Wed 22 May 14:00: Topological defects in spiral spin liquids
Abstract not available
- Speaker: Han Yan, University of Tokyo
- Wednesday 22 May 2024, 14:00-15:00
- Venue: TCM Seminar Room.
- Series: Theory of Condensed Matter; organiser: Gaurav.
Tue 09 Jul 14:00: Random Walk on the symmetric Exclusion process SSDW01 - Self-interacting processes
In this talk, I will overview works on random walks in dynamical random environments. I will recall a result obtained in collaboration with Hilario and Teixeira and then I will focus on a work with Conchon—Kerjan and Rodriguez.Our main interest is to investigate the long-term behavior of a random walker evolving on top of the simple symmetric exclusion process (SSEP) at equilibrium, with density in [0,1].At each jump, the random walker is subject to a drift that depends on whether it is sitting on top of a particle or a hole.We prove that the speed of the walk, seen as a function of the density, exists for all density but at most one, and that it is strictly monotonic. We will explain how this helps understand the non-existence of transient regimes with zero speed. We will provide an outline of the proof, whose general strategy is inspired by techniques developed for studying the sharpness of strongly-correlated percolation models.
SSDW01 - Self-interacting processes
- Speaker: Daniel Kious (University of Bath)
- Tuesday 09 July 2024, 14:00-15:00
- Venue: Seminar Room 1, Newton Institute.
- Series: Isaac Newton Institute Seminar Series; organiser: nobody.
Tue 11 Jun 11:00: The MUonE Experiment: Understanding Muon g−2 Puzzle via Muon- electron Scattering
Abstract not available
- Speaker: Ce Zhang (University of Liverpool)
- Tuesday 11 June 2024, 11:00-12:00
- Venue: Ryle Seminar Room (930), Cavendish Laboratory, Department of Physics.
- Series: Cavendish HEP Seminars; organiser: Dr Steve Dennis.
Thu 11 Jul 16:00: Generalized one-dimensional forest fire model SSDW01 - Self-interacting processes
I will present some generalizations of the one-dimensional forest fire model with ignition occurring only at zero, which was analyzed in particular by Volkov (2009). In more recent work, we allow the rates at which the trees grow to depend on their location, and the fire can spread using long-range connections. We establish that the expected time required for the fire to reach a site at a distance x from the origin is at most of the order (log x)log 2 + o(1) . The talk is based on a recent joint paper with Mikhail Menshikov (Durham) and the late Francis Comets (Paris).
SSDW01 - Self-interacting processes
- Speaker: Stanislav Volkov (Lund University)
- Thursday 11 July 2024, 16:00-16:30
- Venue: Seminar Room 1, Newton Institute.
- Series: Isaac Newton Institute Seminar Series; organiser: nobody.
Wed 22 May 14:00: Communication over many-user channels via Approximate Message Passing
This talk considers communication over the Gaussian multiple-access channel in the regime where the number of users scales linearly with the codelength. I will begin by discussing near-optimal coding schemes for small user payloads, and explain why these cannot be adapted efficiently to larger payloads. I will then describe a coded CDMA scheme for larger payloads, where each user’s information is encoded via a linear code before being transmitted using a signature sequence. With an efficient Approximate Message Passing (AMP) decoder that can be tailored to the structure of the linear code, I show that coded CDMA schemes can achieve state-of-the-art performance for payloads up to hundreds of bits, with exact asymptotic performance guarantees. I will also explain how the proposed schemes can be adapted to incorporate random user activity.
This is joint work with Pablo Pascual Cobo, Kuan Hsieh and Ramji Venkataramanan.
- Speaker: Xiaoqi (Shirley) Liu, University of Cambridge
- Wednesday 22 May 2024, 14:00-15:00
- Venue: MR5, CMS Pavilion A.
- Series: Information Theory Seminar; organiser: Prof. Ramji Venkataramanan.
