BEGIN:VCALENDAR PRODID:-//eluceo/ical//2.0/EN VERSION:2.0 CALSCALE:GREGORIAN BEGIN:VEVENT UID:e7a8b206b67d129d9865e22375557015 DTSTAMP:20260701T194923Z SUMMARY:SPC Seminar – Climate – Claudia Czimczik (UC Irvine) DESCRIPTION:Speaker: Claudia Czimczik (UC Irvine)\nTitle: Closing the Winte r Gap and Digging Deeper: A Radiocarbon View of Permafrost Carbon Loss\nAb stract:\nThe Arctic holds roughly twice as much carbon in permafrost soils as the current atmosphere\, much of it Pleistocene-age. As this ground th aws\, whether the region amplifies warming depends not just on how much CO ₂ is released but on its source: recently fixed carbon\, or legacy carbo n long locked away? Estimates still disagree on whether the permafrost reg ion is a net CO₂ sink or source\, limited by sparse cold-season data and an oversimplified picture of the soils involved. Radiocarbon speaks direc tly to this\, separating plant from microbial respiration and dating the c arbon being lost.\n\nI will show how a rugged\, passive ¹⁴CO₂ sampler enables year-round measurements that close the long-standing winter gap i n Arctic flux records\, revealing a seasonal shift toward older carbon sou rces in fall and winter. A 25-year snow-addition experiment extends this f rom seasonal to decadal time scales: a deeper\, more insulating snowpack s ustained warmer soils and accelerated the loss of legacy carbon.\n\nI will then argue that the standard two-layer picture\, a seasonally thawing act ive layer over permafrost\, hides a climatically labile “transition zone .” Change-point detection on radiocarbon depth profiles resolves active\ , transient\, intermediate\, and permafrost layers\, and shows we may need to sample twice as deep as active-layer observations suggest. Both deeper snow and wildfire collapse this zone\, melting ground ice and bringing Pl eistocene-age carbon to the modern surface. Shallow\, growing-season sampl ing therefore under-represents the transition zone\, biasing the age and d ecomposability assumptions that models use to project permafrost carbon re lease. URL:/events/208553/spc-seminar-climate-claudia-cz imczik-uc-irvine/ DTSTART;TZID=Europe/London:20260630T113000 DTEND;TZID=Europe/London:20260630T123000 LOCATION:711c\, Huxley Building\, South Kensington Campus\, 51Թ Colleg e London\, London\, SW7 2AZ\, United Kingdom END:VEVENT BEGIN:VEVENT UID:83a5f12dfe203e6136e2416db8b4a010 DTSTAMP:20260701T194923Z SUMMARY:Astrophysics Weekly Seminars :Boryana Hadzhiyska- Large-scale struc ture cosmology DESCRIPTION:Astrophysics Weekly Seminars : Boryana Hadzhiyska- Large-scale structure cosmology URL:/events/209513/astrophysics-weekly-seminars-b oryana-hadzhiyska-large-scale-structure-cosmology/ DTSTART;TZID=Europe/London:20260630T143000 DTEND;TZID=Europe/London:20260630T153000 LOCATION:539\, Blackett Building\, South Kensington Campus\, 51Թ Colle ge London\, London\, SW7 2AZ\, United Kingdom END:VEVENT BEGIN:VEVENT UID:49342e210608b377ced025bc2e7ea979 DTSTAMP:20260701T194923Z SUMMARY:Magnons as a non-equilibrium probe and resource in quantum Hall sys tems DESCRIPTION:I will present recent work on magnon-skyrmion crystal scatterin g in quantum Hall heterojunctions\, which establish these neutral collecti ve excitations of the quantum Hall ferromagnet\, as a new probe for topolo gy in such systems. In doing so\,  I will first review a series of pionee ring experiments which allow for the emission and detection of such magnon s in a scattering experiment setup. Then\, I will explain a theoretical fr amework [1] to extract magnon scattering signatures for a skyrmion crystal – a Wigner crystal where the charged particles have an associated topol ogical invariant. This work will highlight how magnon diffraction