Cosmological Observables: Cambridge-LMU Cosmology Meeting

Sitzung

Inference and computing

29.09.2026, 14:00

Ryle room (Kavli Cambridge)

106. Christopher Lovell

29.09.26, 14:00

Cosmological simulations face a fundamental trade-off between volume and resolution: large boxes are representative of the real Universe, but have insufficient fidelity to model the detailed physics of galaxy formation, while high-resolution hydrodynamic simulations must be run in volumes far too small to be cosmologically representative. Zoom simulations can re-simulate small regions from a...

107. Hui Kong - "Forward modeling observational systematics with Source Injection"

29.09.26, 14:20

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Source Injection produces synthetic source catalog by running the image reduction pipeline. The process replicates the complicated process from image to catalogs. The synthetic galaxies produced from source injection have similar observational systematics as real galaxies.

When a galaxy sample is selected, it occupies a continuous color space. Then galaxies within this sample may respond...

108. Anna Cremaschi

29.09.26, 14:40

A question that has gained importance in recent years is how to maximize the cosmological information that can be extracted from observational data.
Approaches based on summary statistics compress the data into a lower-dimensional representation, thereby losing part of the information. In contrast, the core idea of field-level inference is to use the full overdensity field, bypassing the...

109. Zekang Zhang

29.09.26, 14:55

Weak gravitational lensing and photometric galaxy clustering are the two pillars of large-scale-structure cosmology, and both rest on one fragile assumption: that we know the redshift distribution, $n(z)$, of our galaxy samples. In this talk I show that this assumption breaks down in subtle but consequential ways, and present forward-modelling methods to fix it. Galaxies blended in the focal...

118. Stephen Thorp - "pop-cosmos: forward modelling and inference for cosmological galaxy catalogues"

30.09.26, 11:25

Wide-area surveys that measure the clustering and weak lensing of galaxies are some of our most powerful cosmological probes, with Stage IV projects like the Vera C. Rubin Observatory, Euclid, and Dark Energy Spectroscopic Intrument (DESI) set to enable high-precision cosmological measurements in the coming years. Getting the most out of these surveys will rely on careful modelling of the...

119. Alicia Finger

30.09.26, 11:45

This talk will briefly cover the basics of SBI before delving into methods for validating a neural network and its performance demonstrated on neural posterior estimation for cosmological parameters based on analytical simulations of galaxy cluster catalogs. Finally the talk will explain how network performance for this use-case scales with the inferred parameters and number of training...

121. Ivana Nikolac

30.09.26, 12:00

Standard analyses of galaxy clustering rely on summary statistics such as the power spectrum and bispectrum, but extending to higher-order n-point functions quickly becomes intractable. Field-level inference (FLI) offers an alternative by forward-modeling the galaxy density field and explicitly employing the full joint posterior of the initial conditions, cosmological parameters, and bias...

142. Lawrence Berry - "GPU-accelerating CMB cosmology with state of the art ODE solvers"

01.10.26, 16:00

GPUs offer a way to massively parallelise certain types of physical models, allowing us to compare more models for the same compute budget (and hence do more science) whilst avoiding the use of emulators (which must be retrained every time you modify the underlying physics). More efficient forward models also allow us to tackle higher-dimensional problems (map/field-level inference) and more...

143. Kai Lehman: Evidence Networks with Learned References for Fast Simulation-Based Model Inference

01.10.26, 16:15

144. Nikolas Frediani - "Data-driven Galaxy Population Prior for Photometric Redshifts"

01.10.26, 16:30

One of the major frontiers for Stage IV galaxy surveys is photometric redshift estimation. For weak lensing cosmology, the required characterization of redshift distributions is an order of magnitude more precise than current state-of-the-art. Because the true population is not directly accessible to us, every photo-z method relies - implicitly or explicitly - on a prior over galaxy SEDs,...

120. Dily Duan Yi Ong

As cosmological datasets from Large-Scale Structure (LSS) and the Cosmic Microwave Background (CMB) grow in precision and complexity, disparities between datasets demand robust statistical methods for model comparison and tension quantification. However, calculating Bayesian evidences remains a computationally prohibitive bottleneck, limiting the rapid validation of new datasets and extended...

141. Luca Tortorelli

The next-generation of wide-field galaxy surveys, known as Stage IV experiments, aims to investigate the "dark sector" by mapping a significant fraction of the observable Universe at unprecedented depth. In doing so, these surveys will also contribute to transform our understanding of galaxy formation and evolution. Their vast statistical power is however limited by systematic effects that...