Tue 21 May 14:00: Zonostrophic turbulence on gas giants: insights on turbulent transport and mixing from laboratory experiments ADIW03 - Climate Applications of Layering
The colourful bands of Jupiter are sustained by intense east-west winds called zonal jets, which extend well below Jupiter’s weather layer into its mantle of liquid hydrogen. These jets constitute a fascinating natural example of how a rapidly-rotating turbulent flow self-organises at large scale. Despite decades of observations and modelling, understanding the long-term, nonlinear equilibration of zonal jets and the feedback with the underlying turbulence is still a challenge, notably because of the extreme “zonostrophic” regime of turbulence on gas giants. In this talk, I will discuss the challenges that arise to study such extreme regime, and describe insights from recent laboratory experiments built in Marseille where instantaneous turbulent zonal jets spontaneously emerge from the small-scale forcing, equilibrate at large scale, and can contain up to 70% of the total kinetic energy of the flow once in a quasi-steady state. I will show that the spectral properties of the experimental flows are consistent with the theoretical predictions in the zonostrophic turbulence regime. This constitutes the first fully-experimental validation of the zonostrophic theory in a completely three-dimensional framework. Next, I will quantify the local potential vorticity mixing by measuring the equivalent of a Thorpe scale, and confirm that it can be used to estimate the upscale energy transfer rate of the flow, which otherwise needs to be estimated from a much more demanding spectral analysis. Finally, I will analyse Lagrangian trajectories to discuss the turbulent transport properties in terms of effective diffusivity and investigate the effect of the zonal flow on the isotropy and homogeneity of the turbulent transport. Our estimates of meridional diffusivities are consistent with predictions from mixing length and zonostrophic theories, and confirm the so-called suppression effect of zonal flows on eddy-diffusivity, which may hence be important to take into account in models parametrizing small-scale processes. These results are cross-validated by complementary 2D quasi-geostrophic numerical simulations. Contributors – Benjamin Favier (IRPHE, CNRS ), Michael Le Bars (IRPHE, CNRS ), Simon Cabanes (IPGP), Jonathan Aurnou (UCLA)
ADIW03 - Climate Applications of Layering
- Speaker: Daphné Lemasquerier (University of St Andrews)
- Tuesday 21 May 2024, 14:00-15:00
- Venue: Seminar Room 1, Newton Institute.
- Series: Isaac Newton Institute Seminar Series; organiser: nobody.
Thu 23 May 17:00: Little theories for big formal proofs
The growing practice of using proof assistant software to create and mechanically check formal proofs of challenging mathematical results relies crucially on the prior formalisation of their elementary prerequisites. These include both common undergraduate material and mundane, essentially trivial facts about symbol manipulation. The feasibility of bigger proofs depends, sometimes critically, on how one has chosen to formalise these « little theories ». This talk will explore some instances of such dependencies, drawn from my experience in formalising the proofs of the Four Colour and Odd Order theorems.
- Speaker: Georges Gonthier
- Thursday 23 May 2024, 17:00-18:00
- Venue: Live-streamed at MR14 Centre for Mathematical Sciences.
- Series: Formalisation of mathematics with interactive theorem provers ; organiser: Jonas Bayer.
Fri 31 May 16:00: QFT constraints as Bayesian priors for Standard-Model tests
In this talk I will discuss how Standard-Model constraints, for instance due to analyticity and unitarity, can be used to complement theory computations of hadronic observables. Such constraints can play a decisive role in the analysis of lattice-QCD results of exclusive as well as inclusive semileptonic B-meson decays. In the former case, the use of Bayesian inference allows for formulating a model- and truncation independent parameterisation of hadronic form factors. In the latter case, QFT constraints allow for tackling the computation of the inclusive decay rate for the first time.
- Speaker: Andreas Juttner (Southampton U./CERN)
- Friday 31 May 2024, 16:00-17:00
- Venue: MR19 (Potter Room, Pavilion B), CMS.
- Series: HEP phenomenology joint Cavendish-DAMTP seminar; organiser: Nico Gubernari.
Mon 20 May 10:00: Inhomogeneous mixing of ocean tracers at fronts: Implications for energy fluxes and biogeochemistry ADIW03 - Climate Applications of Layering
ADIW03 - Climate Applications of Layering
- Speaker: Mara Freilich (Brown University)
- Monday 20 May 2024, 10:00-11:00
- Venue: Seminar Room 1, Newton Institute.
