20. Kosmologietag

May 6, 2026, 12:30 PM → May 8, 2026, 1:40 PM Europe/Berlin

Dietrich Bödeker (Bielefeld University), Wilfried Buchmüller, Isabel Oldengott, Dominik Schwarz (Bielefeld University - Faculty of Physics), Cora Uhlemann (Bielefeld University)

May 6 to 8, 2026 at Wissenswerkstadt Bielefeld  

Welcome to the webpage of 20. Kosmologietag.

Kosmologietag is an annual conference on cosmology and related fields, happening in the fabled city of Bielefeld... 

The year 2026 marks the 20th anniversary of Kosmologietag and we will celebrate this occasion with a special time, place and programme: The event will span 3 days (starting Wednesday early afternoon until Friday around noon), with a reception on Wednesday evening and the traditional conference dinner on Thursday evening. It will take place at Wissenswerkstadt Bielefeld (https://wissenswerkstadt.de/), a science museum in the city center, and will be rounded off by a public lecture by Günther Hasinger. 

The programme will include three invited talks, contributed talks and short flash-talks.
We especially encourage young scientists to submit abstracts (via the button below). Our selection criteria will focus on curating an exciting, diverse, and balanced program that encompasses the full spectrum of cosmology. 

Please note that this year Kosmologietag does not happen at the usual location but at Wissenswerkstadt which is located at Jahnplatz in the city center.

Invited speakers: 

Renée Hložek (University of Toronto) 

Samaya Nissanke (University of Potsdam, DESY, DZA)

Mikhail Shaposhnikov (Federal Polytechnic School of Lausanne) 

Public talk (in German):

Günther Hasinger (DZA) -> to the event (Additional registration required - free of charge)

 
Conference fee: 150 € early bird registration (180 € regular), including coffee breaks, reception and conference dinner. 

Abstract submission deadline: 16th March 2026
Early bird registration & payment deadline: 30th March 2026
Registration deadline: 27th April 2026

Childcare can be arranged upon request (on the participant's own expense/funding) if we are notified at latest by 30th March. 

Registration may close earlier if the number of 150 participants is reached.

Supported by 

   

20Kosmologietag.jpg

Directions_Wissenswerkstadt.pdf

Kosmologietag_lunch_options.pdf

Welcome_Receptio_Kosmologietag2026.pdf

Wed, May 6

12:30 PM → 1:30 PM Registration

1:30 PM → 1:45 PM Welcome

1:45 PM → 2:30 PM Plenary

Convener: Kai Schmitz

1:45 PM New Perspectives onto the Universe in the Era of Multi-Messenger Astrophysics

tba

Speaker: Samaya Nissanke

Bielefeld2026_nissanke.pdf

2:30 PM → 3:00 PM Session

Convener: Kai Schmitz

2:30 PM Environmental Imprints of Supermassive Black Hole Binaries on the Nanohertz Gravitational-Wave Background

Several pulsar timing array (PTA) collaborations have recently reported compelling evidence for a nanohertz stochastic gravitational-wave background (SGWB), most plausibly produced by a cosmic population of supermassive black hole binaries (SMBHBs). While the spectrum broadly matches predictions for circular, GW-driven binaries, a low-frequency turnover indicates substantial orbital hardening during the transition from early environmental effects to later GW-dominated stages.
We investigate how initial orbital parameters and interactions with stellar and dark matter environments via gravitational three-body slingshots shape the SGWB spectrum. Using a Markov Chain Monte Carlo analysis, we assess the consistency of a SMBHB-generated SGWB with the 15-year NANOGrav and 18-year PPTA data sets.
Despite a strong degeneracy between initial binary eccentricity and environmental coupling, we identify, for the first time, a data-preferred value for the ratio of combined matter density to velocity dispersion of $\rho/\sigma \approx 10^{2}\,\mathrm{M_{\odot}/pc^{3}\,(km/s)^{-1}}$ on parsec scales. We further place upper limits on this ratio that depend on the initial eccentricity, providing new insights into galactic nucleus composition and SMBHB dynamical evolution. Our results have been published in Nature Astronomy (DOI: 10.1038/s41550-026-02782-0).

Speaker: Matthias Daniel (Goethe-Universität Frankfurt)

Bielefeld_Conference_Talk_Matthias_Daniel.pdf

2:45 PM Gravitational Waves from Black Hole Reheating: The High-Frequency Component

We investigate high-frequency gravitational-wave signals associated with ultra-light primordial black holes (PBHs), focusing on GWs generated by PBH binary formation and mergers. Within the standard framework in which PBHs form from the collapse of superhorizon-scale overdensities, we adopt extended PBH mass functions motivated by Press–Schechter theory and peak theory, and analyze their impact on the resulting gravitational-wave signal.
We extend previous studies of the stochastic gravitational-wave background produced during the PBH-induced early matter-dominated era. In particular, we systematically include contributions from PBH binaries formed through the two-body capture channel, three-body interactions, and mergers occurring within PBH clusters, modeled using a Press–Schechter approach arising from both two- and three-body encounters. We then determine the regions of parameter space in which each formation channel dominates the resulting signal.
In addition, we compute the high-frequency GW signal arising from the direct Hawking emission of ultra-light PBHs.

Speaker: Nicholas Leister (Johannes Gutenberg Universität)

Bielefeld_26_Leister.pdf

3:00 PM → 3:30 PM Coffee

3:30 PM → 5:00 PM Session

Convener: Isabel Oldengott

3:30 PM Cosmological constraints on TeV-scale dark matter subcomponents decaying after recombination

Dark matter appears to constitute the majority of the matter budget in our universe, however, its nature remains mysterious. Astrophysical and cosmological observations, along with laboratory experiments, have placed significant constraints on the possible parameter space for dark matter particles. The possibility of unstable dark matter particles decaying to standard model products is only allowed for very long lifetimes, or very small decaying fractions. I will present new projected limits on TeV-scale dark matter decaying into standard model neutrinos during the cosmological dark ages, from the global 21cm temperature signal, as well as CMB constraints for these models. I will compare and contrast this with similar limits and projections for decays to photons and electron-positron pairs, showing the potential of the 21cm signal to place limits on dark matter in the dark ages, and how it complements CMB constraints well, for decays into neutrinos in particular.

