Abstract
All known quantum and statistical systems support defects and extended excitations, which are both described by extended operators in quantum field theory. Examples are Wilson loops and their higher-dimensional generalizations. Extended excitations are instrumental in characterizing the phases and dynamics of physical systems: for example, Wilson lines in the confinement-deconfinement transition, and boundaries/interfaces in topological phases of matter. They also implement generalized symmetries, whose recent paradigm-shifting discovery has already found many applications, ranging from condensed matter systems to statistical models and four-dimensional gauge theories.

Defects are physically interesting observables in many contexts. For instance, defects describe boundaries and impurities in materials at criticality (modeled by Wilson and 't Hooft lines of heavy probe particles). Furthermore, many information-theoretic quantities map directly to defect observables, such as in the calculation of entanglement entropy and in the description of measurement protocols.

The growing interest in defects and extended excitations, their generalized symmetries, inner dynamics, and diverse applications is evidenced by a large number of recent works. Several research groups, in high-energy, condensed matter, and statistical physics, each employing distinct methods and terminologies, share common interests in these topics. The goal of this GGI activity is to bring together theoretical physicists working on extended operators in different domains, to foster cross-disciplinary collaborations.

Topics
- generalized symmetries and higher categorical structures
- defect dynamics
- phases of gauge theories
- defects on the lattice and exact results
- defects and quantum information

Main week topics

w1 Extended operators in quantum field theory
w2 Defects on the lattice and exact results
w3 Extended operators at critical points and in quantum information
w4 Generalized symmetries: synergies between QFT, CM, and QI
w5 Phases of gauge theories and defect dynamics

Typical week program

Monday: morning introductory lecture 1-2h;
Tuesday: morning 1-2 talks 45min; afternoon short talks: up to 6 talks 20min
Wed-Thu-Fri: morning 1-2 talks of 45 min

Organizers
Andrea Cappelli (INFN Firenze),
Gabriel Cuomo (SISSA),
Zohar Komargodski (Stony Brook Univ),
Max Metlitski (MIT),
Adam Nahum (ENS Paris),
Hubert Saleur (IPhT Saclay),
Sakura Schafer-Nameki (Oxford Univ)


Local organizer
Andrea Cappelli, Gabriel Cuomo

Contact
andrea.cappelli@fi.infn.it
gcuomo@sissa.it

Talks

Date	Speaker	Title	Type	Useful Links
May 18, 2026 - 14:30-15:30	Lorenzo Bianchi	Analytic bootstrap for holographic surface defect	Talk					Video
May 18, 2026 - 15:30-16:30	Philine Van Vliet	Sum rules for conformal defect data	Talk					Video
May 19, 2026 - 11:00-12:00	Ryan Lanzetta	Unitarity bounds on cusp anomalous dimension	Talk					Video
May 19, 2026 - 12:00-13:00	Christian Copetti	When symmetries twist: anomaly inflow on monodromy defects	Talk					Video
May 19, 2026 - 14:30-14:45	Jeremias Aguilera-Damia	Confining flux tubes in a gapless phase (part 1)	Talk		Slides			Video
May 19, 2026 - 14:45-15:00	Giovanni Rizi	Confining flux tubes in a gapless phase (part 2)	Talk		Slides			Video
May 19, 2026 - 15:30-15:45	Raquel Izquierdo Garcia	Higher Dimensional Holography	Talk		Slides			Video
May 19, 2026 - 15:45-16:00	Riccardo Villa	Gauging in superconductors and other electronic systems	Talk		Slides			Video
May 19, 2026 - 16:00-16:15	Stathis Vitouladitis	The state/defect correspondence	Talk		Slides			Video
May 20, 2026 - 11:00-13:00	Masaki Oshikawa	Review talk	Talk
May 21, 2026 - 11:00-12:00	Pavel Putrov	TQFT from the ground state	Talk
May 21, 2026 - 12:00-13:00	Ingo Runkel	Extensions of topological symmetries	Talk
May 22, 2026 - 11:00-12:00	Riccardo Argurio	Defects, flat gauging, T-duality: at any radius, in the continuum and on the lattice.	Talk
May 22, 2026 - 12:00-13:00	Hidenori Fukaya	Curved defects and induced gravity	Talk