2026 Simons Collaboration on Learning the Universe Annual Meeting

Aklant Bhowmick
University of Virginia

Multiscale Modeling of Supermassive Black Holes Using Numerical Simulations

The Black Hole working group is developing physically motivated subgrid models for the full life cycle of supermassive black holes, from formation to their impact on galaxy evolution. Aklant Bhowmick will give an overview of the group’s recent progress on black hole seeding as well as work bridging gas flows around black holes on scales from the horizon to galactic scales. Bhowmick will also discuss progress on modeling black hole accretion and feedback in cosmological simulations, including approaches for capturing different modes of AGN feedback and their coupling to the surrounding gas. The talk will close with an outlook on where these seeding, dynamics, accretion, and feedback models are headed next, and how they connect to the collaboration’s flagship simulations.
 

Deaglan Bartlett
University of Oxford

Implicit Likelihood Inference: From Emulators to Cosmological Constraints

The Implicit Likelihood Inference (ILI) working group develops and applies machine-learning techniques for cosmological inference in settings where the likelihood cannot be written down explicitly. Instead, the posterior distribution is directly learned from forward simulations, making it easy to incorporate non-trivial masks, selection effects or scale-cuts, provided the simulations are treated in the same way as the data. Deaglan Bartlett will outline the group’s efforts to scale these techniques for galaxy clustering, which is challenging given the large volume yet high resolution needed for the forward simulations. Bartlett will discuss recent developments in the tools that make this kind of large-scale inference tractable, including sensitivity analyses that diagnose which aspects of a simulation drive constraining power, summary statistics that combine explicit and learned compression, emulators which produce fast yet high-fidelity forward simulations, and validation checks to ensure the group’s results are robust to a variety of types of model-misspecification. Bartlett will give an overview of progress on the LtU-ILI software framework, which provides standardized access to a range of simulation-based inference methods and underpins several of the collaboration’s flagship analyses of survey data. Together, this work aims to make implicit inference both more trustworthy and more efficient as we move toward survey-scale analyses with real data.
 

Jake Bennett
University of Nottingham

Star Formation and Galactic Winds: Calibrating and Deploying Subgrid Physics Modules for Cosmological Simulations

The Resolved Star Formation and Galactic Winds working group bridges high-resolution simulations of the star-forming interstellar medium with larger-scale cosmological simulations. We use simulations with parsec-scale resolution and comprehensive physics modules to characterize star formation and wind scaling relations over a wide range of conditions and to understand what fundamentally drives them, making use of the calibrations and insights so obtained to develop physically motivated and computationally robust subgrid models. Jake Bennett will present early results on the effect on wind loading parameters of cosmic rays now included in the working group’s resolved interstellar medium (ISM) model, as well as report on a new validation of the pressure-regulated, feedback modulated (PRFM) star formation model — developed from local simulations — in global simulations of dwarf galaxies. Additionally, Bennett will report on a project developing and deploying a new resolution-insensitive version of the group’s PRFM subgrid module, demonstrating successful application in large-scale galaxy evolution simulations at resolution of 10 million solar masses, which will enable application of PRFM in very large cosmological boxes. Turning to application of new subgrid models, Bennett will give an overview of recent progress on modeling multiphase galactic winds with the Arkenstone model, including how the choice of feedback treatment determines whether outflows act ejectively — removing gas that would otherwise form stars — or preventatively — suppressing accretion before it fuels star formation — and how outflows propagate differently through a turbulent, multiphase medium depending on how they are driven. The talk will close with a map of how the group’s star formation and wind models are being deployed in large scale simulations.
 

Tjitske Starkenburg & Anshuman Acharya
Northwestern University, University of California Berkeley

From Simulated Galaxies to Observables: Star Formation Histories, Dust Attenuation, Luminosity Functions, and CMB Cross-Correlations

The Synthetic Observations working group turns simulated galaxies from full hydrodynamical simulations, semi-analytic models and emulators into observable quantities that can be compared directly against survey data. Tjitske Starkenburg and Anshuman Acharya will give an overview of the group’s recent progress on connecting galaxy properties like star formation histories, the attenuation of starlight by dust, luminosity functions, and colors back to the underlying feedback physics and cosmological parameters that shape them. Starkenburg and Acharya will also describe ongoing work in cross-correlations of galaxy observables with CMB signals such as the kinetic and thermal Sunyaev-Zel’dovich effect, as a complementary probe of large-scale structure and feedback. The talk will close with a look at how these efforts fit into the collaboration’s broader mock survey pipeline and simulation-based inference framework.
 

