The aim of this Workshop is to bring together theorists and observers working on the broad topic of multi-messenger cosmology and large scale structures. The focus would be on understanding how best to test and at the same time exploit large scale structures to shed light on dark matter / dark energy, modified gravity, and the mysterious sources of high-energy astrophysical particles. The Workshop will bring together experts from disjoint but related fields and the format will provide ample time for interaction and discussion. The workshop is a follow-up to the very successful Multimessengers@Prague workshop held in 2019.

The list of topics includes gravitational waves, standard sirens, pulsar timing, cross-correlations for cosmology and astrophysics, 21cm physics, dark matter indirect detection, and multimessenger tests of fundamental physics and cosmology, from both data and theory perspectives.



SCHEDULE Wednesday
09:00-09:45 ARRIVAL Blas Ilić Camera
09:45-10:30 Bonga Dimastrogiovanni * Alonso *
10:30-11:30 A: Pulsar science
B: Theory of Gravitational Waves
A: Inflation and Gravitational Waves
B: Cosmology with Euclid
A: 21cm cosmology
B: Cross-correlations for cosmology
11:30-12:15 Caprini * Van Vliet * Fialkov
12:15-14:00 REGISTRATION (12:30)
OPENING (13:45)
14:00-14:45 Chluba Korol Bustamante FREE AFTERNOON
14:45-15:30 Sibiryakov * Calore * Weniger
15:30-16:30 A: The CMB and spectral distortions
B: Black Holes and cosmology
A: LISA, Gravitational Waves and cosmology
B: The Hubble tension
16:30-17:15 Hui * Krause * Fang (16:00-16:45) *
17:15-18:00 A: Ultra-light dark matter
B: Cosmic strings and other topological defects
A: Neutrinos in cosmology
B: The Rubin Observatory and other galaxy surveys
A: UHECR physics
B: Open discussion