Speaker: Markus Mosbech (RWTH Aachen)

Kosmologietag 2026 New.pdf

Kosmologietag 2026.pdf

Mosbech Presentation 2026 (online version)

3:45 PM Distinguishing Dark Matter Thermal Histories through Large Scale Structure

It is important to understand the implications of current observational constraints and potential signatures on the thermal history of dark matter. In this talk, we would build the connection between the present-day velocities and the production mechanism of dark matter and find that the current observation on structure formation can be imposed to constrain the decoupling temperatures and the phase-space distribution of dark matter. We further explore the potential of distinguishing different possible thermal histories of dark matter with hypothetical future observational data. Using the freeze-in/-out scenarios as templates, we find that future precision data may uniquely identify the allowed parameter spaces for freeze-in and freeze-out, or even completely rule out one of the scenarios. This method can be more generally applied to other scenarios.

Speaker: Yuan-Zhen Li (CP3, UCLouvain)

DMandLSS_Final.pdf

4:00 PM Constraints on neutrino mass and dark energy agnostic to the sound horizon

Recent BAO observations from DESI DR2 either hint at a possible dynamical dark energy component, which would worsen the Hubble tension, or at a 95\% credible interval for the summed neutrino mass hardly compatible with neutrino oscillation experiments. In this context, it is interesting to investigate constraints on neutrino masses, dark energy and the Hubble parameter that are agnostic to some aspects of the cosmological model. Here we choose to be agnostic to the value of the sound horizon at recombination, while sticking to standard assumptions regarding the time of recombination and the growth of structures. To be consistent, we also disregard information on the full shape of the CMB temperature and polarization spectrum on sub-degree scale. With such agnostic and conservative assumptions, using data mainly on uncalibrated distances, the growth of structures, and laboratory bounds on tritium $\beta$-decay, we find that: (i) the dark energy evolution is well constrained by uncalibrated data on angular and luminosity distances, with a mild preference for dynamical dark energy even in agnostic approach; the values of $\Omega_{M}$, $w_0$, and $w_a$ are fairly insensitive to value of $r_s$;} (ii) large values of the Hubble rate are favoured,
$H_0=74.7^{+3.4}_{-4.4}$
km/s/Mpc (68\%CL), together with low values of the sound horizon,
$r_{\rm s}=131.1^{+6.8}_{-6.9}$
Mpc (68\%CL); the SH0ES value of $H_0$ is thus marginally preferred over the low value returned by the standard inverse distance ladder analysis; (iii) the cosmological neutrino mass bound {\color{blue} gets significantly looser,}
$\sum m_\nu = 0.69^{+0.33}_{-0.47}$ eV (68\%CL), and becomes well compatible with neutrino oscillation experiments.

Speaker: Ravi Sharma (RWTH Aachen Germany)

kosmo_ravi.pdf

4:15 PM Constraining the inflaton potential with gravitational waves from oscillons

Observations of the cosmic microwave background (CMB) lend strong evidence for the paradigm of cosmic inflation, but the specific form of the inflaton potential remains unknown. Under certain conditions, the oscillating inflaton condensate filling the Universe after inflation can fragment and form interesting non-linear structures known as oscillons. These long-lived soliton-like field configurations can dominate the Universe for several e-folds of expansion, leading to an early matter-dominated phase preceding the standard radiation era.

In this talk, I will show how the rapid final decay of the oscillons leads to an enhanced production of induced gravitational waves (GWs), whose energy density can saturate the observational bound on the effective number of relativistic species. We leverage this bound to constrain the inflaton mass, cubic, and quartic self-coupling in generic models that admit oscillon formation, providing novel and complementary constraints in regions of parameter space that are inaccessible with CMB observations alone.

Speaker: Jan Tränkle (ITP Universität Hannover)

Traenkle-oscillon-GWs.pdf

4:30 PM Thermal effects on Dark Matter production during cosmic reheating

The relic abundance of Dark Matter (DM) produced via thermal freeze-in is sensitive to the thermal history during and after cosmic reheating. In minimal models, this opens up the possibility to make predictions for collider observables by combining the requirement to match the DM relic abundance with observations of the Cosmic Microwave Background (CMB). We assess the impact of thermal corrections to the rate of cosmic reheating and the rate of thermal DM production on CMB observables and the relic abundance. We find that such corrections are generally negligible in the regime where perturbation theory can be applied. We construct counter-examples where this general rule is violated.

Speaker: Mr Mubarak A. S. Mohammed (UCLouvain-CP3)

Kosmologeitag-Talk_Mubarak.pdf

4:45 PM Introducing Cosmolattice 2.0

We introduce and report on version 2.0 of the CosmoLattice code, a modern package for lattice simulations for the dynamics of interacting scalar and gauge fields in an expanding universe.
With version 2.0, new physics modules are introduced, among them U(1) axion dynamics, cosmic defects, non-minimal couplings, and simulations in 1 and 2 dimensions.
Furthermore, CosmoLattice 2.0 features greatly improved performance and fully supports large-scale GPU computations on a broad range of hardware, making it ready to run on current and future cluster architectures.

Speaker: Franz Richard Sattler (University Bielefeld)

Sattler_CL.pdf

5:00 PM → 5:30 PM Coffee

5:30 PM → 6:15 PM Session

Convener: Lina Castiblanco Tolosa

5:30 PM KiDS-Legacy: Constraints on Horndeski gravity from weak lensing combined with galaxy clustering and cosmic microwave background anisotropies

In this talk, I will present constraints on modified gravity using the latest weak lensing data from the Kilo-Degree Survey (KiDS-Legacy), in combination with DESI measurements of baryon acoustic oscillations, eBOSS observations of redshift space distortions, and cosmic microwave background anisotropies from Planck. This analysis explores the Horndeski class of modified gravity models within an effective field theory framework that satisfies stability conditions by construction. We find that cosmic shear provides significant constraints on the Horndeski parameter space, matching or surpassing the CMB contribution, and thus highlighting the role of weak lensing as a powerful probe of gravity on cosmological scales. The results show that although modified gravity provides a slightly improved fit to the data, a model comparison indicates only a weak preference over $\Lambda$CDM, while key observables, such as the structure growth parameter $S_8$, remain consistent with $\Lambda$CDM constraints.

