Dark matter across all scales: From large scale structure to laboratory searches
DIAS Seminar Room
University of Southern Denmark
The goal of this workshop is to bring together Danish and international experts on dark matter searches across all scales: from table-top sized laboratory experiments searching for particle dark matter all the way to dark-matter imprints on the large scale structure of the Universe.
This one-day workshop features invited talks from international experts on dark matter searches and a poster session for early career researchers. It is hosted by the Center for Cosmology and Particle Physics Phenomenology (CP3) at the University of Southern Denmark in Odense.
The workshop will take place one day before the Annual Danish Astronomy meeting, which will also be held in Odense: https://event.au.dk/events/adam2026
Please register and submit your abstract. We look forward to welcoming you to Odense!
We particularly encourage students to register and submit an abstract for the poster session. The workshop is free of charge for students.
Abstract submission and registration deadline: April 24
Abstract submission: https://indico.global/event/17334/abstracts/
Registration: https://indico.global/event/17334/registrations/4202/
Odense, Denmark’s third‑largest city, offers a distinguished blend of cultural heritage and contemporary urban development. Renowned as the birthplace of Hans Christian Andersen, Odense features historic quarters, modern public spaces, and a thriving academic and innovation environment. The city is situated on the island of Fyn, approximately 150km west of Copenhagen, making it easily accessible for both national and international visitors.
Confirmed invited speakers:
- Sarah Pearson (DTU)
- Jacob Egge (DESY)
- Hartmut Grote (Cardiff University)
- Marcel Pawlowski (AIP)
- Desiree Della Monica Ferreira (DTU)
- Philip Sørensen (U. Padua / INFN Padua)
Scientific Organizing Committee:
- Manuel Meyer
- Mads Toudal Frandsen
- Marcel Pawlowski
Supported by:
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08:30
Check-in and Breakfast
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Astrophysical Searches for Dark MatterConvener: Manuel Meyer (University of Hamburg)
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1
WelcomeSpeaker: Manuel Meyer (University of Hamburg)
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2
Decoding Dark Matter with Stellar Streams from Beyond the Milky Way
Upcoming and ongoing surveys will enable the detection of thousands of stellar streams around external galaxies. These streams form when dwarf galaxies or star clusters are tidally disrupted by their host gravitational potentials, producing elongated structures of stars with coherent, ordered motion. In this talk, I discuss recent advances in the study of extragalactic stellar streams and their implications for dark matter. I introduce X-Stream, a generative framework that translates stream imaging into constraints on the radial density profiles of dark matter halos, from the inner regions out to the virial radius. X-Stream employs the GPU-accelerated, JAX-based code streamsculptor to generate thousands of stream realizations in trial gravitational potentials, coupled with nested sampling to efficiently explore the parameter space. The resulting halo constraints provide a powerful test of alternatives to cold dark matter, such as self-interacting dark matter, which predicts cored density profiles. I also present Potamides, a rapid stream-curvature–based method that uses projected stream morphologies to constrain the shape and barycenter of host galaxy potentials, jointly probing baryonic and dark matter distributions. With upcoming missions such as Euclid, the Rubin Observatory, and the Roman Space Telescope, extragalactic stellar streams will enable detailed dark matter mapping across thousands of galaxies.
Speaker: Sarah Pearson (DTU Space) -
3
Satellite galaxies challenging cold dark matter expectations – moving from specific hosts to demographic samples
Low-mass dwarf satellites of more massive hosts have been used to test cold dark matter expectations, in particular in their internal dynamics, distributions and motion. The latter identified phase-space correlations such as the planes of satellite galaxies and lopsided asymmetries as serious challenges. These build on several well studied systems of satellite galaxies around hosts in the Local Group and nearby. Yet, these hosts’ individual formation and interaction histories might have played a role in shaping their satellite systems. We therefore now need to supplement such in-depth studies of specific systems with a more statistical approach to fully test expectations of the standard cosmological model, different dark matter types, and other dark matter alternatives. This requires appropriate metrics of phase-space correlations to account for the reduced dimensionality of the available data, and most importantly to allow to combine information of a diverse range of systems. I will discuss related difficulties, biases to account for, and pitfalls to avoid, to ultimately exploit the promises of large amounts of data from upcoming surveys in assessing satellite galaxy phase-space correlations. I will end with first results on how changing the types of dark matter in cosmological simulations from cold to warm or self-interacting affects predicted phase-space correlations.
