I’m extremely happy to see my latest paper with my oustanding former MSc student Giovanni Piccoli and Joe Silk out on arXiv - congratulations to Giovanni who did basically all the work, in what is essentially the result of his MSc thesis! This paper is based on the idea of acoustic reheating, i.e. the dissipation of small-scale perturbations through diffusion damping (a process which at recombination is known as Silk damping), which injects entropy into the photon bath. For certain modes, the dissipation occurs after neutrino decoupling, meaning that this entropy is not shared by the neutrinos, which are therefore colder than expected: we showed that these modifications can potentially show up in experiments aimed at detecting relic neutrinos such as PTOLEMY, which can therefore set constraints on the small-scale power spectrum. This idea has been in the back of my mind ever since I moved to Cambridge as a postdoc 2019 (in fact you can find it “discussed” on my Cambridge whiteboard in this picture appearing in my webpage), and for various reasons took much longer than it should have to appear, so I am extremely happy that it is finally out: plus, it doesn’t happen every day to write a paper on Silk damping with Joe Silk himself! You can read the results in the preprint we just posted on arXiv: 2605.11956.
Giovanni Piccoli's MSc defense
Congratulations to Giovanni Piccoli, who today successfully defended his MSc thesis, by the title of “The very small-scale primordial Universe: complementary tests from Cosmic Neutrinos and Gravitational Waves” (with the opponent being Prof. Alessandro Roggero)! Giovanni’s defense was simply outstanding, and he received top grades and honours, i.e. 110 e Lode. In his thesis which I supervised, Giovanni developed complementary tests of the small-scale power spectrum of primordial fluctuations using the stochastic gravitational wave background measured by pulsar timing arrays, and forecasting the reach in this sense of a potential future measurement of the cosmic neutrino background (CNB) from laboratory experiments. What does the CNB have to do with the small-scale power spectrum? We’re writing up a paper based on Giovanni’s results, and I can guarantee it will be extremely exciting, so no spoilers!
Giovanni Piccoli joins my group!
My group is expanding, and as of today includes also Giovanni Piccoli. He will be working on his Master’s thesis under my supervision, and we plan to explore novel cosmological and terrestrial tests of the (very) small-scale matter power spectrum - no spoilers, you’ll have to wait and see what we come up with! Welcome Giovanni, and looking forward to our work together!