Speaker: Benjamin Stölzner (Ruhr University Bochum)

KiDS-Legacy: Constraints on Horndeski gravity from weak lensing combined with galaxy clustering and cosmic microwave background anisotropies

KiDS_Legacy_Horndeski_Bielefeld26.key

KiDS_Legacy_Horndeski_Bielefeld26.pdf

5:45 PM Staying focused: In-flight monitoring of the Euclid space telescope

One of the Euclid survey's primary cosmological probes is weak gravitational lensing: the apparent coherent distortion of galaxies caused by their light passing through gravitational potentials along the line of sight. Obtaining precise and accurate galaxy shapes is therefore crucial for unbiased cosmological inference. The leading source of systematic error in these measurements is the point-spread function (PSF), which can introduce spurious correlations if not modelled accurately.

During survey operations, the main driver of PSF variability is the defocus wavefront error, which affects the PSF size and consequently the apparent roundness of galaxies. We present a fast, purely empirical method to estimate the telescope image defocus using a simple linear relation between defocus and the lateral displacement of diffraction spikes in bright stars.

This approach enables us to trace the remarkably stable evolution of the Euclid telescope across its full survey timeline. Our defocus estimator provides a tight per-exposure prior for PSF modelling and is generalisable to other diffraction-limited telescopes.

Speaker: Dennis Neumann (Leiden Observatory)

Neumann_Kosmologietag2026.pdf

online google slide deck

6:00 PM Searching for ultralight ALPs with polarimetric observations of gravitational lenses

Axionlike particles (ALPs) are promising candidates for dark matter. A tiny
interaction between photons and ALPs give rise to achromatic birefringence, and
the birefringence angle oscillates with a time-period determined by ALP mass.
Ultralight ALPs with mass $< 10^{-18}$ eV have imprints on astrophysical scales.
Of late, we have established strong gravitationally lensed polarised quasars as
robust and clean probes to measure differential birefringence between multiply
lensed images, and the signal is free of astrophysical assumptions and
calibration systematics. In this talk, I will discuss the discovery potential
of this method through spectropolarimetric monitoring campaign should ALPs
exist, and the recent advances we have made through multi-epoch observations
with the VLA. This has allowed us to put stringent constrain on
ALPs at sensitivity comparable to, or better than, lab-experiments, e.g., the
CERN Axion Solar Telescope (CAST).

Speaker: Shivani Deshmukh

Deshmukh_Kosmologietag2026.pdf

6:15 PM → 6:33 PM Session: Flash Talks

Convener: Lina Castiblanco Tolosa

6:15 PM On the evolution of cosmic filaments in AbacusSummit

The majority of all matter is located in the filamentary structures of the cosmic web that permeate our universe. Despite this, filaments prove difficult to detect due to their low densities, and thus, while strong efforts have been made to characterize them and extract their statistical properties, we still lack a model that connects the initial density field to their present form. To bridge this gap, we start by employing DisPerSE to identify and catalogue filaments in the AbacusSummit simulation suite. We track these filaments across different redshifts by associating each with a main progenitor, thereby reconstructing their formation history, and locate the distribution of their particles in the initial conditions. In this presentation, we will detail our methodology and discuss the resulting insights into the statistical properties of filaments, their evolution, and cosmological potential.

Speaker: Wendy Wallace (University of Hamburg)

EvolutionFilsAbacus_Bielefeld.pdf

EvolutionFilsAbacus.key

6:18 PM Modeling the baryonic content of galaxy clusters with interpretable machine learning

Next-generation cosmological surveys such as Euclid, LSST, and Roman will probe the non-linear regime where baryonic processes significantly suppress power at small scales, which is the key source of systematic uncertainty for high-precision cosmology. Observational probes like the Sunyaev-Zel'dovich effect provide complementary insights into these baryon distributions within halos and their surroundings. However, existing analytical methods, while physically motivated, rely on fixed parametric forms for modelling gas and pressure profiles relevant for these probes. This restricts their flexibility and physical accuracy across different halo mass and redshift. To address this, we propose a machine-learning framework based on an interpretable variational encoder trained on the FLAMINGO simulations. This approach aims to extract physically meaningful latent variables describing baryonic feedback directly from the simulations, enabling a flexible, data-driven representation of pressure and density profiles relevant for tSZ and kSZ measurements. and to compare these results with existing analytical methods. Our framework offers a promising avenue to unify multi-probe constraints on baryonic physics using AI in an interpretable and explainable way.

Speaker: Subarna Chaki

kosmologietag_bielefeld.key

kosmologietag_bielefeld.pdf

6:21 PM Exploring the Delaying Effect of Ultralight Axions on the 21-cm Signal during Cosmic Dawn

I will talk about my master's thesis topic. The aim of my master's thesis is to study the impact of ultralight axions (ULAs) on the 21-cm signal during cosmic dawn. Compared to standard cold dark matter, ULAs suppress the halo mass function below the scale of the Jeans mass $M_J(m_{\alpha})$, which depends on the mass $m_{\alpha}$ of ULAs. ULAs therefore delay the onset of star formation and consequently also delay the evolution of the 21-cm signal. I have developed a mathematical framework that is able to capture the delaying effect of ULAs on the 21-cm signal in terms of their delaying effect on the cumulative star formation rate density. The 21-cm signal is computed using the open-source Python package ZEUS21, which calculates the 21-cm power spectrum analytically through a lognormal approximation of the star formation rate density and has negligible computational costs. Lastly, I have conducted a Fisher matrix forecast to estimate the sensitivity of the Hydrogen Epoch of Reionization Array to the mass and fraction of ULAs.

Speaker: Julian Kleff (Institute of Astrophysics and Geophysics, University of Göttingen, Germany)

Flash_Talk_Julian_Kleff.pdf

6:24 PM Thermal axion production at strong-coupling

tba

Speaker: Eamonn Weitz

weitz_kosmo.pdf

6:27 PM Cosmological Reconstruction with Fuzzy Dark Matter

tba

Speaker: Aoibhinn Gallagher (Universität Bielefeld)

recon_with_fdm.pdf

6:30 PM Likelihood Emulation in Cosmology

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Speaker: Luca Janken

Janken_Luca_flash_talk.pdf

7:00 PM → 9:30 PM Reception

At Wissenswerkstadt

Thu, May 7

9:00 AM → 10:30 AM Session

Convener: Jérôme Vandecasteele

9:00 AM Gaussian Lagrangian Galaxy Bias

Understanding galaxy bias– that is the statistical relation between matter and galaxies – is of key importance for extracting cosmological information from galaxy surveys. While the “bias function” f – that is the probability of forming galaxies in a region with a given density field– is usually approximated through a parametric expansion, we show here, that it can also be measured directly from simulations in a non-parametric way. Our measurements show that the Lagrangian bias function is very close to a Gaussian for halo selections of any mass. Therefore, we newly introduce a Gaussian bias model with several intriguing properties: (1) It predicts only strictly positive probabilities f > 0 (unlike expansion models), (2) It has a simple analytic renormalized form and (3) It behaves gracefully in many scenarios where the classical expansion converges poorly. We show that the Gaussian bias model describes the galaxy environment distribution p(δ|g), the scale dependent bias function f and the renormalized bias function F of haloes and galaxies generally equally well or significantly better than a second order expansion with the same number of parameters. We suggest that a Gaussian bias approach may enhance the range of validity of bias schemes where the canonical expansion converges poorly and further, that it may make new applications possible, since it guarantees the positivity of predicted galaxy densities.

