Tom Abel (KIPAC, Stanford University)
Dark Matter Dynamics
Friday, July 1st, 2022, 11am – Aula D (old SISSA building) & streaming
Abstract We have a standard paradigm that quantitatively succeeds to describe the origin, formation and evolution of structure in the Universe. Dark matter is needed in this model to describe details of the Cosmic Microwave Background radiation, the appearance of high-redshift galaxies as well as many details of the clustering of galaxies. This broadly seems to works for the abundance of massive galaxy clusters, the prevalence of sheets, filaments and voids and the existence of ultra-faint dwarf galaxies. For Dark Matter made of an unknown particle that only interacts via gravity we have made predictions about how structure forms in the Universe using N-body techniques originally developed for plasma physics. These numerical investigations have led to many insights and enabled quantitative comparisons of the real and these simulated Universes. In this talk I describe and show visualizations from recently developed complimentary numerical methods that can describe the dark matter collisionless fluid in the continuum limit. These techniques follow three dimensional manifolds (“sheets”) as they evolve through the six dimensional phase space. The full geometry of the sheets is followed and consequently the noise of traditional N-body methods can be avoided completely. The caustics and detailed phase space structures inherent to the Hamiltonian dynamics of the particles are fully captured. These techniques also explain the origin of the shortcomings of traditional N-body such as artificial fragmentation evident in Warm Dark Matter models. These new approaches now also find application in modeling massive neutrinos in cosmology as well as applications in Laboratory Plasma Physics. The correspondence of the phase space sheet techniques allow for high precision comparisons of simulations and analytical calculations promising an avenue to improve the analytic techniques and supersede standard perturbative approaches.
Luigi Guzzo (Università di Milano)
Here comes the flood: cosmology with galaxy surveys in the Euclid era
Friday, May 27th, 2022, 11am – Aula D (old SISSA building) & streaming
Abstract A new generation of galaxy surveys to map the Universe has started, pushed by the need to uncover the nature of dark matter and dark energy, the mysterious ingredients dominating the highly successful standard model of cosmology. Among these, the ESA Euclid mission stands out as the most comprehensive endeavour, tackling the intertwined nature of gravity and the dark sector through percent precision measurements of cosmic expansion and structure growth. In my talk I will review the current state of affairs approaching Euclid’s launch, currently planned for 2023. Achieving the mission ambitious goals will require the ability to process complex data on one side, while efficiently and intelligently extracting information from large multi-dimensional data sets. I will present some instructive examples on how we are preparing for this. I will also mention how Machine Learning techniques have the potential to produce a paradigm shift in all such applications.
Contact: Emiliano Sefusatti
Video – Luigi Guzzo’s webpage
Marta Volonteri (Institut d’Astrophysique de Paris)
Massive black hole pairs and binaries in the cosmos
Friday, March 25th, 2022, 11am – streaming
Abstract Massive black holes weighing from a few thousands to tens of billions of solar masses inhabit the centers of most galaxies. During their cosmic evolution the galaxies hosting massive black holes interact and merge: this gives rise to pairs of massive black holes that can be observed as dual active galactic nuclei. As the dynamical evolution of the pairs proceeds, eventually binaries are formed, whose coalescence driven by emission of gravitational waves can be detected with ESA’s planned satellite LISA and with Pulsar Timing Arrays. I will discuss the physical processes through which massive black holes pair and bind and present the analysis of cosmological simulations to investigate the properties of dual active galactic nuclei, merging massive black holes and their host galaxies.
Contact: Valentina D’Odorico
Video – Slides – Marta Volonteri’s webpage
Raffaele Tito D’Agnolo (Institut de Physique Théorique, CEA-Saclay)
A New Chapter in the Quest for Dark Matter: The Ultralight Regime
Friday, February 25th, 2022, 11am – Giambiagi lecture hall (ICTP Adriatico GH) & streaming
Abstract Dark Matter was discovered more than 90 years ago through its gravitational effects. It makes up 80% of the matter in our Universe and about a quarter of its present energy density. We have spent decades trying to detect it in the laboratory, but to date its microscopic origin remains mysterious. The vast majority of our theoretical and experimental effort has been devoted to the exploration of relatively heavy dark matter candidates, with masses comparable to particles that we can produce at our highest energy colliders. In this talk I will review how in the last five to ten years a new perspective has emerged in particle theory, shifting our attention to ultralight dark matter candidates, in particularly the axion. This has generated a flurry of experimental activity, with a few pioneering efforts now setting up prototypes, and new ideas appearing almost weekly on the arXiv. I will review both the theoretical appeal of these dark matter candidates and the new ideas proposed to detect them experimentally. Furthermore, ultralight dark matter is well described in the laboratory as a coherent classical field. Its detection has interesting overlaps with that of high-frequency gravitational waves.
