Tue 13 May 14:00: Higher arithmetic duality EHTW03 - New horizons for equivariance in homotopy theory
I will report on joint work in progress with Sanath Devalapurkar andJeremy Hahn. The singular cohomology of a closed, oriented manifoldsatisfies Poincaré duality, and the Galois cohomology of a localnumber field satisfies Tate-Poitou duality. We prove duality theoremsfor syntomic cohomology and topological cyclic homology of a class ofring spectra, tentatively called higher local number rings, subject to anorientability hypothesis. This class of ring spectra includes truncatedBrown-Peterson spectra, complex and real topological K-theory,topological modular forms, and their unramified extensions. The dualitytheorems come in reduced, localized and filtered versions, analogous toknown refinements of Tate-Poitou duality in the case of classical rings.
EHTW03 - New horizons for equivariance in homotopy theory
- Speaker: John Rognes (University of Oslo)
- Tuesday 13 May 2025, 14:00-15:00
- Venue: Seminar Room 1, Newton Institute.
- Series: Isaac Newton Institute Seminar Series; organiser: nobody.
Wed 07 May 14:00: Reconstructing wintertime seawater pCO2 on the data-barren shelf of the western Weddell Sea based on summertime bottom water measurements
The dense waters formed on the broad shelf of the western Weddell Sea are a source of Weddell Sea Bottom Water (WSBW), which transports anthropogenic CO2 along the continental slope to the bottom of the ocean. Our updated time series shows a positive trend of carbon in WSBW . To understand the drivers for this pathway for carbon sequestration, we need to understand the processes affecting carbon concentrations in shelf waters at the time of dense water formation, which is predominantly during sea ice formation in winter. Unfortunately, wintertime marine observations are particularly scarce in the western Weddell Sea. We are therefore testing a method that reconstructs the seawater partial pressure of CO2 (pCO2) representative of wintertime conditions in this dense-water formation region, using carbonate chemistry observations made in WSBW in the summer. Results suggest that atmospheric CO2 uptake is the main driver of increasing carbon in WSBW , and thus that equilibration of surface seawater with the atmosphere is possible despite year-round sea ice cover in this region.
- Speaker: Elise Droste (University of East Anglia)
- Wednesday 07 May 2025, 14:00-15:00
- Venue: BAS Seminar Room 1.
- Series: British Antarctic Survey - Polar Oceans seminar series; organiser: Dr Birgit Rogalla.
Tue 06 May 14:30: Sums along binary cubic forms.
We discuss ongoing work with Joseph Leung in which we obtain estimates for sums of Fourier coefficients of GL(2) and certain GL(3) automorphic forms along the values of irreducible binary cubics.
- Speaker: Mayank Pandey (Princeton)
- Tuesday 06 May 2025, 14:30-15:30
- Venue: MR13.
- Series: Number Theory Seminar; organiser: Jef Laga.
Thu 12 Jun 14:00: Title to be confirmed
Abstract not available
- Speaker: Prof. Marina Filip (Oxford)
- Thursday 12 June 2025, 14:00-15:30
- Venue: Seminar Room 3, RDC.
- Series: Theory of Condensed Matter; organiser: Bo Peng.
Thu 05 Jun 14:00: Title to be confirmed
Abstract not available
- Speaker: Prof. Chris Hooley (Coventry)
- Thursday 05 June 2025, 14:00-15:30
- Venue: Seminar Room 3, RDC.
- Series: Theory of Condensed Matter; organiser: Bo Peng.
Thu 23 Oct 14:00: Title to be confirmed
Abstract not available
- Speaker: Prof. Felix Flicker (Bristol)
- Thursday 23 October 2025, 14:00-15:30
- Venue: Seminar Room 3, RDC.
- Series: Theory of Condensed Matter; organiser: Bo Peng.
Tue 17 Jun 11:15: Love Bites: The Deadly Romance of Spider Pulsars
Pulsars in binary systems are fantastic physics laboratories, primarily because their orbital dynamics allow us to probe binary evolution, test gravity theories, measure neutron star masses, etc. Among them are the “black widows” and “redbacks”, which are nicknamed after the deadly arachnids because the millisecond pulsar they contain gradually destroys their low mass companion. The strongly irradiated dayside displayed by the low-mass companions in these systems is reminiscent of what is observed in exoplanets called “hot jupiters”. In the last decade, the number of known spiders has grown exponentially to the point of becoming the most prevalent type of fast rotating binary pulsars. In this talk, I will present some of the recent efforts undertaken with the MeerKAT telescope to uncover these pulsars and review some of the key advances they have provided for our understanding of binary evolution, stellar physics under extreme irradiation, and measurement of neutron star masses.