Speaker: Dr Marcel Pawlowski (AIP / SDU)
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1
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10:30
Coffee Break
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Axion Dark MatterConvener: Manuel Meyer (University of Hamburg)
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4
Why we should believe in axion dark matter
In this talk, I will review how both QCD axions and axion-like-particles may be produced as dark matter in the early universe. I will start with a quick theoretical motivation for why we should believe in the existence of axions in the first place, and I will then cover the main productions mechanisms which might be responsible for the production of axions as dark matter. This covers, in particular, the misalignment mechanism, but I will also briefly give an overview of other mechanisms, such as the decay of topological defects and misalignment variants such as trapped misalignment and kinetic misalignment.
Speaker: Philip Sørensen (University of Padova / INFN Padova) -
5
Axion Haloscopes: Resonator Design and Quantum-Enhanced Readout
The axion is one of the most compelling dark matter candidates, simultaneously resolving the strong CP problem and accounting for the observed dark matter abundance. Detecting it requires extraordinary sensitivity, as the expected signals are buried far below thermal noise. Haloscopes — instruments exploiting axion-photon conversion in a strong magnetic field — have entered a rapidly evolving phase, with a growing diversity of experimental approaches targeting different regions of axion mass parameter space.
In this talk I give an overview of the main haloscope concepts and their associated resonator designs, discussing the key challenges of achieving high sensitivity while maintaining broad tunability. I then turn to the readout chain, where quantum sensing is emerging as a transformative tool. Beyond the standard quantum limit set by linear amplifiers, photon-counting and other quantum-enhanced detection strategies promise dramatic improvements in search speed and sensitivity. I discuss the prospects and challenges of these new approaches and their implications for the broader axion dark matter search programme.Speaker: Jacob Mathias Egge (DESY)
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4
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12:20
Lunch
Lunch with vouchers in main canteen
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Instrumentation for dark matter searchesConvener: Manuel Meyer (University of Hamburg)
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6
Searching for Dark Matter with Laser Interferometry
Laser interferometry has revolutionized astronomy by introducing a new sense to the observation of the cosmos. We can now hear the ripples of space-time: gravitational waves.
In this talk I will focus on how gravitational-wave detectors and their marvellous technology can also be (ab)used to search for ultra-light Dark Matter candidates, such as axion-like particles, scalar fields or dark photons. These particles or fields may directly interact with gravitational-wave detectors or similar instruments.
Several searches have been performed and are expected to become more sensitivve in the future, expanding the toolbox in the search for Dark Matter.Speaker: Prof. Hartmut Grote (Cardiff University) -
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The Hot and Energetic Universe with NewAthenaSpeaker: Prof. Desiree Della Monica Ferreira (DTU)
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6
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15:00
Coffee Break
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Posters: Lighning talksConvener: Manuel Meyer (University of Hamburg)
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8
Investigating Dark Matter through Cosmological Simulations and Comparisons with Observations
This project investigates current challenges to the cold dark matter (CDM) paradigm by studying the effects of dark matter on cosmological and galactic scales. In particular, it focuses on small scale observations, such as the centres of galaxies, where the data might suggest an alternative dark matter model such as self-interacting dark matter (SIDM).
Using IllustrisTNG as a baseline and AREPO simulations of SIDM and CDM, the project compares simulation results to test whether SIDM provides a better explanation of the data.
