10th Trilateral meeting

Tuesday 9 Dec 2025, 10:00 → 15:30 Europe/Rome

Room 128 (SISSA, Trieste)

The trilateral meetings are a series of one day events designed to strengthen the scientific relations in particle, astroparticle physics and cosmology between Trieste, Nova Gorica and Ljubljana.

Venue

The event will take place in room 128 at SISSA, Trieste.

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Speakers

• Hyungjin Kim (DESY)
• Enrico Morgante (University of Trieste)
• Davide Racco (ETH Zürich)

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Organizing committee:

• Aleksandr Azatov (SISSA)
• Patrick Bolton (IJS)
• Takeshi Kobayashi (SISSA)
• Nejc Košnik (IJS)
• Jonathan Kriewald (IJS)
• David Marzocca (INFN)
• Miha Nemevšek (IJS)
• Toby Opferkuch (SISSA)
• Nicklas Ramberg (SISSA)
• Patrick Stengel (IJS)
• Lorenzo Ubaldi (IJS)
• Gabrijela Zaharijas (UNG)

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Past meetings

• Ljubljana Meeting, 14 May, 2025, at IJS
• Nova Gorica Meeting, 1 March, 2024, at Vipava
• Trieste Meeting, 15 December, 2023 at IFPU
• Ljubljana Meeting, 20 December, 2022 at IJS
• Trieste Meeting, 23 June 2022, at IFPU
• Nova Gorica meeting, 15 September 2021 at Vipava
• Ljubljana meeting, 16 December 2021 at IJS
• Trieste meeting, 5 February 2020, at IFPU
• Ljubljana meeting, 17 October 2019, at IJS

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We acknowledge financial support by SISSA APG and TPP groups.

10:00 → 11:00 Ultralight Dark Matter: New Opportunities from Stochastic Fluctuations

I will discuss a few types of fluctuations that occur in models of ultralight dark matter. In particular, I will show that, when detector / observational observables are quadratically proportional to the underlying dark matter field, stochastic fluctuations naturally arise. I will also discuss how this stochastic fluctuation allows us to probe a wider mass range of ultralight dark matter with a given detector and observational setup. I will demonstrate this with a few examples, mostly focusing on gravity wave detectors and quantum sensors.

Speaker: Hyungjin Kim (DESY)

11:00 → 11:30 Coffee Break

11:30 → 12:30 Post-inflationary kinetic misalignment

Kinetic misalignment is a way to delay the onset of oscillations with respect to the standard axion misalignment scenario. The axion has an initially large velocity that allows it to wind many times before being trapped and start behaving as cold DM. In this talk, I will give a short overview of this scenario, and discuss a possible realization in which the initial velocity is obtained at the end of inflation, similarly to the usual post-inflationary axion case.

Speaker: Enrico Morgante (Università di Trieste & INFN)

12:30 → 14:00 Lunch break

14:00 → 15:00 Revisiting the isocurvature bound for the QCD axion as dark matter

The QCD axion is a well-motivated candidate for dark matter. For one of the two cosmological histories for this candidate, the pre-inflationary scenario, the PQ symmetry is not restored after inflation and the abundance depends on the initial value of the axion field. Depending on the inflationary Hubble rate, this scenario can be constrained by the strong limits on its (isocurvature) perturbations on large scales.
I will discuss how this constraint is naturally evaded when the quartic coupling of the complex U(1)_PQ field is small and its vev is enhanced during inflation, and how this solution is not jeopardised by parametric resonance over a significant portion of parameter space.
The common lore, that isocurvature is a potential downside of the pre-inflationary axion, might be less stringent than what is commonly thought.

Speaker: Davide Racco (U. Zurich and ETH Zurich)