Laura Baudis (University of Zurich)
Direct detection of particle dark matter: where do we stand, where are we going?
Friday, July 3rd, 2020, 11am – streaming
Abstract One of the major challenges of modern physics is to decipher the nature of dark matter. Astrophysical observations provide ample evidence for the existence of an invisible and dominant mass component in the observable universe. The dark matter could be made of new, yet undiscovered elementary particles, with allowed masses and interaction strengths with normal matter spanning an enormous range. Among these, particles with masses in the MeV-TeV range could be directly observed via elastic or inelastic scatters with atomic nuclei or with electrons in ultra-low background detectors operated deep underground. After an introduction to the dark matter problem and the phenomenology of direct dark matter detection, I will discuss the most promising direct detection techniques, addressing their current and future science reach, as well as their complementarity.
Contact: Alfredo Urbano
Video – Slides – Laura Baudis’ webpage
Hitoshi Murayama (UC Berkeley & IPMU Tokyo)
Origin of matter and gravitational waves
Friday, June 19th, 2020, 5pm – streaming
Abstract We exist today thanks to the asymmetry between matter and anti-matter. Its origin, however, has been one of the major mysteries in cosmology and particle physics. Arguably the leading theory called leptogenesis is that the asymmetry is generated by the decay of heavy neutrinos at the temperature above 10^9 GeV. I review this theory and point out that the gravitational wave will be an important test. If time permits, I will also discuss a different origin of the asymmetry which is also tied to the origin of dark matter, again with a gravitational wave signature.
Contact: Serguey Petcov
Video – Hitoshi Murayama’s webpage
Raúl Angulo (Donostia International Physics Center)
Numerical simulations of the large-scale structure of the Universe
Friday, June 5th, 2020, 11am – streaming
Abstract An upcoming generation of observational surveys will map the distribution of matter, gas, and galaxies over large regions of the Universe. These measurements will offer the opportunity for profound discoveries about the nature of dark matter, dark energy, the law of gravity, and fundamental particles. However, the physical interpretation of these observations is a very difficult problem. In this talk, I will discuss the challenges of tackling these problems with the use of cosmological simulations. Specifically, I will discuss recent advances regarding the accuracy and precision of large-scale structure simulations, the modelling of baryonic effects and galaxy formation, and bayesian parameter estimation. I will finish by showing how these advances could help us to optimally exploit current and future measurements and maximise our chances of discovery.
Contact: Emiliano Sefusatti
Video – Slides – Raúl Angulo’s webpage
Anže Slosar (Brookhaven)
PUMA: the next generation intensity mapping experiment
Friday, May 8th, 2020, 11am – streaming
Abstract The Universe is full of neutral hydrogen shining in the 21-cm spin-flip transition. Using this line to trace cosmic structure allows us to map the large scale structure in three dimensions very efficiently and cheaply. Realizing the potential of this technique in practice has proven to be devilishly difficult. Fortunately, the problems are purely technical issues associated with characterization, calibration and stability of the instrument. I will talk about Packed Ultrawideband Mapping Array (PUMA), a proposal for the next generation radio telescope dedicated primarily to intensity mapping. It will measure expansion history and cosmic growth measurements to redshift z = 6, characterize inflation, measure millions of Fast Radio Bursts, monitor thousands of pulsars and perhaps even allow direct measurements of the real-time expansion of the universe. I will discuss the scientific, technological and programmatic issues that we need overcome to make it become real.
Contact: Matteo Viel
Video – Slides – Anže Slosar’s webpage
Marko Simonović (CERN)
Cosmology from current and future spectroscopic galaxy surveys
Friday, April 24th, 2020, 11am – streaming
Abstract Mapping of galaxy density fluctuations on large scales is one of the most important goals of observational cosmology in this decade. These observations can significantly improve our knowledge of the universe, its origins and composition. In this talk I will review science goals of ongoing and future spectroscopic galaxy surveys and explain how these goals can be met. In particular, I will focus on some recent progress in theoretical modelling of the nonlinear structure formation and show how it can be used to extract cosmology from observations of the cosmic web. As an example I will present a measurement of cosmological parameters from the publicly available Baryon Oscillation Spectroscopic Survey (BOSS) data.
Contact: Emiliano Sefusatti
Video – Slides – Marko Simonović ‘s webpage
Julien Lesgourgues (Aachen U)
Cosmic concordance, cosmic discordance, and the dark sector of particle physics
Friday, April 3rd, 2020, 11am – streaming
Abstract Data from the Planck satellite and other cosmological probes offer an overall consistent picture of the standard cosmological model. This concordance is however threatened by growing evidence for a few anomalies: the long-standing “small scale crisis” and “sigma8 anomaly”, a more controversial “Hubble tension”, and an even more controversial “Edges anomaly”. A very interesting case for theorists is that if these tensions are not due to poorly understood systematics or astrophysical effects, there is a potential to explain them thanks to new particle physics ingredients, such as new interactions in the dark sector, that would involve at least two types of dark relic particles.