Contact: Paolo Creminelli
Gary Mamon (Institut d’Astrophysique de Paris)
What lurks in the centers of globular clusters? Intermediate-mass black holes, stellar mass black holes, compact stars, or nothing special?
Friday, January 28th, 2022, 11am – Aula D (old SISSA building) & streaming
Abstract Globular star clusters are the largest self-gravitating systems that are collisional (short 2-body relaxation times). Their inner dynamics are complicated by three- and four-body encounters, mass loss from stellar evolution, and astrophysical phenomena that lead to ejection. I will present recent analyses of the stellar kinematics in nearby globular clusters using proper motions from Gaia and HST. This allows us to map the inner mass profile and test for the existence and extent of a possible dark inner component, which could be an intermediate-mass black hole or populations of stellar-mass black holes, neutron stars, or white dwarfs. This helps answer the question: are globular clusters prime locations for the emission of gravitational waves in the Universe?
Contact: Andrea Biviano
Video – Slides – Gary Mamon’s webpage
Antonio Riotto (Geneva University)
Primordial Black Holes in the era of Gravitational Wave Astronomy
Friday, December 3rd, 2021, 11am – Giambiagi lecture hall (ICTP Adriatico GH) & streaming
Abstract The discovery of a gravitational wave signal coming from the merger of two black holes by the LIGO/Virgo collaboration has initiated the new era of gravitational wave astronomy. Primordialblack holes ( were immediately suggested to be responsible for such a signal thus initiating aflourish research activity on the subject on which we will report the state of the art.
Contact: Matteo Biagetti
Video – Slides – Antonio Riotto’s webpage
Fiorenza Donato (Università di Torino)
Challenges in cosmic ray physics: galactic sources, antimatter, dark matter
Friday, November 19th, 2021, 4pm – Aula D (Old SISSA building) & streaming
Abstract The unprecedented precision of data cosmic rays and gamma rays challenges our understanding of the origin and of the behavior of cosmic rays in the Galaxy. We will discuss possible interpretations of the nuclear component, in terms of sources and propagation in the Galaxy. Special emphasis will be payed to the antimatter channels, where a possible contribution from dark matter annihilation has been argued. Finally, the leptonic component – both positrons and electrons – will be critically assessed in connection with the most recent gamma-ray observations from single Galactic sources.
Contact: Piero Ullio
Video – Slides – Fiorenza Donato’s webpage
Marica Branchesi (Gran Sasso Science Institute)
Multi-messenger astronomy including gravitational-waves
Friday, October 29th, 2021, 11am – streaming
Abstract A new exploration of the Universe has recently started through multi-messenger observations including gravitational-waves. The detection of gravitational-waves and multi-wavelength electromagnetic emissions from a binary neutron star merger has demonstrated the enormous potential of multi-messenger astronomy to investigate the most energetic transients in the sky, probing relativistic astrophysics, nuclear physics, nucleosynthesis, and cosmology. The talk will give an overview of the astrophysical implications of gravitational-wave and multi-messenger observations, the prospects and challenges of the current and future gravitational-wave detectors, such as Einstein Telescope which is expected to undergo a revolution for transient (astro)physics.
Contact: Enrico Barausse
Video – Slides – Marica Branchesi’s webpage
John Miller (University of Oxford & SISSA)
Binary neutron star coalescence – after the merger
Friday, October 1st, 2021, 11am – Giambiagi lecture hall (ICTP Adriatico GH) & streaming
Abstract This talk will give an overview of current understanding of what happens after the coalescence of neutron star binaries, focussing on the particular case of the gravitational wave source GW170817.
Contact: Enrico Barausse
Video – Slides – John Miller‘s webpage
Pasquale Serpico (LAPTH, Annecy)
Massive sterile neutrinos in supernovae and the early Universe
Friday, September 17th, 2021, 11am – Kastler lecture hall (ICTP Adriatico GH) & streaming
Abstract After reviewing some motivation and the relevant parameter space, I will illustrate the impact of massive sterile neutrinos (tens or hundreds of MeV) on core collapse supernovae. An introduction to the topic of neutrinos in supernovae will be included for those unfamiliar with the relevant astrophysics. In particular, I will discuss constraints in the mass-mixing plane and interesting phenomenological signatures measurable at existing or forthcoming neutrino detectors. Cosmological probes (primordial nucleosynthesis, CMB) are also sensitive to some allowed parameter space. I will present recent calculations of the thermal decoupling of these states and the impact on the observables Neff and Yp . Current constraints and forecasts for the reach of the Stage-IV CMB observations will be discussed.