2025 Simons Collaboration on Global Categorical Symmetries Annual Meeting

Ibrahima Bah
Johns Hopkins University

Hanging Branes and Continuous Symmetries in AdS/CFT

I will describe holographic duals of topological operators for continuous symmetries. These can be obtained by considering branes that hang on the boundary. I will comment on how the physics of these branes captures fusion rules and measurements of charges.
 

Alberto Cattaneo
University of Zurich

Surface Observables in 4D BF and Yang–Mills Theories

Maxwell theory possesses an interesting gauge-invariant observable defined as (the exponential of) the Hodge dual of the curvature integrated on a surface Sigma (this can be interpreted as the electric flux through Sigma). As emphasized by ’t Hooft, a nonabelian version would be of significant interest. In this talk, I will first show how to obtain a surface observable for BF theory with cosmological constant. This is a topological field theory, and an AKSZ model, whose fields are a connection and a 2-form B, with equations of motions simply stating that B is proportional, by the “cosmological constant,” to the curvature. This is a nontrivial task which can be achieved through the BV formalism defining a second field theory on Sigma coupled to the ambient fields of BF theory. (As the previously known version for zero cosmological constant, the expectation value of this observable should yield invariants of 2-knots in 4 dimensions.) Subsequently, thanks to a result with F. Bonechi and M. Zabzine, we can recover Yang–Mills theory (plus quantum corrections) from this BF theory via averaging on certain fields (BV pushforward in the terminology developed with P. Mnev and N. Reshetikhin). This procedure also produces a surface observable for Yang–Mills theory which, in the classical limit, corresponds to the nonabelian electric flux.
 

Thomas Dumitrescu
University of California, Los Angeles

Symmetries and Dynamics in Three-Dimensional Quantum Electrodynamics

QED in 2+1 dimensions is a strongly-coupled quantum field theory, whose dynamics is relevant to different areas of study. In this talk, I will summarize recent progress on understanding the phase diagram of this theory, e.g., as a function of mass parameters or a magnetic field. Symmetries, anomalies, and non-renormalization theorems play a crucial role.
 

Daniel Freed
Harvard

Lie Group Quiche

In ongoing work with Greg Moore and Constantin Teleman, we explore quiche with relaxed finiteness conditions, in particular those that encode compact Lie group symmetries of quantum field theories. The modern arsenal of results and techniques in topological field theory, some developed in the Collaboration, are deployed.
 

Iñaki Garcia Etxebarria
Durham University

Symmetry TFTs for Continuous Spacetime Symmetries

I will review joint work with F. Apruzzi, N. Dondi, H. T. Lam and S. Schäfer-Nameki, in which we propose a SymTFT description for the part of the spacetime symmetry group connected to the identity and discuss its connection to gravity.
 

Theo Johnson-Freyd
Dalhousie University

How to Build a Hopf Algebra

As observed by Severa, Freed–Teleman, and Dimofte–Niu in various levels of generality, if you take a 3D TQFT with a transverse pair of boundary conditions, then the vector space assigned to a square with alternating boundary conditions carries the structure of a Hopf algebra: the multiplication and comultiplication are intervals times open parts, and the antipode is a 180-degree rotation. I will explain a version of this construction which is fully-\infty-coherent, fully-framed, and essentially sharp: I do not require full dualizability, but rather say exactly the dualizability needed; every Hopf algebra, in every presentable \infty-category, arises from this construction. At this level of generality, the existence of the antipode is highly nontrivial: this version can produce (infinite-dimensional) Hopf algebras with nonbijective antipode. The technology going into the construction and proof is not bordism calculus, but rather the “Gray,” aka “lax,” tensor product of (\infty,\infty)-categories. From this perspective, the construction turns out to arise as a “tensor square” of the construction of a monad from an adjunction. This talk is based on arXiv:2508.16787, joint with David Reutter.
 

