Dr Francesco Muia | Unlocking the Universe’s Secrets with Ultra-high-frequency Gravitational Waves
About this episode
In the early 1900s, Einstein revolutionized our understanding of space and time, revealing them as interconnected aspects of the universe’s fabric – known as ‘spacetime’. Spacetime isn’t a rigid background. Like a ball on a trampoline, heavy objects like the Sun warp spacetime around them, drawing the planets into orbits. When heavy objects move extremely fast – such as when two black holes orbit each other and merge or in highly energetic events like those occurring in the early universe – the warping becomes extreme, generating waves that spread through spacetime. These ‘gravitational waves’, first discovered in 2015, offer scientists new tools to explore the universe. Read More
Dr Francesco Muia, at the Centre for Theoretical Cosmology at the University of Cambridge, is exploring new ways of using these tools to solve some long-standing mysteries in physics.
Just like light, gravitational waves can have different frequencies. In a 2020 report, Dr Muia and collaborators discussed ultra-high-frequency gravitational waves, whose frequency is above the range experimentally explored thus far.
Experimentally established theories don’t predict astrophysical events that would create gravitational waves of this frequency. As such, ultra-high-frequency detectors could offer scientists an opportunity to explore physics beyond our current understanding.
Dr Muia and collaborators have established a specific program, The Ultra-High-Frequency Gravitational Waves Initiative, to promote the development of this research direction.
To support this idea, Dr Muia and his colleagues recently focused on ‘dark matter’, the mysterious and invisible substance that makes up most of the mass in the universe. Some theories suggest that dark matter exists as primordial black holes: small black holes that may have formed in the first second after the Big Bang.
These would be much lighter than the black holes considered so far, perhaps between the mass of an asteroid and the Sun. The merger of these light black holes would produce ultra-high-frequency gravitational waves. Therefore, if we built detectors capable of discovering such a signal, we could get strong evidence that primordial black holes exist, potentially solving the mystery of dark matter.
Additionally, using an open-source code developed at various UK institutions called GRChombo, Dr Muia and collaborators recently explored theories that describe the very first moments of the universe’s history.
Physicists believe that the early universe underwent a period of extreme, accelerated expansion called ‘inflation’. However, we do not fully understand how inflation is connected with later periods that are tested experimentally.
Some potential explanations predict the existence of very dense, star-like objects called ‘oscillons’, whose dynamics would produce a constant background buzz of ultra-high-frequency gravitational waves, providing another tantalizing target for detectors operating in this frequency range.
A century after Einstein’s revolution, the new tools and ideas promoted by Dr Muia and collaborators could guide us to the next paradigm shift in physics.
Original Article Reference
Summary of the papers: ‘Challenges and opportunities of gravitational-wave searches at MHz to GHz frequencies’, doi.org/10.48550/arXiv.2011.12414; ‘Hunt for light primordial black hole dark matter with ultrahigh-frequency gravitational waves’, doi.org/10.48550/arXiv.2205.02153 and ‘Oscillon formation during inflationary preheating with general relativity’, doi.org/10.48550/arXiv.2304.01673
For further information, you can connect with Dr Francesco Muia at firstname.lastname@example.org
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