- Series: Isaac Newton Institute Seminar Series; organiser: nobody.
Thu 06 Jun 16:00: Cobalt-Catalysed Selective Hydroboration and Multi-Borylation of Unsaturated Hydrocarbons
Abstract not available
- Speaker: Prof. Shaozhong Ge, National University of Singapore
- Thursday 06 June 2024, 16:00-17:00
- Venue: Dept. of Chemistry, Wolfson Lecture Theatre.
- Series: Synthetic Chemistry Research Interest Group; organiser: Dr. Robert J. Phipps.
Fri 07 Jun 13:00: Changing fast and slow: Hydrographic variability along the West Antarctic Peninsula Shelf during the recent sea ice extremes
Antarctic sea ice extent has been anomalously low since 2016, and reached extreme circumpolar minima in 2022/23. The causes of this change are the subject of lively scientific debate, including the relative roles of atmospheric and ocean processes in modulating sea ice evolution. The role of the ocean is particularly challenging to address due to the lack of sustained oceanographic data under the ice. Here, we examine the ocean’s response and potential role in the extreme sea ice minima using data collected by the Palmer Long-Term Ecological Research program and BAS along the West Antarctic Peninsula (WAP). This region has undergone dramatic change during many decades, including atmospheric and deep ocean warming, glacier retreat, and sea ice loss even prior to the most recent minima. Our observations show the extreme sea ice minimum followed after sustained wind anomalies that modulate ice advection, and occurred as the upper ocean stratification that typically prevents the ventilation of warm Circumpolar Deep Water to the surface broke down. We also show that this event reverted decades of upper-ocean change along the WAP .
- Speaker: Carlos Moffat, University of Delaware
- Friday 07 June 2024, 13:00-14:00
- Venue: BAS Seminar Room 330b.
- Series: British Antarctic Survey - Polar Oceans seminar series; organiser: Dr Birgit Rogalla.
Tue 21 May 11:15: Diffusion meets Nested Sampling
Sampling techniques are a stalwart of reliable inference in the physical sciences, with the nested sampling paradigm emerging in the last decade(s) as a ubiquitous tool for model fitting and comparison. Parallel developments in the field of generative machine learning have enabled advances in many applications of sampling methods in scientific inference pipelines. This work explores the synergy of the latest developments in diffusion models and nested sampling. I will review the challenges of precise model comparison in high dimension, and explore how score based generative models can provide a solution. This work builds towards a public code that can apply out of the box to many established hard problems in fundamental physics, as well as providing potential to extend precise inference to problems that are intractable with classical methods. I will motivate some potential applications at the frontiers of inference that can be unlocked with these methods.
- Speaker: David Yallup (University of Cambridge)
- Tuesday 21 May 2024, 11:15-12:00
- Venue: Coffee area, Battcock Centre.
- Series: Hills Coffee Talks; organiser: David Buscher.
Fri 05 Jul 11:45: Interaction of in-plane waves with a structured penetrable line defect in an elastic lattice WHTW02 - WHT Follow on: the applications, generalisation and implementation of the Wiener-Hopf Method
We investigate the scattering of in-plane waves in a triangular elastic lattice by a penetrable inertial line defect [1]. Through the application of the discrete Fourier transform, this problem can be reduced to the analysis of two scalar Wiener-Hopf equations involving the transformed displacements along the defected lattice row. From there, essential information can be extracted about: (i) all dynamic modes appearing in the scattering process, (ii) the symmetry properties of each mode, and (iii) parameter subdomains, defined by the incident wave frequency and inertial properties of the defect, where dynamic localised modes supported by the defect can appear. Upon solving the Wiener-Hopf equations, the lattice displacements can be represented by a contour integral, which can be used to investigate unusual scattering responses of the defect encountered outside of the low frequency regime. All analytical results presented are accompanied by numerical illustrations that demonstrate their effectiveness. Acknowledgement: MJN gratefully acknowledges the support of the EU H2020 grant MSCA -RISE-2020-101008140-EffectFact. MJN would also like to thank the Isaac Newton Institute for Mathematical Sciences (INI) for their support and hospitality during the programme ``Mathematical theory and applications of multiple wave scattering” (MWS), where work on the research in the talk was undertaken and supported by EPSRC grant no. EP/R014604/1. Additionally, MJN is grateful for the funding received from the Simons Foundation that supported his visit to INI during January-June 2023 and participation in MWS programme. References:[1] M.J. Nieves, B.L. Sharma (2024): Interaction of in-plane waves with a structured penetrable line defect in an elastic lattice, Int. J. Eng. Sci 197, 104011, 10.1016/j.ijengsci.2023.104011
WHTW02 - WHT Follow on: the applications, generalisation and implementation of the Wiener-Hopf Method
- Speaker: Michael Nieves (Keele University)
- Friday 05 July 2024, 11:45-12:15
- Venue: Seminar Room 1, Newton Institute.