- Speaker: Prof. Rene Breton (University of Manchester)
- Tuesday 17 June 2025, 11:15-12:00
- Venue: Martin Ryle Seminar Room, Kavli Institute.
- Series: Hills Coffee Talks; organiser: Charles Walker.
Wed 07 May 16:15: Quantum Computational Physics
Computational physics —the third pillar of physics exploration next to theory and experiment — has, for the past seven decades, evolved alongside tremendous progress in computing hardware. Today the field is on the verge of leaving behind classical computing resources, and pivoting towards quantum hardware, allowing for “quantum on quantum” simulations. In this talk will discuss the “assembler-level” of such quantum computing, asking what kind of quantum many-body phenomena one can induce in digital quantum circuits that employ not only the conventional set of unitary gates, but also mid-circuit measurements and active feedback. In essence, such quantum circuits allow for the dynamical creation, manipulation and decoding of collective entanglement structures.
As an example, I will discuss novel types of quantum criticality that can arise from shallow quantum circuits and which are generally described by (2+0)-dimensional non-unitary conformal field theories. Nishimori universality has emerged as a seemingly ubiquitous fixed point for such critical theories, which we discuss for mixed-state transitions arising from weak measurement or incoherent noise (or both). Putting Nishimori physics in competition to other critical theories, such as percolation, self-dual (Kramers-Wannier) quantum criticality or a novel tricritical theory at the intersection of phases with strong, weak or broken Z_2 symmetry, RG flows between these critical theories can be established and embedded in rich phase diagrams — some of which we have numerically explored on IBM ’s 127-qubit quantum processors.
- Speaker: Simon Trebst (Cologne)
- Wednesday 07 May 2025, 16:15-17:15
- Venue: Lecture Teatre, Ray Dolby Centre.
- Series: Cavendish Quantum Colloquium; organiser: Lucas Sá.
Fri 30 May 14:00: Title to be confirmed
Abstract not available
- Speaker: Johanna Ziegel (ETH Zurich)
- Friday 30 May 2025, 14:00-15:00
- Venue: MR12, Centre for Mathematical Sciences.
- Series: Statistics; organiser: Qingyuan Zhao.
Fri 06 Jun 10:15: Score-based calibration testing for multivariate forecast distributions RCLW02 - Calibrating prediction uncertainty : statistics and machine learning perspectives
Malte Knüppel (Deutsche Bundesbank), Fabian Krüger (Karlsruhe Institute of Technology), Marc-Oliver Pohle (Heidelberg Institute for Theoretical Studies) Calibration tests based on the probability integral transform (PIT) are routinely used to assess the quality of univariate distributional forecasts. However, PIT -based calibration tests for multivariate distributional forecasts face various challenges. We propose two new types of tests based on proper scoring rules, which overcome these challenges. They arise from a general framework for calibration testing in the multivariate case, introduced in this work. The new tests have good size and power properties in simulations and solve various problems of existing tests. We apply the tests to forecast distributions for macroeconomic and financial time series data.
RCLW02 - Calibrating prediction uncertainty : statistics and machine learning perspectives
- Speaker: Marc-Oliver Pohle (Heidelberg Institute for Theoretical Studies)
- Friday 06 June 2025, 10:15-10:30
- Venue: Seminar Room 1, Newton Institute.
- Series: Isaac Newton Institute Seminar Series; organiser: nobody.
Tue 17 Jun 14:30: Title to be confirmed
Abstract not available
- Speaker: Patrick Allen (McGill)
- Tuesday 17 June 2025, 14:30-15:30
- Venue: MR13.
- Series: Number Theory Seminar; organiser: Rong Zhou.
Thu 05 Jun 11:00: Discussion session following the morning talks RCLW02 - Calibrating prediction uncertainty : statistics and machine learning perspectives
RCLW02 - Calibrating prediction uncertainty : statistics and machine learning perspectives
- Speaker: Richard Wilkinson (University of Nottingham)
- Thursday 05 June 2025, 11:00-11:15
- Venue: Seminar Room 1, Newton Institute.
