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

Many real-life fluids are not Newtonian and have to be modelled with something more complex than a single scalar viscosity. In this talk we will look specifically at dilute polymer solutions. We’ll see some simple models that capture the essential features of their behaviour, and then investigate how the properties of these models affect the stability of channel flow.

The story spans my whole research career so far, from an early theoretical prediction which was later observed in experiments, to a more recent realisation that there is still quite a lot we don’t understand. If time permits I will also discuss the latest place the research has taken me, which is neither viscoelastic nor unstable.

• Speaker: Prof Helen Wilson, University College London
• Friday 02 May 2025, 16:00-17:00
• Venue: MR2.
• Series: Fluid Mechanics (DAMTP); organiser: Professor Grae Worster.

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Abstract not available

• Speaker: Isabel Papanagnou
• Friday 16 May 2025, 16:00-17:00
• Venue: Tea Room, Old House.
• Series: Bullard Laboratories Tea Time Talks; organiser: David Al-Attar.

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Abstract not available

• Speaker: Jaap Jumelet (University of Groningen)
• Friday 13 June 2025, 12:00-13:00
• Venue: Room SS03 with Hybrid Format. Here is the Zoom link for those that wish to join online: https://cam-ac-uk.zoom.us/j/4751389294?pwd=Z2ZOSDk0eG1wZldVWG1GVVhrTzFIZz09.
• Series: NLIP Seminar Series; organiser: Suchir Salhan.

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Abstract not available

• Speaker: Zachary Sudholz
• Friday 20 June 2025, 16:00-17:00
• Venue: Tea Room, Old House.
• Series: Bullard Laboratories Tea Time Talks; organiser: David Al-Attar.

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Abstract not available

• Speaker: Sergei Lebedev ( University of Cambridge)
• Friday 23 May 2025, 16:00-17:00
• Venue: Tea Room, Old House.
• Series: Bullard Laboratories Tea Time Talks; organiser: David Al-Attar.

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Abstract not available

• Speaker: Prof. Sarah Teichmann, FMedSci, FRS (Cambridge)
• Thursday 01 May 2025, 14:00-15:30
• Venue: Seminar Room 3, RDC.
• Series: Theory of Condensed Matter; organiser: Bo Peng.

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Abstract not available

• Speaker: Professor Julio Cordioli, University of Santa Catarina,Brazil
• Friday 20 June 2025, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering - Dynamics and Vibration Tea Time Talks; organiser: div-c.

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Some stringed instruments, such as the piano, have multiple strings associated with each note.  This has a consequence for the sound which is not immediately obvious: coupling between the strings can produce a decay profile for the note which starts steep, but gives way to a slower decay later in the note. To an extent, a piano tuner can tailor this double-decay profile by subtle adjustments. The talk will explore the physics behind this phenomenon, and examine whether other stringed instruments would be expected to display a similar effect. A criterion based on a measurement of the soundboard vibration at the string’s attachment point will be developed, and illustrated with data from several different stringed instruments.

• Speaker: Professor Jim Woodhouse, Emeritus, CUED
• Friday 02 May 2025, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering - Dynamics and Vibration Tea Time Talks; organiser: div-c.

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Abstract not available

• Speaker: Dr Zack X Conti, Alan Turing Institute
• Friday 13 June 2025, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering - Dynamics and Vibration Tea Time Talks; organiser: div-c.

