The first period of the O4 observing run, O4a, started at 15:00 UTC 24 May 2023, and ended at 16:00 UTC 16 January 2024 for a period of commissioning between O4a and O4b.
The two LIGO detectors are now running with a sensitivity of 155-175 Mpc, and with duty cycles in recent days of 80-98%. There will be further minor adjustments to optimize the performance during the O4b observing...
Reconstructing the expansion history of the universe and properties of dark energy have been among of the main goals of physical cosmology. I will discuss about reconstructing dark energy in light of most recent cosmological observations including DESI-2024 BAO observations, Union3 supernova compilation and Planck CMB data.
Gravitational wave has been observed since LIGO first detected. Also, gravitational wave noise classification became needed. There have been many methods to classify them. We tried PCA preprocessing method on t-SNE algorithm to increase its performance.
Coating thermal noise (CTN) is identified as one of the limitations on the sensitivity of advanced LIGO (aLIGO) within its most sensitive frequency range. To enhance sensitivity, it is essential to replace the high reflective index material in the high reflective mirror coating of the test mass in gravitational wave (GW) detectors with a new material that has lower mechanical loss properties....
Spectral lines for a star light are the result of electromagnetic interaction between a single photon and a quantum system such as atoms or molecules. Observations of such absorption or emission lines can be used to extract various astrophysical information for the chemical elements of stars or interstellar medium. Similarly, we have considered the possibility of spectral lines for a...
Gravitational wave (GW) signals are inherently weak, making effective denoising techniques crucial in the presence of detector and environmental noise. In this talk, we introduce our recently published work (Kim et al. 2024), which presents a methodology for denoising gravitational wave data using an autoregressive approach. Furthermore, as the number of studies incorporating machine learning...
Applying the quantum field theoretic perturbiner approach to Einstein gravity, we compute the metric of a Schwarzschild black hole order by order in perturbation theory. Using recursion, this perturbative calculation can be carried out in de Donder gauge to all orders in Newton’s constant. The result is a geometric series which is convergent outside a disk of finite radius, and it agrees within...
The ringdown gravitational waves resulting from the merger of binary black holes have been extensively studied and are well-known. However, our recent study has revealed that ringdown gravitational waves can also be generated in very close encounters without merging. In this talk, we will briefly introduce our research on the ringdown gravitational waves arising from non-merging close...
We investigate the characteristics of gravitational waves from the hyperbolic encounters between two black holes.
We first examine the angular dependence of the trajectory-driven part of the gravitational waves in hyperbolic orbits by summing the individual modes of $\psi_4$ obtained from NR data.
To confirm whether ringdown patterns occur in each black hole, we analyze the xy-plane...
In this presentation, we will delve into our ongoing project, which focuses on applying deep learning methodologies to identify and classify eccentric gravitational wave signals according to their eccentricity: non-eccentric, mildly eccentric, and strongly eccentric.
It is well known that photon and neutrino physics cannot probe cosmological evolution beyond Big Bang Nucleosynthesis (BBN), but gravitational waves (GW) can.
In particular, the GW produced by the Standard Model of Particle Physics plasma are undoubtedly a way to probe the evolution of the universe beyond BBN. When comparing the profile of gravitational waves propagating according to the...
Recently, Pulsar Timing Arrays (PTAs) around the world have provided strong evidence for a stochastic gravitational wave (GW) background. The second historic event defining the discovery of the GW background is imminent. We would like to review the essential knowledge a GW astronomer needs regarding the GW background. Firstly, we review the basics of the GW background and its statistical...
The increasing number of Gravitational Wave (GW) events detected by the Ligo-Virgo-Kagra collaboration provide better constraints on models of Compact Binary Coalescences (CBCs) astrophysical populations. Said constraints notably include redshift-dependent merger rates and source parameters probability distributions (chirp masses, spins).
Therefore, generating catalogues of CBCs...
Gravitational waves emitted by binary neutron star provides information about the internal structure of neutron star, which help us verify dense matter equations of state.
We investigate how the measurement accuracy of neutron star's tidal deformability can be improved by incorporating the higher-order post-Newtonian tidal corrections.
To compute the measurement errors, we use the Fisher...
The 7-Dimensional Telescope (7DT) is a multiple telescope system designed for optical follow-up observation of gravitational-wave (GW) sources and the spectral mapping survey of the sky. In this talk, we will update the current status of 7DT, including some scientific observations carried out with the telescope. Our updates will also include the 7DT construction stage that will bring 7DT from...
This presentation introduces an application of machine learning method, Gaussian Mixture Modelling, to the coherent WaveBurst for short duration gravitaional wave transients. The cWB+GMM methodology is applied to generic Burst all-sky short search for both LH and LHV networks in the LIGO-Virgo O3 observing run. cWB+GMM has achieved comparable sensitivities to an array of generic signal...
The Mode Matching Telescope (MMT) relays the Gaussian beam waist from one location to another. A reflective confocal off-axis MMT can be optimally configured so there is no central obscuration. However, such an off-axis system may induce polarization loss, affecting not only the irradiance of the light but also the phase, while interferometry-based gravitational wave detectors strive to...
KAGRA, the gravitational wave detector in Japan, is experiencing some issues from uniformity of the crystal. So it's needed to characterize samples' property to minimize this issues by selecting a good sample. We developed a photo-thermal common-path interferometer(PCI) system for KAGRA test mass characterization in KASI. A simple explanation for PCI system and current development status and...
Frequency-dependent squeezed (FDS) quantum states of light have been largely
found to reduce Quantum Noise in GW detectors along their entire bandwidth (10 Hz
- 10 kHz). In view of O4b, one of the major hardware improvements for Advanced
Virgo+ (AdV+) consisted in the implementation of a FDS source. It has been proven
to yield 5.6 dB of squeezing level at its best in standalone...
We designed reflective mode-matching telescopes (MMT) for an Einstein-Podolsky-Rosen (EPR) squeezing experiment, demonstrating a mode-matching loss of less than 0.1%. EPR squeezing is a proposed method for reducing broadband quantum noise in gravitational wave detectors. To ensure precise alignment and reproducibility of the MMT, we placed optomechanics on a base plate with a reference...
Quantum shot noise dominates the total noise for existing gravitational-wave (GW) detectors based on the Fabry-Perot Michelson interferometer. By squeezing the vacuum fluctuations entering a interferometer's readout port, the sensitivity of the GW detector can be significantly improved. Experimental work has recently been carried out at KASI to demonstrate the generation of squeezed vacuum. In...
On 14 September 2015, a century after Einstein predicted their existence, the first direct detection of a Gravitational Wave (GW) from a binary black hole merger was achieved, thus opening a new window of observation on the Universe and marking the birth of GW Astronomy [1]. This important result has been possible thanks to many years of R&D efforts done by the LIGO-Virgo collaborations for...
GW astronomy focused on 100-1000 Hz traditionally but this has been rapidly broadened toward the next decades. In this talk, I'll touch on GW astronomy available in nHz up to THz ranges and introduce the main detector concepts, target science and/or sources.