- Series: Isaac Newton Institute Seminar Series; organiser: nobody.
Mon 02 Jun 15:30: An introduction to the calibration of computer models RCLW02 - Calibrating prediction uncertainty : statistics and machine learning perspectives
In the context of computer models, calibration is the process of estimating unknown simulator parameters from observational data, variously referred to as model fitting, parameter estimation/inference, an inverse problem, and model tuning. The need for calibration occurs in most areas of science and engineering, and although the statistical methods used for calibration can vary substantially, the underlying approach is essentially the same and can be considered abstractly. In this talk, I will review the decisions that need to be taken when calibrating a model, and discuss a range of computational methods (new and old) that can be used to compute Bayesian posterior distributions.
RCLW02 - Calibrating prediction uncertainty : statistics and machine learning perspectives
- Speaker: Richard Wilkinson (University of Nottingham)
- Monday 02 June 2025, 15:30-16:30
- Venue: Seminar Room 1, Newton Institute.
- Series: Isaac Newton Institute Seminar Series; organiser: nobody.
Fri 20 Jun 13:00: Well-posed initial value formulation of general effective field theories of gravity
In this talk, I will show that all higher-derivative effective field theories (EFTs) of vacuum gravity admit a well-posed initial value formulation when augmented by suitable regularising terms. These regularising terms can be obtained by field redefinitions and do not affect the dynamics in the regime of validity of EFT . I will explain how our result applies to the quadratic, cubic, and quartic truncations of the EFT of gravity and to various truncations of a simple EFT of a scalar field. Finally, I will also discuss some numerical results on the non-linear dynamics of this simple scalar field theory.
- Speaker: Aron Kovacs, Queen Mary University of London
- Friday 20 June 2025, 13:00-14:00
- Venue: Potter room/Zoom.
- Series: DAMTP Friday GR Seminar; organiser: Daniela Cors.
Tue 06 May 14:00: Cocktail Effects in Superconductivity: High-Entropy Approach to Antimonide Compounds
High-entropy compounds, stabilized by configurational entropy, have attracted considerable attention due to their unique properties and functionalities [1-3]. In this study, we applied the high-entropy concept to antimonide systems and discovered an entropy-stabilized antimonide compound with a NiAs-type structure [4]. Specifically, we investigated the superconducting properties of (RuRhPdIr)₁₋ₓPtₓSb and found that the superconducting transition temperature (Tc) and upper critical field (Hc₂) exhibit strong composition dependence [5]. A maximum Tc of 3.1 K and a significant enhancement in Hc₂ were observed at intermediate compositions, indicating a novel “cocktail effect” arising from chemical disorder. These results demonstrate the potential of entropy engineering in designing new superconducting materials.
[1] J. W. Yeh et al., Adv Eng Mater 6, 299 (2004).
[2] B. Cantor et al., Materials Science and Engineering: A 375 –377, 213 (2004).
[3] C. M. Rost etal., Nat. Commun. 6, 8485 (2015).
[4] D. Hirai et al., Inorg. Chem. 62, 14207 (2023).
[5] D. Hirai et al., Chem. Mater. 36, 9547 (2024).
- Speaker: Professor Daigorou Hirai, Nagoya University
- Tuesday 06 May 2025, 14:00-15:00
- Venue: RDC Seminar East.
- Series: Quantum Matter Seminar; organiser: Mads Fonager Hansen.
Wed 07 May 14:30: Excitations with a Twist
Quantum geometry allows us to quantify the distance between quantum states. It underpins numerous phenomena in condensed matter physics, from electron transport in flat band systems to topological twists of electronic wave functions. In this talk, I will give an overview of how quantum geometry can be extended to explore the excited states of materials. Focusing on excitons, bound electron-hole pairs, I will first give an overview of the possible exciton topological phases as they arise from the underlying electron and hole states. I will next describe how quantum geometry dictates that topological excitons are larger than their trivial counterparts and show how this results in enhanced exciton diffusion. I will use a family of organic semiconductors hosting topological excitons to illustrate these ideas.
- Speaker: Professor Bartomeu Monserrat, University of Cambridge
- Wednesday 07 May 2025, 14:30-15:30
- Venue: Unilever Lecture Theatre, Yusuf Hamied Department of Chemistry.
- Series: Theory - Chemistry Research Interest Group; organiser: Lisa Masters.