can serv e as an analogue for Bragg scattering\, in such crystals. Finally\, I wil l discuss work from a recent theory-experiment collaboration [2]\, which e xplores such scattering but in a different limit\, where the magnons can b e treated as particles\, and their interaction with skyrmions can be thoug ht of simplistically as Rutherford-type scattering. In this “geometric o ptics” limit\, I will present the back-action of magnons on a linear arr ay of confined skyrmions as an explanation for sharp and narrow windows of noise in the magnon detectors. I will also highlight the dipole nature of such magnons in quantum Hall ferromagnets and explore their dynamics in p resence of a confining potential. I will end with a discussion on future u se-cases of such quantum Hall magnons as a spin-valley entanglement witnes s\, to detect complex internal entanglement patterns in multi-component sk yrmion crystals [3]\, and also potentially as a resource for non-equilibri um exploration in the quantum Hall paradigm.\n\n[1] N. Chakraborty\, R. Mo essner and B. Doucot:  Physical Review B 112 (15)\, 155111\n[2] R. Ayach e*\, N. Chakraborty* et. al: https://www.researchsquare.com/article/rs-834 3376/v1\n[3] N. Chakraborty\, R. Moessner and B. Doucot: Physical Review L etters 133 (20)\, 206604 URL:/events/211260/magnons-as-a-non-equilibrium-p robe-and-resource-in-quantum-hall-systems/ DTSTART;TZID=Europe/London:20260702T140000 DTEND;TZID=Europe/London:20260702T150000 LOCATION:539\, Blackett Building\, South Kensington Campus\, 51Թ Colle ge London\, London\, SW7 2AZ\, United Kingdom END:VEVENT BEGIN:VEVENT UID:972e94bf791ccaa75a62ed0f434edb6a DTSTAMP:20260701T194923Z SUMMARY:SPC Seminar – Climate – Anubhab Roy (IIT Madras) DESCRIPTION:Title: Collisions of cloud droplets: non-continuum lubrication and the warm-rain size gap\n \nSpeaker: Anubhab Roy (IIT Madras)\n\nAbstr act: The growth of cloud droplets into raindrops hinges on collisions\, ye t classical microphysics leaves a stubborn “size gap”: above ~15 micro ns\, condensation is slow\, while gravitational coalescence becomes effici ent only beyond ~40 microns. A central obstacle is hydrodynamic: as two dr oplets approach\, the air between them must drain\, and continuum lubricat ion predicts a resistance that diverges\, so droplets on a collision cours e never actually touch. I will show that this singularity is an artefact o f the continuum approximation: once the gap falls below the air’s mean f ree path (~70 nm)\, the gas flow becomes rarefied\, and the resistance gro ws far more slowly\, allowing coalescence in finite time without invoking van der Waals attraction. Building on the kinetic-theory analysis of Sunda rarajakumar & Koch (1996)\, we construct uniformly valid resistance and mo bility functions spanning the far-field continuum and near-contact non-con tinuum regimes\, and use them to compute collision rates and efficiencies for droplet pairs settling in quiescent\, sheared and turbulent flows. The collision efficiency depends systematically on the size ratio\, the Knuds en number\, and droplet inertia\; turbulence is found to augment different ial sedimentation\; and the results condense into compact\, closed-form co llision kernels suited to cloud and aerosol models. I will close with the effect of atmospheric electric fields on droplet collisions and the open q uestions these raise for rain initiation.