http://talks.cam.ac.uk/show/rss/5408

Multiphase flows are of central importance to a wide range of industrial applications and environmental settings. Examples of these include mixing in stirred vessels and static mixers, flows in micro-channels and microfluidics devices, falling films for CO2 capture, and aerosol formation via bubble bursting through interfaces in the oceans. Some of these flows feature the presence of surface-active agents (surfactants), present either by design or as contaminants. Furthermore, multiphase flows are often punctuated by topological transitions related to the coalescence of dispersed drops or bubbles, and the breakup of threads or ligaments. Here, we provide a few examples of interest to the JFM community but focus on drop impact on hydrophobic substrates in the presence of surfactants above the critical micelle concentration. Our model accounts for the spatio-temporal evolution of the surfactants along the interface and within the bulk; the bulk and interfacial species are fully-coupled via sorptive fluxes. Micellar formation and breakup are also accounted for, and the surfactant dynamics are coupled to the flow through the dependence of the surface tension on the local interfacial surfactant concentration. Our numerical procedure is based on the use of a hybrid interface-tracking/level-set approach. The results of our parametric study help identify the various physical mechanisms underlying the observed flow phenomena.

• Speaker: Prof Omar Matar, Imperial College London
• Friday 06 June 2025, 16:00-17:00
• Venue: https://cassyni.com/s/fmws.
• Series: Fluid Mechanics (DAMTP); organiser: Professor Grae Worster.

Add to your calendar or Include in your list

Understanding the neural mechanisms of reward-guided learning is a long-standing goal of computational neuroscience. Recent methodological innovations enable us to collect ever larger neural and behavioral datasets. This presents opportunities to achieve greater understanding of learning in the brain at scale, as well as methodological challenges. In the first part of the talk, I will discuss our recent insights into the mechanisms by which zebra finch songbirds learn to sing. Dopamine has been long thought to guide reward-based trial-and-error learning by encoding reward prediction errors. However, it is unknown whether the learning of natural behaviours, such as developmental vocal learning, occurs through dopamine-based reinforcement. Longitudinal recordings of dopamine and bird songs reveal that dopamine activity is indeed consistent with encoding a reward prediction error during naturalistic learning.

In the second part of the talk, I will talk about recent work we are doing at DeepMind to develop tools for automatically discovering interpretable models of behavior directly from animal choice data. Our method, dubbed CogFunSearch, uses LLMs within an evolutionary search process in order to “discover” novel models in the form of Python programs that excel at accurately predicting animal behavior during reward-guided learning. The discovered programs reveal novel patterns of learning and choice behavior that update our understanding of how the brain solves reinforcement learning problems.

• Speaker: Kimberly Stachenfeld (DeepMind, Columbia)
• Tuesday 03 June 2025, 11:00-12:30
• Venue: CBL Seminar Room, Engineering Department, 4th floor Baker building.
• Series: Computational Neuroscience; organiser: Daniel Kornai.

Add to your calendar or Include in your list

When making predictions under uncertainty, neural networks often exhibit behaviors reminiscent of probabilistic inference—even without explicit inductive biases. In reinforcement learning (RL), uncertainty about latent variables is naturally captured by Partially Observable Markov Decision Processes (POMDPs). These models apply broadly, from games like poker to domains such as healthcare and autonomous driving.

In POMD Ps, the optimal agent performs sequential Bayesian filtering under a generative model to infer the latent state of the environment—maintaining a “belief” over that state. Surprisingly, naively trained recurrent neural networks (RNNs) can outperform dedicated probabilistic inference methods tailored to POMD Ps. Recent work has shown that RNNs trained to learn value functions can develop belief-like representations without access to the generative model—though lacking theoretical justification for this phenomenon.

In this talk, I will connect these observations by presenting theoretical arguments for when and why belief-like representations emerge in deep RL agents. I will also demonstrate how such theoretical insights can inform and justify auxiliary loss objectives used in state-of-the-art architectures, such as DreamerV3.

• Speaker: Daniel Kornai (CBL)
• Tuesday 03 June 2025, 13:30-15:00
• Venue: CBL Seminar Room, Engineering Department, 4th floor Baker building.
• Series: Computational Neuroscience; organiser: Daniel Kornai.

