Gravitational Wave Events: Detection and Present Status

• Liang Dai (IAS)

Chirping gravitational wave signals from compact binary coalescence were detected for the first time during LIGO/Virgo O1 and O2 observing runs. The majority of the events reported thus far came from binary systems of fairly heavy stellar mass black holes located at cosmological distances. In addition, one spectacular binary neutron star merger event from just 40 Mpc away was detected in synergy with detailed electromagnetic counterparts. The O3 observing run is ongoing with the two LIGO detectors and the Virgo detector in simultaneous operation, and has reportedly increased the detected number of compact binary sources by great amount. I will summarize the present status of compact binary sources detected through gravitational waves and their apparent population properties. In addition to events reported from LIGO/Virgo analysis, I will summarize existing efforts by independent groups to analyze the publicly released O1/O2 strain data in search of compact binary coalescence events. In particular, I will present work done by the IAS group, as a result of which we managed to decrease the detection threshold and uncovered many additional binary black hole merger events.

Variational Methods and Algorithms for GW Denoising and Reconstruction: Applications

• Alejandro Torres

This talk presents various methods to detect GW signals obtained from simulations under different noise conditions and their application to real data from detectors, comparing results with Gaussian and real noise. We also test dictionary learning to distinguish signals from glitches.

Glitch classification and de-noising in Gravitational Wave data

• Miquel Llorens

One of the most challenging problems in GW data analysis is noise removal. In this talk I present an alternative method for de-noising and classification of one kind of transient noise signals known as 'glitches', using learned dictionaries (as a supervised machine learning algorithm). Several tests are performed as a proof of concept over two data sets, the first one composed of simulated glitches, and the second one composed of actual glitches.

GWxLSS: Combining Large-Scale Structure and Gravitational Waves

• Nicola Bellomo (Institute of Cosmos Sciences - University of Barcelona)

During the next decade there will be an unprecedented opportunity to combine data coming from galaxy surveys and gravitational wave observatories to address open questions in Cosmology. In this talk I will show a worked example, in which the cross correlation of large-scale structure and gravitational waves data is used to establish whether the black holes detected by LIGO have an astrophysical or primordial origin. I will also briefly present some numerical tools recently developed that allow to estimate the cosmological signal generated by resolved events and a stochastic gravitational wave background.

Detecting GWs from core-collapse supernovae using machine learning

• Pablo Cerda

Core collapse supernovae is among the most exciting events that we expect to observe in the future by gravitational wave interferometers. They provide a unique multi messenger opportunity with the combined emission of gravitational waves, neutrinos and electromagnetic waves. In this talk I will focus in the current understanding of core-collapse GW signals and how they can be modelled in terms of normal oscillations modes of proto-neutron stars excited during the post-bounce phase before the onset of the SN explosion. The observation of such modes in the future by gravitational wave observatories (Virgo, LIGO) may allow to infer the properties of proto-neutron stars and learn about the engine powering supernova explosions. Here we present a machine learning method to analyse the data of the LIGO, Virgo, and KAGRA network to enhance the detection efficiency of this category of signals.

Gravitational waves from primordial black holes orbiting around stellar black holes

• Jordi Miralda-Escude

If dark matter is made of primordial black holes of planetary mass formed in the early Universe, there are processes through which they might be captured around massive stars which later become stellar black holes through normal stellar evolution. The primordial black holes could then merge with the stellar black hole on orbits that may be circular or highly elliptical, and produce gravitational waves detectable at the frequencies of LIGO-VIRGO.

Challenges to global solutions in Horndeski’s theory

• Raimon Luna

We explore the question of obtaining global solutions in Horndeski’s theories of gravity. Towards this end, we study a relevant set of the theory and, by employing the Einstein frame we simplify the analysis by exploiting known results on global solutions of wave equations. We identify conditions for achieving global solutions as well as obstacles that can arise to spoil such goal. We illustrate these problems via numerical simulations.

Activities of the ICCUB Virgo group

• Jordi Portell

In this talk I will make a brief introduction to the several activities being carried out or planned by the ICCUB Virgo group, which includes instrumentation and electronics, computing, data analysis and science exploitation.

Status of the implementation of denoising techniques in LIGO/Virgo data

• Pablo Barneo

As part of the Virgo collaboration, the ICCUB is working on the practical implementation of the denoising methods and techniques proposed by the University of Valencia, through articles from Alejandro Torres, Jose Antonio Font, et alia. The current status of this project will be presented.

Contributions to Virgo and LISA on instrumentation

• David Gascon

ICCUB contributes to the AdV+ upgrade of Virgo in two subsystems. The main goal of AdV+ Phase I is to reduce the interferometer sensing noise and this activity is organized in the Quantum Noise Reduction (QNR) workpackage. The ICCUB-TU contributes to the Squeezing Injection (SIN) subsystem. A second contribution, in collaboration with Pisa University, is to develop a highly integrated data acquisition card for the superattenuators (SAT) upgrade to suspend 100 kg mirrors. LISA is a selected large-class mission by the European Space Agency (ESA) for the L3 launch opportunity, scheduled in 2034. The IEEC will probably lead the Spanish contribution. This contribution will mainly consist of the payload control system and the payload diagnostics package with different sensors (and some actuators as well): thermal, magnetic and radiation monitor. The ICCUB-TU (as part of IEEC) intends to contribute to the radiation monitor including a comprehensive study of the charging effect of the test masses.

Population synthesis of black hole binary mergers from star clusters

• Mark Gieles

Black hole (BH) binary mergers formed through dynamical interactions in dense star clusters are believed to be one of the main sources of gravitational waves for Advanced LIGO and Virgo. Here we present a fast numerical method for simulating the evolution of star clusters with BHs, including a model for the dynamical formation and merger of BH binaries. We validate our method using direct N-body simulations, and find it to be in excellent agreement with results from recent Monte Carlo models of globular clusters. Finally, we compute the rate and eccentricity distributions of merging BH binaries for a wide range of cluster initial conditions, spanning more than two orders of magnitude in mass and radius.

Variational Learning, overfitting and LASSO regularization

• Antonio Marquina

We shall examine some variational model problems for different signal reconstruction problems. We will study the role of regularization and its relation to the so called "overfitting" and how to avoid it. We will present some model examples, including linear regression, ridge regression and LASSO regression, and we will numerically solve them by means of different (stochastic) gradient descent procedures.

Characterizing Noise and analyzing Gravitational Wave signals with high precision

• Liang Dai

It is crucial to accurately treat data to maximize as much as possible the sensitivity of the GW signal search. In this talk, I will discuss several issues encountered in the IAS effort to analyze the LIGO/Virgo public data. These include dealing with slow time-variability in the noise power spectrum of the detector, excision of corrupted data segments, properly measuring the noise power spectral density, as well as fast likelihood valuation for GW parameter estimation.

Scalar Induced gravitational waves from inflation: non-linear effects

• Diego Cruces

There are various ways of producing GW from inflation. I will focus on GW sourced by scalar perturbations, or induced GW, which are only significant when relatively large scalar perturbations re-enter the Hubble horizon after inflation and collapse forming a black hole (PBHs). I will then explain how we can produce a large enough peak in the scalar power spectrum of inflation using the so-called stochastic approach, a natural way to introduce non-linear effects during inflation.