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David Sanchez-Cid (University of Zurich)04/06/2026, 10:00
We present cosmological constraints from the full six-year Dark Energy Survey (DES) combining weak gravitational lensing and galaxy clustering in a joint 3 $\times$ 2pt analysis over $\sim$5000 sq. deg. This represents the legacy large-scale structure result of DES, culminating more than a decade of survey operations and analysis development. We derive constraints on $\Lambda$CDM and several...
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Benedetta Rosatello (University of Geneva)04/06/2026, 10:15
A direct, model-independent probe of the validity of theories beyond General Relativity and the concordance LCDM model is provided by the Weyl potential, the sum of the temporal and spatial distortions of the spacetime geometry. Its measurement, obtained by combining galaxy clustering and galaxy-galaxy lensing data from the Dark Energy Survey (DES-Y3), is in tension with the LCDM prediction at...
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Laura Reymond (ETH Zurich)04/06/2026, 10:30
In the context of soon to be released data from large-scale structure (LSS) Stage IV surveys that offer extremely precise and broad measurements, I will present $\texttt{SwiftC}_\ell$: a fast, accurate and differentiable Python pipeline for the beyond Limber computation of the angular power spectrum. $\texttt{SwiftC}_\ell$ includes all relevant contributions to wide-angle surveys that are...
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Andreas Nygaard (University of Zurich)04/06/2026, 10:45
Precision cosmology increasingly relies on repeated evaluations of computationally expensive observables, such as Cosmic Microwave Background (CMB) anisotropy spectra and large-scale structure statistics, posing a significant bottleneck for parameter inference and model comparison. Emulation techniques have emerged as a powerful solution, enabling fast and accurate interpolation of these...
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Veronika Oehl (ETH Zürich)04/06/2026, 11:00
Two-point correlation functions are a standard tool in cosmology. However, their estimators have intrinsically non-Gaussian likelihoods, even for perfectly Gaussian random fields.
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We present a framework for computing exact correlation-function likelihoods for the spin-2 fields of cosmic shear. These likelihood distributions show significant skewness and can systematically shift parameter... -
Gen Ye04/06/2026, 11:15
We present a non-parametric, model-independent reconstruction of the cosmological background and perturbation dynamics in non-minimally coupled theories of gravity. Within the Effective Field Theory (EFT) of dark energy framework, we reconstruct the time-dependent cosmological constant, $\Lambda(t)$, and the non-minimal coupling function, $\Omega(t)$, from cosmological data.
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To ensure... -
Silvan Fischbacher04/06/2026, 11:30
Stage-IV galaxy surveys will soon deliver data of unprecedented depth and volume. Extracting the maximum information from these data while keeping systematics under control poses new challenges for the field. In this talk, I will present GalSBI, an open-source framework that addresses both simultaneously by constructing highly realistic synthetic galaxy catalogs through simulation-based...
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Shengyu HE (EPFL)04/06/2026, 11:45
DESI DR2 delivers over 30 million redshifts from the first three years of the main survey, enabling high-precision large-scale structure measurements. In this talk, I will present an assessment of spectroscopic systematics in DR2, with a focus on redshift uncertainties and catastrophic redshift errors. Using repeated observations of BGS, LRG, ELG, and QSO targets, we empirically characterize...
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Yu Liu (EPFL)04/06/2026, 12:00
Tessellation methods are extensively employed in the analyses of cosmic large-scale structure (LSS). However, these techniques are highly sensitive to perturbations in both densities and positions of points, often leading to substantial rearrangements of tessellation configurations. As a result, considerable additional statistical errors are introduced in various tessellation-based statistics,...
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Ajith Sampath (University of Geneva)04/06/2026, 14:00
The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a radio interferometer currently being deployed in the Karoo Desert, South Africa. It aims to constrain the dark energy equation-of-state parameter using accurate measurements of baryon acoustic oscillations (BAO) via 21cm intensity mapping. It will be equipped with 1024 dishes, each 6m in diameter, arranged in a...
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Julian Adamek (ETH Zürich)04/06/2026, 14:15
Spatial curvature is a fundamental cosmological parameter that is routinely constrained with cosmological observations. Even a small non-zero value would have huge implications if detected. Large-volume galaxy surveys can provide constraints independent of the CMB, reducing the dependence on model assumptions, but only if we have forward models that can treat spatial curvature consistently. I...