* Remote


David Alonso University of Oxford
Cross-correlations and the large-scale structure [PDF] Combining data from different probes of the same underlying large-scale structure can have a transformative impact on the type of constraints we can obtain from current and next-generation datasets. In this talk I will discuss three cases where cross-correlations can have a transformative effect: the tomographic reconstruction of background quantities, the calibration of redshift distributions, and the detection of new signals. I will cover examples from existing data, as well as the potential of these analysis for near-future experiments.
Diego Blas UAB/IFAE, Barcelona
Binary systems as gravitational wave detectors [PDF] The passage of gravitational waves (GWs) through a binary perturbs the trajectories of the two bodies, potentially causing observable changes to their orbital parameters. In the presence of a stochastic GW background (SGWB) these changes accumulate over time, causing the binary orbit to execute a random walk through parameter space. In this talk I will present a new formalism for calculating the full statistical evolution of a generic binary system in the presence of a SGWB, capturing all six of the binary's orbital parameters. I will show how this formalism can be applied to timing of binary pulsars and lunar laser ranging, thereby setting novel upper limits on the SGWB spectrum in a frequency band that is currently inaccessible to all other GW experiments.
Béatrice Bonga IMAPP, Nijmegen
Foundations of gravitational waves in cosmology [PDF] There exists a solid framework to study gravitational waves in full, non-linear general relativity when the spacetime is asymptotically flat. It does not require the splitting of the metric in a background piece and a linearly perturbed part and therefore describes all non-linearities of the theory. The situation for cosmological spacetimes is different, however. Expanding spacetimes, whose expansion is decelerating such as matter- or radiation-dominated universes, share some similarities with the asymptotically flat case nonetheless. I will discuss some of the recent developments in this area.
Mauricio Bustamante Bohr Institute, Copenhagen
Fundamental physics with high-energy and ultra-high-energy neutrinos [PDF] High-energy (TeV-PeV) and ultra-high-energy (> 100 PeV) neutrinos of cosmic origin have a vast potential to probe neutrino physics in regimes of energy and distance otherwise unreachable. Notable examples include precision tests using the flavor composition of the neutrino flux, new neutrino-neutrino interactions, and measuring the neutrino-nucleon cross section. Today, we are already tapping into this potential at high energies, thanks to spectacular discoveries by the IceCube neutrino telescope. In the coming decade, we may extend our reach to ultra-high energies, thanks to an ambitious experimental program under planning. I will survey the rich landscape of high-energy physics with cosmic neutrinos, from the perspectives of theory and experiment. By means of illustration, I will campaign for the notion that in order for the field to mature, we must embrace the natural synergy between low-energy and high-energy neutrino experiments, and adopt an earnest, comprehensive treatment of the relevant particle-physics and astrophysical unknowns. If we do, then our progress, while hard-earned, could lead to transformative insight.
Francesca Calore LAPTh, Annecy-le-Vieux
Cross correlating galaxy catalogs and GW: a tomographic approach [PDF] Unveiling the origin of the coalescing binaries detected via gravitational waves (GW) is challenging, notably if no multi-wavelength counterpart is detected. One important diagnostic tool is the coalescing binary distribution with respect to the large scale structures (LSS) of the universe, which one can quantify via the cross-correlation of galaxy catalogs with GW ones. I will present sensitivity prospects for the search of such a cross-correlation signal, by using both existing and forthcoming galaxy catalogs and using realistic Monte Carlo simulations of GW events. The cross-correlation signal should be marginally detectable in a 10-year data taking of advanced LIGO-Virgo detectors at design sensitivity, at least for binary neutron star mergers, while the expected addition of KAGRA and LIGO-India to the GW detector network would allow for a firmer detection of this signal and, in combination with future cosmological surveys, would also permit the detection of cross-correlation for coalescing black holes. I will show how adopting a tomographic approach as well as reaching a sufficiently accurate localization of GW events will be crucial to attain rather advanced model discrimination capabilities.
Stefano Camera Università di Torino
Synergies across the spectrum for astrophysics and cosmology [PDF] Cross-correlations between cosmological and astrophysical observables at different wavelengths have the potential to lift degeneracies and obtain results that are 'more than the sum of the parts'. In this talk, I shall explore how such synergistic cross-correlations between experiments will be able to deepen our knowledge about most pressing unanswered questions, such as the nature of dark matter, dark energy, and inflation.
Chiara Caprini APC, Paris
Cosmology with the LISA mission [PDF] Abstract
Jens Chluba Jodrell Bank Centre for Astrophysics, Manchester
Setting the sails for CMB spectral distortions [PDF] CMB spectral distortions provide a unique probe of physical processes occurring the early Universe. Our understanding of how distortion signals are created and what they can tell us about fundamental physics has greatly improved over the past years. In this talk, I will highlight some of the latest developments on the theoretical and experimental frontiers, trying to convince you that the time is ripe for opening a new window into the early Universe and particle physics with CMB spectrometers. I will also describe some of the important step that are ahead in paving the path towards measuring CMB spectral distortions in the ESA Voyaye 2050 program.
Emanuela Dimastrogiovanni University of Groningen
Gravitational waves from inflation [PDF] Primordial gravitational waves have the potential to shed new light on the very early universe. In this talk I will discuss gravitational wave production in a variety of models beyond the simplest, single-field, scenarios and highlight some of their implications for testing inflation with interferometers.
Ke Fang Wisconsin University, Madison
