TCS+

The next (and last of the season!) TCS+ talk will take place this coming Wednesday, December 3rd at 1:00 PM Eastern Time (10:00 AM Pacific Time, 19:00 Central European Time, 18:00 UTC). Natalie Collina from U Penn will speak about “Swap regret and correlated equilibria beyond normal-form games ” (abstract below).

You can reserve a spot as an individual or a group to join us live by signing up on the online form. Registration is not required to attend the interactive talk, and the link will be posted on the website the day prior to the talk; however, by registering in the form, you will receive a reminder, along with the link. (The recorded talk will also be posted on our website afterwards) As usual, for more information about the TCS+ online seminar series and the upcoming talks, or to suggest a possible topic or speaker, please see the website.

Abstract: Swap regret is a notion that has proven itself to be central to the study of general-sum normal-form games, with swap-regret minimization leading to convergence to the set of correlated equilibria and guaranteeing non-manipulability against a self-interested opponent. However, the situation for more general classes of games – such as Bayesian games and extensive-form games – is less clear-cut, with multiple candidate definitions for swap-regret but no known efficiently minimizable variant of swap regret that implies analogous non-manipulability guarantees. In this paper, we present a new variant of swap regret for polytope games that we call “profile swap regret”, with the property that obtaining sublinear profile swap regret is both necessary and sufficient for any learning algorithm to be non-manipulable by an opponent (resolving an open problem of Mansour et al., 2022). Although we show profile swap regret is NP-hard to compute given a transcript of play, we show it is nonetheless possible to design efficient learning algorithms that guarantee at most O(√T) profile swap regret. Finally, we explore the correlated equilibrium notion induced by low-profile-swap-regret play, and demonstrate a gap between the set of outcomes that can be implemented by this learning process and the set of outcomes that can be implemented by a third-party mediator (in contrast to the situation in normal-form games).

A guest post by the General Chair of FOCS 2025, Clément Canonne.

FOCS 2025 is less than a month away, with an early bird deadline coming up on November 21, and the summer sun already shining in Sydney. Below are a few important announcements, not necessarily only relevant to attendees (though we do hope you will attend!):

Graduating Bits (afternoon, Sunday – Day 1): Following the (now) long-standing tradition initiated at ITCS, graduating PhD students and postdoctoral researchers will give short 2-minute presentations introducing themselves, their research interests and plans. Many of these junior researchers will be looking for positions in the upcoming year. Please see 🔗 this page to register as a presenter, and for their slides and information after the event.

Job Openings Spreadsheet (asynchronous): The 🔗 Job Openings page has a spreadsheet with information about job openings in Theoretical CS, to help graduating students and junior researchers. If your group plans to hire a postdoc, or a researcher (e.g., in industry), you can use the following form to provide information about the position: https://forms.gle/JSCaHfV5pVGCLXhM7.

Job Applicants Form: To complement the above two initiatives, If you are on the job market, you can provide your information at this form: https://forms.gle/ipAQg4cmBsmj3gwu6 . This will not be made public, and only shared with the FOCS 2025 sponsors and relevant parties/attendees for them to contact you during FOCS.

Visa: if you need a visa letter (esp. as a presenter), please reach out to the general chair ASAP for a letter: clement.canonne@sydney.edu.au. You can check how to obtain a visa, and which visa to apply to (including ETA for American citizens) on this government website.

Childcare support: To reduce barriers to attendance, we will try to facilitate childcare for the duration of the conference. We have some limited funding, thanks to our Australian sponsors, to provide partial childcare support to attendees, with as little red tape or administrative overhead on your end as possible: see this page for details

Satellite events: there will be two free “unaffiliated” satellite events, both held at the University of Sydney, prior and after the conference: “A Celebration of TCS,” December 11–13, and “Trends in Approximation and Online Algorithms,” December 18–19. See this page for more details.

The next TCS+ talk will take place this coming Wednesday, November 19th at 1:00 PM Eastern Time (10:00 AM Pacific Time, 19:00 Central European Time, 18:00 UTC). Haotian Jiang from U Chicago will speak about “Beck-Fiala and Komlós Bounds Beyond Banaszczyk” (abstract below).

You can reserve a spot as an individual or a group to join us live by signing up on the online form. Registration is not required to attend the interactive talk, and the link will be posted on the website the day prior to the talk; however, by registering in the form, you will receive a reminder, along with the link. (The recorded talk will also be posted on our website afterwards) As usual, for more information about the TCS+ online seminar series and the upcoming talks, or to suggest a possible topic or speaker, please see the website.

Abstract: The Beck-Fiala Conjecture asserts that any set system of n elements with degree k has combinatorial discrepancy . A substantial generalization is the Komlós Conjecture, which states that any m by n matrix with columns of unit Euclidean length has discrepancy O(1).

