News from FZU

The all-sky diffuse astrophysical neutrino spectrum is measured by IceCube with increasing statistical significance, since more than 10 years. In addition, recent observational findings manifest some connections with astrophysical sources, and for the first time a non-electromagnetic image of our galaxy has been delivered by IceCube. In this seminar I will present the most recent experimental results on high-energy neutrinos, and I will deeply discuss the connections with other astrophysical messengers. In particular, I will show how the study of interactions of cosmic rays, in the extragalactic propagation and in the candidate sources, might help in unveiling the origin of high-energy neutrinos and ultra-high-energy cosmic rays. Prospects from future experimental upgrades will be also highlighted, as well as the importance of a multimessenger approach in the modelling of astrophysical sources.

The seeds of the Universe’s large scale structure are widely thought to have been generated during a period of cosmic inflation. Simple, generic models of inflation lead to a smooth, almost scale-invariant spectrum of primordial curvature perturbations. However, this prediction relies on a set of physical assumptions, which, if broken, could lead to a power spectrum with strong scale dependence in the form of, e.g., cutoffs spikes or modulations – commonly referred to as inflationary “features”. The search for features is complicated by increased numerical precision requirements and typically non-trivial shapes of the likelihood function – taking conventional random sampling-based analysis methods to their limits. I will introduce a new, efficient machine-learning approach based on Gaussian Process Regression and Bayesian Optimisation. Applying it to search for inflationary features in Planck data, I will demonstrate its effectiveness and discuss further applications, such as the calculation of Bayesian evidences for model selection.

   

At the beginning of his New Year's speech, Director Michael Prouza thanked the employees at all three facilities for coping with the difficult situation in 2023, when owing to their joint efforts FZU managed to overcome all the difficulties.