Jens Jasche
Stockholm University

Building the Universe’s Digital Twin: Progress from the BORG Working Group

The BORG working group develops Bayesian field-level inference techniques to reconstruct the initial conditions of the Universe from present-day galaxy catalogues, coupling fast dark matter forward models with flexible galaxy bias models. Jens Jasche will give an overview of progress on the group’s flagship reconstruction efforts, which combine data from an expanding set of galaxy and other tracer catalogues with high-fidelity simulations to infer dynamically consistent maps of matter and velocity across large volumes of the local Universe. Jasche will discuss recent methodological extensions, including new approaches for optimizing initial conditions and pushing reconstructions to larger scales and additional tracer populations, and touch on how these reconstructions are being applied to open questions about the local Universe. The talk will close with an outlook on the path toward a fully realized digital twin incorporating forthcoming survey data.
 

Christopher Lovell
Kavli Institute for Cosmology, Cambridge

Designing Training Sets for the Next Generation of Cosmological Emulators

The Training Set Generation working group designs the suites of cosmological simulations that underpin the collaboration’s emulators and inference pipelines. Christopher Lovell will give an overview of recent work extending these training sets, including the CAMELS 50 Mpc suite, new extended CAMELS simulation models, generative models for semi-analytic model merger trees, Backlight simulations of CMB foregrounds, and zoom suite applications. Lovell will discuss how these developments feed into the broader training set strategy for the collaboration, and the tradeoffs between simulation volume, resolution, and parameter coverage that shape the group’s planning for the next generation of flagship LtU simulations.
 

Carolina Cuesta-Lazaro
Flatiron Institute

Generative Models for Cosmological Fields: Diffusion, Point Clouds, and Beyond

The Accelerated Forward Modeling working group develops machine learning techniques to rapidly emulate the outputs of cosmological simulations, from dark matter fields to full galaxy catalogues. Carolina Cuesta-Lazaro will give an overview of the group’s recent progress using generative models, particularly diffusion-based approaches that represent galaxies and halos directly as point clouds in three-dimensional space, avoiding the information loss that comes with binning or voxelization. These models can be used both for emulation, generating new realizations that reproduce key statistics, and for inference, using the model’s likelihood estimate to constrain cosmological parameters directly from a field. Cuesta-Lazaro will touch on a range of applications, from painting realistic galaxy and subhalo populations onto dark-matter-only simulations to reconstructing the underlying dark matter distribution from biased tracers, and discuss the challenges that remain in scaling these approaches to realistic survey volumes and observational effects.
 

Francisco Maion
Columbia University

Bridging Initial Conditions and Cosmological Simulations for the LtU Flagship Program

The Cosmology working group is responsible for carrying out the large-scale simulations that incorporate new subgrid physics from across the collaboration and provide training data for the accelerated forward modeling and inference groups. Francisco Maion will give an overview of the group’s ongoing effort to combine the BORG working group’s Bayesian reconstructions of cosmological initial conditions with hydrodynamical simulations, aiming to simulate the local Universe using initial conditions directly constrained by observed galaxy distributions, rather than random realizations. Maion will also discuss complementary work on multi-zoom techniques for efficiently simulating a preselected halo mass function, balancing completeness against computational cost, and outline how these approaches are converging toward the next generation of LtU flagship simulations.

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 3 nights at the conference hotel, arriving on Wednesday, September 16, 2026 and departing on Saturday, September 19, 2026.

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 3 nights at the conference hotel, arriving on Wednesday, September 16, 2026 and departing on Saturday, September 19, 2026.

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 3 nights at the conference hotel, arriving on Wednesday, September 16, 2026 and departing on Saturday, September 19, 2026.

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
Events Manager
[email protected]

Travel & Hotel Support

FCM Travel Meetings & Events
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