In this talk, we describe an bound for the Komlós problem, improving upon the bound due to Banaszczyk from 1998. We will also see how these ideas can be used to resolve the Beck-Fiala Conjecture for , and give a bound for smaller k, which improves upon Banaszczyk’s bound. These results are based on a new technique of “Decoupling via Affine Spectral Independence” in designing rounding algorithms, which might also be useful in other contexts.

This talk is based on joint work with Nikhil Bansal (University of Michigan).

The next TCS+ talk will take place this coming Wednesday, November 5th at 1:00 PM Eastern Time (10:00 AM Pacific Time, 19:00 Central European Time, 18:00 UTC). Aparna Gupte from MIT will speak about “Quantum One-Time Programs, Revisited” (abstract below).

You can reserve a spot as an individual or a group to join us live by signing up on the online form. Registration is not required to attend the interactive talk, and the link will be posted on the website the day prior to the talk; however, by registering in the form, you will receive a reminder, along with the link. (The recorded talk will also be posted on our website afterwards) As usual, for more information about the TCS+ online seminar series and the upcoming talks, or to suggest a possible topic or speaker, please see the website.

Abstract: One-time programs (Goldwasser, Kalai and Rothblum, CRYPTO 2008) are functions that can be run on any single input of a user’s choice, but not on a second input. Classically, they are unachievable without trusted hardware, but the destructive nature of quantum measurements seems to provide a quantum path to constructing them. Unfortunately, Broadbent, Gutoski and Stebila showed that even with quantum techniques, a strong notion of one-time programs, similar to ideal obfuscation, cannot be achieved for any non-trivial quantum function. On the positive side, Ben-David and Sattath (Quantum, 2023) showed how to construct a one-time program for a certain (probabilistic) digital signature scheme, under a weaker notion of one-time program security.

There is a vast gap between achievable and provably impossible notions of one-time program security, and it is unclear what functionalities are one-time programmable under the achievable notions of security.In this work, we present new, meaningful, yet achievable definitions of one-time program security for probabilistic classical functions. We show how to construct one time programs satisfying these definitions for all functions in the classical oracle model and for constrained pseudorandom functions in the plain model. Finally, we examine the limits of these notions: we show a class of functions which cannot be one-time programmed in the plain model, as well as a class of functions which appears to be highly random given a single query, but whose one-time program must leak the entire function, even in the oracle model.

This is joint work with Jiahui Liu, Justin Raizes, Bhaskar Roberts, and Vinod Vaikuntanathan.

The next TCS+ talk will take place this coming Wednesday, October 22nd at 1:00 PM Eastern Time (10:00 AM Pacific Time, 19:00 Central European Time, 17:00 UTC). Ian Mertz from Charles University will take us through “A Random Walk Down Full Memory Lane” (abstract below). You can reserve a spot as an individual or a group to join us live by signing up on the online form.

Registration is not required to attend the interactive talk, and the link will be posted on the website the day prior to the talk; however, by registering in the form, you will receive a reminder, along with the link. (The recorded talk will also be posted on our website afterwards) As usual, for more information about the TCS+ online seminar series and the upcoming talks, or to suggest a possible topic or speaker, please see the website.

Abstract: Can full memory be an asset to computation? This is the question underlying catalytic computing (Buhrman et al. 2014), a recent paradigm in which a space-bounded machine has access to additional read-write catalytic memory, which is much larger than the regular work tape but whose initial contents must be reset by the computation.

We survey major techniques and results in the field by proving BPL is contained in CL, i.e. how to estimate random walk distributions using a catalytic tape. We will see three distinct proofs: 1) compression-based (Dulek 2015) 2) arithmetic reversibility (Buhrman et al. 2014); and 3) a simple algorithm using ideas from both (Cook-Pyne 2025).

We’re back! The very first TCS+ talk of the season will take place on Wednesday, October 8th at 1:00 PM Eastern Time (10:00 AM Pacific Time, 19:00 Central European Time, 17:00 UTC). Janani Sundaresan from the University of Waterloo will speak about “Distributed Triangle Detection is Hard in Few Rounds” (abstract below).

You can reserve a spot as an individual or a group to join us live by signing up on the online form. Registration is not required to attend the interactive talk, and the link will be posted on the website the day prior to the talk; however, by registering in the form, you will receive a reminder, along with the link. (The recorded talk will also be posted on our website afterwards)

As usual, for more information about the TCS+ online seminar series and the upcoming talks, or to suggest a possible topic or speaker, please see the website.

Abstract: In the CONGEST model, vertices with information only about their neighborhoods are allowed to communicate to each other over the edges of the input graph. Communication happens in synchronous rounds with a bandwidth of . We prove that detecting a triangle in this model requires rounds. Prior to our work, the only lower bound was that at least two rounds are necessary.

It is known that standard communication complexity arguments that have been used to get lower bounds in the CONGEST model in the past are incapable of giving any meaningful multi-round lower bounds for this problem. Our main contribution is a new information-theoretic technique that combines classical round elimination arguments of communication complexity with the point-to-point communication aspects of distributed networks and can be of independent interest.

