Ralf Schutzhold (Dresden University of Technology)
Ultra-cold atoms as quantum simulators for relativistic phenomena
Friday, September 29th, 2025, 11:30am
Abstract. This talk will review developments regarding the use of ultra-cold atoms as quantum simulators, where special emphasis is placed on relativistic quantum phenomena. First, relativistic quantum phenomena of linear fields are discussed, including Hawking radiation as well as Sauter-Schwinger and Breit-Wheeler pair creation. After that, the focus is shifted to phenomena of non-linear fields, such as the Kibble-Zurek mechanism and false-vacuum decay.
Paola Popesso (ESO, Garching)
A CLEVeR view on “halo baryonification”: from galaxy groups to massive clusters
Friday, September 12th, 2025, 11:30am
Abstract. Understanding the baryonification of haloes — the redistribution of baryons between galaxies, hot gas, and diffuse stellar components — is a fundamental step in modern astrophysics. While dark matter defines the gravitational potential of haloes, it is the baryons that govern observable processes such as star formation, quenching, AGN feedback, and chemical enrichment. Yet, there is substantial uncertainty in both the measured and predicted fractions of baryons in different phases, particularly at the group mass scale, where feedback processes are most efficient and diffuse components are hardest to detect. In this context, I present new results from the CLEVeR project (Cluster and groups Environment as viewed by eROSITA), based on the exploitation of eROSITA X-ray data combined with deep optical spectroscopic surveys. Using a robust stacking technique, validated against simulated data, we trace the distribution of hot gas, stellar mass, and dark matter across haloes spanning from Milky Way-sized groups to the most massive galaxy clusters. Our analysis delivers the most stringent observational constraints to date on key scaling relations — including X-ray luminosity, gas temperature, and central galaxy stellar mass versus halo mass — and enables direct measurements of hot gas and total baryon fractions over three decades in halo mass. These results challenge prevailing models of CGM–ICM thermodynamics and AGN feedback, highlighting the need to account not only for the energy budget of feedback processes, but also for their timing, spatial distribution, and halo mass dependence. The CLEVeR project provides a critical empirical benchmark to test and refine theoretical models of galaxy formation and the co-evolution of baryons and large-scale structure.
Alberto Nicolis (Columbia University)
Spontaneously broken spacetime symmetries and a quantum bound on transparency
Friday, June 11th, 2025, 11:30am – Aula D (old SISSA building) & streaming
Abstract. I will show how the low-energy dynamics of different phases of matter—different “materials”—can be conveniently described within the framework of relativistic quantum field theory, in particular in terms of spontaneous symmetry breaking, Goldstone excitations, and effective field theory. As an application of the formalism, I will show how to derive an absolute bound on how transparent a material can be.
Masashi Hazumi (IPNS & KEK)
Seeking the New World of Spin Zero – Fundamental mysteries of nature and cosmic microwave background (CMB) polarization
Friday, June 6th, 2025, 11:30am – Aula D (old SISSA building) & streaming
Abstract. Particle cosmology is a discipline seeking a fundamental understanding of the Universe based on particle physics. Five mysteries drive our research today: cosmic inflation, baryon asymmetry, neutrino properties, dark matter, and dark energy. Resolving any of the five mysteries will revolutionize our picture of the Universe. Numerous interesting theoretical hypotheses have been proposed to this end. Many require new scalar particles, such as inflatons, axions, supersymmetric particles, etc. They are essentially an attempt to expand the role of the vacuum. Since we have not yet found such spin-zero particles, we shall invent new eyes to make an experimental or observational breakthrough. To this end, the observation of CMB polarization is one of the keys today. In this seminar, I focus on research topics to which I have contributed, including observations of CMB polarization for studying inflatons and searches for light axion-like particles.
Gianfranco Bertone (University of Amsterdam)
Gravitational wave probes of dark matter
Friday, May 30th, 2025, 11:30am – Aula D (old SISSA building) & streaming
Abstract. After a brief introduction on the status of dark matter searches, I will discuss the prospects for discovering and identifying dark matter using gravitational waves. I will focus in particular on the environmental effects induced by different types of dark matter overdensity on the dynamical evolution of black hole binaries, and argue that future interferometers may enable precision studies of the dark matter distribution and particle properties.
Contact: Piero Ullio
Video
Diego Redigolo (INFN Florence)
The Dark Sector and the Large Scale Structure of the Universe
Friday, May 9th, 2025, 11:30am – Stasi lecture room (ICTP Leonardo building) & streaming
Abstract. The universe we observe today was shaped by mysterious ingredients—dark matter, dark energy, and inflation. These may all arise from particles and forces that are neutral under the Standard Model, interacting only through gravity. In this picture, dark matter leaves no trace through conventional means, but its gravitational pull still influences the Cosmic Microwave Background and drives the formation of galaxies and large-scale structures. In this talk, I will show how the cosmic distribution of galaxies can be used to uncover the nature of dark matter, independently of any interaction with the Standard Model. I will outline the types of signatures we can search for in the large-scale structure of the universe and what they can reveal about the underlying physics of the dark sector. I will also argue that developing precise theoretical predictions is essential to disentangle fundamental signals from astrophysical effects. With upcoming surveys like DESI and EUCLID set to deliver data of unprecedented precision, this theoretical effort is more urgent than ever.