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From an engineering point of view, it is convenient to describe composite materials using homo- geneous effective properties. When the microstructure is periodic, asymptotic homogenizationis particularly well suited for this aim. Classical homogenization corresponds to the dominant order model and yields an effective standard Cauchy medium. At next orders, we can derive addi- tional corrections that depend on the successive strain gradients. These corrections are typically of interest to capture size-effects appearing for microstructures with contrasted stiffness properties. However, these higher-order models present two major limitations. First, the corrections producedby homogenization can handle size-effects that occur in the bulk region, but are not suited to the analysis of the boundaries. In fact, they miss significant boundary effects which can degrade significantly the quality of the predictions. Secondly, these higher-order models present several mathematical inconsistencies, including non-positive strain-gradient stiffnesses. As a result, the effective energy is not necessarily positive and any equilibrium solution is unstable with respect to short-scale oscillations. To handle these two limitations simultaneously, we elaborate a newhomogenization procedure that includes boundary effects. By contrast with usual approaches, inour procedure the homogenization is carried at the energy level, rather than on the strong formof the equilibrium. Besides, the positivity of the resulting energy is guaranteed by an original truncation method [1]. As an example, we consider a 1D spring network. The resulting effective energy contains a bulk term that is positive, plus a boundary term that accounts for the energy generated by the boundary effects. We show that, by contrast with usual asymptotic homogenization, this higher-order model is able to capture size-effects occurring in the interior domain, as well as near the boundaries.

• Speaker: Manon Thbaut, Ecole Polytechnique
• Friday 09 May 2025, 14:00-15:00
• Venue: Oatley 1 Meeting Room, Department of Engineering.
• Series: Engineering - Mechanics and Materials Seminar Series; organiser: div-c.

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Abstract not available

• Speaker: John Rudge
• Friday 06 June 2025, 16:00-17:00
• Venue: Tea Room, Old House.
• Series: Bullard Laboratories Tea Time Talks; organiser: David Al-Attar.

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In this session, Amy Orben, the leader of the Digital Mental Health Group at the MRC Cognition and Brain Sciences Unit, will talk about her experience of having to support evidence-based policy in the area of teen mental health and social media. Her vision on how this could be improved was described in Orben, Amy, and J. Nathan Matias, ‘Fixing the science of digital technology harms’, Science 388, no. 6743 (2025): 152–155.

• Speaker: Amy Orben (MRC Cognition and Brain Sciences Unit)
• Friday 13 June 2025, 15:30-17:00
• Venue: Board Room, Department of History and Philosophy of Science.
• Series: Coffee with Scientists; organiser: Marta Halina.

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Abstract not available

• Speaker: Helene Scott-Fordsmand (Clare Hall & HPS, Cambridge) and Anatolii Kozlov (Science & Technology Studies, UCL)
• Friday 30 May 2025, 15:30-17:00
• Venue: Board Room, Department of History and Philosophy of Science.
• Series: Coffee with Scientists; organiser: Marta Halina.

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Abstract not available

• Speaker: Zachary Sudholz
• Friday 20 June 2025, 16:00-17:00
• Venue: Tea Room, Old House.
• Series: Bullard Laboratories Tea Time Talks; organiser: David Al-Attar.

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Abstract not available

• Speaker: James Jackson
• Friday 13 June 2025, 16:00-17:00
• Venue: Tea Room, Old House.
• Series: Bullard Laboratories Tea Time Talks; organiser: David Al-Attar.

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Abstract not available

• Speaker: John Rudge
• Friday 06 June 2025, 16:00-17:00
• Venue: Tea Room, Old House.
• Series: Bullard Laboratories Tea Time Talks; organiser: David Al-Attar.

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Abstract not available

• Speaker: Alex Copley
• Friday 02 May 2025, 16:00-17:00
• Venue: Tea Room, Old House.
• Series: Bullard Laboratories Tea Time Talks; organiser: David Al-Attar.

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I have been “officially” formalizing Fermat’s Last Theorem for 6 months now, and unofficially I’ve been doing so for around a year. In this talk I’ll give you an update on where we are, how it’s going, and what I’ve learnt so far. More precisely, I’ll talk about infrastructure (what we’ve settled on, the problems that we’ve had, and how we solved them). I’ll talk about what the goals of the project are, what we have achieved, and where we’re going. And I’ll talk about what were (to me) some unexpected consequences of the formalization procedure, namely some old mathematics which we’ve poked holes in, and some new mathematics which has come out of the project. Finally I want to stress that I will not be assuming that the audience knows anything at all about the details of the proof! The talk will be suitable for a general scientific audience.