Multi-messenger Astrophysics: Probing Compact Objects with Cosmic Particles [PDF] The study of compact objects such as black holes and neutron stars is an important component of modern astrophysics. Recent detections of astrophysical neutrinos, gamma-rays, ultrahigh energy cosmic rays, and gravitational waves open up opportunities to study compact objects with multi-messengers. In this talk, we first review the latest progress in Astroparticle Physics, including some surprising puzzles revealed by new observations of neutrinos and gamma rays. We demonstrate that the key to Multi-messenger Astrophysics is to understand and establish the link between the messengers. We then illustrate how to reach this goal from both theoretical and observational perspectives. From the theoretical side, we show that high-energy particle propagation in the vicinity of compact objects may play an important role in connecting multi-wavelength observation and source physics. From the observational side, we investigate analysis frameworks aiming to exploit data across multiple wavelengths and messengers.
Anastasia Fialkov KICC, Cambridge
Unveiling cosmic dawn [PDF] Cosmic Dawn and the Epoch of Reionization (EoR) are some of the least explored stages of cosmic history. The faint 21-cm signal of hydrogen atoms in the intergalactic medium provides a unique way to probe these epochs. Once this signal is robustly measured, it will inform us about the early populations of stars, galaxies and black holes. Recently, several radio telescopes published their first upper limits on the 21-cm power spectrum including LOFAR, MWA and HERA, while the EDGES radiometer claimed the first (yet unconfirmed) detection of the sky-averaged signal from redshift ~17. In my talk I will discuss implications of these data on our understanding of the high-redshift Universe.
Lam Hui Columbia University, New York City
Vortices and interference substructures in wave dark matter [PDF] We will discuss the possibility that dark matter is composed of sufficiently light particles that it effectively behaves as a collection of waves. We will review the particle physics motivations and the rich wave phenomenology, and discuss the implications for astronomical observations and experimental axion detection.
Stéphane Ilić LERMA, Ivry
Forecasting the joint analysis of Euclid and CMB experiments [PDF] Through weak lensing and galaxy clustering measurements, Euclid will provide unprecedented constraints on the late Universe. On the other hand, high-quality CMB observations (Planck and future CMB experiments) can -- and already do -- put tight constraints on the early Universe. Combining these two sources of cosmological information can yield a significant lever arm and improve tremendously the constraints on our cosmological model, especially its non-standard extensions. In this talk, I will present the validated forecasts of the future Euclid x CMB cross-correlation constraints, performed by the CMB-cross correlations Science Working Group. These results culminated in the writing of an official Euclid Collaboration paper, accepted for publication.
Valeriya Korol University of Birmingham
Prospects for multi-messenger studies of the Milky Way with LISA [PDF] White dwarf stars are a well-established tool for studying Galactic stellar populations. Two white dwarfs in a tight orbit forming a double white dwarf (DWD) binary offer us an additional messenger - gravitational waves - for exploring the Milky Way and its immediate surroundings. Gravitational waves emitted by DWDs can be detected by the future Laser Interferometer Space Antenna (LISA). While awaiting the LISA’s launch, DWDs can be discovered as faint electromagnetic transients in wide-field sky optical surveys. I will discuss what we will learn about our Galaxy from the multi-messenger sample of DWDs. In particular, I will demonstrate how well the density distribution of DWDs constrains scale parameters of the Milky Way's bulge, disc and central bar. I will highlight how the power to constrain the overall properties of the Galactic baryonic potential will be significantly enhanced by using gravitational waves in combination with electromagnetic observations. Finally, I will show that massive Galactic satellites can be seen in the gravitational wave sky and I will present which of their properties we will be able to investigate with LISA.
Elisabeth Krause University of Arizona
Internal and external synergies for Rubin LSST cosmology analyses [PDF] Abstract
Sergey Sibiryakov McMaster University, Hamilton and Perimeter Institute, Waterloo and INR, Moscow
Black hole catalysis of false vacuum decay: The semiclassical decay rate and importance of greybody factors [PDF] It was suggested over thirty years ago that microscopic black holes can exponentially enhance the decay rate of a metastable false vacuum. The interest in this phenomenon has revived recently due to its possible phenomenological relevance for the physics of the early universe. Upon reviewing the motivation, I will discuss challenges raised by the attempts to describe black hole catalysis of vacuum decay using standard semiclassical methods. I will then present a generalized method applicable to the case of a realistic black hole which is not in equilibrium with its environment. The method will be illustrated on an example of a two-dimensional toy model, with emphasis on the role played by the black hole greybody factors. The proposed formalism is not limited to black holes and applies to tunneling in out-of-equilibrium systems in general.
Arjen Van Vliet DESY, Hamburg
Ultra-High Energy Cosmic Rays and fundamental physics [PDF] Recent advances in measurements of the energy spectrum, composition and arrival directions of ultra-high-energy cosmic rays (UHECRs) provide ways to probe the properties of the sources of UHECRs and of the environment the UHECRs travel through. The secondary neutrinos and ultra-high-energy photons that are produced in photohadronic interactions of UHECRs give additional insight about the sources. This multimessenger approach can especially be used to explore the composition of UHECRs and the source evolution with redshift. In addition, recent UHECR anisotropy measurements suggest correlations between UHECR arrival directions and local starforming galaxies or Active Galactic Nuclei (AGN). These results provide information about the magnetic fields in between these sources and Earth, both on Galactic and extragalactic scales.
Christoph Weniger GRAPPA, Amsterdam
Multimessenger dark matter searches with neural simulation-based inference and differentiable programming [PDF] The nature of dark matter is one of the most exciting open questions in theoretical physics and cosmology. Astrophysical observations ranging from gravitational waves over radio to gamma rays contentiously improve in quality and quantity and could lead to breakthroughs in the next years. Unfortunately, classical simulation and inference techniques increasingly become bottlenecks for fully exploiting upcoming data. In this talk, I will highlight recent developments on the front of machine learning, focusing on neural simulation-based inference and differentiable programming. Those statistical and computational techniques start helping us to interpret upcoming observations with higher precision, and they could become key to gain new insight about the nature of dark matter. I discuss promising techniques, pitfalls and challenges.