Add to your calendar or Include in your list

When making predictions under uncertainty, neural networks often exhibit behaviors reminiscent of probabilistic inference—even without explicit inductive biases. In reinforcement learning (RL), uncertainty about latent variables is naturally captured by Partially Observable Markov Decision Processes (POMDPs). These models apply broadly, from games like poker to domains such as healthcare and autonomous driving.

In POMD Ps, the optimal agent performs sequential Bayesian filtering under a generative model to infer the latent state of the environment—maintaining a “belief” over that state. Surprisingly, naively trained recurrent neural networks (RNNs) can outperform dedicated probabilistic inference methods tailored to POMD Ps. Recent work has shown that RNNs trained to learn value functions can develop belief-like representations without access to the generative model—though lacking theoretical justification for this phenomenon.

In this talk, I will connect these observations by presenting theoretical arguments for when and why belief-like representations emerge in deep RL agents. I will also demonstrate how such theoretical insights can inform and justify auxiliary loss objectives used in state-of-the-art architectures, such as DreamerV3.

• Speaker: Daniel Kornai (CBL)
• Tuesday 03 June 2025, 13:30-15:00
• Venue: CBL Seminar Room, Engineering Department, 4th floor Baker building.
• Series: Computational Neuroscience; organiser: Daniel Kornai.

Add to your calendar or Include in your list

When making predictions under uncertainty, neural networks often exhibit behaviors reminiscent of probabilistic inference—even without explicit inductive biases. In reinforcement learning (RL), uncertainty about latent variables is naturally captured by Partially Observable Markov Decision Processes (POMDPs). These models apply broadly, from games like poker to domains such as healthcare and autonomous driving.

In POMD Ps, the optimal agent performs sequential Bayesian filtering under a generative model to infer the latent state of the environment—maintaining a “belief” over that state. Surprisingly, naively trained recurrent neural networks (RNNs) can outperform dedicated probabilistic inference methods tailored to POMD Ps. Recent work has shown that RNNs trained to learn value functions can develop belief-like representations without access to the generative model—though lacking theoretical justification for this phenomenon.

In this talk, I will connect these observations by presenting theoretical arguments for when and why belief-like representations emerge in deep RL agents. I will also demonstrate how such theoretical insights can inform and justify auxiliary loss objectives used in state-of-the-art architectures, such as DreamerV3.

• Speaker: Daniel Kornai (CBL)
• Tuesday 02 June 2026, 13:30-15:00
• Venue: CBL Seminar Room, Engineering Department, 4th floor Baker building.
• Series: Computational Neuroscience; organiser: Daniel Kornai.

Add to your calendar or Include in your list

The Australian Antarctic Program Partnership (AAPP) is focused on understanding the nature and impacts of Southern Ocean Change. The Biogeochemistry Project, one of the seven complementary initiatives within the AAPP , combines observations, models and data syntheses to understand changes in the Southern Ocean carbon cycle. This work is undertaken in collaboration with other government agencies, national infrastructure programs, and academic institutions, and highlights the use of essential ocean observations and models to improve understanding and deliver impact. An overview of recent field programs will be presented, along with new work to quantify the uptake and storage of anthropogenic CO2 in the ocean, to validate estimates of ocean carbon export from autonomous platforms, and to improve model representation of air-sea CO2 exchange.

• Speaker: Elizabeth H. Shadwick, CSIRO Environment
• Wednesday 04 June 2025, 13:00-14:00
• Venue: BAS Seminar Room 1.
• Series: British Antarctic Survey - Polar Oceans seminar series; organiser: Dr Birgit Rogalla.

Add to your calendar or Include in your list

This is a joint seminar with the LJC .