- Series: Isaac Newton Institute Seminar Series; organiser: nobody.
Mon 27 May 14:00: Title to be confirmed
Abstract not available
- Speaker: Christoph Kehle, ETH Zurich
- Monday 27 May 2024, 14:00-15:00
- Venue: MR13.
- Series: Partial Differential Equations seminar; organiser: Amelie Justine Loher.
Mon 20 May 14:00: Coercive Hamilton-Jacobi equations: equivalent boundary conditions and new uniqueness results.
In this talk, I will report on recent works joint with N. Forcadel and R. Monneau about Hamilton-Jacobi equations posed on domains. The equation is of evolution type, that is to say the solution depends on time and space, and the Hamiltonian is coercive but not necessarily convex. We will see that different boundary conditions can lead to the same weak solutions.
- Speaker: Cyril Imbert, ENS Rue d'Ulm, CNRS
- Monday 20 May 2024, 14:00-15:00
- Venue: MR13.
- Series: Partial Differential Equations seminar; organiser: Amelie Justine Loher.
Mon 20 May 14:00: Fourier transform: from abelian schemes to Hitchin systems I EMG - New equivariant methods in algebraic and differential geometry
This is a series of 3 talks, where we will focus on geometry and topology of abelian fibrations—- these are maps whose general fibers are complex tori but special fibers may be highly singular and complicated. The decomposition theorem of Beilinson, Bernstein, Deligne, and Gabber (BBDG) and the support theorem of Ngô provide powerful tools for studying these maps; Corti-Hanamura further predicted that the sheaf-theoretic BBDG decomposition is governed by algebraic cycles. In recent years, the study of Hitchin system predicts a list of surprising properties concerning the cohomological shadow of the BBDG decomposition theorem for the Hitchin system and related geometries. In my talks, I will explain a geometric tool, a theory of Fourier transform, which helps us to understand various questions and conjectures for abelian fibrations. I will start with the case of an abelian scheme (i.e. an abelian fibration without singular fiber), where the Fourier theory has been established by Beauville and Deninger-Murre more than 30 years ago. Then I will discuss the case with singular fibers. Our ultimate goal is to explain how to use the Fourier transform to construct the desired algebraic cycles for Hitchin’s integrable system as predicted by Corti-Hanamura. If time permits, I will discuss further applications of the Fourier transform and the algebraic cycles constructed from it; this includes connections to the P=W conjecture, \chi-independence phenomanon etc. Based on joint work (in progress) with Davesh Maulik and Qizheng Yin.
EMG - New equivariant methods in algebraic and differential geometry
- Speaker: Junliang Shen (Yale University)
- Monday 20 May 2024, 14:00-15:00
- Venue: Seminar Room 2, Newton Institute.
- Series: Isaac Newton Institute Seminar Series; organiser: nobody.