=== Hybrid talk ===

Join Zoom Meeting https://cam-ac-uk.zoom.us/j/87143365195?pwd=SELTNkOcfVrIE1IppYCsbooOVqenzI.1

Meeting ID: 871 4336 5195

Passcode: 541180

• Speaker: Kevin Buzzard (Imperial College London)
• Thursday 01 May 2025, 17:00-18:00
• Venue: MR14 Centre for Mathematical Sciences.
• Series: Formalisation of mathematics with interactive theorem provers ; organiser: Anand Rao Tadipatri.

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The ultralow frequency variability of the Earth’s climate features an interplay of typically long periods of stasis accompanied by critical transitions between qualitatively different regimes associated with metastable states. Such transitions have often been accompanied by massive and rapid changes in the biosphere. Multiple transitions between the coexisting warm and snowball climates occurred more than 600 Mya and eventually led to conditions favourable to the development of multicellular life. The coexistence of such states is due to the instability associated with the positive ice-albedo feedback, Yet, this behaviour repeats itself across a wide range of timescales, spatial domains, and physical processes. Building on Hasselmann’s program, we propose here to interpret the time-evolution of the Earth system as a trajectory taking place in a dynamical landscape, whose multiscale features describe a hierarchy of metastable states and associated tipping points. We introduce the concept of climatic Melancholia states, saddle embedded in the boundary between the basins of attraction of the stable climates and explain under which conditions they act as gateways of noise-induced transitions. Using a hierarchy of numerical models, we discuss in detail the dichotomy between warm and snowball climate by bringing together the deterministic and stochastic viewpoint on the related global stability properties. We then discuss the paleoclimatically-relevant case where multiple competing climatic states are present and show the relevance of our angle for interpreting proxy data. Finally, if time allows, we will present some very recent results suggesting that our viewpoint might explain some intriguing aspects of the dynamical features of the tipping points of the Atlantic Meridional Overturning Circulation.

Key References V. Lucarini and T. Bodai, Transitions across Melancholia States in a Climate Model: Reconciling the Deterministic and Stochastic Points of View, Phys. Rev. Lett. 122, 158701 (2019) G. Margazoglou et al., Dynamical landscape and multistability of a climate model, Proc. R. Soc. A.477 210019 (2021) V. Lucarini, M.D. Chekroun, Theoretical tools for understanding the climate crisis from Hasselmann’s programme and beyond, Nature Reviews Physics 5 (12), 744-765 (2023) D. D. Rousseau et al., A punctuated equilibrium analysis of the climate evolution of cenozoic exhibits a hierarchy of abrupt transitions. Sci Rep 13, 11290 (2023) J. Lohmann et al., Multistability and Intermediate Tipping of the Atlantic Ocean Circulation, Sci. Advances 10 DOI : 10.1126/sciadv.adi4253 (2024)

• Speaker: Prof Valerio Lucarini, University of Leicester
• Friday 09 May 2025, 16:00-17:00
• Venue: MR2.
• Series: Fluid Mechanics (DAMTP); organiser: Professor Grae Worster.

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Join us for the June Milner Seminar. Presentations will include time for Q&A and will be followed by refreshments and networking.

4:00pm

Namshik Han, CardiaTec Biosciences and Milner Therapeutics Institute – “Integrating human-centric multi-omics and AI for cardiovascular therapeutics”

4:30pm

Sanjay Sinha, Cambridge Stem Cell Institute, University of Cambridge – “Application of iPSC-based cardiovascular systems for disease modelling, drug discovery and genomic medicine”

If you’d like to attend this event, please register at: https://milner.glueup.com/event/milner-seminars-focus-on-cardiovascular-research-139525/

• Speaker: Namshik Han, CardiaTec Biosciences and Milner Therapeutics Institute and Sanjay Sinha, Cambridge Stem Cell Institute, University of Cambridge
• Wednesday 04 June 2025, 16:00-17:00
• Venue: Lecture Theatre, Jeffrey Cheah Biomedical Centre.
• Series: Milner Seminar Series; organiser: Mary-Jane Roebuck.

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