Institute for Advanced Study

Salvatore Pace discusses the order of anomalies in global symmetries: the number of identical copies needed before their diagonal symmetry becomes anomaly-free. Familiar lattice examples often have finite order, whereas perturbative continuum anomalies have infinite order. The seminar examines Onsager symmetry as a lattice counterpart of chiral symmetry for a massless Dirac fermion in one spatial dimension. Its anomaly has order two, but imposing CPT symmetry on the lattice changes it to infinite order, bringing the lattice description closer to the continuum. The work was carried out with Elijah Lew-Smith and Shu-Heng Shao and is reported in arXiv:2606.12510. Attendance is at the IAS Bloomberg Lecture Hall; the organizer also offers Zoom access by request through the contact listed on the event page.

Michael Hutchings introduces Reeb vector fields and explains why their periodic orbits are substantially better understood in three dimensions through Seiberg-Witten theory. The colloquium develops Irie's closing lemma, which creates a periodic orbit through a selected region after a small perturbation, and discusses a quantitative refinement connecting the perturbation size to an upper bound on the orbit period.

This seminar discusses a proof-of-concept gravitational-waveform model described in arXiv:2511.10522. It augments post-Newtonian equations using physics-informed neural-network methods and universal differential equations. The talk also covers ongoing development of a precessing surrogate model designed to evaluate in less than one millisecond while covering a broader portion of the LVK frequency band.

JWST observations reveal sources earlier and brighter than anticipated. This talk examines their implications for cosmological and galaxy-formation models. It considers the unexpectedly numerous galaxies during the first few hundred million years, at redshifts above nine, and how cosmological clustering measurements can distinguish competing explanations. It then presents an initial empirical measurement of the dependence of star-formation variability, or burstiness, on galaxy mass, which may help explain the excess. Finally, it discusses tensions between JWST measurements of reionization and evidence from the cosmic microwave background and Lyman-alpha forest, including implications for DESI’s recent dark-energy results.

Planets form from dust embedded in gaseous protoplanetary disks. Hydrodynamic instabilities can hinder growth by stirring turbulence, yet also help by creating structures that collect solids and promote planetesimal formation. Min-Kai Lin will discuss analytical and numerical studies of the vertical shear instability and convective overstability, their interactions with dust, and generalisations of the streaming instability to disks with accretion or magnetic fields. The seminar examines how these processes alter the conditions for concentrating solids and the challenges that remain in connecting disk dynamics to planet formation.