Wed 22 May 16:00: Atoms Interlinked by Light: Programmable Interactions and Entanglement
The power of quantum information lies in its capacity to be non-local, encoded in correlations among entangled particles. Yet the interactions between particles are typically local, forming a bottleneck in the production of entanglement. To circumvent this limitation in the laboratory, we trap an array of atom clouds in an optical resonator, in which photons act as messengers conveying information between distant atoms. We have developed a versatile experimental toolbox for programming the network of interactions and correlations arising from these photon-mediated interactions, including a broadly applicable protocol for preparing entangled graph states with arbitrary connectivity. I will present experiments illustrating implications for multiparameter quantum sensing and for quantum simulations of phenomena ranging from topological physics to quantum gravity.
- Speaker: Prof Monika Schleier-Smith, Stanford University
- Wednesday 22 May 2024, 16:00-17:00
- Venue: Small Lecture Theatre, Cavendish Laboratory, J.J. Thomson Avenue.
- Series: Cavendish Quantum Colloquium; organiser: Dr Nur Unal.
Thu 23 May 12:00: Understanding fluid dynamics for climate using reduced models ADIW03 - Climate Applications of Layering
Fluid dynamics for climate (and indeed for geophysics and astrophysics more generally) requires the modelling of nonlinear process over a vast range of spatial and temporal scales. Current (and future!) computational methods are not capable of modelling the range of scales required, so some compromises are required. In this talk I will describe possible methods for modelling the types of interaction that are needed for problems of relevance to the climate. I will focus on two methods; the generalised quasilinear approximation, which is a first step to providing robust conservative, realisable, subgrid models and the solution of the PDEs on a logarithmic lattice. This is joint work with Curtis Saxton (Leeds), Rich Kerswell (Cambridge), Keaton Burns (MIT) and Brad Marston (Brown).
ADIW03 - Climate Applications of Layering
- Speaker: Steven Tobias (University of Leeds)
- Thursday 23 May 2024, 12:00-12:30
- Venue: Seminar Room 1, Newton Institute.
- Series: Isaac Newton Institute Seminar Series; organiser: nobody.
Mon 03 Jun 11:30: Whole-heart electromechanical simulations using latent neural ordinary differential equations FHTW02 - Fickle Heart: The intersection of UQ, AI and Digital Twins
Co-Authors: Marina Strocchi, Francesco Regazzoni, Christoph Augustin, Luca Dede’, Steven Niederer, Alfio Quarteroni. Cardiac digital twins provide a physics- and physiology-informed framework for predictive and personalized medicine. However, high-fidelity multi-scale and multi-physics cardiac models remain a barrier to adoption due to their high computational cost and the large number of model evaluations required for patient-specific personalization. Artificial intelligence-based methods can enable the creation of fast and accurate whole-heart digital twins. We use Latent Neural Ordinary Differential Equations (LNODEs) to learn the temporal pressure-volume dynamics of a heart failure patient. Our LNODE -based surrogate model is trained from 400 3D-0D whole-heart closed-loop electromechanical simulations, taking into account 43 model parameters describing cell-to-organ scale cardiac electromechanics and cardiovascular hemodynamics. The trained system of LNOD Es provides a compact and efficient representation of the 3D-0D model in a latent space using a feed-forward fully connected artificial neural network that retains 3 hidden layers with 13 neurons per layer, enabling faster than real-time numerical simulations of cardiac function on a single processor. This surrogate model is employed to perform global sensitivity analysis and robust parameter estimation with uncertainty quantification in time frames compatible with clinical practice, still using a single processor. This framework introduces several computational tools for digital twinning in computational cardiology.
FHTW02 - Fickle Heart: The intersection of UQ, AI and Digital Twins
- Speaker: Matteo Salvador (Stanford University)
- Monday 03 June 2024, 11:30-11:50
- Venue: Seminar Room 1, Newton Institute.
- Series: Isaac Newton Institute Seminar Series; organiser: nobody.
Tue 21 May 11:30: Layering in strongly stratified geophysical and astrophysical turbulence (with Chini, Garaud, Caulfield, Cope) ADIW03 - Climate Applications of Layering
ADIW03 - Climate Applications of Layering
- Speaker: Kasturi Shah (University of Cambridge)
- Tuesday 21 May 2024, 11:30-12:00
- Venue: Seminar Room 1, Newton Institute.
- Series: Isaac Newton Institute Seminar Series; organiser: nobody.