Anabella Araudo LUPM, Univ. of Montpellier, CNRS, and ELI Beamlines, Institute of Physics, Czech Academy of Sciences
Stefano Bondani University of Insubria
James Creswell University of Munich
Will Emond CEICO, Institute of Physics of the Czech Academy of Sciences, Prague
Cem Eröncel DESY
Stephanie Escoffier CPPM, Marseille
Dražen Glavan CEICO, Institute of Physics of the Czech Academy of Sciences, Prague
Sk Jahanur Hoque Institute of Theoretical Physics, Charles University, Prague.
Pavel Kůs CEICO, Institute of Physics of the Czech Academy of Sciences, Prague
Samantha Rossiter Università di Torino
Ippocratis Saltas CEICO, Institute of Physics of the Czech Academy of Sciences, Prague
Unnikrishnan Sureshkumar Astronomical observatory of the Jagiellonian University, Kraków, Poland
Georg Trenkler CEICO, Institute of Physics of the Czech Academy of Sciences, Prague
Leonardo Trombetta CEICO, Institute of Physics of the Czech Academy of Sciences, Prague
Johannes Werthebach TU Dortmund University
Vojtěch Witzany University College Dublin
Rahma Alfarsy Institute of Cosmology and Gravitation
Chandranathan Anandavijayan National institute of science education and research, Bhubaneshwar, Odisha, India
Amjad Ashoorioon Institute for Research in Fundamental Sciences (IPM), Tehran
Hemza Azri UAEU
Tessa Baker Queen Mary University of London
Matilde Barberi Squarotti Università degli Studi di Torino
Marianthi Bataki University of Cyprus
Zakaria Belkhadria Unica / INFN / ICG
Kunal Bhardwaj CEICO, Institute of Physics of the Czech Academy of Sciences, Prague
Sandipan Bhattacherjee Birla Institute of Technology Mesra, Ranchi, India
Karthika Bhuvanendran Cochin University of Science And Technology, CUSAT, Kerala , India
Percy Caceres Puc Rio de Janeiro
Carmelita Carbone INAF - Istituto di Astrofisica Spaziale e Fisica cosmica, Milano (IASF -MI)
Isabella Paola Carucci University of Torino
Srija Chakraborty Scuola Normale Superiore
Stephanie Escoffier CPPM, Marseille
Peter Filip Institue of Physics of the Czech academy of Sciences
Abhirup Ghosh Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Potsdam-Golm
Pooyan Goodarzi SBU Physics
Deanna Hooper University of Helsinki
Shubham Ilhe Indian Institute of Science Education and Research, Kolkata
Sonia Jose Bishops university, sherbrooke, Québec, Canada
Vladimír Karas Astronomical Institute, Czech Academy of Sciences
Shilpa Kastha AEI, Hannover
Sobhan Kazempour Ishka University of Tabriz
Morteza Khamedi University of Padova
Diana Lopez Nacir University of Buenos Aires
Georgios Loukes Gerakopoulos Astronomical Institute of the Czech Academy of Sciences
Ameek Malhotra University of New South Wales
Ibrahim Mirza University of Tennessee
Ana Laura Müller ELI Beamlines, Institute of Physics, Czech Academy of Sciences
Syed Naqvi Jagiellonian Universtiy
Elham Nazari Ferdowsi University of Mashhad
Johannes Noller ICG Portsmouth
Sourav Pal Junior Research Fellow at Indian Statistical Institute,Kolkata
Naresh Kumar Patra BITS Pilani K K Birla Goa Campus, Goa
Elena Pinetti Fermilab
Christoph Raab CEICO, Institute of Physics of the Czech Academy of Sciences, Prague
Wolfram Ratzinger Johannes Gutenberg University Mainz
Narasimha Reddy University of Lethbridge, Canada
Tania Regimbau LAPP, Annecy-le-vieux
Naomi Robertson University of Cambridge
Shun Saito Missouri University of Science and Technology
Francesco Sergio Università di Trento
Rahul Shah Indian Statistical Institute, Kolkata
Katie Short ICCUB
Prashant Thakur BITS Pilani K K Birla Goa Campus, Goa
Hareesh Thuruthipilly National Centre for Nuclear Research, Poland
Caner Unal Ben Gurion University
Saboura sadat Zamani Golestan University
Stefano Zazzera Queen Mary University of London
Juxhin Zhuleku CEICO, Institute of Physics of the Czech Academy of Sciences, Prague

Venue and Accommodation

Health regulations
The workshop will take place in person and following all current regulations as indicated by the Ministry of Health of the Czech Republic. For further information please visit its dedicated portal. All information about travelling to the Czech Republic can be found here. Another very useful resource that can help you plan your travels to and from Prague is the Re-open EU website and app.


There will be a welcome reception on Wednesday, December 8, to be held in the Fata Morgana Tropical Greenhouse (Google Maps, Mapy) from 18:30 (6:30pm).

The workshop social dinner will be held on Friday, December 10, in the Old Town of Prague, at the traditional Kolkovna Celnice restaurant (Google Maps, Mapy) from 19:00 (7pm).

We have reserved a few tables at the closest cafeteria Jídelna Slovanka. In addition to that, within walking distance from the Institute of Physics one can find a few restaurants, bistros and cafes. The closest options are


The workshop is open to external participants who plan to participate in person, and it will be possible to attend all the talks virtually upon registration: please fill in the form below at your earliest convenience. There is no registration fee, but the workshop physical attendance is limited to 45 people. For those who wish to participate in person, we will confirm your participation by email by November 25.