Speaker: Jens Stücker (University of Vienna)

stuecker_gaussian_bias.pdf

9:15 AM Constraining Cosmology from Radio Surveys with Simulation-Based Inference

Modern radio surveys, such as LOFAR, generate rich datasets that contain information on both large-scale cosmic structure and the astrophysical properties of galaxy populations. Traditional inference methods require weeks to months of computation and struggle to model the full complexity of survey data. In this talk, I will present a simulation-based inference (SBI) framework using invertible neural networks (INNs) that provides a faster, more flexible alternative with reliable uncertainty estimates. Our approach relies on lognormal simulations that accurately reproduce observed clustering properties up to the relevant cosmological scales, providing the training set for neural density estimators that learn the mapping between observables and parameters. A key advantage of SBI is its flexibility: we can work directly with sky maps or angular power spectra, and unlike traditional inference, no explicit likelihood function is required. I will show how we validate the reliability of our framework through detailed tests and confirm that uncertainties are well-calibrated. Applied to LoTSS DR2, we obtain results comparable to MCMC-based methods while being orders of magnitude faster. As radio surveys scale toward the SKA era, where traditional approaches are computationally unmanageable, this framework offers a practical path forward for efficient cosmological analyses of next-generation observations.

Speaker: Vrund Patel (Institute for Theoretical Physics, Heidelberg University)

Patel_Kosmologietag.pdf

9:30 AM Simulation-based inference with the integrated 3PCF

We present a simulation-based inference (SBI) framework for analysing a higher-order weak lensing statistic, the integrated 3-point correlation function (i3PCF). Our approach forward-models the cosmic shear field using a suite of N-body simulations, including a comprehensive set of systematic effects such as intrinsic alignment, baryonic feedback, photometric redshift uncertainty, shear calibration bias, and shape noise. Using this, we have produced a set of DES Y3-like synthetic measurements for 2-point shear correlation functions and i3PCFs across 6 cosmological and 11 systematic parameters. Having validated these measurements against theoretical predictions and thoroughly examined for potential systematic biases, we have found that the impact of source galaxy clustering and reduced shear on the i3PCF is negligible for Stage-III surveys. Furthermore, we have tested the Gaussianity assumption for the likelihood of our data vector and found that the likelihood of the combined 2PCF + i3PCF data vector including filter sizes of 90' and larger can deviate from this assumption. Our SBI pipeline employs masked autoregressive flows to perform neural likelihood estimation and is validated to give statistically accurate posterior estimates. On mock data, we find that including the i3PCF yields a substantial 63.8% median improvement in the figure of merit. These findings are consistent with previous works on the i3PCF and demonstrate that our SBI framework can achieve the accuracy and realism needed to analyse the i3PCF in wide-area weak lensing surveys.

Speaker: David Gebauer (Universität Bielefeld)

Simulation-based inference with the integrated 3PCF

9:45 AM Warm Inflation with the Standard Model

We show for the first time that warm inflation is feasible with standard model (SM) gauge interactions alone. Our model consists of a minimal extension of the SM by a single scalar inflaton field with an axionlike coupling to gluons and a monomial potential. The effects of light fermions, which were previously argued to render warm inflation with the SM impossible, are alleviated by Hubble dilution of their chiral chemical potentials. Our model features only one adjustable combination of parameters and accommodates all inflationary observables. We briefly discuss implications for axion experiments, dark matter, and the strong CP problem.

Speaker: Marco Drewes (Université catholique de Louvain (UCLouvain))

Drewes Kosmologietag 2026.pdf

10:00 AM NLO calculation of N_eff in the Standard Model

The effective number of neutrinos $N_\mathrm{eff}^\mathrm{SM}$ is an important parameter in standard cosmology. It directly affects observbles like the primordial abundances of light elements and correlations in the cosmic microwave background and is potentially sensitive to physics beyond the Standard Model. Theoretical calculations have now reached a level of precision, where next-to-leading-order QED effects must be taken into account. In this talk, we present preliminary results on the full QED corrections with finite-temperature and -density effects, taking also into account the finite electron mass. The presented work extends and completes our previous calculation of the t-channel enhanced contribution. Numerically, our results indicate that the complete calculation is consistent with our previous estimate that the QED corrections are of $\mathcal{O}(10^{-5})$. This contrasts with the estimate of another group, who found a value up to two orders of magnitude larger by adapting calculations developed for the very different energy regime of stellar plasmas to the post-neutrino-decoupling epoch.

Speaker: Adrian Finke (Uni Münster)

Neff_Adrian_Finke.pdf

10:15 AM QCD corrections to the electroweak sphaleron rate

The hot electroweak sphaleron rate determines the speed of Baryon number violating processes in the high temperature phase of the Standard Model and is therefore an important input for predictions of the primordial Baryon asymmetry. This rate is inversely proportional to the weak-isospin conductivity, which is a constant that governs the in-medium dynamics of soft non-Abelian gauge fields. So far, only electroweak interactions were included in the computation of the conductivity. Presenting work published in 2510.20594, we for the first time account for the impact of quark scatterings via strong interactions at leading-log order. These reduce the quark contribution to the conductivity by up to 15 %, and the total conductivity by up to 6 %.

Speaker: Philipp Klose (Nikhef)

klose_kosmologietag.pdf

10:30 AM → 11:00 AM Coffee

11:00 AM → 12:30 PM Session

Convener: Ashim Sen Gupta

11:00 AM BullFrog integrator for large-scale structure: quantum analogue and beyond ΛCDM

Upcoming cosmological experiments will deliver unprecedented measurements of the matter distribution on the largest cosmic scales, enabling tests of physics beyond the standard models of cosmology and particle physics. Extracting this information requires accurate and efficient predictions of cosmic structure formation. I present results from classical and semiclassical simulations that use second-order Lagrangian perturbation theory as a time integrator. The BullFrog integrator significantly outperforms existing classical and semiclassical approaches, achieving accurate predictions with only a few time steps. The method is not restricted to ΛCDM and can be applied straightforwardly to cosmological models beyond the standard paradigm.

