[Astro] [CAPT] CAPT Weekly Bulletin (w/c 08-12-25)

Mon Dec 8 08:21:25 GMT 2025

Monday 8th December at 3pm, A113 CAPT – Theoretical Physics Student Seminar

Raphael Doza

Dimensional analysis is a gauge theory

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Tuesdays at 11am, CAPT Foyer – Astro Coffee

Tuesday 9th December at 1pm, A113 CAPT – Particle Cosmology and Gravity Seminar

James Alvey (Cambridge)

AI and the Era of Big Data Challenges in Gravitational Waves

The next generation of observatories, such as LISA and the Einstein Telescope, will usher in a big data era for gravitational wave astrophysics. These instruments will detect thousands of coincident signals, resulting in a complex data analysis challenge. Standard Bayesian inference techniques, such as MCMC and nested sampling, scale poorly with the high dimensionality of this problem, rendering a full analysis computationally challenging. In this seminar, I will discuss the ways in which I believe AI and machine learning can provide a viable path forward. I will pay particular attention to a class of Bayesian inference techniques called simulation-based inference (SBI) and discuss their application to the gravitational wave data analysis problem. I will also present a potential framework for integrating SBI and other GPU-based tools into a unified, scalable analysis pipeline.

Link to join: https://teams.microsoft.com/l/meetup-join/19%3ameeting_OGM3OTk5NzQtZWEwZS00ZmUyLTk3MGUtZjFhY2M5OTU2MjI1%40thread.v2/0?context=%7b%22Tid%22%3a%2267bda7ee-fd80-41ef-ac91-358418290a1e%22%2c%22Oid%22%3a%22f3250584-4b5f-48fa-a897-08e77f2246b7%22%7d
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Wednesday 10th December at 11am, A113 CAPT – CAPT Coding Club

Wednesday 10th December at 11am, C5 Physics – Particle Cosmology and Gravity Seminar

Javier Carballo (Southampton)

A complete mode decomposition of black hole perturbations

It is well known that quasinormal modes (QNMs) do not form a complete basis for linear black hole perturbations. In particular, retarded Green's functions of black holes can only be decomposed as a convergent sum of QNMs at sufficiently late times. In this talk, I will show that Green's functions can be expanded as a convergent mode sum everywhere in spacetime. When QNMs fail at early times, a sum of Matusbara modes (MMs) associated to the horizon temperature converges instead. I will present the case of the Schwarzschild black hole, where the branch cut is resolved into a set of de Sitter modes by adding a small positive cosmological constant. Based on 2510.18956.

Wednesday 10th December at 3.30pm, C4 Physics – Astronomy Weekly Seminar

Dr Kate Harbourne (Durham)

Swooping in on the drivers of the spin-age relation using COLIBRE

Observations from the SAMI integral field spectroscopic survey have demonstrated that older galaxies have lower spin and younger galaxies have higher spin, even when the effects of stellar mass and environment are controlled. Possible driver of this “spin-age” relation include the presence of internal secular heating driven by bars and spiral arms, progenitor bias and the impact of mergers. In the next-generation EAGLE simulation, COLIBRE, we find a population of high-spin, flattened galaxies and evaluate the origin of the spin-age relation in this new cosmological, hydrodynamical simulation. This presentation will demonstrate the emergence of a realistic spin-age relation in COLIBRE, explore the role of bars, mergers and progenitor bias in driving this relation, and make comparison to the same observed relation in the SAMI survey. I'll also be demonstrating how consistent comparisons between observations and simulations are important, and advocate for the use of mock observations towards this aim. Using the open-source, mock-IFU software, SimSpin, I'll show how observational systematics are properly accounted for in this investigation.

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Thursday 11th December at 1pm, A113 CAPT – Astronomy Lunch Talk

Callum Bellhouse

Morpho-Kinematic Decomposition of Intracluster Light with MUSE

The Intracluster Light (ICL) is a diffuse component which contributes a substantial yet poorly constrained portion (5-25%) of a cluster's stellar population. ICL is tightly linked to the hierarchical evolution of galaxy clusters and is a possible luminous tracer of the dark matter halo's profile, tracing the same gravitational potential. One of the biggest challenges in ICL observations is decomposing the ICL from the Brightest Cluster Galaxy (BCG), which is impossible using photometry alone without making significant assumptions about the relative profiles.

I will present a pilot project which incorporates MUSE integral-field spectroscopy and HST imaging to carry out morpho-kinematic decomposition of the ICL and BCG in AS1063, measuring spatially-resolved kinematics and spectral properties of the BCG and ICL out to >100kpc from the cluster centre, and comparing with the phase-space and mass distribution of cluster galaxies to test the utility of the ICL as a dark matter tracer. Multicomponent decomposition of the ICL and BCG will allow us to drastically improve our understanding of the transition region between the BCG and ICL, to constrain the relative contribution of the BCG and ICL with unprecedented precision, and to determine the utility of ICL as a luminous tracer of dark matter.

Thursday 11th December at 3pm, A113 CAPT – Particle Cosmology Journal Club
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Fridays at 4pm, CAPT Foyer – CAPT Cakes
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If you have any events/visitors you would like included in next week’s bulletin, please let me know.

Best wishes

Ella

Ella Batchelor (she/her)
Administrator

School of Physics & Astronomy

University of Nottingham
A112a Centre for Astronomy & Particle Theory
University Park
Nottingham, NG7 2RD

+44 (0) 115 74 86778 |  nottingham.ac.uk<http://nottingham.ac.uk/>

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