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Ethan Tregidga (EPFL)04/06/2026, 14:30
Dark matter accounts for 85% of all matter in the Universe, yet its nature remains elusive. Next-generation telescopes are providing a wealth of observations of dark matter-dominated galaxy clusters, which contain subtle clues to its nature. However, traditional methods either compress the data into summary statistics or require computationally expensive forward modelling. We present a machine...
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Aymeric Galan (Department of Astronomy, UNIGE)04/06/2026, 14:45
Time-delay cosmography with lensed quasars is a one-step method for estimating the Hubble constant in the local Universe independently of the cosmic distance ladder. It does not require any intermediate calibration and relies on measuring the time delays between multiple images of strongly lensed quasars, which are inversely proportional to the Hubble constant.
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In this talk, I will present... -
Martin Millon (University of Geneva)04/06/2026, 15:00
Measurements of the kinematic cosmic dipole continue to show an intriguing tension between the value inferred from the CMB and that obtained from high-redshift source number counts. While the measured dipole direction appears consistent, the amplitude, set by the observer’s peculiar velocity v_o, remains in significant disagreement. Here, we propose using strong gravitational lenses with...
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Francesco Sorrenti (ICC - University of Barcelona)04/06/2026, 15:45
Peculiar velocities have emerged as essential tools in modern cosmology and astrophysics. A particularly compelling application lies in the use of Type Ia Supernovae (SNIa) luminosity distances to map the underlying large-scale matter structure. In this talk, I will show that the observed luminosity-distance multipoles effectively encode the expansion and shear of the local velocity field,...
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Antonino Salvino Midiri (University of Geneva)04/06/2026, 16:00
In this talk I am going to focus on the study of the power spectrum of the velocity field induced in the primordial plasma by expanding scalar-field bubbles during a first-order phase transition occurring in the radiation-dominated era.
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Contrary to previous expectations, we find that the breaks in the velocity spectrum are not associated to the bubble size and the sound shell thickness,
but... -
Davide Perrone (University of Geneva)04/06/2026, 16:15
I will discuss the construction of an effective field theory for a compact body coupled to gravity, whose key feature is that the dynamics of gravitational perturbations is explicitly determined by known solutions in black hole perturbation theory in four dimensions. In this way the physics of gravitational perturbations in curved space is already encoded in the effective field theory. I will...
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Giona Sala (RWTH Aachen)05/06/2026, 09:15
The number of gravitational wave (GW) events observed is rapidly growing, and will soon reach statistical significance with the next generation of detectors. Astrophysically sourced GW are expected to be a new complementary and totally independent tracer of large-scale structure. Consequently, cross-correlation techniques offer the opportunity to fully exploit the potential of this new channel...
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14. Gravitational wave Hubble constant measurement using the DES Y6 Gold galaxy catalog and GWTC-4.0Isaac McMahon (University of Zürich)05/06/2026, 09:30
Gravitational wave (GW) standard sirens enable independent measurements of the Hubble constant. In the absence of electromagnetic counterparts, the "dark siren" method statistically correlates GW events with potential host galaxies. We present a measurement of H0 using 142 events from the GWTC-4.0 GW event catalog and the DES Y6 Gold photometric galaxy catalog. We jointly infer cosmological...
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Raphael Bertrand-Delgado (University of Zurich)05/06/2026, 09:45
We investigate the detectability of the stochastic gravitational wave background (SGWB) anisotropies by cross-correlating them with a galaxy distribution. We develop two independent and complementary approaches: galaxy-informed simulations of SGWB maps and a physically motivated analytical modelling. We implement an empirically driven method to map SGWB anisotropies by simulating compact...
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Julien Carron (IRSOL)05/06/2026, 10:00
Thanks to exquisite CMB B-mode data, we should see within the next few years massive improvements in constraints on a background of gravitational waves from inflation. In particular, SPT-3G and BICEP (SPO) have collected now enough data to achieve, in principle, 3 times better constraints on the tensor-to-scalar ratio than currently published, after the delicate removal of their main...
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Giovanni Piccoli (University of Zurich)05/06/2026, 10:15
Scalar Induced Gravitational Waves (SIGW) are generated at second order in perturbation theory and to achieve observational relevance, inflationary dynamics must evade the standard slow-roll scenario at small scales, generating large curvature perturbations following strongly non-gaussian statistics. We propose a method to efficiently compute the SIGW spectrum including arbitrary...
