Shorts stories 1 - Planets

You know those annoying social media films where a mic is shoved in front of a bunch of students and they're asked questions that have nothing to do with their studies or their lives, hoping they say something vaguely funny or interesting that might get a billion views on TikTok?

Register for Developing Academic Skills workshops

Colleagues are invited to register for the Centre for Teaching and Learning’s final two Developing Academic Skills workshops this academic year. The in-person sessions support colleagues involved in teaching or supporting undergraduate and postgraduate taught students’ academic skills development. Topics are structuring and editing (Monday 26 January), and developing exam and revision skills (Monday 23 February).

Hilary Term Planner for Careers and Employability

From application and interview support to sector insights and inspiring guest speakers, Hilary term offers a wide range of opportunities for students at every stage of career planning. Term planner highlights include the Creative Careers Festival in 4th week, the Crankstart and Diversity Fair in 7th week, and ongoing internship application support throughout the term.

Talk About Your Thesis

The Radcliffe Science Library invites science and medicine postgraduates to give a short, engaging 5–7 minute talk on their research. It’s a great chance to practice explaining your work clearly and succinctly - perfect preparation for the DPhil transfer or upcoming conferences - and to connect with other researchers in a relaxed setting. A complimentary pizza lunch will follow the talks.

Radcliffe Science Library , Friday 20 March 2026, 12:00–13:00 followed by lunch.

Fri, 23 Jan 2026
13:00
L6

Latschev’s theorem in persistent homotopy theory

Lukas Waas
(Oxford University)
Abstract
A central question in topological data analysis is whether the sublevel-set persistent homology of a function from a sufficiently regular metric space can be recovered from a finite point sample. A natural approach is to equip the Vietoris–Rips complex of the sample, at a fixed scale, with an appropriate filtration function and to compute persistent homology of the resulting filtered complex.
 
Despite its appeal, this approach has so far lacked theoretical guarantees. Existing results instead rely on image persistence, computing the image of transition morphisms between Rips homology at two different scales. By contrast, Latschev’s theorem in metric inference shows that, under suitable regularity and sampling assumptions, the Vietoris–Rips complex of the sample at a single scale is already homotopy equivalent to the underlying space.
 
In this talk, I will explain how tools from persistent homotopy theory yield a persistent version of Latschev’s theorem, which in particular resolves this classical question of estimating persistent homology at the level of persistent homotopy types.
Tue, 03 Mar 2026
13:00
L2

Beyond Wigner - How Non-Invertible Symmetries Preserve Probabilities

Thomas Bartsch
(Oxford )
Abstract

Recent years have seen the expansion of the traditional notion of symmetry in quantum theory to so-called generalised or categorical symmetries, which may in particular be non-invertible. This seems to be at odds with Wigner's theorem, which asserts that quantum symmetries ought to be implemented by (anti)unitary -- and hence invertible -- operators on the Hilbert space. In this talk, we will try to resolve this puzzle for generalised symmetries that are described by (higher) fusion categories. After giving a gentle introduction to the latter, we will discuss how one can associate an inner-product-preserving operator to (possibly non-invertible) symmetry defects and illustrate our construction through concrete examples. Based on the recent work 2602.07110 with Gai and Schäfer-Nameki.

Tue, 24 Feb 2026
13:00
L2

The Geometry of Gravitational Radiation

Jelle Hartong
(Edinburgh)
Abstract
Future null infinity of an asymptotically flat spacetime is a conformal Carroll manifold. I will not assume any familiarity with Carroll geometry and explain the relevant geometrical notions as we go along. We will consider asymptotic solutions to the 4D vacuum Einstein equations where future null infinity is endowed with the most general Carroll metric data that is allowed by the Einstein equations. This can be used to define an energy-momentum tensor (EMT) at future null infinity by varying a suitably renormalised action with respect to the boundary Carroll metric data. It is shown that the Ward identities obeyed by this boundary EMT agree with the Bondi loss equations that describe the loss of energy and momentum due to the emission of gravitational waves. The metric near future null infinity can be formulated in terms of a Cartan geometry based on the conformal Carroll algebra. The non-vanishing curvatures of said algebra dictate how radiative the spacetime is. For example, the vacuum degeneracy is described by a flat conformal Carroll connection. We will see that the Bondi loss equations can be rewritten as flux-balance laws where the fluxes are determined by the Cartan geometry for the conformal Carroll algebra.


 

Tue, 10 Feb 2026
13:00
L2

Dynamics of the Fermion-Rotor System

Vazha Loladze
(Oxford )
Abstract

In this talk, I will examine the dynamics of the fermion–rotor system, originally introduced by Polchinski as a toy model for monopole–fermion scattering. Despite its simplicity, the system is surprisingly subtle, with ingoing and outgoing fermion fields carrying different quantum numbers. I will show that the rotor acts as a twist operator in the low-energy theory, changing the quantum numbers of excitations that have previously passed through the origin to ensure scattering consistent with all symmetries, thereby resolving the long-standing Unitarity puzzle. I will then discuss generalizations of this setup with multiple rotors and unequal charges, and demonstrate how the system can be viewed as a UV-completion of boundary states for chiral theories, establishing a connection to the proposed resolution of the puzzle using boundary conformal field theory.

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