for a galaxy to be
observationally identified as a host for LGRBs detected by present
observational facilities. This new tool allows us to build an observable host
galaxy catalogue which is required to reproduce the current stellar mass
distribution of observed hosts. This observability pipeline predicts that the
minimum mass for the progenitor stars should be ~75 solar masses in order to be
able to reproduce BATSE observations. Systems in our observable catalogue are
able to reproduce the observed properties of host galaxies, namely stellar
masses, colours, luminosity, star formation activity and metallicities as a
function of redshift. At z>2, our model predicts that the observable host
galaxies would be very similar to the global galaxy population. We found that
~88 per cent of the observable host galaxies with mean gas metallicity lower
than 0.6 solar have stellar masses in the range 10^8.5-10^10.3 solar masses in
excellent agreement with observations. Interestingly, in our model observable
host galaxies remain mainly within this mass range regardless of redshift,
since lower stellar mass systems would have a low probability of being observed
while more massive ones would be too metal-rich. Observable host galaxies are
predicted to preferentially inhabit dark matter haloes in the range
10^11-10^11.5 solar masses, with a weak dependence on redshift.Comment: 11 pages, 10 figures, accepted for publication in MNRA
Neanderthal selective hunting of reindeer? The case study of Abri du Maras (south-eastern France)
Fieldwork was supported by the Regional Office of Archaeology RhĂŽne-Alpes, the French Ministry of Culture and Communication and the ArdĂšche Department through several scientific programs. M.G.Chacon, F. Rivals and E. AlluĂ© research are funded by âCERCA Programme/Generalitat de Catalunyaâ. Thanks to Jean-Jacques Hublin, Annabell Reiner and Steven Steinbrenner from the Max Planck Institute (MPI-EVA) for analytical support (isotope analysis). We are grateful to the two anonymous reviewers for their constructive remarks on this manuscript. The English manuscript was edited by L. Byrne, an official translator and native English speaker.Peer reviewedPostprin
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