Ultra-high frequency gravitational waves: where to next ?

Europe/Zurich
4/3-006 - TH Conference Room (CERN)

4/3-006 - TH Conference Room

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Description

The direct detection of gravitational waves has opened a new window of observation for phenomena in which gravity, instead of light, is the messenger. The goal of the Ultra-High-Frequency Gravitational Waves (UHF-GW) initiative is to promote scientific progress in a new area of research, gravitational waves at ultra-high-frequency, both from theoretical and experimental points of view. The ultra-high-frequency band (above 10 kHz) is particularly important and interesting because gravitational wave detection in this range would give us important insights about the very early Universe and particle physics at energy scales that cannot be probed with colliders in the foreseeable future.

This workshop, hosted by CERN TH and the CERN-Korea Theory Collaboration, is the third in a series of workshops organized by the UHF-GW initiative, aiming at addressing theoretical open questions about the nature of ultra-high-frequency gravitational wave sources and at stimulating the technological progress that is necessary to detect gravitational waves in this frequency range. This workshop will be focussed on assessing various new detector concepts that have been proposed recently, discussing progress and challenges in implementing high frequency GW detectors as well as on discussing recent progress in the understanding of some UHF-GW sources.

This workshop will feature a small number of longer talks on different aspects of UHF GW detection, as well as plenary sessions of short contributed talks and topical discussion sessions. In addition, there will be ample time for informal discussions and work on collaborative projects. We encourage submissions for short contributed talks on all aspects of UHF GWs by September 15th.

Previous editions of this series where held in Trieste (2019) and online (2021), leading to a Living Review on UHF GWs.

This workshop is partially funded by the CERN-Korea Theory Collaboration and by the UKRI/EPSRC Stephen Hawking fellowship, grant reference EP/T017279/1.

Organizers: Nancy Aggarwal (Northwestern University), Mike Cruise (University of Birmingham), Valerie Domcke (CERN),  Sunghoon Jung (Seoul National University), Joachim Kopp (CERN/ Mainz U.), Francesco Muia (University of Cambridge), Fernando Quevedo (University of Cambridge), Andreas Ringwald (DESY).

Invited speakers:

Aldo Ejlli (Cardiff U.)
Sebastian Ellis (Geneva U.)
Gabriele Franciolini (Rome U.)
Elina Fuchs (Hannover U., Braunschweig U.)
Camilo Garcia-Cely (Valencia U.)
Andrew Geraci (Northwestern U.)
Bianca Giacconi (Fermilab)
Gianluca Gregori (Oxford U.)
Axel Lindner (DESY)
Tao Liu (Hong Kong U.)
Kaliroe Pappas (MIT)
Krisztian Peters (DESY)
Mikel Sanchez-Garitaonandia (Barcelona U.)
Jacob Sprague (Northwestern U.)
Tommaso Tabarelli (Milano Bicocca U.)

Conference Photo
Participants
  • Adil Jueid
  • Alberto Roper Pol
  • Aldo Ejlli
  • Andreas Ringwald
  • Andrew Geraci
  • Anish Ghoshal
  • Anushka Doke
  • Asuka Ito
  • Augustin Tinon
  • Axel Lindner
  • Blas Diego
  • Camilo Alfredo Garcia Cely
  • Caner Unal
  • Carlos Tamarit
  • Christoph Reinhardt
  • Chu Yiwen
  • Easther Richard
  • Francesco Muia
  • Gabriele Franciolini
  • Garcia-Bellido Juan
  • Gary Stephenson
  • Georgios Vacalis
  • Geraldine Servant
  • Germain Tobar
  • Giampaolo Pisano
  • Giancarlo Cella
  • Gonzalo Villa
  • Gregorio Carullo
  • Hyerim Noh
  • Hyun Min Lee
  • Jaanita Mehrani
  • Jamie McDonald
  • Jan Schutte-Engel
  • Josep Maria Batllori Berenguer
  • Killiam Martineau
  • Krisztian Peters
  • Lee Sung Mook
  • Marios Maroudas
  • Martin Teuscher
  • Matthias Schott
  • Mauro Pieroni
  • Michael Tobar
  • Mikel Sanchez Garitaonandia
  • Nancy Aggarwal
  • Pedro Schwaller
  • Piotr Gasik
  • Pyungwon Ko
  • Sebastian Ellis
  • Sebastien Clesse
  • Seong Chan Park
  • Sunghoon Jung
  • Tao Liu
  • Valerie Domcke
  • Vipin Kumar Sharma
  • William Campbell
  • Xavier Rojas
  • Xue Xiao
  • Yutong He
  • +36
TH workshop secretariat
    • 9:30 AM 9:45 AM
      Introduction 4/3-006 - TH Conference Room

