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

Abstract not available

• Speaker: Peter Varju (University of Cambridge)
• Wednesday 05 March 2025, 13:30-15:00
• Venue: MR4, CMS.
• Series: Discrete Analysis Seminar; organiser: Julia Wolf.

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Abstract not available

• Speaker: Sergio Blanes (Universidad Politécnica de Valencia)
• Thursday 05 June 2025, 15:00-16:00
• Venue: Centre for Mathematical Sciences, MR14.
• Series: Applied and Computational Analysis; organiser: Georg Maierhofer.

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Abstract not available

• Speaker: Cecilie Glittum (Freie Universität Berlin)
• Thursday 27 March 2025, 14:00-15:30
• Venue: TCM Seminar Room.
• Series: Theory of Condensed Matter; organiser: Bo Peng.

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Completely randomized experiment is the gold standard for causal inference. When the covariate information for each experimental candidate is available, one typical way is to include them in covariate adjustments for more accurate treatment effect estimation. In this paper, we investigate this problem under the randomization-based framework, i.e., that the covariates and potential outcomes of all experimental candidates are assumed as deterministic quantities and the randomness comes solely from the treatment assignment mechanism. Under this framework, to achieve asymptotically valid inference, existing estimators usually require either (i) that the dimension of covariates p grows at a rate no faster than O(n3/4) as sample size n→∞; or (ii) certain sparsity constraints on the linear representations of potential outcomes constructed via possibly high-dimensional covariates. In this paper, we consider the moderately high-dimensional regime where p is allowed to be in the same order of magnitude as n. We develop a novel debiased estimator with a corresponding inference procedure and establish its asymptotic normality under mild assumptions. Our estimator is model-free and does not require any sparsity constraint on potential outcome’s linear representations. We also discuss its asymptotic efficiency improvements over the unadjusted treatment effect estimator under different dimensionality constraints. Numerical analysis confirms that compared to other regression adjustment based treatment effect estimators, our debiased estimator performs well in moderately high dimensions.

• Speaker: Yuhao Wang (Tsinghua University)
• Tuesday 28 January 2025, 13:00-14:00
• Venue: MR14, Centre for Mathematical Sciences, Wilberforce Road, Cambridge.
• Series: Causal Inference Reading Group; organiser: Qingyuan Zhao.

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Graphical continuous Lyapunov models offer a new perspective on modeling causally interpretable dependence structure in multivariate data by treating each independent observation as a one-time cross-sectional snapshot of a temporal process. Specifically, the models consider multivariate Ornstein-Uhlenbeck processes in equilibrium. This leads to Gaussian models in which the covariance matrix is determined by the continuous Lyapunov equation. In this setting, each graphical model assumes a sparse drift matrix with support defined by a directed graph. The talk will discuss the identifiability of such sparse drift matrices and their regularized estimation.

Note unusual location

• Speaker: Mathias Drton (Technical University of Munich)
• Friday 07 February 2025, 14:00-15:00
• Venue: Centre for Mathematical Sciences MR15, CMS.
• Series: Statistics; organiser: Qingyuan Zhao.

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Immediately following the CNHS AGM , Jim Woodhouse will give a Presidential Address on the various uses of natural materials in the making of traditional musical instruments.

The talk will focus mostly on wood: why instrument makers prefer certain particular types of wood, what it is in the cellular structure that makes these timbers special, and what scope there may be to use alternative materials in the light of climate pressure and CITES restrictions.

Please note the start time, being after the AGM, is approximate.

• Speaker: Jim Woodhouse, CNHS President; Emeritus Professor of Structural Dynamics
• Thursday 20 March 2025, 19:00-20:30
• Venue: Main Seminar Room (First Floor) David Attenborough Building, University of Cambridge Pembroke St, Cambridge CB2 3QZ.
• Series: Cambridge Natural History Society; organiser: president.

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The people, the places and the birds, losers and winners – a century of the most remarkable changes.

• Speaker: Bob Jarman
• Thursday 13 March 2025, 18:45-20:00
• Venue: Main Seminar Room (First Floor) David Attenborough Building, University of Cambridge Pembroke St, Cambridge CB2 3QZ.
• Series: Cambridge Natural History Society; organiser: events.

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This talk will summarise the various CNHS fieldwork projects during 2024.

Jonathan will talk about plants and fungi, Duncan about moth-trapping.

