N. Christensen
A5043299278- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- Cosmology and Gravitation Theories
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Geophysics and Sensor Technology
- Radio Astronomy Observations and Technology
- Astronomical Observations and Instrumentation
- Advanced Frequency and Time Standards
- Seismic Waves and Analysis
- High-pressure geophysics and materials
- Atomic and Subatomic Physics Research
- Cold Atom Physics and Bose-Einstein Condensates
- Statistical and numerical algorithms
- Seismology and Earthquake Studies
- Magnetic confinement fusion research
- Medical Imaging Techniques and Applications
- Quantum chaos and dynamical systems
- Seismic Imaging and Inversion Techniques
- Statistical Mechanics and Entropy
- Black Holes and Theoretical Physics
- Superconducting Materials and Applications
- Computational Physics and Python Applications
- Solar and Space Plasma Dynamics
Université Côte d'Azur
2016-2025
Observatoire de la Côte d’Azur
2016-2025
Centre National de la Recherche Scientifique
2015-2024
Carleton College
2014-2023
Abastumani Astrophysical Observatory
2022
Institut National de Physique Nucléaire et de Physique des Particules
2015
Aarhus University
2015
Université Paris-Sud
2015
Goddard Space Flight Center
2014
European Gravitational Observatory
2007-2012
The Advanced LIGO and Virgo gravitational wave (GW) detectors will begin operation in the coming years, with compact binary coalescence events a likely source for first detections. waveforms emitted directly encode information about sources, including masses spins of objects. Recovering physical parameters sources from GW observations is key analysis task. This work describes LALInference software library Bayesian parameter estimation signals, which builds on several previous methods to...
On August 17, 2017 at 12:41:06 UTC the Fermi Gamma-ray Burst Monitor (GBM) detected and triggered on short gamma-ray burst GRB 170817A. Approximately 1.7 s prior to this GRB, Laser Interferometer Gravitational-Wave Observatory (LIGO) a binary compact merger candidate associated with GRB. This is first unambiguous coincident observation of gravitational waves electromagnetic radiation from single astrophysical source marks start gravitational-wave multi-messenger astronomy. We report GBM...
The goal of the Laser Interferometric Gravitational-Wave Observatory (LIGO) is to detect and study gravitational waves (GWs) astrophysical origin. Direct detection GWs holds promise testing general relativity in strong-field regime, providing a new probe exotic objects such as black holes neutron stars uncovering unanticipated astrophysics. LIGO, joint Caltech–MIT project supported by National Science Foundation, operates three multi-kilometer interferometers at two widely separated sites...
Current interferometric gravitational-wave detectors are limited by quantum noise over a wide range of their measurement bandwidth. One method to overcome the limit is injection squeezed vacuum states light into interferometer's dark port. Here, we report on successful application this technology improve shot sensitivity Advanced Virgo detector. A enhancement up 3.2±0.1 dB beyond achieved. This nonclassical improvement corresponds 5%–8% increase binary neutron star horizon. The squeezing was...
With an instantaneous view of 70% the sky, Fermi Gamma-ray Burst Monitor (GBM) is excellent partner in search for electromagnetic counterparts to gravitational wave (GW) events. GBM observations at time Laser Interferometer Gravitational-wave Observatory (LIGO) event GW150914 reveal presence a weak transient above 50 keV, 0.4~s after GW event, with false alarm probability 0.0022 (2.9$\sigma$). This lasting 1 s was not detected by any other instrument and does appear connected previously...
This paper presents a complete description of Virgo, the French-Italian gravitational wave detector. The detector, built at Cascina, near Pisa (Italy), is very large Michelson interferometer, with 3 km-long arms. In this paper, following presentation physics requirements, leading to specifications for construction detailed all its different elements given. These include civil engineering infrastructures, huge ultra-high vacuum (UHV) chamber (about 6000 cubic metres), optical components,...
Abstract We perform a statistical standard siren analysis of GW170817. Our does not utilize knowledge NGC 4993 as the unique host galaxy optical counterpart to Instead, we consider each within GW170817 localization region potential host; combining redshifts from all galaxies with distance estimate provides an Hubble constant, H 0 . Considering brighter than equally likely binary neutron star merger, find km s −1 Mpc (maximum posteriori and 68.3% highest density posterior interval; assuming...
The characterization of the Advanced LIGO detectors in second and third observing runs has increased sensitivity instruments, allowing for a higher number detectable gravitational-wave signals, provided confirmation all observed events. In this work, we present methods used to characterize curate publicly available datasets, including strain data quality products. We describe essential role these datasets LIGO-Virgo Collaboration analyses gravitational-waves from both transient persistent...
We discuss entanglement of multiparticle quantum systems. propose a potential measure type pure states n qubits, the n-tangle. For system two qubits n-tangle is equal to square concurrence, and for systems three it ''residual entanglement''. show that -tangle, also generalization concurrence squared even n, use this fact prove an monotone. However, undefined odd n>3. Finally we related mixed state find analytical formula n.
We report on the experimental observation of environment induced decoherence in quantum delta-kicked rotor. Ultracold cesium atoms are subjected to a pulsed standing wave near resonant light. Spontaneous scattering photons destroys dynamical localization thereby giving rise diffusion, which approaches classical diffusion with an increasing degree decoherence. This tendency is enhanced by stronger stochasticity underlying system. A comparison theoretical predictions presented.