      4/3-006 - TH Conference Room

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      Convener: Valerie Domcke (CERN)
    • 9:45 AM 10:40 AM
      EM-GW detectors 4/3-006 - TH Conference Room

      4/3-006 - TH Conference Room

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      Convener: Andreas Ringwald
      • 9:45 AM
        SRF cavities 25m
        Speaker: Sebastian Ellis (Universite de Geneve (CH))
      • 10:15 AM
        The MAGO cavity and prospects for HFGW searches 25m

        The former MAGO collaboration, led by INFN Genoa, developed in the past SRF cavities in order to perform R&D with the aim to search for gravitational waves. In a collaborative effort, DESY/U.Hamburg and Fermilab continues this R&D programme. Since July the MAGO cavity is at DESY for measurements and matching simulations to characterise the cavity before surface treatment and cold measurements at Fermilab. The aim is to use this cavity for a first GW search and to develop new cavities and the necessary dedicated cryostat and suspension system for improved GW measurements in the future.

        Speaker: Krisztian Peters (Deutsches Elektronen-Synchrotron (DE))
    • 10:40 AM 11:00 AM
      Q&A session 4/3-006 - TH Conference Room

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      Convener: Andreas Ringwald
    • 11:00 AM 11:30 AM
      Coffee break 30m 4/2-011 - TH common room

      4/2-011 - TH common room

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    • 11:30 AM 12:30 PM
      EM-GW detectors 4/3-006 - TH Conference Room

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      Convener: Andrew Geraci
    • 12:30 PM 1:00 PM
      Q&A session 4/3-006 - TH Conference Room

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      Convener: Andrew Geraci
    • 1:00 PM 2:30 PM
      Lunch 1h 30m
    • 2:30 PM 4:00 PM
      Review and update of the white paper 4/3-006 - TH Conference Room

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      Convener: Dr Francesco Muia (University of Cambridge)
    • 4:00 PM 4:30 PM
      Coffee break 30m 4/2-011 - TH common room

      4/2-011 - TH common room

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    • 4:30 PM 5:30 PM
      Discussion/collaboration session 4/3-006 - TH Conference Room

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    • 6:00 PM 7:30 PM
      Social activities: Welcome drink 61/1-201 - Pas perdus - Not a meeting room -

      61/1-201 - Pas perdus - Not a meeting room -

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    • 9:30 AM 10:00 AM
      Mechanical resonators 4/3-006 - TH Conference Room

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      Convener: Dr Sunghoon Jung (Korea Institute for Advanced Study (KIAS))
    • 10:00 AM 10:30 AM
      Theory 4/3-006 - TH Conference Room

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      Convener: Dr Sunghoon Jung (Korea Institute for Advanced Study (KIAS))
    • 10:30 AM 11:00 AM
      Q&A session 4/3-006 - TH Conference Room

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      Convener: Dr Sunghoon Jung (Korea Institute for Advanced Study (KIAS))
    • 11:00 AM 11:30 AM
      Coffee break 30m 4/2-011 - TH common room

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    • 11:30 AM 12:30 PM
      Mechanical resonators 4/3-006 - TH Conference Room

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      Convener: Michael Tobar (The University of Western Australia)
      • 11:30 AM
        Bulk Acoustic Wave devices 25m
        Speaker: Tommaso Tabarelli de Fatis (Universita & INFN, Milano-Bicocca (IT))
      • 12:00 PM
        Partially-levitated membranes for high-frequency gravitational wave (HFGW) detection 12m

        Patterned thin films that are freely suspended from a silicon chip (i.e., membranes) are some of the lowest-loss mechanical oscillators.

        As such, they provide an exceptional level of isolation from the noisy environment, similar to what has been achieved with levitated nanoparticles.

