4th Meeting on Gravitational Wave Science in Denmark-Norway

23 May 2024, 12:00 → 24 May 2024, 14:10 Europe/Oslo

KE A-204

The meeting aims to bring together researchers working in gravitational wave science and related areas. This is the fourth meeting in the series and the first to be hosted in Norway. The third meeting was hosted in Aalborg in 2023. The format is very informal as usual, and similar to previous meetings there will be several short talks from researchers to summarize current activities.

Thursday 23 May

Welcome

1 Studying first-order phase transitions numerically

Speaker: Anders Tranberg (UiS - TN - IMF)

2 Measuring first-order phase transitions at LISA

The LISA mission has been adopted, with launch scheduled in 2035. This leaves us with just a decade to complete the data analysis pipelines and prepare the science interpretation of the potentially observed signals. In this talk we will briefly review the status of the mission, some possible data analysis approaches to isolate the primordial stochastic GW background (SGWB), and some potential bounds on BSM models predicting first-order phase transitions.

Speaker: Germano Nardini (UiS TN IMF)

3 Cosmic redshift drift in gravitational waveforms

For a merger located at a constant redshift, the redshift of the merger is degenerate with the chirp mass of the system in the measured waveform. However, when the redshift can no longer be considered a constant over the duration of the merger in band, this degeneracy is broken. When the Universe undergoes accelerated expansion, the redshift to sources will grow in time, a signal that is in principle detectable in gravitational waveforms through a drift in the measured frequency of the system. The effect is tiny, however, since the expected frequency drift due to accelerated expansion is expected to be of order the Hubble constant for mergers at cosmological distances. It thus requires extremely precise measurements of gravitational waves to observe the drift, and the signal is a priori too small to be observed with the next generation of detectors. I am interested in ways of analysing waveforms that may amplify the signal.

Speaker: Asta Heinesen (Niels Bohr Institute)

GWStavanger.pdf

14:30 Coffee break

4 Possible Causes of False General Relativity Violations in Gravitational Wave Observations

Speaker: Alex Nielsen

5 Looking for new physics beyond the merger of black holes

Black Holes are possibly the most enigmatic objects in our Universe. These cosmic enigmas continue to be active arenas for strong gravity and quantum effects, providing fertile ground for exploring elusive aspects of quantum gravity. Indeed, there are strong motivations for why Quantum black holes may be radically different from their classical counterparts in Einstein's General Relativity (GR). On the other side gravitational wave astronomy strives to experimentally verify the Kerr nature of black holes, presenting a critical avenue for testing this aspect observationally. Observing multiple Quasi Normal Modes (QNMs), also referred to as black hole spectroscopy, is one of the most robust tests under minimal additional assumptions. In this talk I will present my pioneer work looking for signatures of Hawking radiation along with black hole spectroscopy in gravitational wave data.

Speaker: Jahed Abedi (University of Stavanger)

6 Measuring deviations from Kerr using LVK ringdown data

According to the black hole no-hair theorem, the emitted ringdown spectra are constrained by the mass and spin of the remnant black hole and thus offer an excellent test of the Kerr-nature of black holes. As a parameterization of beyond-Kerr effects, we employ the Johannsen-Psaltis metric ansatz and analyze the ringdown of two binary black hole merger events- GW150914 and GW190521 to constrain the deviation from Kerr. We find improvement in constraints on the deviation parameter in the case of GW190521 as compared to GW150914.

Speaker: Zaryab Ahmed (Universitetet i Stavanger)

Contributed talks

19:45 Social dinner

Gådjå restaurant
https://maps.app.goo.gl/xMVJyhbn6V5vQsxe9

Friday 24 May

7 Gravitational waves from a non-abelian dark sector coupled to axion inflation

Taking axion inflation as an example, we study the evolution of a non-Abelian dark sector coupled to the inflaton for different choices of the confinement scale. For confinement scales just a few orders of magnitude below the Planck scale, large temperatures are reached in the dark sector and gravitational wave signal could be generated due to fluctuations in the thermal plasma. Another possible source of gravitational waves is the confinement phase transition; however, this signal might be strongly suppressed due to the presence of an early matter-dominated era.

Speaker: Helena Kolesova (University of Stavanger)

GW_Stavanger_Kolesova.pdf

8 Gravitational waves from strongly interacting dark matter

Speaker: Daniil Krichevskiy (University of Stavager)

9 Prospects for gravitationally-lensed gravitational-wave transients

With the Advanced LIGO and Virgo detector network in operation, we now routinely detect gravitational-wave (GW) transients such as binary black hole mergers at cosmological distances, directly confirming one of the major predictions from general relativity. As another famous prediction from the theory, it has already been observed that light can be deflected in the presence of a gravitational field, referred to as gravitational lensing. We expect GWs can also be lensed, but we have yet to make the first discovery of gravitationally lensed GW. In this talk, I will first briefly introduce the theory of gravitational lensing of GWs. Next, I will go over the kinds of astronomical objects that could be responsible for such lensing phenomena, which affect our strategies to search for lensed GWs. Also, I will discuss the challenges of identifying lensed GWs in data and what we can learn and probe using these lensed transients.

Speaker: Rico Lo (Niels Bohr Institute)

11:00 Coffee break

10 Gravitational waves and equation of state inference

Speaker: Aleksi Kurkela (Univ. Stavanger)

11 Equation of state of neutron stars

Speaker: Oleg Komoltsev (University of Stavanger)

12 Detecting Gravitational Waves Using the Moon

It has been suggested to measure the eigenmodes of the Moon excited by gravitational waves. Such a resonant bar detector could become a valuable partner observatory for gravitational waves working alongside LISA and other future detectors. I will discuss in this talk the excitation of resonant eigenmodes by gravitational waves within Einstein and Brans-Dicke gravity. In the latter case, gravitational waves obtain an additional polarisation. In spherical detectors, it is possible to extract information on the polarisation of the gravitational wave. Such detectors are therefore a way to search for theories of gravity beyond general relativity. I will discuss the calculations of the displacement by gravitational wave resonant with the eigenmodes of the Earth and Moon, and comment on the frequency range for the potential Lunar gravitational wave antenna.

Speaker: Mathias Pavely Nødtvedt (NTNU (Norwegian University of Science and Technology))

13 Tales from a LIGO shifter and other stuff Vegard does

In this talk I will present publically available information on the candidate event S231123a, which was detected while I was on shift for PyCBC-live. Remaining time might be filled with other stuff.

Speaker: Mr Vegard Undheim (University of Stavanger - TN - IMF)

GW in Denmark-Norway conference.pptx

Closing