**Join the UHF-GW google group and stay up to date on the next steps of the initiative!**

### Goals of the initiative

The first direct detection of gravitational waves by the LIGO and VIRGO collaborations has spawned new avenues for the exploration of the Universe. Currently operating and planned gravitational wave detectors mostly focus on the frequency range below 10 kHz, where signatures from the known astrophysical sources are expected to be discovered. However, based on what happens with the electromagnetic spectrum, there may well be interesting physics to be discovered at every scale of the gravitational wave frequencies. Gravitational waves at frequencies higher than 10 kHz are bound to be sourced by some phenomenon involving beyond the Standard Model physics, such as exotic astrophysical objects or cosmological events in the early Universe. In particular, several cosmological sources - for instance preheating after inflation and phase transitions at high energies - would leave their imprint in the gravitational wave spectrum at frequencies around the GHz. Hence, the search for gravitational waves at frequencies above the LIGO/VIRGO range is a promising and challenging search for new physics, providing an opportunity to test many theories beyond the Standard Model, that could not be tested otherwise.

The UHF-GW (Ultra-High-Frequency Gravitational Wave) initiative promotes the creation of a network of researchers for the development of gravitational wave science in the frequency range above 10 kHz. We strongly believe that a fruitful collaboration between experimentalists and theorists is necessary to make progress in this quest and we facilitate it by organising meetings and workshops aimed at putting in contact these two worlds. One of the goals of the initiative is to support the testing phase of currently existing detector proposals and stimulate the technological developments necessary to come up with new schemes for gravitational wave detectors at frequencies above 10 kHz.

**Code of Governance of the UHF-GW community**

### Ultra-High-Frequency Gravitational Waves: A Theory and Technology Roadmap Workshop

CERN, 12-15 October 2021

The main theme of the second workshop on ultra-high-frequency gravitational waves has been the technology development that is required in the ultra-high-frequency band. In particular, we have discussed:

1. new detector concepts;

2. feasibility studies and construction of prototypes for proposed detector concepts;

3. coordinating an international effort to support collaborations working on UHF-GW detectors;

4. the science case for UHF-GW searches.

All the slides and recordings of the talks and discussion sessions can be found at this link.

Recordings are also available on our Youtube channel.

The workshop has given rise to various working groups that will develop their projects during the next months. The topics chosen so far include:

- The analysis of resonant electromagnetic gravitational wave detectors.

- The analysis of solid-state detectors.

- The analysis of Bose-Einstein condensate detectors.

- The analysis of the suitability of axion searches technology for gravitational wave detection.

- The optimisation of optically levitated sensors.

- Various theoretical developments of the subject.

If you are interested in any of these topics and would like to join a working group, please contact the organisers of the workshop.

### Members of the initiative:

**Nancy Aggarwal**

Affiliation: Center for Fundamental Physics; Centre for Interdisciplinary Exploration and Research in Astrophysics (CIERA); Department of Physics and Astronomy, Northwestern University.

Contact: nancy[dot]aggarwal[at]northwestern[dot]edu**Mike Cruise**

Affiliation: University of Birmingham.

Contact: cruiseam1[at]gmail[dot]com**Valerie Domcke**

Affiliation: CERN; Laboratory for Particle Physics and Cosmology, EPFL, Lausanne.

Contact: valerie[dot]domcke[at]cern[dot]ch**Francesco Muia**

Affiliation: The Stephen Hawking Centre for Theoretical Cosmology; DAMTP, University of Cambridge.

Contact: fm538[at]cam[dot]ac[dot]uk**Fernando Quevedo**

Affiliation: The Stephen Hawking Centre for Theoretical Cosmology; DAMTP, University of Cambridge.

Contact: fq201[at]damtp[dot]cam[dot]ac[dot]uk**Andreas Ringwald**

Affiliation: Deutsches Elektronen-Synchrotron DESY, Hamburg.

Contact: andreas[dot]ringwald[at]desy[dot]de**Jessica Steinlechner**

Affiliation: Maastricht University; Nikhef, Amsterdam; SUPA, School of Physics and Astronomy, University of Glasgow.

Contact: jessica[dot]steinlechner[at]maastrichtuniversity[dot]nl**Sebastian Steinlechner**

Affiliation: Maastricht University; Nikhef, Amsterdam.

Contact: s[dot]steinlechner[at]maastrichtuniversity[dot]nl

### Challenges and Opportunities of High Frequency Gravitational Wave Detection

Details of our October 2019 workshop in Trieste can be found here:

http://indico.ictp.it/event/9006/

The workshop was summarised in the following paper:

https://arxiv.org/abs/2011.12414

Prof. Odylio D. Aguiar, Instituto Nacional de Pesquisas Espaciais (INPE), Sao Paulo, Brazil

The Schenberg Gravitational Wave Antenna: a resonant mass spherical antenna

Slides

Video

Prof. Andreas Bauswein, GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany

Neutron star mergers and kHz gravitational wave emission

Slides

Video

Prof. Mike Cruise, School of Physics and Astronomy, University of Birmingham, Birmingham, UK

Strategies for GW science above 1GHz

Slides

Video

Prof. Daniel G. Figueroa, Instituto de Fisica Corpuscular (IFIC), University of Valencia, Valencia, Spain

Introduction to cosmological sources of high frequency gravitational waves

Slides

Video

Prof. Andrew Geraci, Center for Fundamental Physics, Department of Physics and Astronomy, Northwestern University, Evanston, USA

Detecting high-frequency gravitational waves with optically levitated sensors

Slides

Video

Dr. Maxim Goryachev, ARC Centre of Excellence for Engineered Quantum Systems, Department of Physics, University of Western Australia, Crawley, Australia

High Frequency Gravitational Wave Detection with Bulk Acoustic Devices: From Technology to First Data

Slides

Video

Prof. Hartmut Grote, Cardiff University, Cardiff, UK

Experimental upper limits on (ultra) high frequency gravitational waves and prospects for more: Magnetic conversion detection and correlated interferometry

Slides

Video

Prof. Mark Hindmarsh, Department of Physics and Helsinki Institute of Physics, Helsinki, Finland; Department of Physics and Astronomy, University of Sussex, Brighton, UK

Gravitational Waves from Phase Transitions

Slides

Video

Prof. David Ottaway, Department of Physics, School of Physical Sciences and The Institute of Photonics and Advanced Sensing (IPAS), University of Adelaide, Adelaide, Australia; Australian Research Council Centre of Excellence for Gravitational Wave Discovery (OzGrav)

OzGrav HF: A detector for studying nuclear matter at extreme pressure, temperature and density

Slides

Video

Prof. Marco Peloso, Dipartimento di Fisica e Astronomia Galileo Galilei, Università di Padova, Padova, Italy; INFN, Sezione di Padova, Italy

Gravitational Waves from Inflation and Primordial Black Holes

Slides

Video

Dr. Francisco Torrenti, Department of Physics, University of Basel, Basel, Switzerland

Gravitational waves from preheating: parameter dependence

Slides

Video

Dr. Toby Opferkuch, CERN, Geneva, Switzerland

Gravitational Imprints of Flavour Hierarchies

Slides

Video

Prof. Seyed M. S. Movahed, Department of Physics, Shahid Beheshti University, Tehran, Iran

A pipeline for searching Stochastic Gravitational Wave by Pulsar Timing Residuals

Slides

Video

Discussion: How to move forward?

Slides

Video