A study of the method detecting a stochastic gravitation-wave background (SGWB) with laser-interferometric gravitational-wave antennas is presented. The SGWB can be measured by correlating output two or more detectors. results in this paper applied to planned new generation kilometer length interferometers, such as Laser Interferometer Gravitational-Wave Observatory (LIGO) United States, similar systems other countries. Advanced detectors will able limit gravity-wave energy density per...
We present direct upper limits on gravitational wave emission from the Crab pulsar using data first 9 months of fifth science run Laser Interferometer Gravitational-wave Observatory (LIGO). These are based two searches. In we assume that follows observed radio timing, giving an limit beats indirect inferred spin-down and braking index energetics nebula. second allow for a small mismatch between signal frequencies interpret our results in context possible mechanisms.
Data collected by the GEO 600 and LIGO interferometric gravitational wave detectors during their first observational science run were searched for continuous waves from pulsar J1939+2134 at twice its rotation frequency. Two independent analysis methods used are demonstrated in this paper: a frequency domain method time method. Both achieve consistent null results, placing new upper limits on strength of pulsar's emission. A model emission mechanism is to interpret as constraint equatorial...
We report on a search for gravitational waves from coalescing compact binary systems in the Milky Way and Magellanic Clouds. The analysis uses data taken by two of three LIGO interferometers during first science run illustrates method setting upper limits inspiral event rates using interferometer data. pipeline is described with particular attention to selection coincidence between interferometers. establish an observational limit R<1.7×102 per year Equivalent Galaxy (MWEG), 90% confidence,...
We present upper limits on the gravitational wave emission from 78 radio pulsars based data third and fourth science runs of LIGO GEO 600 detectors. The both have been combined coherently to maximize sensitivity. For first time, within binary (or multiple) systems included in search by taking into account signal modulation due their orbits. Our are therefore measured for 56 these pulsars. remaining 22, our results improve previous up a factor 10. example, tightest limit strain is...
We analyzed the available LIGO data coincident with GRB 070201, a short-duration, hard-spectrum γ-ray burst (GRB) whose electromagnetically determined sky position is spiral arms of Andromeda galaxy (M31). Possible progenitors such short, hard GRBs include mergers neutron stars or star and black hole, soft repeater (SGR) flares. These events can be accompanied by gravitational-wave emission. No plausible candidates were found within 180 s long window around time 070201. This result implies...
We carry out two searches for periodic gravitational waves using the most sensitive few hours of data from second LIGO science run. The first search is targeted at isolated, previously unknown neutron stars and covers entire sky in frequency band 160-728.8 Hz. targets accreting star low-mass X-ray binary Scorpius X-1, bands 464-484 Hz 604-624 Hz, orbit parameters. Both look coincidences between Livingston Hanford 4-km interferometers. For isolated our 95% confidence upper limits on wave...
We report on a search for gravitational waves from the coalescence of compact binaries during third and fourth LIGO science runs. The focused generated inspiral phase binary evolution. In our analysis, we considered three categories systems, ordered by mass: (i) primordial black hole with masses in range 0.35 M(sun) < m1, m2 1.0 M(sun), (ii) neutron stars 3.0 (iii) holes M(sun)< m_(max) additional constraint m1+ m_(max), where was set to 40.0 80.0 runs, respectively. Although detectors...
We introduce a novel cooling technique capable of approaching the quantum ground state kilogram-scale system—an interferometric gravitational wave detector. The detectors Laser Interferometer Gravitational-wave Observatory (LIGO) operate within factor 10 standard limit (SQL), providing displacement sensitivity 10−18 m in 100 Hz band centered on 150 Hz. With new feedback strategy, we dynamically shift resonant frequency 2.7 kg pendulum mode to lie this optimal band, where its effective...
The merger rate of black hole binaries inferred from the detections in first Advanced LIGO science run, implies that a stochastic background produced by cosmological population mergers will likely mask primordial gravitational-wave background. Here we demonstrate next generation ground-based detectors, such as Einstein Telescope and Cosmic Explorer, be able to observe binary throughout universe with sufficient efficiency confusion can potentially subtracted at level $\Omega_{\mathrm{GW}}...
We present a search for periodic gravitational waves from the neutron star in supernova remnant Cassiopeia A. The coherently analyzes data 12 day interval taken fifth science run of Laser Interferometer Gravitational-Wave Observatory. It searches gravitational-wave frequencies 100 to 300 Hz and covers wide range first second frequency derivatives appropriate age different spin-down mechanisms. No signal was detected. Within frequencies, we set 95% confidence upper limits (0.7–1.2) × 10−24 on...
We have searched for gravitational waves from coalescing low mass compact binary systems with a total between 2M⊙ and 35M⊙ minimum component of 1M⊙ using data the first year fifth science run three LIGO detectors, operating at design sensitivity. Depending on mass, we are sensitive to coalescences as far 150 Mpc Earth. No gravitational-wave signals were observed above expected background. Assuming population objects Gaussian distribution representing neutron star systems, black hole–neutron...