Kantaro Ohmori
RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences

Symmetry Spans and Enforced Gaplessness

When do symmetries enforce gaplessness? In 1+1 dimensions, we give a span criterion that certifies gaplessness from partial symmetry data. For a span C ← Vect_H → Vect_G, where C is a fusion-category symmetry and Vect_G/Vect_H denote the categories of G- and H-graded vector spaces encoding a non-anomalous continuous group G and a finite group H, we provide a simple, checkable condition that rules out any symmetric gapped infrared (IR) phase described by a 2D TQFT. In examples (compact bosons, WZW models, bosonized free fermions on lattices), the span generates a larger symmetry that is known to forbid gapping: either a perturbatively anomalous continuous symmetry (WZW) or an infinite-dimensional Onsager algebra (fermions). Clarifying what symmetries can arise from such spans in general is an interesting direction. This talk is based on ongoing work with Takamasa Ando (Yukawa Institute for Theoretical Physics).
 

Mayuko Yamashita
Perimeter Institute

A Merger of Elliptic Cohomology and Global Categorical Symmetries

In this talk, I will illustrate that the Segal–Stolz–Teichner paradigm and global categorical symmetries are starting to merge, by explaining the ongoing work with Theo Jonhson-Freyd and Daniel Berwick-Evans, titled “Extending equivariant TMF to the cusp using vertex algebras.” The spectrum “TMF,” topological modular forms, is related to 2-dimensional supersymmetric quantum field theories (SQFTs). There is an equivariant refinement of TMF which reflects the group-symmetry in SQFTs. The interpretation of its variant “Tmf” has been a mystery, and its equivariant refinement has not been constructed. We provide an answer to both questions using the theory of vertex operator algebras and modular tensor categories.

Participation in the meeting falls into the following four categories. An individual’s participation category is communicated via their letter of invitation.

The Simons Foundation will never ask for credit card information or require payment for registration to our events.

Group A – Speakers & Organizers

Individuals in Group A receive travel and hotel coordination within the following parameters:

Travel
Economy Class: For flights that are three hours or less to your destination, the maximum allowable class of service is Economy class.
Premium Economy Class: For flights where the total air travel time (excluding connection time) is more than three hours and less than seven hours per segment to your destination, the maximum allowable class of service is premium economy.
Business Class: When traveling internationally (or to Hawaii/Alaska) travelers are permitted to travel in Business Class on those segments that are seven hours or more. If the routing is over budget, a premium economy or mixed-class ticket will be booked.

Hotel
Up to three nights at the conference hotel, arriving on Wednesday, November 19, 2025 and departing on Saturday, November 22, 2025.

Group B – Funded Participants

Individuals in Group B receive travel and hotel coordination within the following parameters:

Travel
Economy class travel will be booked regardless of flight length.

Hotel
Up to three nights at the conference hotel, arriving on Wednesday, November 19, 2025 and departing on Saturday, November 22, 2025.

Group C – Unfunded Participants

Individuals in Group C will not receive financial support but are encouraged to enjoy all conference-hosted meals.

Group D – Remote Participants

Individuals in Group D will participate in the meeting remotely.

Air and Rail

For funded individuals, the foundation will arrange and pay for round-trip travel from their home city to the conference city. All travel and hotel arrangements must be booked through the Simons Foundation’s preferred travel agency.

Travel Deviations

The following travel specifications are considered deviations and will only be accommodated if the cost is less than or equal to the amount the Simons Foundation would pay for a standard round-trip ticket from your home city to the conference city:

• Preferred airline
• Preferred travel class
• Specific flights/flight times
• Travel dates outside those associated with the conference
• Arriving or departing from an airport other than your home city or conference city airports, i.e. multi-segment or triangle trips.

All deviations must be reviewed and approved by the Simons Foundation and, if the cost is more than what would normally be paid, a reimbursement quote must be obtained through the foundation’s travel agency before proceeding to booking and paying for travel out of pocket. All reimbursements for travel booked directly will be paid after the conclusion of the meeting.

Changes After Ticketing

All costs related to changes made to ticketed travel are to be paid for by the participant and are not reimbursable. Please contact the foundation’s travel agency for further assistance.

Personal & Rental Cars

Personal car and rental trips over 250 miles each way require prior approval from the Simons Foundation via email.

Rental cars must be pre-approved by the Simons Foundation.