Speaker: Cornelius Rampf (Ruđer Bošković Institute)

Rampf-Biel26.pdf

11:15 AM Stone-Skipping Orbits: Resonant Dynamics in ULDM Solitons

The solitonic core is a prediction of ultralight dark matter (ULDM), yet its dynamical response to perturbations from orbiting compact objects remains poorly understood.

The orbit of a black hole embedded within a ULDM soliton is naively expected to decay due to dynamical friction. However, simulations have shown that single black holes can instead undergo “stone skipping”, in which the orbital radius varies quasi-periodically.

In Zhang et al. (2026), we show that this behaviour is driven by dipole excitation of the soliton. Using fully nonlinear simulations together with a pipeline for eigenmode decomposition, we identify the dipole mode as the dominant channel mediating the interaction. A complementary forced, damped oscillator description provides a useful interpretation of the resonant energy exchange, demonstrating that the coherent response of the soliton can significantly modify the orbital dynamics.

These results extend linear eigenmode analyses into the nonlinear regime and reveal a dynamical coupling between compact objects and ULDM cores. I will discuss the physical mechanism underlying this resonance, its dependence on mass ratio and damping, and its implications for supermassive black hole dynamics in ULDM halos.

Speaker: Yourong Frank Wang (University of Göttingen)

AxioNyx 1.1 Info Page

Backup_Bielefeld_2026_YWAN.pdf

Bielefeld_2026_YWAN.key

Public-Friendly Summary of the Work

11:30 AM Core collapse beyond the fluid approximation: The late evolution of self-interacting dark matter halos

The nature of dark matter is one of the big open questions about our Universe, and has been a problem in astronomy and cosmology for almost a century. Although making up most of the matter in the Universe, being more than five times more abundant than all of the known, “luminous” matter, the current Standard Model of Cosmology (ΛCDM) makes few statements on its properties.

If the dark matter has a sufficiently large elastic self-interaction, energy transported by scatterings can lead to gravitational collapse in the core of dark matter halos, which are the hosts of galaxies such as our own Milky Way. I will present numerical results following this collapse obtained using the new code KiSS-SIDM (Kinetic, Spherically Symmetric Self-Interacting Dark Matter). In contrast to the commonly adopted “conducting fluid” model, the code requires no calibration parameters. Further, its high accuracy enables simulating deeper into the collapse than traditional N-body methods. In this regime, we find that non-equilibrium effects alter the evolution compared to the predictions of the fluid model. I will discuss potential consequences of these findings as they concern detectability of self-interacting dark matter and the formation of black holes resulting from dark matter core collapse.

Speaker: Simon May (Universität Bielefeld)

talk.pdf

11:45 AM Bubble velocities in local equilibrium from a pseudopotential

First-order phase transitions in the early universe can lead to the nucleation and expansion of bubbles of the broken phase in a hot plasma. The velocity of the expanding bubble walls plays a crucial role in determining the dynamics of the transition and its phenomenological consequences, such as electroweak baryogenesis and the production of gravitational waves. /

/In this talk, I will present a method to estimate terminal bubble wall velocities in a plasma in local equilibrium. The approach is based on analyzing the extrema of a modified scalar potential, the so-called pseudopotential, whose shape depends on the wall velocity. The terminal velocity is determined by the condition that two relevant minima of this pseudopotential become degenerate. Physically, the pseudopotential provides an intuitive picture of the balance of forces acting on the bubble wall. Moreover, the framework also allows one to study configurations away from the stationary case, where the net pressure acting on the wall does not vanish. The method allows bubble velocities to be computed without solving the scalar field equation of motion and without relying on simplified plasma equations of state or a specific ansatz for the scalar field profile. As an illustration, I will discuss results obtained in a simple extension of the Standard Model and the resulting behavior of the net pressure acting on the bubble wall.

Speaker: Martin Münzberg

bubble velocities in local equilibrium from a pseudopotential.pdf

12:00 PM Slow-down effects on an expanding bubble in the early Universe

We study slow-down effects of bubbles generated during a cosmological first-order phase transition. We focus on deflagrations and hybrids, where the bubble wall is preceded by a shockwave. Slow-down of bubble walls and the resulting suppression of the gravitational wave signal has been observed in hydrodynamic multi-bubble simulations, most dominantly for small wall velocities.
Using static single-bubble and droplet solutions, we investigate to what extent the slow-down can be explained by heating effects in the shock region and by the non-zero fluid velocity of an impeding shock. We find that the suppression of the wall velocity in the Bag model, as it is often implemented in simulations, is weaker than in models whose change in the number of degrees of freedom (dofs) more closely resembles that of the Standard Model. By studying the Bag model with varying changes in the number of dofs, we observe that the difference in dofs between the two phases constitutes an additional relevant parameter– beyond the four parameters that are usually used to characterize the gravitational wave signal. Significant slow-down occurs, due to heating of the plasma region for both slow and fast walls. We also observe a strong correlation between the suppression of gravitational waves observed in hydrodynamic simulations and the width of the shock.

Speaker: Nabeen Bhusal (DESY)

Slow-down of an expanding bubbles in the early universe_Nabeen.pdf

12:15 PM Scalar-Induced Gravitational Waves from a QCD-induced Tachyonic Phase Transition

We investigate the gravitational wave signatures of a supercooled phase transition in the early Universe within the Classically Conformal $B−L\,$ Standard Model extension, where QCD-induced tachyonic instabilities can trigger a phase transition via spinodal decomposition instead of conventional bubble nucleation. By studying the resulting amplification of scalar fluctuations in the linear regime, we estimate the associated scalar-induced stochastic gravitational wave background. Lastly, we assess the prospects for their detection by comparing the predicted signals with the sensitivities of future gravitational wave experiments.