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Lucas Lombriser (FHGR & UNIGE)05/06/2026, 11:00
Atom interferometer experiments offer interesting prospects for searches for interactions of ultralight bosonic dark matter with Standard Model particles, detection of gravitational waves in a frequency band inaccessible to experiments that are operating or under construction, as well as tests of dark energy and modified gravity. The 140-m PX46 access shaft to the LHC at CERN and an 870-m...
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Chiara Caprini (CERN and University of Geneva)05/06/2026, 11:15
The second data release of the European Pulsar Timing Array (EPTA) collaboration provides evidence for the presence of a gravitational-wave (GW) background. In this work, we explore a potential cosmological interpretation of this signal in terms of inflationary scenarios.
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We parametrize the tensor power spectrum in terms of the tensor-to-scalar ratio $r$, the tensor spectral index $n_t$, the... -
Dr Nils Schöneberg05/06/2026, 11:30
Using the most recent available cosmological datasets the Hubble tension has climbed to beyond 7 sigma significance. Different families of measurements point towards two hardening camps, and in this talk I review the efforts of the H0DN collaboration on testing the consistency of local measurements, outlining the lessons learned from this systematic audit. With the tension increasingly...
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Guandi Zhao (ETH Zurich)05/06/2026, 14:00
Baryonic feedback processes play a central role in the evolution of galaxy formation and in the interpretation of cosmological constraints from galaxy surveys. The thermal Sunyaev-Zel’dovich (tSZ) effect traces this feedback by probing hot gas content over a broad redshift range. We cross-correlate Atacama Cosmology Telescope DR6 tSZ y-map and the Dark Energy Survey Year 6 galaxy positions to...
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Dominique Eckert (Department of Astronomy, University of Geneva)05/06/2026, 14:15
Large upcoming cosmic shear experiments like Euclid and LSST are attempting to retrieve cosmological information by constraining the matter power spectrum in the local Universe and its redshift evolution. This approach requires that the shape and evolution of the power spectrum can be accurately predicted from cosmological parameters. In recent years, it has become clear that baryonic...
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Riccardo Seppi (University of Geneva)05/06/2026, 14:30
Upcoming cosmological surveys aim to measure the matter power spectrum with percent-level precision, but baryonic effects, in particularly AGN feedback, remain a major source of systematic uncertainty, suppressing power on small scales. Constraining how feedback redistributes gas in dark matter haloes is therefore essential for robust cosmological inference.
Galaxy groups, with their...
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Jozef Bucko (ETH Zurich)05/06/2026, 14:45
Diffuse X-ray emission from hot intracluster gas and emission from active galactic nuclei (AGN) provide complementary tracers of large-scale structure, encoding rich information about baryonic feedback, black hole and galaxy formation, and cosmology. These observables are particularly promising for cross-correlation studies with upcoming wide-field X-ray surveys.
We present a...
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Felix Vecchi (EPFL)05/06/2026, 15:00
Offsets between the Brightest Cluster Galaxy (BCG) and the gravitational potential minimum in relaxed galaxy clusters, known as a “BCG wobble”, provide a smoking-gun signature of dark matter self-interactions. Our previous work shows that such self-interactions can produce a wobble with an amplitude of ~5 kpc in massive clusters - requiring exquisitely accurate and precise modelling. In order...
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Sebastian Ljung (Department of Astronomy, University of Geneva)05/06/2026, 15:15
A large fraction of stars interact with a close companion during their lifetime, during which the transfer of mass and angular
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momentum shapes their evolution and final fate. Standard rotationally limited accretion models predict that accretors reach
critical rotation after gaining only a small fraction of their mass, severely suppressing further accretion. This is in tension... -
Pascal Hitz (ETHZ)
Cosmological neutral hydrogen (HI) surveys provide a powerful tomographic probe of the post-reionization universe to test the standard model of cosmology. Efficiently simulating the HI signal is essential for optimizing the design and analysis strategies of upcoming surveys. We present a fast simulation method for the cosmological HI distribution employing the halo model framework. Dark matter...
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Gravitational wave (GW) standard sirens enable independent measurements of the Hubble constant 𝐻0. In the absence of electromagnetic counterparts, the "dark siren" method statistically correlates GW events with potential host galaxies. We present a measurement of 𝐻0 using compact binary coalescences from the fifth Gravitational-Wave Transient Catalog, combined with the Dark Energy Legacy...
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Borna Salehian (ETH)
Tidal Love number is a measure of deformability of compact objects in an external tidal gravitational potential. I will argue for positivity of static Love number of electric type, using Kramers-Kronig relations, under certain condition. I will also discuss a few examples including dark matter halos.
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