Niobium diselenide has garnered significant attention over the past few decades because of the coexis tence of superconductivity and charge density waves (CDWs), observable down to the monolayer limit. Introducing relative twist angles between monolayers, in the field of twistronics, offers a new variable to tune these systems, yet a fundamental question remains: do CDWs persist in moiré structures, and how are they altered compared to the pristine monolayer/bilayer? Traditional first-principles methods face limitations due to the computational resources required for long-wavelength moiré patterns; for instance, a 1-degree twist angle necessitates modeling over 10,000 atoms, making simulations impractical. This study employs first-principles data to develop machine learning interatomic potentials with the Allegro architecture, enabling scalable and accurate simulations. We investigate the formation and evolution of CDW order in monolayers and twisted bilayers, validating our results against density functional theory calculations with minimal errors in energy and forces. Beyond niobium diselenide, our goal is to establish a protocol for studying CDWs in two-dimensional systems. We outline strategies for producing training data and perform a detailed hyperparameter scan to identify key aspects for studying these systems [1].

1. Norma Rivano et al. arXiv.2504.13675 2025

• Speaker: Dr Zac Goodwin (Oxford)
• Wednesday 04 June 2025, 11:00-12:00
• Venue: Seminar Room 3, RDC.
• Series: Theory of Condensed Matter; organiser: Bo Peng.

Add to your calendar or Include in your list

In this talk, I will briefly describe two of our recent pieces of work on the physics of the J1-J2 Heisenberg spin chain, a one-dimensional array of quantum spins coupled by first- and second-neighbour exchange interactions. The first piece of work [1] concerns the case where J1 and J2 are both antiferromagnetic: in this case there is a phase transition from a Luttinger liquid to a valence bond solid as J2/J1 is increased, and we provide a novel direct method to derive the field theory that describes the critical point between these two phases. The second piece [2] concerns the case where J1 is antiferromagnetic but J2 is strongly ferromagnetic: counter-intuitively, there is a transition in this case as well, but this time of a ‘liquid-to-liquid’ type. We present a field-theory description of it, and an analogue system of three coupled chains that helps to illustrate the physics.

[1] F. Azad, A. J. McRoberts, CAH , and A. G. Green, “Generalized Haldane map from the matrix product state path integral to the critical theory of the J1-J2 chain,” Phys. Rev. Research 7, L012037 (2025).

[2] A. J. McRoberts, CAH , and A. G. Green, “Transition between critical antiferromagnetic phases in the J1-J2 spin chain,” arXiv:2411.08095v2 (2025).

• 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.

Add to your calendar or Include in your list

Abstract TBC

• Speaker: Dr. Weiyang Wang (University of Chinese Academy of Sciences)
• Tuesday 21 October 2025, 11:15-12:00
• Venue: TBC.
• Series: Hills Coffee Talks; organiser: Charles Walker.

Add to your calendar or Include in your list

Abstract TBC

• Speaker: Prof. Howard Reader
• Tuesday 01 July 2025, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

Add to your calendar or Include in your list

Abstract not available

Host: Juliana Naldoni

• Speaker: Prof Beth Okamura, Natural History Museum
• Wednesday 11 June 2025, 16:00-17:00
• Venue: Lecture Theater, Department of Pathology, Tennis Court Road.
• Series: Parasitology Seminars; organiser: jn472.

Add to your calendar or Include in your list

Abstract tbc

• Speaker: Davi de Castro Silva (University of Cambridge)
• Wednesday 11 June 2025, 13:30-15:00
• Venue: MR4, CMS.
• Series: Discrete Analysis Seminar; organiser: Julia Wolf.

Add to your calendar or Include in your list

Nitroprusside is an important prebiotic molecule, thought to contribute to reaction pathways that lead to the production of amino acid chains (Mariani et al. [2018]). Nitroprusside can be made from Ferrocyanide photochemically. It has been found that the timescales for this reaction on Early Earth would have been between an order of days to months , making this route of abiotic production very useful in further prebiotic reaction networks and an important factor to consider when discussing the viability of life to evolve on a planet (Rimmer et al. [2021]). Here we investigate this reaction with a focus on constant and time varied radiation, meaning experimental runs involving the sample being subjected to a constant flux of UV light and runs with UV flux changing over time. FlareLab makes use of a broad band UV-Vis Laser Driven Light Source (LDLS), to experimentally simulate stellar irradiation and stellar flaring activity. The reasoning behind investigating flares is based on recent findings that have shown that M-dwarves are prone to flaring (G¨unther et al. [2020]). Flaring for M-dwarves is also shown to be the best way to get enough UV to an exoplanet’s surface for good yield of photochemical products (Ranjan et al. [2017]). With M-dwarves seen as the best stars to look at to detect small rocky planets, it is important to consider how flaring could effect the production of Nitroprusside and if there’s a discrepancy between assuming a constant irradiation of the surface or taking into account flaring.