Speaker: Tamara Caldas (Goethe University Frankfurt)

Talk_Kosmologietag2026_Tamara_Caldas.pdf

1:45 PM → 2:30 PM Plenary

Convener: Adrien Florio

1:45 PM Einstein-Cartan gravity and its applications in particle physics and cosmology

It has been known since the works of Utiyama, Kibble, and Sciama that gravity can be formulated as a gauge theory of the Lorentz group. This gauge-theoretic approach naturally leads to Einstein–Cartan gravity, placing gravity on a similar conceptual footing as the interactions of the Standard Model. I will outline the basic construction of this framework and discuss its applications in particle physics and cosmology, including implications for inflation, mechanisms for dark matter production, and new perspectives on the strong CP problem.

Speaker: Mikhail Shaposhnikov

Bielefeld.pdf

Bielefeld.pdf

2:30 PM → 3:15 PM Session

Convener: Adrien Florio

2:30 PM The equation of state of the Universe after a first-order phase transition

Cosmological first-order phase transitions are caused by a scalar field that tunnels to a new vacuum state, triggering the nucleation and expansion of bubbles. In scenarios where the scalar field interacts only weakly with the surrounding plasma, the assumption of instantaneous reheating after the transition breaks down. As a result, the evolution of the universe may become dominated by oscillations of the scalar field. Such scenarios are often presumed to result in a phase of matter domination. In this talk, I examine this assumption using results from lattice simulations that track the scalar field’s energy distribution over time. By analyzing the system’s equation of state after the transition, I will show that it depends on the mean bubble separation, with large separations leading to sizable deviations from matter domination. These insights carry significant implications for the universe's later evolution and potentially the production of dark matter.

Speaker: Henda Mansour (KIT - Institute of Theoretical Particle Physics (TTP))

HendaMansour_Kosmologietag2026.pdf

2:45 PM Dark Sector Karaoke: A 3D EFT for a Pitch-Perfect Phase Transition.

We explore the dynamics of cosmological phase transitions in a dark sector model featuring a dark photon associated with a U(1)D gauge symmetry and radiative symmetry breaking. Our analysis focuses on different approaches to construct the effective potential: the high-temperature approximation, a full numerical evaluation of the thermal integrals, and a dimensionally reduced 3D effective theory built with DRalgo, at both leading and next-to-leading order. We as well explore the effect of including the running of the parameters in order to respect the hiercarchy scales.
We investigate how these methods impact the characterization of the phase transition, particularly in the supercooled regime.

Speaker: Cristina Puchades Ibáñez (JGU)

Cristina-Dark_Sector_karaoke.pdf

3:00 PM Colour-Flavour Locked SIDM

We present a self-interacting dark matter (SIDM) model based on a dark $SU(N)$ gauge theory spontaneously broken to a non-abelian global symmetry. The non-abelian structure naturally separates self-scattering and annihilation channels, allowing resonant enhancement of self-interactions to address the core–cusp problem while remaining consistent with experimental bounds. The relic abundance is set by freeze-out into light dark sector states, which couple to the Standard Model via effective kinetic mixing. The model’s parameters are fixed by relic density, small-scale structure, and resonance conditions, making it testable in upcoming direct detection experiments.

Speaker: Lorenzo De Ros (JGU Mainz)

Kosmologietag_LDR.pdf

3:15 PM → 3:45 PM Coffee

3:45 PM → 4:45 PM Session

Convener: Anna Berger (Universität Bielefeld)

3:45 PM 21cm cosmology at the cosmic dawn

In this talk, I will discuss that status and prospects for 21cm observations of the Epoch of Reionization and Cosmic Dawn. My focus will be on a mix of the work going on to prepare for SKA, which aims to measure the 21cm power spectrum and directly image ionized regions. I'll also discuss the status of REACH, a global 21cm experiment currently taking data and which aims to make a robust detection of the Cosmic Dawn absorption feature.

Speaker: Jonathan Pritchard (jpritchard@mpifr-bonn.mpg.de)

pritchard_kosmologiestag_v2_pdf.pdf

4:00 PM Probing Beyond-LCDM cosmologies with the 21cm signal

The cosmological 21cm signal promises great insights into the Epoch of Reionization and Cosmic Dawn. Up- coming Square Kilometre Array (SKA) observations will allow access to information previously inaccessible, offering new opportunities to constrain cosmology. To connect these observations with theory, accurate and flexible simulations are needed. I will present a modified version of the semi-numerical code 21cmFAST that couples to the Boltzmann solver CLASS to dynamically generate matter transfer functions for arbitrary cosmologies. Beyond-LCDM cosmologies are, for example, incorporated via the CPL parametrization of the dark energy equation of state. Building on these modifications, we create beyond-LCDM databases of the 21cm signal (light cones) and implement our simulation-based inference (SBI) framework to derive posteriors of cosmological parameters from mock 21cm observations. I will demonstrate the performance of this approach and discuss its implications for constraining beyond-LCDM cosmologies.

Speaker: Maike Voelkel (Institute for Theoretical Physics Heidelberg)

Kosmologietag_Maike_Voelkel.pdf

4:15 PM Constraining Reionization Morphology and Source Properties with 21cm–Galaxy Cross-Correlation Surveys

Cross-correlations between 21cm observations and high-redshift galaxy surveys provide a uniquely powerful probe of reionization, combining robustness to foreground contamination with direct sensitivity to the connection between ionization morphology and the galaxy population. In this talk, I will present results from our recent study quantifying the constraining power of 21cm–Galaxy cross-power spectra for inferring both reionization morphology and the properties of ionizing sources. Using our simulation-based inference framework EoRFlow applied to realistic mock observations, we explore how survey design choices, including galaxy survey field of view, redshift precision, and minimum detectable halo mass, impact constraints on the neutral hydrogen fraction, ionization morphology, and key source parameters such as the escape fraction of ionizing photons and star formation efficiency. Most notably, we find that cross-correlations enable strong constraints on ionizing source properties that remain highly degenerate in 21cm auto-power analyses, while also enhancing constraints on the global neutral fraction and ionization morphology compared to SKA-only measurements. Our results show that spectroscopic redshift precision is essential under foreground avoidance, and that detecting faint galaxies in low-mass halos or achieving improved 21cm foreground cleaning dramatically enhances the scientific return. These findings have direct implications for the design of future high-redshift galaxy surveys, such as those possible with the Nancy Grace Roman Space Telescope or the proposed WST, in synergy with SKA observations, and demonstrate the transformative potential of joint 21cm–Galaxy analyses for uncovering the sources that reionized the Universe.

