Calendar
- 29September 29, 2021
CMSA Colloquium: Langlands duality for 3 manifolds
Langlands duality began as a deep and still mysterious conjecture in number theory, before branching into a similarly deep and mysterious conjecture of Beilinson and Drinfeld concerning the algebraic geometry of Riemann surfaces. In this guise it was given a physical explanation in the framework of 4-dimensional super symmetric quantum field theory by Kapustin and Witten. However to this day the Hilbert space attached to 3-manifolds, and hence the precise form of Langlands duality for them, remains a mystery.
In this talk I will propose that so-called “skein modules” of 3-manifolds give natural candidates for these Hilbert spaces at generic twisting parameter Psi , and I will explain a Langlands duality in this setting, which we have conjectured with Ben-Zvi, Gunningham and Safronov.Intriguingly, the precise formulation of such a conjecture in the classical limit Psi=0 is still an open question, beyond the scope of the talk.Zoom link: https://harvard.zoom.us/j/95767170359 (Password: cmsa)
CMSA JOINT QUANTUM MATTER IN MATH & PHYSICS and STRONGLY CORRELATED QUANTUM MATERIALS & HIGH-TEMPERATURE SUPERCONDUCTORS SEMINAR: Oscillations in the thermal conductivity of a spin liquid*
The layered honeycomb magnet alpha-RuCl3 orders below 7 K in a zigzag phase in zero field. An in-plane magnetic field H||a suppresses the zigzag order at 7 Tesla, leaving a spin-disordered phase widely believed to be a quantum spin liquid (QSL) that extends to ~12 T. We have observed oscillations in the longitudinal thermal conductivity Kxx vs. H from 0.4 to 4 K. The oscillations are periodic in 1/H (with a break-in-slope at 7 T). The amplitude function is maximal in the QSL phase (7 –11.5 T). I will describe a benchmark for crystalline disorder, the reproducibility and intrinsic nature of the oscillations, and discuss implications for the QSL state. I will also show detailed data on the thermal Hall conductivity Kxy measured from 0.4 K to 10 K and comment on recent half-quantization results.
*Czajka et al., Nature Physics 17, 915 (2021).
Collaborators: Czajka, Gao, Hirschberger, Lampen Kelley, Banerjee, Yan, Mandrus and Nagler.
https://harvard.zoom.us/j/977347126
Password: cmsaDensity of arithmetic Hodge loci
1 Oxford Street, Cambridge, MA 02138 USAI will explain a conjecture on density of arithmetic Hodge loci which includes and generalizes several recent density results of these loci in arithmetic geometry. This conjecture has also analogues over functions fields that I will survey. As a particular instance, I will outline the proof of the following result: a K3 surface over a number field admits infinitely many specializations where its Picard rank jumps. This last result is joint work with Ananth Shankar, Arul Shankar and Yunqing Tang.