        Here, I will present a concept for a HFGW detector, which corresponds to a Michelson interferometer with a membrane incorporated in each arm cavity.

        In addition to explaining the underlying operating principle, I will provide details on achieving a sensitivity comparable to the target for the Levitated Sensor Detector, which relies on optically levitated stacks instead of membranes. (see dedicated talks).

        In this regard, a particular focus will be on realizing suitable membranes, which requires significantly reducing their intrinsic loss.

        Speaker: Christoph Reinhardt (DESY)
      • 12:15 PM
        Sensing High Frequency Gravitational Waves with Acoustic Resonators: an update on the MAGE experiment 12m

        The Multimode Acoustic Gravitational wave Experiment (MAGE) is a high frequency gravitational wave detection experiment [1] that utilises quartz bulk acoustic wave resonators as precision strain sensors. In its first stage, the experiment features two near-identical quartz bulk acoustic wave resonators that act as strain antennas with spectral sensitivity as low as $6.6\times 10^{-21}\left[\textrm{strain}\right]/\sqrt{\textrm{Hz}}$ in multiple narrow bands across MHz frequencies. As a natural continuation of the initial pathfinding run [2] in which strong background features were observed at $\approx$ 5 MHz; MAGE features various hardware upgrades in order to disentangle such signals from target gravitational events. The primary goals of MAGE will be to explore potential gravitational signals sourced by physics beyond that of the standard model, as well as identifying the source of the events seen in its predecessor run. Here we present an update and the current status of the MAGE experiment.

        [1] https://arxiv.org/abs/2307.00715
        [2] https://arxiv.org/abs/2102.05859

        Speaker: William Campbell
    • 12:30 PM 1:00 PM
      Q&A session 4/3-006 - TH Conference Room

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      Convener: Michael Tobar (The University of Western Australia)
    • 1:00 PM 2:30 PM
      Lunch 1h 30m
    • 2:30 PM 3:15 PM
      Theory 4/3-006 - TH Conference Room

      4/3-006 - TH Conference Room

      CERN

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      Convener: Pedro Schwaller
      • 2:30 PM
        High-Frequency Gravitational Waves in Electromagnetic Waveguides 12m

        The interaction between a very-high-frequency gravitational wave (VHFGW) and an electromagnetic wave (EMW) in a rectangular waveguide is discussed in the weak field limit. The background EMW is assumed to be initially in the TE10 mode along the waveguide. It is then shown that a VHFGW, having the same frequency and direction of propagation of the EMW, induces through the waveguide a TE mode with a frequency doubled when compared to the original EMW frequency. In that respect, the GW acts similar to a non-linear medium, giving rise to a Second Harmonic Generation (SHG) effect.

        Speaker: Francesco Sorge
      • 2:45 PM
        Detecting single gravitons with quantum sensing 12m

        The quantization of gravity is widely believed to result in gravitons -- particles of discrete energy that form gravitational waves. But their detection has so far been considered impossible. Here we show that signatures of single gravitons can be observed in laboratory experiments 1. We show that stimulated and spontaneous single-graviton processes can become relevant for massive quantum acoustic resonators and that stimulated absorption can be resolved through continuous sensing of quantum jumps. We analyze the feasibility of observing the exchange of single energy quanta between matter and gravitational waves. Our results show that single graviton signatures are within reach of experiments. In analogy to the discovery of the photo-electric effect for photons, such signatures can provide the first experimental evidence of the quantization of gravity.

        Our work is outlined in
        G. Tobar, S. K. Manikandan, T. Beitel and I. Pikovski, arXiv:2308.15440
        Corresponding author: pikovski@stevens.edu

        Speaker: Germain Tobar
      • 3:00 PM
        Graviton detection and the quantization of gravity 12m

        A key dividing line in the dark matter community is between the wave and particle regimes. This division can be applied to any bosonic state, and for gravitational energy density the boundary cuts right through the ultra-high frequency regime. I will discuss the implications of this for instruments looking to detect a signal in the regime where gravity is a dilute gas of gravitons, and explain why contrary to what analogies with the photoelectric effect might suggest, a detection in that parameter space would not prove gravity was quantized.