Speaker: Yannic Pietschke (Institute for Theoretical Physics, Heidelberg)

21cmGalaxySBI.pdf

4:30 PM Capturing non-Gaussian cosmic information with Neutral Hydrogen one-point statistics

Neutral hydrogen (HI) traces the dark matter distribution of the Universe. Upcoming surveys such as the Square Kilometre Array Observatory (SKAO) will trace the neutral hydrogen up to $z \leq 6$ using several detection techniques including Intensity Mapping, which offers a unique window to explore the post-reionization Universe. Beyond two-point statistics promise to extract additional non-Gaussian information but require an accurate modelling of observational systematics such as foregrounds and the telescope beam. This work develops a theoretical model for the HI one-point probability density function (PDF) in spherical cells . It incorporates foreground removal and telescope beam effects via a simple variance rescaling that is validated against high-resolution simulations. We show that, despite these observational systematics, the HI PDF is able to capture additional non-Gaussian information from HI intensity maps compared to the power spectrum.

Speaker: Bernhard Vos Ginés

20. Kosmologietag_BVG.pdf

4:45 PM → 5:00 PM Mini break

5:00 PM → 6:00 PM Session

Convener: Dominik Schwarz (Bielefeld University - Faculty of Physics)

5:00 PM Enhanced Axion Fluctuations in the Pre-Inflationary Scenario

In the pre-inflationary scenario, axion dark matter is expected to be highly homogeneous on observable scales, with small perturbations sourced primarily by gravitational effects. In this talk, we present a comprehensive study of a recently proposed mechanism in which the axion field couples directly to temperature fluctuations in the primordial plasma, and consistently analyse its interplay with standard gravitational perturbations. We investigate how these plasma-induced fluctuations are transferred to the axion field, identify the range of scales over which this effect is relevant, and quantify the resulting enhancement in density perturbations. In particular, we follow the evolution of these fluctuations up to radiation–matter equality and determine how they modify the standard picture. Our results show that this mechanism can generate significantly larger overdensities compared to the conventional gravity-induced scenario, with potential implications for the small-scale structure of axion dark matter.

Speaker: Yeray Garcia del Castillo

yeraykosmologie.pdf

5:15 PM Enhancing curvature with an axion

We propose a model-independent mechanism to modify standard predictions of single-field inflation via the addition of a spectator axion field, only coupled to the inflaton via gravity. Allowing the two-field system to evolve past the end of inflation triggers a tachyonic instability in the isocurvature mode that in turn feeds into and enhances the curvature spectrum on all super-horizon scales. This yields a suppression of $r$ (once $\mathcal{P}_\zeta$ is renormalized to the observed CMB amplitude) and a correction to $n_s$ that is inherited from the tilt of the isocurvature spectrum. Due to the multi-field nature of the scenario, a non-trivial $f_{\rm NL}$ is also obtained. This mechanism is applicable to any single-field model of inflation. We perform a simple analytical study as well as a detailed numerical analysis using PyTransport.

Speaker: Diogo S. Gorgulho (University of Groningen)

Kosmologietag26.pdf

5:30 PM Primordial Black Holes: Galaxy Genesis, Correlation Characteristics and Quantum Quiddity

Primordial black holes are black holes that may have formed in the early Universe. Their masses potentially span a range from as low as the Planck mass up to many orders of magnitude above the solar mass. This, in particular, includes those black holes recently discovered through gravitational waves, and (part of) these may conceivably be of primordial origin. After a general introduction, I will discuss three recent aspects of primordial black holes: 1) their role in the formation of the earliest galaxies and stars; 2) new results regarding their formation from the largest-scale simulation to date of spatially-correlated random fields; and 3) the implications of recent advances in our understanding of quantum effects for their evaporation dynamics.

Speaker: Dr Florian Kühnel

5:45 PM The cosmic equation of state & primordial black holes

Gravitational wave detection has revived primordial black holes (PBHs) as a compelling dark matter candidate. PBH formation from overdensity collapse during the radiation-dominated era depends sensitively on the cosmic equation of state, particularly across the QCD transition. Following Bödeker et al. 2021, I investigate how lepton flavor asymmetries—poorly constrained prior to neutrino decoupling—impact the cosmic trajectory through the 5+1 dimensional space of chemical potentials (μ_B, μ_Q, μ_Le, μ_Lμ, μ_Lτ) and temperature. High lepton asymmetries could remain hidden in the undetectable cosmic neutrino background, enabling exploration of a large parameter space with significant effects on both the cosmic phase diagram trajectory and the resulting PBH mass distribution. I compute the equation of state for various lepton flavor asymmetry scenarios, extending beyond previous work by incorporating charm quark contributions using the latest lattice QCD and functional QCD data.

Speaker: Mr Maël Gonin

Google docs link

6:30 PM → 7:30 PM Public lecture

7:30 PM → 9:30 PM Conference dinner

At Brauhaus Johannes Albrecht

Fri, May 8

9:00 AM → 9:45 AM Plenary

Convener: Cora Uhlemann (Bielefeld University)

9:00 AM Constraining cosmology beyond the standard model with precision CMB experiments

I will present cosmology constraints from the Data Release 6 of the Atacama Cosmology Telescope (ACT) in both temperature and polarization, paying special attention to what ACT tells us about models of dark matter, and the initial fluctuations of inflation. I will describe the upcoming science from the next-generation experiments also located in the Atacama desert of Northern Chile such as the Simons Observatory currently taking data, and the soon-to-be-online CCATp observatory.

Speaker: Renée Hložek (University of Toronto)

Hlozek_KosmologieTag2026.pdf

9:45 AM → 10:30 AM Session

Convener: Cora Uhlemann (Bielefeld University)

9:45 AM Machine-learning Assisted Reionization Simulations

I present a diffusion-based super-resolution framework for generating high-resolution reionization simulations from computationally inexpensive low-resolution inputs.
Observables of reionization invoke simulations of physics across a high dynamic range of scales in the Universe. While 21cm and CMB explore both cosmological and astrophysical scales, probes like CO and CII whose modeling becomes integral to source characterization work specifically at sub-Mpc astrophysical scales. This necessitates high-resolution simulations of ionization volumes spanning redshifts 6-15 in large box sizes (≥250\geq 250
≥250 Mpc). Achieving this will allow for systematic reionization analysis and cross-correlation studies among multiple observational windows.