• Speaker: Duncan Mackay and Jonathan Shanklin
• Thursday 27 February 2025, 18:45-20:00
• Venue: Main Seminar Room (First Floor) David Attenborough Building, University of Cambridge Pembroke St, Cambridge CB2 3QZ.
• Series: Cambridge Natural History Society; organiser: events.

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Find out the latest from the Great Fen.

With so much going on at the Fen since the purchase of Speechly’s Farm, it’s never too soon for an update.

With the usual sights and sounds from the Great Fen, including trail camera and drone videos.

• Speaker: Henry Stanier, Monitoring & Research Officer at the BCN Wildlife Trust
• Thursday 20 February 2025, 18:45-20:00
• Venue: Main Seminar Room (First Floor) David Attenborough Building, University of Cambridge Pembroke St, Cambridge CB2 3QZ.
• Series: Cambridge Natural History Society; organiser: events.

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This talk will explore the life of Alice Hibbert-Ware, a little-known naturalist with a Cambridge connection.

Hibbert-Ware was a teacher and promoter of school nature study in the early twentieth century, and also undertook a survey of the Little Owl’s eating habits in the 1930s, which contributed to the bird’s protection at a time when landowners blamed them for attacking game bird chicks. The enquiry was a fascinating early case of “citizen science”, with volunteers recruited via a public call in the press, including BBC Radio and the ZSL ’s Zoo magazine.

• Speaker: Max Long
• Thursday 06 February 2025, 18:45-20:00
• Venue: Main Seminar Room (First Floor) David Attenborough Building, University of Cambridge Pembroke St, Cambridge CB2 3QZ.
• Series: Cambridge Natural History Society; organiser: events.

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This talk will look at the current squirrel population of the UK from the ancient, native red squirrel to the relatively recent introductions of the American grey squirrel.

We will look at the changing ranges of these two species over time. We will look at what has been done so far, and what could be done in the future to protect the red squirrel. We will also look at the genetics of squirrel colouration, looking at the fascinating origin of the black genetic variant of the grey squirrel.

• Speaker: Helen McRobie, Anglia Ruskin University
• Thursday 13 February 2025, 18:45-20:00
• Venue: Main Seminar Room (First Floor) David Attenborough Building, University of Cambridge Pembroke St, Cambridge CB2 3QZ.
• Series: Cambridge Natural History Society; organiser: events.

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This talk will survey life in the ocean, from seashore pools, through underwater forests and grassy meadows, to tropical reefs, the wide open ocean and the deep, dark depths.

The oceans are home to an astonishing array of marine creatures, from tiny coral polyps to immense whales. New marine species are being discovered and described every year, especially from the deep ocean. Submersibles and special cameras are needed to see these, but with just a pair of wellies and sharp eyes you can see many fascinating animals and seaweeds on our own seashores.

• Speaker: Frances Dipper
• Thursday 30 January 2025, 18:45-20:00
• Venue: Main Seminar Room (First Floor) David Attenborough Building, University of Cambridge Pembroke St, Cambridge CB2 3QZ.
• Series: Cambridge Natural History Society; organiser: events.

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Abstract not available

• Speaker: Sarah Penington (Bath)
• Tuesday 25 February 2025, 14:00-15:00
• Venue: MR12.
• Series: Probability; organiser: ww295.

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A peculiarity of the ∞-categories literature is that proofs are often written without reference to a concrete definition of an ∞-category, a practice that creates an impediment to formalization. We describe three broad strategies that would make ∞-category theory formalizable, which may be described as “analytic,” “axiomatic,” and “synthetic.” We then highlight two parallel ongoing collaborative efforts to formalize ∞-category theory in two different proof assistants: the “axiomatic” theory in Lean and the “synthetic” theory in Rzk. We show some sample formalized proofs to highlight the advantages and drawbacks of each approach and explain how you could contribute to this effort. This involves joint work with Mario Carneiro, Nikolai Kudasov, Dominic Verity, Jonathan Weinberger, and many others.

=== Online talk ===

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

Meeting ID: 871 4336 5195

Passcode: 541180

• Speaker: Emily Riehl (Johns Hopkins University)
• Thursday 30 January 2025, 17:00-18:00
• Venue: MR14 Centre for Mathematical Sciences.
• Series: Formalisation of mathematics with interactive theorem provers ; organiser: Jonas Bayer.