Fri 16 May 14:00: Algebraic models of rational circle-equivariant spectra (spectra, commutative ring spectra, equivariantly commutative ring spectra) EHTW03 - New horizons for equivariance in homotopy theory
The real subject of this talk is joint work with Magdalena Kedziorek in which we identify an algebraic model for equivariantly commutative ring T-spectra (for the circle group T, and leaving `rational’ as understood). However to explain this it is helpful to begin with the algebraic model of ordinary T-spectra and for naive-commutative ring T-spectra. In this case the space of closed subgroups of T is very simple, so we can give an explicit description of the models and how to work with them. In particular, the strong message is that once again the `standard’ model captures the principal features much more clearly than the `complete’ model. (This is supposed to be an antidote to my recent talk `Rational SU(3)-spectra in 18 blocks’)
EHTW03 - New horizons for equivariance in homotopy theory
- Speaker: John Greenlees (University of Warwick)
- Friday 16 May 2025, 14:00-15:00
- Venue: Seminar Room 1, Newton Institute.
- Series: Isaac Newton Institute Seminar Series; organiser: nobody.
Fri 30 May 14:00: PhD Students' talks
Abstract not available
- Speaker: Speakers listed in abstract in due course
- Friday 30 May 2025, 14:00-17:00
- Venue: MR3.
- Series: Fluid Mechanics (DAMTP); organiser: Professor Grae Worster.
Fri 16 May 14:00: Does AI help humans make better decisions? A statistical evaluation framework for experimental and observational studies.
The use of Artificial Intelligence (AI), or more generally data-driven algorithms, has become ubiquitous in today’s society. Yet, in many cases and especially when stakes are high, humans still make final decisions. The critical question, therefore, is whether AI helps humans make better decisions compared to a human-alone or AI-alone system. We introduce a new methodological framework to empirically answer this question with a minimal set of assumptions. We measure a decision maker’s ability to make correct decisions using standard classification metrics based on the baseline potential outcome. We consider a single-blinded and unconfounded treatment assignment, where the provision of AI-generated recommendations is assumed to be randomized across cases with humans making final decisions. Under this study design, we show how to compare the performance of three alternative decision-making systems— human-alone, human-with-AI, and AI-alone. Importantly, the AI-alone system includes any individualized treatment assignment, including those that are not used in the original study. We also show when AI recommendations should be provided to a human-decision maker, and when one should follow such recommendations. We apply the proposed methodology to our own randomized controlled trial evaluating a pretrial risk assessment instrument. We find that the risk assessment recommendations do not improve the classification accuracy of a judge’s decision to impose cash bail. Furthermore, we find that replacing a human judge with algorithms— the risk assessment score and a large language model in particular—- leads to a worse classification performance.
- Speaker: Kosuke Imai (Harvard University)
- Friday 16 May 2025, 14:00-15:00
- Venue: MR12, Centre for Mathematical Sciences.
- Series: Statistics; organiser: Qingyuan Zhao.
Mon 12 May 11:45: Splittings in rational equivariant homotopy theory EHTW03 - New horizons for equivariance in homotopy theory
When G is a finite group, rational genuine G-spectra split as a product of simpler categories: rational spectra with Weyl group actions. Algebraically, this is the statement that rational Mackey functors are semi-simple and the category of rational G-Mackey functors splits as a product of module categories with Weyl group actions. Classically, the homotopy theory of G-spectra depended on a choice of a universe – this was modelled, for example, by the orthogonal G-spectra of Mandell and May. In modern language, Blumberg and Hill generalised the construction of the homotopy theory of G-spectra and show that one can choose an additive structure of it to be modelled by a homotopy type of an N_\infty operad O (or equivalently a transfer system associated to O). Thus homotopy groups of a G-spectrum with additive structure given by O have those additive transfers that are parametrised by O. We call such a structure a G-Mackey functor for O. The purpose of this talk is to describe splittings of rational G-Mackey functors for incomplete transfer systems and discuss how this extends to the topological setting. This is joint work with Anna Marie Bohmann, Dave Barnes and Mike Hill.
EHTW03 - New horizons for equivariance in homotopy theory
- Speaker: Magdalena Kedziorek (Radboud Universiteit Nijmegen)
- Monday 12 May 2025, 11:45-12:45
- Venue: Seminar Room 1, Newton Institute.
- Series: Isaac Newton Institute Seminar Series; organiser: nobody.