Searching for the Stochastic Gravitational-Wave Background with Terrestrial Detectors Prof. Vuk Mandic, University of Minnesota Topic: Detection of GW of cosmological origin using terrestrial detectors Title: Searching for the Stochastic Gravitational-Wave Background with Terrestrial Detectors Date: October 12, 09:00 am Abstract: Stochastic gravitational wave background (SGWB) arises as a superposition of many uncorrelated gravitational wave sources. It could be of either cosmological or astrophysical origin, and therefore it could carry unique information about the very early universe and about its evolution. The upcoming observing runs of terrestrial gravitational wave detectors are expected to detect the stochastic background due to unresolvable compact binary mergers. I will review the most recent results of SGWB searches and I will highlight some of the challenges that are facing the field in the coming years.

GW research in South Korea Room: Zoom Hyung Mok Lee, Emeritus Professor from Seoul National University Topic: GW research in South Korea Date: November 2, 10:00 am Abstract: Gravitational wave research in Korea started in early 2000s after a Korean Gravitational Wave Group was formed as a voluntary group. KISTI began supporting our activity by opening a permanent position for numerical relativity, providing computing resources, and supporting the annual summer schools, together with APCTP. KGWG joined LIGO Scientific Collaboration (LSC) in 2009, with about 14 members. Initial contribution to LSC was to carry out data analysis of simulated data and provision of computing resources which were supported by the Global Science experimental Data hub Center (GSDC). Currently, GSDC computing facility is Tier-2 computing center in LIGO Data Grid (LDG) which is open to all members of LSC. Our contribution has been extended to detector characterization, parameter estimation, waveform research for eccentric binaries, multi-messenger astronomy, and characterization of coating material for near future upgrade of LIGO. KGWG is now also contributing to KAGRA in both data analysis and instrumentations, including squeezing research for future upgrade and support of optical components. In 2021, a major funding by NRF was approved to establish the Center for the Gravitational-Wave Universe (GWUniverse in short) at SNU, that includes the construction of the 7-Dimension Telescope, which is composed of 20 telescopes of 0.5 m aperture to be installed in Chilean Andes. The 7-DT will carry out search and monitoring of the Electro-Magnetic counterpart of the Gravitational-Wave sources with low-resolution spectroscopy in optical band, augmented by other optical telescope systems operated by SNU and KASI located throughout the world. There are other large area survey projects to be done concurrently by the 7DT. GWUniverse also carries out active research on gravitational-wave astronomy, including development of accurate waveforms from eccentric binaries using post-Newtonian approaches supplemented by the numerical relativity, and cosmological application of gravitation-wave data from current and future detectors. A few examples recent research from the GWUniverse will be presented in this talk. You can see this seminar at Youtube : https://youtu.be/-8rM0brvwUM

The search for cosmological phase transitions through their gravitational wave signals Room: Online Marek Lewicki, University of Warsaw Topic: GW from First Order Phase Transitions Title: The search for cosmological phase transitions through their gravitational wave signals Date: November 16, 16:30 pm Abstract: We are currently witnessing the dawn of a new era in astrophysics and cosmology, started by the LIGO/Virgo observations of Gravitational Waves (GWs). In this talk I will discuss prospects for detection of GW signals from cosmological phase transitions with the currently running experiments and the upcoming next generation. Including the problems associated with observation of a primordial signal in the presence of foregrounds produced by astrophysical objects. You can see this seminar at Youtube : https://youtu.be/BJsSLcvphmI

Beyond Einstein: Gravitational waves from Extended Gravities Room: Online Salvatore Capozziello, University of Naples(Universita' di Napoli "Federico II") Topic: Gravitational Waves signatures in Modified Gravity Models Title: Beyond Einstein: Gravitational waves from Extended Gravities Date: November 23, 16:30 Abstract: Modified theories of gravity are today extensively studied as possible wayout for General Relativity shortcomings both at UV and IR scales. However, gravitational waves have not been studied enough in this framework both from teoretical and observational points of view. Here, we discuss gravitational waves in theories of gravity aimed to extend General Relativity. The goal is to classify new polarizations in view of possible detection to finally fix the theory of gravity. You can see this seminar at Youtube : https://youtu.be/G-G7kRmgDgE

Grand Unified Theories: Topological Defects, Inflation, and Gravitational Waves Room: Online Rinku Maji, Physical Research Laboratory, Navarangpura, Ahmedabad, India Topic: Gravitational Waves in Inflation Models Title: Grand Unified Theories: Topological Defects, Inflation, and Gravitational Waves Date: December 7, 16:30 pm Abstract: The grand unified theory (GUT) provide rationales to the arbitrariness of the Standard Model (SM) and explains many enigmas of nature at the outset of a single gauge group. GUTs predict the proton decay and, the spontaneous symmetry breaking (SSB) of the higher symmetry group may lead to the formation of topological defects which are indispensable in the context of the cosmological observations. We explore the evolution of monopoles and cosmic strings in an inflationary universe, driven by Coleman-Weinberg potential of a GUT-singlet with minimal and non-minimal coupling to gravity. We discuss the gravitational wave from the decay of topologically stable and quasi-stable strings formed at the intermediate scale and the impact of inflation on the spectra. You can see this seminar at Youtube : https://youtu.be/3sFCf2WSIsw

COSMIC STRING NETWORKS and GRAVITATIONAL WAVES Room: Online José Juan Blanco Pillado, Date: December 14, 16:30 Title: COSMIC STRING NETWORKS and GRAVITATIONAL WAVES Abstract: In this talk, we will review how cosmic strings appear as solitonic solutions in many models of high-energy physics beyond the Standard Model. We will also describe the main ingredients for the cosmological formation and evolution of a network of strings. We will then discuss the latest results from large-scale simulations of these networks and their implications for the expected stochastic background of gravitational waves. Finally, we will comment on the current bounds of these models coming from current and future gravitational wave observatories. You can see this seminar at Youtube: https://youtu.be/pcXnGmY2xAQ

GW of cosmological sources with LISA Room: Online Germano Nardini, University of Stavanger, Norway Topic: GW of cosmological sources with LISA Date: December 21, 16:30

Hunting for the gravitational-wave background: detection methods and implications for astrophysics, high energy physics and the early Universe Room: Online Mairi Sakellariadou, King's College London Date: TBA (Date is postponed) Title: Hunting for the gravitational-wave background: detection methods and implications for astrophysics, high energy physics, and the early Universe Abstract: I will first define the gravitational-wave background and highlight the currently used detection method. The first three observing runs by the LIGO/Virgo/KAGRA collaboration have not detected such a background placing stringent upper limits which depend on the source (compact binaries, cosmic strings, phase transitions). I will then discuss how these limits can be used to constrain astrophysical models, high-energy physics models beyond the Standard Model, and early Universe cosmological scenarios.