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A weather forecast is only useful if appropriate decisions are made on the basis of the forecast. This presents a challenge, because weather forecasts are innately uncertain. How do we ensure that the likelihood of an event, particularly for extreme and impactful weather, is understood and acted upon? This is where psychology meets physics, and where the application of mathematical understanding is key.

• Speaker: Helen Roberts (Met Office)
• Monday 24 February 2025, 13:00-14:00
• Venue: MR3, CMS.
• Series: Quantitative Climate and Environmental Science Seminars; organiser: Bethan Wynne-Cattanach.

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The security of many widely used communication systems hinges on the presumed difficulty of factoring integers or computing discrete logarithms. However, Shor’s celebrated algorithm from 1994 demonstrated that quantum computers can perform these tasks in polynomial time. In 2023, Regev proposed an even faster quantum algorithm for factoring integers. Unfortunately, the correctness of his new method is conditional on an ad hoc number-theoretic conjecture. Using tools from analytic number theory, we establish a result in the direction of Regev’s conjecture. This enables us to design a provably correct quantum algorithm for factoring and solving the discrete logarithm problem, whose efficiency is comparable to Regev’s approach.

In the first part of this talk, we will provide an accessible overview of these developments and their place within the broader context of cryptography. The discussion will require no prior background as we will cover the necessary concepts, including a brief introduction to quantum computing from a mathematician’s perspective.

The second part of the talk will focus on the number-theoretic aspects of this work. We will outline the proof of a variant of Regev’s conjecture, using lattice techniques, character sums and zero-density estimates for Dirichlet L-functions.

• Speaker: Cédric Pilatte (University of Oxford)
• Wednesday 05 February 2025, 13:30-15:00
• Venue: MR4, CMS.
• Series: Discrete Analysis Seminar; organiser: Julia Wolf.

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Abstract not available

• Speaker: Mrinal Dasgupta (Manchester U.)
• Friday 02 May 2025, 16:00-17:00
• Venue: MR19 (Potter Room, Pavilion B), CMS.
• Series: HEP phenomenology joint Cavendish-DAMTP seminar; organiser: Terry Generet.

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Abstract not available

• Speaker: Rene Poncelet (Cracow, INP)
• Friday 21 February 2025, 16:00-17:00
• Venue: MR19 (Potter Room, Pavilion B), CMS.
• Series: HEP phenomenology joint Cavendish-DAMTP seminar; organiser: Terry Generet.

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Cells in multicellular organisms are exposed to local tissue microenvironments with various chemical and physical properties. Increasing evidence shows that these microenvironmental properties are a key regulator of cellular behavior by shaping their signaling cascades, gene expression, and functionality. In the first part of the talk, I will show novel discoveries on how the cellular microenvironment influences the integrity of intracellular organelles. In particular, we identify that the centrosome is susceptible to mechanical forces during cellular navigation, unravel underlying protective molecular pathways, and describe the detrimental consequences of centrosome breakage for the functionality of the microtubule cytoskeleton and for the motility of immune cells. In the second part of the talk, I will present new findings on how the sampling of the microenvironment is regulated by the properties of the microenvironment. Using macrophages as a cellular model highly active in microenvironmental sampling by macropinocytosis, we identified cellular adhesiveness to their local surrounding as an important regulator of macropinocytosis. Overall, these new findings show important principles of cell-matrix interplay and cytoskeleton regulation.

• Speaker: Jörg Renkawitz, LMU Munich
• Thursday 06 February 2025, 16:00-17:00
• Venue: Hodgkin Huxley Seminar Room, Physiology building, Downing Site CB2 3EG.
• Series: Foster Talks; organiser: foster.

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Upper bounds on the number of incidences between points and lines, tubes, and other geometric objects, have many applications in combinatorics and analysis. On the other hand, much less is known about lower bounds. We prove a general lower bound for the number of incidences between points and tubes in the plane under a natural spacing condition. In particular, if you take n points in the unit square and draw a line through each point, then there is a non-trivial point-line pair with distance at most n-2/3+o(1). This quickly implies that any n points in the unit square define a triangle of area at most n-7/6+o(1), giving a new upper bound for the Heilbronn’s triangle problem. Joint work with Alex Cohen and Cosmin Pohoata.

• Speaker: Dmitrii Zakharov (Massachusetts Institute of Technology)
• Wednesday 29 January 2025, 13:30-15:00
• Venue: MR4, CMS.
• Series: Discrete Analysis Seminar; organiser: Julia Wolf.

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