Speaker: Julie Magaard Knudsen (University of Southern Denmark) -
9
Exploring the Nature of Dark Matter with Cosmological Simulations and Machine Learning
This project investigates the impact different theoretical dark matter models can have on galactic structure on small-scale. The two models being considered is the Cold Dark Matter (CDM) and Self-Interacting Dark Matter (SIDM), since SIDM is a current proposal to a solution of the small-cale problem arising from the most succesful dark matter model, CDM. To investigate detailed differences between the two models, machine learning is implemented. Simulations of CDM and SIDM made from the AREPO-code is used as the baseline for the analysis.
Speaker: Pernille Truong (University of Southern Denmark) -
10
Searches for spectral upturns due to photon to Axion-like particle (ALP) conversions using H.E.S.S. and Fermi-LAT observations
High- and very-high-energy gamma rays from distant extragalactic sources are severely attenuated due to interactions with the extragalactic background light (EBL). This effect could be partially alleviated by introducing Axion-like particles (ALPs), a beyond-Standard Model dark matter candidate that allows for photon-to-ALP oscillations in astrophysical magnetic fields. These oscillations would allow photons to convert into light ALPs in the intergalactic magnetic field and propagate freely towards our galaxy, where they can then reconvert back into detectable photons, producing characteristic high-energy spectral upturns for each source. The search for these upturns offers a way to constrain the allowed parameter space of ALP models while studying gamma-ray propagation over cosmological distances.
We analyze the intrinsic spectra of a large sample of extragalactic gamma-ray sources using observations from both the Fermi-LAT and H.E.S.S. instruments. A statistical search is performed for spectral upturns by introducing spectral break features in the intrinsic source models and comparing them to simulated ALP-induced signatures. This framework enables tests of the photon-ALP oscillation hypothesis and places further constraints on the relevant ALP parameter space and its impact on gamma-ray propagation over cosmological distances.
Speaker: Dominik Pastuszka Malek (University of Southern Denmark) -
11
Towards a Cryogenic Optical Filtering System for Background Suppression in High-Efficiency Single-Photon Detectors
Cryogenic Single-Photon Detectors, such as Transition-Edge-Sensors (TES) and Superconducting Nanowire Single-Photon Detectors (SNSPD), have achieved high detection efficiency larger than 85\% for optical and near-infrared wavelengths. Fiber-Coupled Blackbody photons has been identified as the dominant source of background signals for both detector systems. In order the achieve ultra-low background rates while maintaining high detection efficiency an Optical Filtering System is currently in development. The system is a cryo-compatible optical U-bench, housing a ultra-narrow bandpass filter with a center wavelength of $1065\,\text{nm}$. The Cryogenic Optical Filter Bench (COFB) is mounted on the $50\,\text{K}$ stage of a dilution refrigerator, and is designed with eleven mechanical degrees of freedom (DOF), seven of which are remote-controllable and four requires manual adjustment. The seven remote-controllable DOF allows for ongoing alignment of the open optical beam through the ultra-narrowband filter to compensate for thermal contractions and the resulting transmission loses. In addition, the COFB enhances the energy-resolving capabilities of TES detectors and enables energy-selective single-photon detection for SNSPDs. We present the design, performance and current limitations of the COFB system and discuss it's applicability to ultra-low-background optical experiments, such as the rare-event search for the hypothetical axions and axion-like particles with the experiment Any Light Particle Search II (ALPS II).
Speaker: Joakim Rützou Rosenkilde (CP3 - University of Southern Denmark) -
12
The radial acceleration relation at the EDGE of galaxy formation: challenging its universality in low-mass dwarf galaxies
Nearby dwarf galaxies are strongly dark matter-dominated, making them ideal laboratories for testing empirical relations between dynamical and baryonic properties. A key example is the Radial Acceleration Relation (RAR), describing a tight correlation between baryonic and observed acceleration across a wide mass range. Whether this relation holds in the lowest-mass, dark matter–dominated dwarfs remains an open question, with hints of deviations from early studies.
