2021-2022 Seminars

May
17
2022

Computer Science/Discrete Mathematics Seminar II

Association schemes and codes II: Completeness of the hierarchy of high-order Hamming schemes
10:30am|Simonyi Hall 101 and Remote Access

One of the central problems of coding theory is to determine the trade-off between the amount of information a code can carry (captured by its rate) and its robustness to resist message corruption (captured by its distance). One of the main methods...

May
16
2022

Computer Science/Discrete Mathematics Seminar I

Thresholds
4:00pm|Simonyi 101 and Remote Access

Thresholds for increasing properties of random structures are a central concern in probabilistic combinatorics and related areas.  In 2006, Kahn and Kalai conjectured that for any nontrivial increasing property on a finite set, its threshold is...

May
10
2022

Computer Science/Discrete Mathematics Seminar II

Association schemes and codes I: The Delsarte linear program
10:30am|Simonyi Hall 101 and Remote Access

One of the central problems of coding theory is to determine the trade-off between the amount of information a code can carry (captured by its rate) and its robustness to resist message corruption (captured by its distance). On the existential side...

May
09
2022

Computer Science/Discrete Mathematics Seminar I

Polynomial Bounds on Parallel Repetition For All 3-Player Games with Binary Inputs
Kunal Mittal
11:15am|Simonyi 101 and Remote Access

Understanding the behavior of multi-player (multi-prover) games under parallel repetition is an important problem in theoretical computer science.

In a $k$-player game $G$, a referee chooses questions $(x^{1}, ..., x^{k})$ from a (publicly known)...

Apr
19
2022

Computer Science/Discrete Mathematics Seminar II

A Tutorial on Gaussian Elimination
10:30am|Simonyi Hall 101 and Remote Access

Gaussian elimination is one of the oldest and most well-known algorithms for solving a linear system. In this talk, we give a basic, yet thorough overview of the algorithm, its variants, and standard error and conditioning estimates. In addition, a...

Apr
18
2022

Computer Science/Discrete Mathematics Seminar I

Set Chasing, with an application to online shortest path
Sébastien Bubeck
11:15am|Simonyi 101 and Remote Access

Since the late 19th century, mathematicians have realized the importance and generality of selection problems: given a collection of sets, select an element in each set, possibly in a ``nice” way.  Of particular importance in computer science is the...

Apr
12
2022

Computer Science/Discrete Mathematics Seminar II

Multi-group fairness, loss minimization and indistinguishability
Parikshit Gopalan
10:30am|Simonyi Hall 101 and Remote Access

Training a predictor to minimize a loss function fixed in advance is the dominant paradigm in machine learning. However, loss minimization by itself might not guarantee desiderata like fairness and accuracy that one could reasonably expect from a...

Apr
11
2022

Computer Science/Discrete Mathematics Seminar I

The Long Arm of Theoretical Computer Science: A Case Study in Blockchains/Web3
Tim Roughgarden
11:15am|Simonyi 101 and Remote Access

Blockchains that support a general contract layer (e.g., Ethereum) export the functionality of a general-purpose, ownerless, and open-access computer that can enforce property rights for digital data.  How is such functionality implemented?  Using a...

Apr
05
2022

Computer Science/Discrete Mathematics Seminar II

A magnetic interpretation of the nodal count on graphs
10:30am|Wolfensohn Hall and Remote Access

The study of nodal sets, i.e. zero sets of eigenfunctions, on geometric objects can be traced back to De Vinci, Galileo, Hook, and Chladni. Today it is a central subject of spectral geometry. Sturm (1836) showed that the n-th eigenfunction of the...

Apr
04
2022

Computer Science/Discrete Mathematics Seminar I

Many Nodal Domains in Random Regular Graphs
11:15am|Wolfensohn Hall and Remote Access

A nodal domain of a Laplacian eigenvector of a graph is a maximal connected component where it does not change sign.  Sparse random regular graphs have been proposed as discrete toy models of "quantum chaos", and it has accordingly been conjectured...