        Speaker: Nicholas Llewellyn Rodd (CERN)
    • 3:15 PM 4:00 PM
      Q&A session 4/3-006 - TH Conference Room

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      Convener: Pedro Schwaller
    • 4:00 PM 4:30 PM
      Coffee break 30m 4/2-011 - TH common room

      4/2-011 - TH common room

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    • 4:30 PM 5:30 PM
      Discussion/collaboration session 4/3-006 - TH Conference Room

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    • 9:30 AM 10:30 AM
      EM-GW detectors 4/3-006 - TH Conference Room

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      Convener: Diego Blas (UAB/IFAE)
      • 9:30 AM
        Axion haloscopes 25m
        Speaker: Camilo Alfredo Garcia Cely (Technical University Munich)
      • 10:00 AM
        Searching for Axions and High-Frequency Gravitational Waves with ABRACADABRA-10cm 25m

        ABRACADABRA-10cm has had great success as a lumped-element axion dark matter pathfinder experiment. Now, using the electrodynamics of gravitational waves and a simple change of pickup structures, we are using the ABRACADABRA detector to search for high-frequency gravitational wave in the kHz to MHz range. These higher frequencies may indicate signs of in-spiraling primordial black holes, or other beyond the standard model phenomena. With careful calibration used to distinguish between the two signals, we introduce the first simultaneous search for both axions and gravitational waves. I will present on the design and first data from the ABRACADABRA-10cm high-frequency gravitational wave search.

        Speaker: Kaliroe Pappas (Massachusetts Institute of Technology, Laboratory For Nuclear Science)
    • 10:30 AM 11:00 AM
      Q&A session 4/3-006 - TH Conference Room

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      Convener: Diego Blas (UAB/IFAE)
    • 11:00 AM 11:30 AM
      Coffee break 30m 4/2-011 - TH common room

      4/2-011 - TH common room

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    • 11:30 AM 12:30 PM
      EM-GW detectors 4/3-006 - TH Conference Room

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      Convener: Matthias Schott (CERN / University of Mainz)
    • 12:30 PM 1:00 PM
      Q&A session 4/3-006 - TH Conference Room

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      Convener: Matthias Schott (CERN / University of Mainz)
    • 1:00 PM 2:00 PM
      Lunch 1h
    • 2:00 PM 3:00 PM
      Theory 4/3-006 - TH Conference Room

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      • 2:00 PM
        Primordial black holes: a dark matter candidate in the ultra-high frequency gravitational wave window 1h

        Primordial Black Holes might have originated in the early universe from the collapse of large overdensities and could constitute a sizeable portion of dark matter. Recently, they have gained considerable attention because of the various gravitational wave (GW) signatures associated with this scenario, making them testable with current and future GW experiments. In this talk, I will provide an overview of the current status of GW searches for this distinctive dark matter candidate, and discuss, in particular, the GW signatures that could be present in the ultra-high frequency window.

        Speaker: Gabriele Franciolini (CERN)
    • 3:00 PM 3:30 PM
      Coffee break 30m 4/2-011 - TH common room

      4/2-011 - TH common room

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    • 3:30 PM 4:15 PM
      EM-GW detectors 4/3-006 - TH Conference Room

      4/3-006 - TH Conference Room

      CERN

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      Convener: Asuka Ito
      • 3:30 PM
        Prospects for HFGW searches with the axion experiments ALPS II and BabyIAXO 25m

        At DESY in Hamburg, axions search experiments not relying on the dark matter paradigm are taking data (ALPS II) or have good prospects to start construction soon (BabyIAXO). Due to the similarity of axion-photon and GW-photon conversions in background magnetic fields, both experiments will also be sensitive to high frequency gravitational waves (HF-GW). The status of ALPS II and BabyIAXO as well as potential dedicated HF-GW searches will be sketched.

        Speaker: Axel Lindner
      • 4:00 PM
        Detection of high-frequency gravitational waves using high-energy pulsed lasers 12m

        We propose a new method for detecting high-frequency gravitational waves (GWs) using high-energy pulsed lasers. Through the inverse Gertsenshtein effect, the interaction between a GW and the laser beam results in the creation of an electromagnetic signal. The latter can be detected using single-photon counting techniques. We present the minimal strain of a detectable GW which only depends on the laser parameters. Interestingly, we find that a resonance occurs in this process when the frequency of the GW is twice the frequency of the laser. With this method, the ultra-high GW-frequency range 10^{13} - 10^{19} Hz is explored non-continuously for strains $h \gtrsim 10^{-20}$ for current laser systems and can be extended to $h \gtrsim 10^{-26}$ with future generation facilities.