\n\nA few references to our work that the talk draws on:\n1. Dhanasekaran\, Roy & Koch\, Collision rate of bidisperse spheres settling in a compressional non-continuum gas flow\, J. Fluid Mech. 910\, A10 (2021). https://doi.org/10.1017/jfm.2020.942\n2. Dh anasekaran\, Roy & Koch\, Collision rate of bidisperse\, hydrodynamically interacting spheres settling in a turbulent flow\, J. Fluid Mech. 912\, A5 (2021). https://doi.org/10.1017/jfm.2020.1113\n3. Patra\, Koch & Roy\, Co llision efficiency of non-Brownian spheres in a simple shear flow – the role of non-continuum hydrodynamic interactions\, J. Fluid Mech. 950\, A18 (2022). https://doi.org/10.1017/jfm.2022.817\n4. Patra & Roy\, Gravity-in duced collisions of uncharged cloud droplets in an electric field\, J. Atm os. Sci. 82\, 11 (2025). https://doi.org/10.1175/JAS-D-25-0040.1\n URL:/events/211047/spc-seminar-climate-anubhab-ro y-iit-madras/ DTSTART;TZID=Europe/London:20260710T140000 DTEND;TZID=Europe/London:20260710T150000 LOCATION:139\, Huxley Building\, South Kensington Campus\, 51Թ College London\, London\, SW7 2AZ\, United Kingdom END:VEVENT BEGIN:VEVENT UID:2012d81d28c6b8b35eb45eac47db87f3 DTSTAMP:20260701T194923Z SUMMARY:[Full] Particle Physics Masterclass – Friday 17th July 2026 DESCRIPTION: \nTHIS EVENT IS NOW FULLY BOOKED\nThe Department of Physics a t 51Թ is again hosting a full day Particle Physics Mas terclass.\nWe invite Sixth form Physics students and their teachers to com e and find out about the exciting world of Experimental Particle Physics f rom one of the largest Particle Physics research groups in the country. We have run the Masterclass successfully in a similar format for a number of years.\nThe day will start with an Introduction to the Group and the expe riments and talks about current hot topics in Particle Physics. After lunc h\, the programme will continue and the students can have a tour of the c urrent undergraduate projects followed by further talks and discussions.\ nRegistration\nReservations\, indicating the number of students and accomp anying teachers\, can be made using our online registration form. \nPlea se note\, this event will be free of charge\, A maximum number of 10 stude nts per school can attend\, students may also register to attend individua lly.\nIMPORTANT\nIf you register for this event and are subsequently unabl e to attend\, please let us know as soon as possible.  Demand for this ev ent is usually very high and notifying us allows us to offer your place to someone on the waiting list.\nPlease note that a £10 no-show fee may be charged if you do not attend and have not informed us in advance that you are unable to attend.\nBooking deadline 9th July 2026\n\nAll attendees wil l be contacted with further details via email prior to the event.\nPlease contact Particle Physics Community Admin (Paula Brown and Paula Consiglio) on  fundamental@imperial.ac.uk if you need any further information.\nWe are looking forward to seeing you!\nProgramme\n09:00-17:00\n \nTBC URL:/events/210351/particle-physics-masterclass-f riday-17th-july-2026/ DTSTART;TZID=Europe/London:20260717T090000 DTEND;TZID=Europe/London:20260717T170000 LOCATION:Lecture Theatre 1\, level 2 \,\, Blackett Building\, South Kensin gton Campus\, 51Թ\, London\, SW7 2AZ\, United Kingdom END:VEVENT BEGIN:VTIMEZONE TZID:Europe/London BEGIN:DAYLIGHT DTSTART:20260630T113000 TZNAME:BST TZOFFSETTO:+0100 TZOFFSETFROM:+0100 END:DAYLIGHT END:VTIMEZONE BEGIN:VTIMEZONE TZID:Europe/London BEGIN:DAYLIGHT DTSTART:20260630T143000 TZNAME:BST TZOFFSETTO:+0100 TZOFFSETFROM:+0100 END:DAYLIGHT END:VTIMEZONE BEGIN:VTIMEZONE TZID:Europe/London BEGIN:DAYLIGHT DTSTART:20260702T140000 TZNAME:BST TZOFFSETTO:+0100 TZOFFSETFROM:+0100 END:DAYLIGHT END:VTIMEZONE BEGIN:VTIMEZONE TZID:Europe/London BEGIN:DAYLIGHT DTSTART:20260710T140000 TZNAME:BST TZOFFSETTO:+0100 TZOFFSETFROM:+0100 END:DAYLIGHT END:VTIMEZONE BEGIN:VTIMEZONE TZID:Europe/London BEGIN:DAYLIGHT DTSTART:20260717T090000 TZNAME:BST TZOFFSETTO:+0100 TZOFFSETFROM:+0100 END:DAYLIGHT END:VTIMEZONE END:VCALENDAR