Contact: Piero Ullio
Eugene Lim (King’s College, London)
Can Inflation actually Inflate?
Friday, April 11th, 2025, 11:30am – Aula D (old SISSA building) & streaming
Abstract. Inflation is the paradigmatic theory of initial conditions. It claims to drive the universe from generic initial conditions to the universe we see today which is homogeneous, isotropic and spatially flat. But can it actually begin from “generic” initial conditions? We put this idea to the test with numerical relativity.
Contact: Amelia Drew
Video
Franco Vazza (University of Bologna)
New clues on the origin of cosmic magnetism from large-scale structures: a smooking gun from primordial magnetic fields?
Friday, February 14th, 2025, 11:30am – Stasi lecture room (ICTP, Leonardo building) & streaming
Abstract. The rarefied medium in between galaxies and clusters of galaxies is permeated by magnetic fields. These fields are robustly observed but their ultimate origin is debated since a few decades. Are they be the result of galaxy evolution or of cosmic batteries? Or were these magnetic fields put in place by high energy processes in the primordial Universe? The new extragalactic radio surveys with precursors and pathfinders of the Square Kilometre Array have already started giving us an unprecedented tool to study the origin of cosmic magnetism. I will show that their recent results, combined with new realistic simulations of the cosmic web and higher energy probes in the gamma-ray window, are collectively hinting to a primordial origin of cosmic magnetism, with exciting implications for cosmology, galaxy formation and cosmic rays physics.
Contact: Piero Ullio
Video
Astrid Eichhorn (Heidelberg University)
Probing Quantum Gravity at all Scales
Friday, November 15th, 2024, 11:30am – Aula D (old SISSA building) & streaming
Abstract. To make progress in our understanding of the quantum structure of spacetime, we need observational tests of proposed theories of quantum gravity. However, this is challenging, because the Planck scale is many orders of magnitude removed from scales that we can probe directly with observations. Thus, we require lever arms that translate Planck-scale predictions into predictions at observationally accessible scales. In my talk, I will use asymptotically safe quantum gravity as a case study. I will show, how the interplay of quantum gravity with matter (both visible and “dark”) shapes the properties of matter fields in and beyond the Standard Model at the Planck scale. I will then show how to translate these Planck-scale predictions into predictions of Standard-Model properties as well as predictions about the properties of the dark matter and the dark energy.
Contact: Piero Ullio
Video
Mark Hindmarsh (University of Helsinki & University of Sussex)
Gravitational waves from early universe phase transitions
Friday, October 11th, 2024, 11:30am – Aula D (old SISSA building) & streaming
Abstract. A few picoseconds after the beginning of the Universe, the Higgs field turned on. In extensions of the Standard Model of particle physics, this could have been a first order phase transition, with the spontaneously nucleated bubbles of the Higgs phase expanding and colliding at relativistic speeds. The resulting sound waves would have been a powerful source of gravitational radiation. I will survey ongoing work to characterise the spectrum of gravitational radiation from early universe phase transitions, prospects for observing the radiation at the future space-based gravitational wave detector LISA, and outline how LISA can complement the LHC as a probe of phase transitions and physics beyond the Standard Model.
Contact: Enrico Morgante
Video
Stefano Profumo (University of California, Santa Cruz, and Santa Cruz Institute for Particle Physics)
The Primordial Black Holes Variations
Friday, October 4th, 2024, 11:30am – Stasi lecture room (ICTP) & streaming
Abstract. In the era of gravitational wave astronomy and direct black hole imaging, the possibility that some of the black holes in the universe have a primordial, rather than stellar, origin, and that they might be a non-negligible fraction of the cosmological dark matter, is both timely and intriguing. I will review the status of the field, describe search strategies and future prospects for detection across many decades in black hole mass, discuss how light primordial black holes could seed both baryonic and particle dark matter in the very early universe, and comment on how the search for primordial black holes may lead to a deeper understanding of the elusive Galactic “rogue planets”.
Contact: Piero Ullio
Video
Kazuya Koyama (University of Portsmouth)
Observational probes of dark energy and modified gravity models
Friday, September 13th, 2024, 11:30am – Aula D (old SISSA building) & streaming
Abstract. The discovery of the accelerated expansion of the Universe has come relatively late in our study of the cosmos, but in showing that gravity can act repulsively, it has opened up many new questions about the nature of gravity and what the Universe might contain. Is the acceleration being driven by dark energy? Or is general relativity itself in error, requiring a modification at large scales to account for the late acceleration? Structure formation in our Universe can be different even if the geometry of the homogeneous and isotropic universe is the same in these two classes of models, offering a possibility to distinguish between them observationally. I will discuss cosmological tests of dark energy and modified gravity models using latest cosmological observations.
Contact: Emilio Bellini
Video
Erminia Calabrese (Cardiff University)
Cosmology in the era of Cosmic Microwave Background Polarization
Friday, September 6th, 2024, 11:30am – Aula D (old SISSA building) & streaming
Abstract. We discuss the opportunities for cosmology in light of the start of the Stage III+ CMB observations, targeting primordial gravitational waves and lensing. We highlight the near and far future objectives, describing the opportunities for combining CMB probes, in this and the next decade, with Large Scale Structure surveys.
Contact: Carlo Baccigalupi
Video – Slides