        Speaker: Georgios Vacalis
    • 4:15 PM 4:45 PM
      Q&A session 4/3-006 - TH Conference Room

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      Convener: Asuka Ito (Tokyo institute of technology)
    • 4:45 PM 6:00 PM
      Discussion/collaboration session 4/3-006 - TH Conference Room

      4/3-006 - TH Conference Room

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    • 9:30 AM 10:00 AM
      Theory 4/3-006 - TH Conference Room

      4/3-006 - TH Conference Room

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    • 10:00 AM 11:00 AM
      Topical discussion: comparing sensitivities 4/3-006 - TH Conference Room

      4/3-006 - TH Conference Room

      CERN

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      Convener: Michael Tobar (The University of Western Australia)
    • 11:00 AM 11:30 AM
      Coffee break 30m 4/2-011 - TH common room

      4/2-011 - TH common room

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    • 11:30 AM 12:15 PM
      Theory 4/3-006 - TH Conference Room

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      Convener: Anish Ghoshal (University of Warsaw, Poland)
      • 11:30 AM
        Ultra-high frequency gravitational waves from inflaton decay 12m

        Since the models of inflation compatible with CMB data require non-renormalizable inflaton potentials, it is natural to have extra couplings between inflaton and gravitons. The suppression scale of such operators can well be lower than the Planck scale. Due to these couplings, inflaton can produce high frequency gravitons during reheating due to both decay and bremsstrahlung process. In my talk, I will present results of computation of the gravitational wave signal strength coming from these processes, as well as graviton contribution to the number of relativistic degrees of freedom. Remarkably, in the case of low reheating temperature, even Planck-suppressed operators lead to potentially measurable contribution to the dark radiation.

        Speaker: Anna Tokareva (Hangzhou Institute for Advanced Study & ICTP-AP Centre Beijing/Hangzhou)
      • 11:45 AM
        High Temperature Effects in the Cosmic Gravitational Microwave Background 12m

        The thermal plasma in the early universe produced a guaranteed stochastic gravitational wave (GW) background, which peaks today in the microwave regime and was dubbed the cosmic gravitational microwave background (CGMB). The CGMB spectrum encodes fundamental information about particle physics and gravity at ultra high energies. In particular, one can determine from the CGMB spectrum the maximum temperature of the universe and the effective degrees of freedom at the maximum temperature.
        In previous works only single graviton production processes that contribute to the CGMB have been considered. In this talk I show that graviton pair production processes can also yield a significant contribution to the CGMB spectrum if the ratio between the maximum temperature and the Planck mass, $T_{\rm max}/m_{\rm p}$, divided by the internal coupling in the heat bath is large enough.
        In addition I discuss how quantum gravity effects appear in single graviton production processes and are smaller by a factor $(T_{\rm max}/m_{\rm p})^2$ than the leading order contribution.

        Speaker: Jan Schuette Engel (UC Berkeley)
      • 12:00 PM
        Towards coordinate independent estimates for electro-magnetic GW detectors 12m

        There has recently been an increased interest in electro-magnetic GW detectors, due to the first detections of GWs and the rapid evolution of the technology driven by searches for light dark matter. The question how to calculate the response of e.g. a cavity to a GW has been debated since the 80s and the current understanding is that the usage of a special frame, the proper detector frame, is necessary to get the correct result. This idea is however somewhat disturbing, since coordinate invariance lies at the heart of general relativity, and criticism of this approach is therefore as old as the approach itself. We hope to clarify some of the issues leading to this apparent contradiction.