Joint work with Sepehr Assadi (arXiv:2504.01802)

This announcement is meant to spread the word about a new award in Theoretical Computer Science, dedicated to Luca Trevisan. Please nominate your fellow researchers!

The deadline for nominations is August 2025 (with a notification of intent due July 31). More information about the call for nominations and the award can be found on the website; some of it is reproduced below.

The prize is named in honor of Luca Trevisan in recognition of his major contributions to the Theory of Computing. It aims to recognize outstanding work in the field, and to broaden the reach of awards both in terms of research areas and recognition of individuals. 

The prize is biennial (given once every two years) and consists of two prizes, given to:

• A mid-career scientist whose work has had a significant and lasting impact (15K EUR)
• An early-career scientist whose work has demonstrated exceptional promise (10K EUR)

In addition to the one-time monetary prize, the Italian Academy of Sciences will contribute a commemorative statue, presented to the winners as a symbol of their excellence.

And that’s a wrap for this season of TCS+! As usual, you can watch the recordings of the talks, and peruse the slides, on our website and YouTube channel.

2025/03/05: Prasanna Ramakrishnan, “How to Appease a Voter Majority”
2025/03/19: Tom Gur, “A Zero-Knowledge PCP Theorem”
2025/04/09: Or Zamir, “Optimality of Frequency Moment Estimation”
2025/04/23: Ryan Williams, “Simulating Time With Square-Root Space”
2025/05/07: Palak Jain, “Enforcing Demographic Coherence: A Harms-Aware Framework for Reasoning about Private Data Release”
2025/06/04: Irit Dinur, “Agreement Tests: Local Consistency, Global Structure”

Thanks to our speakers and audience for yet another great season! See you in a couple months… and in the meantime, subscribe to our newsletter to stay informed, and do suggest talks!

The next TCS+ talk (and the last of the season!) will take place this coming Wednesday, June 4th at 1:00 PM Eastern Time (10:00 AM Pacific Time, 19:00 Central European Time, 17:00 UTC: check your timezone here). Irit Dinur from the IAS will speak about “Agreement Tests: Local Consistency, Global Structure” (abstract below).

You can reserve a spot as an individual or a group to join us live by signing up on the online form. Registration is not required to attend the interactive talk, and the link will be posted on the website the day prior to the talk; however, by registering in the form, you will receive a reminder, along with the link. (The recorded talk will also be posted on our website afterwards) As usual, for more information about the TCS+ online seminar series and the upcoming talks, or to suggest a possible topic or speaker, please see the website.

Abstract: Suppose you are given a noisy collection of partial views of an object — how much can you recover just by checking how often these views agree with each other? Agreement testing theorems show that under certain conditions, remarkably, local consistency can guarantee the existence of a coherent global object.

These agreement tests (also known as direct product tests) are central tools in the proofs of PCP theorems, low-degree tests, and more general locally testable codes. In this talk, I will describe recent advances in agreement testing on high-dimensional expanders — powerful combinatorial structures that provide robust frameworks for local-to-global inference — and show how they open new doors for constructing efficient, highly resilient systems.

The next TCS+ talk will take place this coming Wednesday, May 7th at 1:00 PM Eastern Time (10:00 AM Pacific Time, 19:00 Central European Time, 17:00 UTC). Palak Jain from Boston University will speak about “Enforcing Demographic Coherence: A Harms Aware Framework for Reasoning about Private Data Release” (abstract below).

You can reserve a spot as an individual or a group to join us live by signing up on the online form. Registration is not required to attend the interactive talk, and the link will be posted on the website the day prior to the talk; however, by registering in the form, you will receive a reminder, along with the link. (The recorded talk will also be posted on our website afterwards) As usual, for more information about the TCS+ online seminar series and the upcoming talks, or to suggest a possible topic or speaker, please see the website.

Abstract: Our work introduces demographic coherence enforcement, a framework for reasoning about privacy which is purposefully designed with socio-technical usability in mind. It contains sufficient formalism to enable rigorous analysis and provable realisation, all while keeping tangible harms compellingly salient. The framework also lends itself to natural experimental evaluation, which could help build practical intuition and support tangible assessment of risks.

In this talk, I will present our approach, which characterises the adversary as a predictive model and reframes the question of privacy loss in terms of potential inferential harms to vulnerable groups. I will then define demographic coherence enforcement, a property that we argue is necessary for privacy-preserving data curation. Finally, I will briefly touch on the connections between our framework and some existing privacy tools.

Based on joint work with Mark Bun, Marco Carmisino, Gabe Kaptchuk, and Satchit Sivakumar.

Speaker Bio: Palak Jain is a Ph.D. candidate in Theoretical Computer Science at Boston University advised by professors Adam Smith and Mayank Varia.  Their work focuses on bringing robust data protections into practice through the lenses of cryptography, differential privacy, and ML. More information about them is available on their website (https://thepalakjain.com).