Contact: Matteo Viel
Slides – Julien Lesgourgues’ webpage
Konstantin Zioutas (University of Patras)
Signatures from the “dark” Universe
Thursday, December 5th, 2019, 4pm – Euclid lecture hall, ICTP
Abstract The manifestation of the dark Universe begun with unexpected large-scale astronomical observations. Though, known physics fails to explain also a plethora of persisting small-scale atmospheric observations. The key signature of all observations is their planetary relationship. However, planetary remote interactions are too feeble to cause any significant effect, while they are independently excluded by this work. The derived signatures are suggestive for streams of invisible particles, which interact “strongly” , e.g., with the outer layers of atmosphere. The streams must be not relativistic, for gravitational (self)focusing effects by the Sun and/or its planets to be effective. Experiments searching for dark matter, either on purpose (e.g. CAST) or not, could profit from the concept of invisible streams. A few favourite particle candidates will also be presented. If time allows, some question(s) and a spin-off will be mentioned.
Contact: Giovanni Cantatore
Konstantin Zioutas’ webpage
Vincent Desjacques (Technion Haifa)
Fuzzy dark matter: constraints on parsec scales
Wednesday, October 2nd, 2019, 4pm – Euclid lecture hall, ICTP
Abstract Fuzzy Dark Matter (FDM) – a condensate of very light bosons – has been proposed as an alternative to weakly interacting massive fermions in order to alleviate tensions at small scales between the data and the standard Cold Dark Matter (CDM) scenario. In this talk, I will outline how cosmic structure formation differs in FDM models, discuss the large scale structure constraints on an hypothetical FDM particle, and argue that (the non-detection of) supermassive black holes in galaxies set a lower bound on the FDM mass which is 3 orders of magnitude stronger than the current Lyman-alpha forest limits.
Contact: Emiliano Sefusatti
Vincent Desjacques’ webpage
Cristiano Porciani (AIfA Bonn)
Myth and truth about halo formation in CDM models
Wednesday, October 2nd, 2019, 2:30pm – Euclid lecture hall, ICTP
Abstract The conventional wisdom in cosmology is that that cold-dark-matter haloes form out of initial density peaks and continuously accrete matter from the surroundings becoming more and more massive with time. These concepts form the basis of several semi-analytical tools that are regularly used to interpret data from galaxy and cluster surveys and develop galaxy-formation models (e.g. for the halo mass function, merger trees, and galaxy biasing). Using a suite of numerical simulations, we present thorough tests of the established scenario and show that it is mandatory to introduce new elements in the theory of the gravitational collapse of cold matter. In particular, we demonstrate that filamentary structures in the cosmic web inhibit accretion of new matter onto collapsed haloes. We also illustrate how this phenomenon explains the origin of the so-called `assembly bias’ for galaxy-sized haloes and also influences the dynamics of satellite galaxies.
Contact: Emiliano Sefusatti
AIfa Cosmology Group
Christine Jones Forman (CfA Harvard)
Chandra, HST, and Radio Observations of Clusters of Galaxies
Tuesday, September 24th, 2019, 2:30pm – Euclid lecture hall, ICTP
Abstract Clusters of galaxies are the most massive gravitationally bound objects in the Universe. While most of their mass is Dark Matter, the primary component of their visible matter is hot X-ray gas. A significant fraction of clusters are still growing through the infall of groups of galaxies or through the mergers of clusters. These cluster mergers are the most energetic events in the present Universe, after the Big Bang, releasing energies up to 10^64 ergs. Cluster mergers leave distinct signatures on the intracluster medium in the form of shocked gas and diffuse radio sources, relics. Most of the gravitational energy released during the merger is converted into shocks and gas turbulence in the cluster gas. This talk will highlight Chandra X-ray and radio results on the HST Frontier Fields clusters MACSJ017.5+3745, MACSJ1149.6+2223, and A2744, which are undergoing major mergers. Recent results on the merger of the A3411 and A3412 clusters show strong evidence for the electron re-acceleration at the merger site. Finally this talk will highlight results from the HST RELICS (Reionization Lensing Cluster Survey) which has led to the detection of very high redshift (z~10) galaxies which are strongly lensed by foreground clusters.
Contact: Stefano Borgani
William Forman (CfA Harvard)
Supermassive Black Holes (SMBH) at Work: The Effects of SMBH Outbursts on theEvolution of Gas Rich Galaxies, Groups, and Galaxy Clusters
Tuesday, September 24th, 2019, 2:30pm – Euclid lecture hall, ICTP
Abstract Data from the Planck satellite and other cosmological probes offer an overall consistent picture of the standard cosmological model. This concordance is however threatened by growing evidence for a few anomalies: the long-standing “small scale crisis” and “sigma8 anomaly”, a more controversial “Hubble tension”, and an even more controversial “Edges anomaly”. A very interesting case for theorists is that if these tensions are not due to poorly understood systematics or astrophysical effects, there is a potential to explain them thanks to new particle physics ingredients, such as new interactions in the dark sector, that would involve at least two types of dark relic particles.
Contact: Stefano Borgani