We show that FlareLab can be used as a means of detecting the production of Nitroprusside in-situ during the irradiation period. We also compare the constant flux and variable flux regimes, and discuss the implications of these findings.

• Speaker: Lukas Rossmanith
• Tuesday 03 June 2025, 11:15-12:00
• Venue: Martin Ryle Seminar Room, Kavli Institute.
• Series: Hills Coffee Talks; organiser: David Buscher.

Add to your calendar or Include in your list

Positional encodings are essential for transformer-based language models to understand sequence order, yet their influence extends far beyond simple position tracking. This talk explores the landscape of positional encoding methods in LLMs and reveals surprising insights about how these architectural choices shape model behavior.

We begin with the fundamental challenge: why attention mechanisms require explicit positional information. We then survey the evolution of encoding strategies, from sinusoidal approaches to modern techniques like RoPE, examining their architectural implications and trade-offs.

The talk delves into how these different encoding strategies fundamentally shape model architectures and representations. We analyze the specific limitations and trade-offs of each approach, examining how positional information propagates through transformer layers and influences the learned representations.

• Speaker: Valeria Ruscio
• Thursday 04 June 2026, 17:00-17:45
• Venue: Lecture Theatre 2, Computer Laboratory, William Gates Building.
• Series: Foundation AI; organiser: Pietro Lio.

Add to your calendar or Include in your list

Abstract TBC

• Speaker: Prof. Natasha Hurley-Walker (Curtin University)
• Thursday 12 June 2025, 11:15-12:00
• Venue: Martin Ryle Seminar Room, Kavli Institute.
• Series: Hills Coffee Talks; organiser: Charles Walker.

Add to your calendar or Include in your list

Given two algebraic theories S and T, their commuting tensor product is a new algebraic theory in which the operations of S and T are required to commute with each other. The analogue of this operation for symmetric operads is the famous Boardman-Vogt tensor product. A unified account of these commuting tensor products was given by Garner and Lopez-Franco.

Here, we extend their analysis in two respects. First, we generalise it so as to make it applicable to the many-object case, recovering as special case the Boardman-Vogt tensor product of symmetric multicategories, subsuming work of Elmendorf and Mandell. Secondly, we investigate how the commuting tensor product acts on bimodules, generalising work of Dwyer and Hess.

This is joint work with Richard Garner and Christina Vasilakopoulou.

• Speaker: Nicola Gambino ( University of Manchester)
• Friday 06 June 2025, 14:00-15:00
• Venue: SS03, Computer Laboratory.
• Series: Logic and Semantics Seminar (Computer Laboratory); organiser: Thibaut Benjamin.

Add to your calendar or Include in your list

Many cancers are driven by hyperactive point mutants, most of which remain undruggable by the conventional approach with small molecule drugs. I will discuss biologics-based strategies to effectively target mutated cancer drivers, including the development of biologics that are exquisitely selective to cancer driver mutants and the use of covalent inhibitors to create actionable neoantigens for immune therapy.

• Speaker: Shohei Koide, NYU Langone Health
• Monday 16 June 2025, 12:30-13:30
• Venue: CRUK CI Lecture Theatre.
• Series: Seminars on Quantitative Biology @ CRUK Cambridge Institute ; organiser: .