        Speaker: Wolfram Ratzinger (Weizmann Institute)
    • 12:15 PM 1:00 PM
      Q&A session 4/3-006 - TH Conference Room

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      Convener: Anish Ghoshal (University of Warsaw, Poland)
    • 1:00 PM 2:30 PM
      Lunch 1h 30m
    • 2:30 PM 3:00 PM
      Theory 4/3-006 - TH Conference Room

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    • 3:00 PM 3:15 PM
      Q&A session 4/3-006 - TH Conference Room

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    • 3:15 PM 4:00 PM
      Discussion/collaboration session
    • 3:15 PM 4:00 PM
      Topical discussion: comparing sensitivities 4/3-006 - TH Conference Room

      4/3-006 - TH Conference Room

      CERN

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      Convener: Valerie Domcke (CERN)
    • 4:00 PM 4:30 PM
      Coffee break 30m 4/2-011 - TH common room

      4/2-011 - TH common room

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    • 4:30 PM 5:30 PM
      Discussion/collaboration session 4/3-006 - TH Conference Room

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    • 7:00 PM 9:00 PM
      Social activities: Social dinner
    • 9:30 AM 10:15 AM
      Theory 4/3-006 - TH Conference Room

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      Convener: Geraldine Servant (Deutsches Elektronen-Synchrotron (DE))
      • 9:30 AM
        Gravitational waves from high-power twisted light 12m

        Recent advances in high-energy and high-peak-power laser systems have opened up new possibilities for fundamental physics research.
        I propose to discuss the potential of twisted light for the generation of gravitational waves in the high frequency regime.
        Focusing on Bessel beams, analytic expressions and numerical computations for the generated metric perturbations and associated powers are presented. Notably, we show that properties of the generated gravitational waves, such as frequency, polarisation states and direction of emission,
        can be controllable by the laser pulse parameters and optical arrangements.
        Based on: https://arxiv.org/pdf/2309.04191.pdf

        Speaker: Killian MARTINEAU (Laboratoire de Physique Subatomique et de Cosmologie)
      • 9:45 AM
        Bremsstrahlung High-frequency Gravitational Wave Signatures of High-scale Non-thermal Leptogenesis 12m

        Inflaton seeds non-thermal leptogenesis by pair producing right-handed neutrinos in the seesaw model. We show that the inevitable graviton bremsstrahlung associated with inflaton decay can be a unique probe of non-thermal leptogenesis. The emitted gravitons contribute to a high-frequency stochastic gravitational waves background with a characteristic fall-off below the peak frequency. Besides leading to a lower bound on the frequency (f≳1011 Hz), the seesaw-perturbativity condition makes the mechanism sensitive to the lightest neutrino mass. For an inflaton mass close to the Planck scale, the gravitational waves contribute to sizeable dark radiation, which is within the projected sensitivity limits of future experiments such as CMB-S4 and CMB-HD.

        Speaker: Anish Ghoshal
      • 10:00 AM
        Detection of ultra high frequency gravitational waves from compact binary coalescenses with resonant cavities 12m

        In this talk I will try to clarify the situation about astrophysical sources that might be observed with haloscope experiments like GrAHal, sensitive to gravitational waves in the 1-10 GHz band. The GrAHal setup is taken as a benchmark. We follow a very pedagogical path so that the full analysis can easily be used by the entire community who might not be familiar with the theoretical framework. Different relevant physical regimes are considered in details and some formulas encountered in the literature are revised. The distances that can be probed and expected event rates are carefully evaluated, taking into account degeneracies between physical parameters. We show where experimental efforts should be focused to improve the sensitivity.

        Speaker: Prof. Juan Garcia-Bellido (IFT-UAM/CSIC)
    • 10:15 AM 11:00 AM
      Q&A session 4/3-006 - TH Conference Room

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      Convener: Geraldine Servant (Deutsches Elektronen-Synchrotron (DE))
      • 10:15 AM
        Q&A 45m
        Speaker: Valerie Domcke (CERN)
    • 11:00 AM 11:30 AM
      Coffee break 30m 4/2-011 - TH common room

      4/2-011 - TH common room

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    • 11:30 AM 12:00 PM
      Theory 4/3-006 - TH Conference Room

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      Convener: Giancarlo Cella (INFN - National Institute for Nuclear Physics)
    • 12:00 PM 1:00 PM
      Topical discussion: landscape and characteristics of sources 4/3-006 - TH Conference Room

      4/3-006 - TH Conference Room

      CERN

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      Convener: Andreas Ringwald
    • 1:00 PM 2:30 PM
      Lunch 1h 30m
    • 2:30 PM 4:00 PM
    • 4:00 PM 4:30 PM
      Coffee break 30m 4/2-011 - TH common room

      4/2-011 - TH common room

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