Recent advances demonstrate diffusion models substantially outperform GANs for cosmological super-resolution, offering training stability, and statistical fidelity \citep{2020arXiv200611239H}. Denoising diffusion probabilistic models learn to generate high-fidelity cosmological fields through iterative denoising processes, achieving percent-level accuracy in power spectra \citep{2021PNAS..11822038L,2023arXiv231006929S}. Further, a diffusion architecture with transformer-based training will specifically redistribute scale importance in pixel-wise objectives \citep{2022arXiv221209748P}. This is essential for preserving both large-scale coherence and small-scale bubble topology, a fundamental requirement for reionization studies.
I will show how transformer-based conditional diffusion models can alleviate a major computational bottleneck—accessing ionization field at high resolution. By leveraging low-resolution semi-numerical simulations as conditioning inputs, these models synthesize sub-grid physics while preserving the large-scale characteristics of the simulation box. I will discuss the model's performance on reionization summary statistics including power spectra, and one-point statistics, and its implications for resolution limitations inherent in semi-numerical codes relevant to upcoming SKA, CMB-HD, and CCAT experiments.

Speaker: Divesh Jain (University of Heidelberg)

Divesh_Jain_08.05.pdf

10:00 AM Joint Astrophysical and Cosmological Constraints from Cross-Correlated 21 cm and Line-Intensity Maps

In the near future, large surveys such as The Square Kilometre Array (SKA) will collect vast amounts of data with the aim of mapping large-scale structure across cosmic time using the 21 cm hydrogen line. However, connecting 21 cm intensity measurements to underlying cosmological parameters is highly non-trivial due to the complexity of structure formation and galaxy evolution. Robust theoretical modelling and realistic simulations are therefore essential for interpreting this upcoming data. I will therefore present how cross-correlating the 21 cm signal with other line-intensity maps (LIMs), such as H-α and Lyman-α, provides a powerful way to increase robustness and can be used to constrain astrophysical parameters and the matter density parameter jointly. Building on the semi-numerical code 21cmFAST, which predicts halo properties and derives quantities such as the 21cm brightness temperature, line luminosities for several spectral lines are modelled based on empirical relations. I will also give an outlook on how these simulated LIMs will be used for simulation-based inference (SBI), investigating the possible information gain using field-level information compared to 2-point statistics such as power spectrum. By incorporating realistic error models from both SKA and multi-line surveys such as SPEREx, these simulations aim to demonstrate how multi-line IMs can serve as powerful cosmological probes for the next generation of surveys.

Speaker: Klara Jons (Institute for Theoretical Physics Heidelberg)

KosmologieTag.pdf

10:15 AM Testing LCDM with LOFAR

tba

Speaker: Morteza Pashapour-Ahmadabadi (University Bielefeld)

Testing_Lambad_CDM_KosmologieTag_2026-3.pdf

10:30 AM → 11:00 AM Coffee

11:00 AM → 12:15 PM Session

Convener: Eamonn Weitz

11:00 AM Characterizing galactic foregrounds with SKAMPI: New S-band observations of the Large Magellanic Cloud

tba

Speaker: Nick Horstmann

Horstmann Kosmologietag2026.pdf

11:15 AM Superhorizon Isocurvature as a Window into Dark Matter Production

In the presence of primordial isocurvature perturbations, the superhorizon evolution of curvature perturbations becomes nontrivial. If the dark sector is radiation-like, its isocurvature can imply isocurvature in the inflaton sector even without non-gravitational interactions between the sectors. In this talk, we draw a simple picture of how to understand the nature of these fluctuations from first principles and without brute-force cosmic perturbation theory. We show how this setup is able to source isocurvature in simple models such as dark matter freeze-in and freeze-out and demonstrate that future measurements can potentially discriminate between these two mechanisms.

Speaker: Christopher Gerlach (Johannes Gutenberg-Universität Mainz)

Kosmologietag_2026_Gerlach_Isocurvature_Export.pdf

11:30 AM Secluded Dark Sectors and Isocurvature Perturbations

Understanding the origin of dark matter (DM) remains a central challenge in cosmology and particle physics. In this work, we investigate dark matter production via freeze-out and freeze-in, focusing on a secluded dark sector with its own temperature distinct from the visible sector.
A non-equilibrium temperature ratio between the dark and visible sectors can significantly shift the freeze-out and therefore influences the relic abundance. We map the resulting parameter space consistent with the observed dark matter abundance and existing bounds from CMB.
In a decoupled dark sector, isocurvature perturbations provide an observable signature to probe DM that was never in thermal equilibrium with the visible sector. Therefore, we explore how the amplitudes of the isocurvature modes depend on the dark sector dynamics.

Speaker: Sabrina Saul (Johannes Gutenberg University Mainz)

Kosmologietag-SSaul.pdf

11:45 AM Higgs vacuum stability and reheating in a kination-dominated Universe

Current measurements of the top quark mass indicate that the electroweak vacuum we live in might not be absolutely stable, i.e. the Higgs has a chance to undergo a catastrophic phase transition to the true minimum of its effective potential. The problem is even more severe in the early Universe due to the inherently higher energy scales. In general, the Higgs’ non-minimal coupling to the background curvature can stabilise it during inflation and avoid the problem of vacuum stability. However, for a subsequent stiff expansion phase of kination, the Higgs can be further destabilised by the tachyonic nature of such coupling to curvature. In this talk, I will present how this tachyonic instability makes it possible for the spectator Higgs to reheat the early Universe through non-perturbative particle production, while the classical stability of the electroweak vacuum is guaranteed for a large parameter space that depends on the exact value of the top quark pole mass. The particle production process generates a sizeable stochastic background of gravitational waves that carries information on cosmological parameters and particle-physics measurements.

Speaker: Giorgio Laverda (JGU Mainz)

kosmologietag_2026_laverda.pdf

12:00 PM Physical effects of Gravitational Waves at second order: resolving gauge ambiguities

In cosmological perturbation theory, gravitational waves are associated with tensor fluctuations of the metric. However, such an association is ambiguous at the second order. This gauge issue is very important for induced gravitational waves, a gravitational-wave signature characteristic of primordial black holes. I will review the issue and show a resolution: the strain measured at second order by a GW detector.

Speaker: Guillem Domenech (Leibniz University Hannover)

gauge_bielefeld_domenech.pdf

12:15 PM → 12:45 PM Farewell

Speaker: Cora Uhlemann (Bielefeld University)

Kosmologietag2026_Farewell.key

Kosmologietag2026_Farewell.pdf

12:15 PM → 12:45 PM Farewell and famous last words