We present radially resolved measurements of the RAR for 12 nearby dwarf galaxies with baryonic masses 10^4 < Mbar/M⊙ < 10^7.5, combining literature data with new measurements from the MUSE-Faint survey. Using stellar kinematics and Jeans modelling with GravSphere, we infer mass distributions and compare the resulting acceleration profiles with isolated dwarf galaxies from the EDGE simulations in a ΛCDM cosmology.
We find that most of the observed dwarf galaxies systematically lie above the low-mass extrapolation of the RAR, which was originally calibrated on more massive galaxies. The simulated EDGE dwarf galaxies exhibit a similar behaviour to the observed data, with a higher observed acceleration at a fixed baryonic acceleration compared to the extrapolated RAR. Additionally, there is significant scatter across galaxies, suggesting that the RAR is not universal for low-mass dwarf galaxies and that baryonic acceleration alone does not contain enough information to fully determine the observed acceleration, providing new near-field constraints on dark matter in the faintest galaxies.Speaker: Mariana P. Júlio (Leibniz-Institut für Astrophysik Potsdam) -
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Andromeda's asymmetric satellite system as a challenge to cold dark matter cosmology
The distribution of dwarf satellite galaxies around massive hosts serves as a useful probe of dark matter at small scales, especially since the effect of baryonic matter within the galaxies themselves on their spatial distribution is minimal. Here, I examine our neighbouring galaxy Andromeda, which hosts a strikingly asymmetrical distribution of satellites aligned towards the Milky Way. I characterise the Andromeda system’s asymmetry and test its agreement with expectations from concordance cosmology, which predicts that most satellite galaxy systems are near-isotropic – in line with other dwarf associations observed in the local Universe, which remain only weakly asymmetric. All but one of Andromeda’s 37 satellite galaxies are contained within 107 degrees of our Galaxy. In standard cosmological simulations, less than 0.3% (0.5% when accounting for possible observational incompleteness) of Andromeda-like systems show a comparably significant asymmetry, and none are as collectively lopsided as the observed satellite configuration. In conjunction with its well-studied satellite plane, these results paint the Andromeda system as an extreme outlier in the prevailing cosmological paradigm, further challenging our understanding of structure formation at small scales.
Speaker: Kosuke Kanehisa (Leibniz-Institute for Astrophysics Potsdam (AIP)) -
14
Detection of Single Photons under Strong Parallel Magnetic Fields Using NbTiN-based Superconducting Nanowires
Superconducting nanowire single-photon detectors (SNSPDs) are a leading technology for single-photon detection in quantum science and its applications, thanks to their high detection efficiency, low noise, and unmatched timing resolution. These properties make SNSPDs attractive candidates for novel rare-event searches, such as those for axions and axion-like particles. However, the presence of strong magnetic fields generally hinders the direct, low-loss implementation of superconducting single-photon detectors within such experiments. We present our investigations of the performance and limitations of a NbTiN-based SNSPD for detecting 1064 nm photons under parallel magnetic fields of up to 6 T, while also providing insights into the underlying physics governing the nanowire’s photon response. In particular, the effect of parallel-field-induced Pauli (paramagnetic) pair breaking of spin-singlet superconductivity is discussed together with existing photon response models in the literature. Our results show that quasiparticle diffusion and multiplication play an important role in the physical processes resulting in voltage pulse after photon absorption.
Speaker: Elmeri Rivasto -
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Developing Diversity with Self-Interacting Dark Matter in Low-Mass Halos and Milky Way SubhalosSpeaker: Maya Sophia Silverman (University of Copenhagen)
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8
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PostersConvener: Manuel Meyer (University of Hamburg)
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19:00
Dinner
Dinner at Storms Pakhus: https://stormspakhus.dk/en/
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08:30