GATP Seminar – Geordie Williamson (Sydney): Intersection homology over rings
Tue 20 Oct · 12:00
Huxley Building, South Kensington Campus
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15°C · 10% rain
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Geordie Williamson from the University of Sydney speaks at the GATP Seminar on 20 October 2026 at 12:00. His talk focuses on intersection homology over rings and self-dual theory over p-adic rings in room 658 of the Huxley Building. Admission is free.
Intersection (co)homology is a beautiful invariant of singular spaces, e.g. singular complex algebraic varieties. Over the rationals it satisfies a raft of strong properties (e.g. Poincaré duality, hard Lefschetz, pure Hodge structure,…) which still seem like a miracle. In their paper introducing these groups, Goresky and MacPherson point out that (unlike the integral cohomology of smooth manifolds) it fails to satisfy Poincaré duality over the integers. Subsequent sheaf theoretic approaches have clarified the situation, and in fact one can prove that there is no reasonable theory over the integers which satisfies Poincaré duality. I will discuss intersection cohomology, given several simple examples that illustrate the theory. Then I will discuss work in progress with F. Klein and T. Fell where we introduce self-dual theory over certain p-adic rings. Interestingly, a self-dual theory exists if one is allowed to add enough roots of p. We don’t quite know what to make of this, but maybe someone in the audience does…
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Frequently asked questions
GATP Seminar – Geordie Williamson (Sydney): Intersection homology over rings takes place on Tuesday, 20 October 2026 at 12:00.
GATP Seminar – Geordie Williamson (Sydney): Intersection homology over rings is held at Huxley Building, South Kensington Campus in London (Huxley 658, Huxley Building, SW7 2AZ).
Entry to GATP Seminar – Geordie Williamson (Sydney): Intersection homology over rings is free.
The forecast for GATP Seminar – Geordie Williamson (Sydney): Intersection homology over rings is Overcast · 15°C.
Yes — hotels within walking distance of Huxley Building, South Kensington Campus can be compared using the accommodation search further down this page.
Tickets for GATP Seminar – Geordie Williamson (Sydney): Intersection homology over rings can be booked via imperial.ac.uk using the "Check Tickets & Live Prices" button on this page, which opens the official booking site in a new tab.
Editorial summaryAbout this event
Geordie Williamson from the University of Sydney speaks at the GATP Seminar on 20 October 2026 at 12:00. His talk focuses on intersection homology over rings and self-dual theory over p-adic rings in room 658 of the Huxley Building. Admission is free.
This summary was automatically generated from event data sourced from official ticketing providers.
Intersection (co)homology is a beautiful invariant of singular spaces, e.g. singular complex algebraic varieties. Over the rationals it satisfies a raft of strong properties (e.g. Poincaré duality, hard Lefschetz, pure Hodge structure,…) which still seem like a miracle. In their paper introducing these groups, Goresky and MacPherson point out that (unlike the integral cohomology of smooth manifolds) it fails to satisfy Poincaré duality over the integers. Subsequent sheaf theoretic approaches have clarified the situation, and in fact one can prove that there is no reasonable theory over the integers which satisfies Poincaré duality. I will discuss intersection cohomology, given several simple examples that illustrate the theory. Then I will discuss work in progress with F. Klein and T. Fell where we introduce self-dual theory over certain p-adic rings. Interestingly, a self-dual theory exists if one is allowed to add enough roots of p. We don’t quite know what to make of this, but maybe someone in the audience does…
Description supplied by the event organiser.
StayStaying overnight?
Hotels within walking distance of Huxley Building, South Kensington Campus. Searching near Huxley 658, Huxley Building, SW7 2AZ; check-in Tuesday, 20 October 2026.
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WhereHuxley Building, South Kensington Campus
Before you goFrequently asked questions
When is GATP Seminar – Geordie Williamson (Sydney): Intersection homology over rings?
GATP Seminar – Geordie Williamson (Sydney): Intersection homology over rings takes place on Tuesday, 20 October 2026 at 12:00.
Where is GATP Seminar – Geordie Williamson (Sydney): Intersection homology over rings taking place?
GATP Seminar – Geordie Williamson (Sydney): Intersection homology over rings is held at Huxley Building, South Kensington Campus in London (Huxley 658, Huxley Building, SW7 2AZ).
How much are tickets for GATP Seminar – Geordie Williamson (Sydney): Intersection homology over rings?
Entry to GATP Seminar – Geordie Williamson (Sydney): Intersection homology over rings is free.
What will the weather be like at GATP Seminar – Geordie Williamson (Sydney): Intersection homology over rings?
The forecast for GATP Seminar – Geordie Williamson (Sydney): Intersection homology over rings is Overcast · 15°C.
Is there anywhere to stay near GATP Seminar – Geordie Williamson (Sydney): Intersection homology over rings?
Yes — hotels within walking distance of Huxley Building, South Kensington Campus can be compared using the accommodation search further down this page.
How do I get tickets for GATP Seminar – Geordie Williamson (Sydney): Intersection homology over rings?
Tickets for GATP Seminar – Geordie Williamson (Sydney): Intersection homology over rings can be booked via imperial.ac.uk using the "Check Tickets & Live Prices" button on this page, which opens the official booking site in a new tab.
Price
Free Entry
Date
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Weather
feels like 12°C · chance of rain 10% · wind 17 km/h
Venue
Huxley 658, Huxley Building, SW7 2AZ
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