The Hotel Seville NoMad offers valet parking. Please note there are no in-and-out privileges when using the hotel’s garage, therefore it is encouraged that participants walk or take public transportation to the Simons Foundation.

Hotel

Funded individuals who require hotel accommodations are hosted by the foundation for a maximum of three nights at the conference hotel, arriving on Wednesday, November 19, 2025 and departing on Saturday, November 22, 2025.

Any additional nights are at the attendee’s own expense. To arrange accommodations, please register at the link included in your invitation.

Hotel Seville NoMad
22 E 29th St
New York, NY 10016
(between 28th and 29th Streets)
https://www.hyatt.com/unbound-collection/en-US/nycud-hotel-seville-nomad

For driving directions to the Hotel Seville NoMad, please click here.

Overview

In-person participants will be reimbursed for meals and local expenses including ground transportation. Expenses should be submitted through the foundation’s online expense reimbursement platform after the meeting’s conclusion.

Expenses accrued because of meetings not directly related to the Simons Foundation-hosted meeting (a satellite meeting or meeting held at another institution, for example) will not be reimbursed by the Simons Foundation and should be paid by other sources.

Below are key reimbursement takeaways; a full policy will be provided with the final logistics email circulated approximately 2 weeks prior to the meeting’s start.

Meals

The daily meal limit is $125; itemized receipts are required for expenses over $24 USD. The foundation DOES NOT provide a meal per diem and only reimburses actual meal expenses up the following amounts.

• Breakfast $20
• Lunch $30
• Dinner $75

Allowable Meal Expenses

• Meals taken on travel days (when you traveled by air or train).
• Meals not provided on a meeting day, dinner on Friday for example.
• Group dinners consisting of fellow meeting participants paid by a single person will be reimbursed up to $75 per person and the amount will count towards the $125 daily meal limit.

Unallowable Meal Expenses

• Meals taken outside those provided by the foundation (breakfast, lunch, breaks and/or dinner).
• Meals taken on days not associated with Simons Foundation-coordinated events.
• Minibar expenses.
• Meal expenses for a non-foundation guest.

• Ubers, Lyfts, taxis, etc., taken to and from restaurants in Manhattan.

  • Accommodations will be made for those with mobility restrictions.

Ground Transportation

Expenses for ground transportation will be reimbursed for travel days (i.e. traveling to/from the airport or train station) as well as subway and bus fares while in Manhattan are reimbursable.

Transportation to/from satellite meetings are not reimbursable.

Attendance

In-person participants and speakers are expected to attend all meeting days. Participants receiving hotel and travel support wishing to arrive on meeting days which conclude at 2:00 PM will be asked to attend remotely.

Entry & Building Access

Upon arrival, guests will be required to show their photo ID to enter the Simons Foundation and Flatiron Institute buildings. After checking-in at the meeting reception desk, guests will be able to show their meeting name badge to re-enter the building. If you forget your name badge, you will need to provide your photo ID.

The Simons Foundation and Flatiron Institute buildings are not considered “open campuses” and meeting participants will only have access to the spaces in which the meeting will take place. All other areas are off limits without prior approval.

If you require a private space to conduct a phone call or remote meeting, please contact your meeting manager at least 48-hours ahead of time so that they may book a space for you within the foundation’s room reservation system.

Guests & Children

Meeting participants are required to give 24-hour advance notice of any guests meeting them at the Simons Foundation either before or after the meeting. Outside guests are discouraged from joining meeting activities, including meals.

With the exception of Simons Foundation and Flatiron Institute staff, ad hoc meeting participants who did not receive a meeting invitation directly from the Simons Foundation are not permitted.

Children under the age of 18 are not permitted to attend meetings at the Simons Foundation. Furthermore, the Simons Foundation does not provide childcare facilities or support of any kind. Special accommodations will be made for nursing parents.

Meeting & Policy Questions

Christina Darras
Event Manager
[email protected]

Travel & Hotel Support

FCM Travel Meetings & Events
[email protected]
Hours: M-F, 8:30 AM-5:00 PM ET
+1-888-789-6639