Add to your calendar or Include in your list

This talk coincides with the publication by Cambridge University Press of “The Geometry of Equilibrium: James Clerk Maxwell and 21st-Century Structural Mechanics”, edited by Bill Baker and Allan McRobie. Bill is Senior Partner at Skidmore Owings and Merrill in Chicago and has been the design lead for many of the world’s iconic structures, including the world’s tallest, the Burj Khalifa in Dubai. Bill is Honorary Professor here at CUED and visits each year to give a fourth-year module on Advanced Structural Design. The new book collates the recent work of Bill, Allan and many others which revisits the works of James Clerk Maxwell. Alongside his famous unification of electricity and magnetism, Maxwell also provided a highly geometric approach to structural mechanics. In this talk, Allan will: describe the contents of the book, focusing on the mathematics of 3D and 4D projective geometry, with the polarities and Legendre transforms that underpin the geometry of equilibrium; explain the applications in design; describe the more recent progress.

• Speaker: Allan McRobie, Professor of Structural Engineering, CUED
• Friday 20 June 2025, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering - Dynamics and Vibration Tea Time Talks; organiser: div-c.

Add to your calendar or Include in your list

Peter C. Collins joined the Department of Materials Science and Engineering at Iowa State University in July, 2015. Dr. Pete Collins received his undergraduate degree in Metallurgical Engineering from the University of Missouri-Rolla, and his MS and PhD from The Ohio State University in Materials Science and Engineering. Prior to joining ISU , Dr. Collins served as a faculty member and undergraduate coordinator in the Department of Materials Science and Engineering at the University of North Texas. Dr. Collins has also spent time standing-up a not-for-profit 501-3© manufacturing laboratory, and regularly engages with both industry and the government. His experiences and interests involve the practical and theoretical treatments of microstructure-property relationship, with an extension into composition-microstructure-property relationships derived for complex multi-phase, multi-component engineering alloys. He has extensive experience in participating in large industrial programs, has conducted studies into novel metal matrix composites, and has significant research experience with additive manufacturing techniques, and combinatorial materials science. Dr. Collins is an active member of TMS , past chairman of the ICME committee, member of the Titanium committee, and a member of the Materials Processing and Manufacturing Division. In recent years, Collins and his group have been actively involved in developing and building new types of instrumentation and experiments. These include developing the first 3D SRAS (spatially resolved acoustic spectroscopy) microscope, bicombinatorial techniques, reduced-cost wire-fed metal AM systems, and other techniques aimed at characterizing defects in additive manufactured materials.

• Speaker: Dr Peter C. Collins, Iowa State University
• Friday 13 June 2025, 14:00-15:00
• Venue: Oatley 1 Meeting Room, Department of Engineering.
• Series: Engineering - Mechanics and Materials Seminar Series; organiser: div-c.

Add to your calendar or Include in your list

Abstract: Mobile computing technologies have advanced substantially over the last two decades. Today, the smart devices enabled by economies of scale, incorporate high-quality wireless sensors such as acoustic and RF sensors and the trend shows an increase in both the quantity and quality of these sensors. These sensors can be leveraged to enable a contactless passive monitoring of physiological signals of subjects and early diagnoses of various health conditions. In this talk, I will present a privacy aware wireless sensing technology to enable equitable, passive contactless monitoring of breathing and heart rate signals to detect opioid overdose in a timely manner.

Bio: Rajalakshmi Nandakumar is an Assistant Professor at the Jacobs Technion-Cornell Institute at Cornell Tech and in the Information Science department at Cornell University. She received her Ph.D. from University of Washington in Computer Science and Engineering in 2019. Her research focuses on developing wireless sensing technologies that enable novel applications in various domains including mobile health, user interfaces and IoT networks. She developed the first contactless smartphone-based sleep apnea diagnosis system that was licensed by ResMed Inc. and now used by millions of users for sleep staging. She was recognized with the UW Medicine Judy Su Clinical Research award, Paul Baran Young Scholar award by the Marconi Society and also named as the rising star in EECS by MIT .

Zoom: https://cam-ac-uk.zoom.us/j/82442600092?pwd=DfDLE12p2Kmnh532rSMVB8mOn7uLDa.1

• Speaker: Rajalakshmi Nandakumar, Cornell University
• Tuesday 03 June 2025, 16:00-17:00
• Venue: Online.
• Series: Mobile and Wearable Health Seminar Series; organiser: Cecilia Mascolo.

Add to your calendar or Include in your list