Seminars Sorted by Series

As machine learning is widely deployed, it is increasingly important to ensure that predictors will perform well not only on average (across the entire population), but also on specific socially salient subgroups. In this talk, I will present...

Over the last three decades, the online bipartite matching (OBM) problem has emerged as a central problem in the area of Online Algorithms. Perhaps even more important is its role in the area of Matching-Based Market Design.  The resurgence of this...

Proving a 2009 conjecture of Itai Benjamini, we show:  For any C, there is a > 0 such that for any simple random walk on an n-vertex graph G, the probability that the first Cn steps of the walk hit every vertex of G is at most exp[-an].  A first...

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...

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...

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...

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)...

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...

It may seem quite obvious that graphs carry a lot of geometric structure.  Don't we learn in algorithm classes how to solve all-pairs-shortest-paths, minimum spanning trees etc.?  However, in this talk, I will try to impress on you the idea that...

A central topic in the theory of computation is derandomization: say we have an algorithm which flips coins to achieve some goal, and succeeds with high probability. Can we transform this algorithm into a deterministic procedure, while maintaining...

The notion of Schmidt rank/strength for a collection of m polynomials plays an important role in additive combinatorics, number theory and commutative algebra; high rank collections of polynomials are “psuedorandom”.  An arbitrary collection of...

Algorithms for understanding data generated from distributions over large discrete domains are of fundamental importance.  In this talk, we consider the sample complexity of *property testing algorithms* that seek to to distinguish whether or not an...

In interactive coding, Alice and Bob wish to compute some function f of their private inputs x and y. They do this by engaging in a non-adaptive (fixed speaking order, fixed length) protocol to jointly compute f(x,y). The goal is to do this in an...

Suppose we are given a random rank-r order-3 tensor---that is, an n-by-n-by-n array of numbers that is the sum of r random rank-1 terms---and our goal is to recover the individual rank-1 terms. In principle this decomposition task is possible when...

Many algorithms and heuristics that work well in practice have poor performance under the worst-case analysis, due to delicate pathological instances that one may never encounter. To bridge this theory-practice gap, Spielman and Teng introduced the...

In this talk, I'll discuss a recent result where we settle the complexities of the maximum-cardinality bipartite matching problem (BMM) up to poly-logarithmic factors in five models of computation:  The two-party communication, AND query, OR query...

In this talk, we show a strong XOR lemma for bounded-round two-player randomized communication.  For a function f:X×Y→{0,1}, the n-fold XOR function f^⊕n:X^n×Y^n→{0,1} maps n input pairs (x_1,...,x_n), (y_1,...,y_n) to the XOR of the n output bits f...

Sampling from high-dimensional, multimodal distributions is a computationally challenging and fundamental task.  This talk will focus on a family of random instances of such problems described by random quadratic potentials on the hypercube known as...

The classic algorithm AdaBoost allows to convert a weak learner, that is an algorithm that produces a hypothesis which is slightly better than chance, into a strong learner, achieving arbitrarily high accuracy when given enough training data. We...

Our goal is to develop a generic framework for converting modern gradient-descent based optimization algorithms into mechanisms where inputs come from self-interested agents.

We focus on aggregating preferences from n players in a context without...

Over a high-dimensional vector space $F_p^n $over a fixed finite field $F_p$, the inverse theorem for the Gowers norm asserts that a bounded function f on this space that has a large Gowers $U^{k+1}$ norm, must necessarily correlate with a phase...

Determining the complexity of matrix multiplication is a fundamental problem of theoretical computer science. It is popularly conjectured that matrices can be multiplied in nearly-linear time. If true, this conjecture would yield similarly-fast...

Let K be a convex body in $R^n$. In some cases (say when K is a cube), we can tile $R^n$ using translates of K. However, in general (say when K is a ball) this is impossible. Nevertheless, we show that one can always cover space "smoothly" using...

Efficient verification of computation is fundamental to computer science and is at the heart of the P vs. NP question. Recently it has had growing practical significance, especially with the increasing popularity of blockchain technologies and cloud...

Tree decompositions are a powerful tool in both structural graph theory and graph algorithms. Many hard problems become tractable if the input graph is known to have a tree decomposition of bounded “width”. Exhibiting a particular kind of a tree...

In the minimum cost set cover problem, a set system is given as input, and the goal is to find a collection of sets with minimum cost whose union covers the universe. This NP-hard problem has long been known to admit logarithmic approximations...

A central goal of physics is to understand the low-energy solutions of quantum interactions between particles. This talk will focus on the complexity of describing low-energy solutions; I will show that we can construct quantum systems for which the...

Suppose you have a set S of integers from {1 , 2 , … , N} that contains at least N / C elements. Then for large enough N , must S contain three equally spaced numbers (i.e., a 3-term arithmetic progression)?

In 1953, Roth showed that this is indeed...

Extremal combinatorics is a central research area in discrete mathematics. The field can be traced back to the work of Turán and it was established by Erdős through his fundamental contributions and his uncounted guiding questions. Since then it has...

Several classical results in Ramsey theory (including famous theorems of Schur, van der Waerden, Rado) deal with finding monochromatic linear patterns in two-colourings of the integers.  Our topic will be quantitative extensions of such results.  A...

A CSS quantum code $\mathcal{C} = (W_1, W_2)$ is a pair of orthogonal subspaces in $\mathbb{F}_2^n$. The distance of $\mathcal{C}$ is the smallest hamming weight of a vector in $W_1^{\perp}-W_2$ or $W_2^{\perp}-W_1$. A large distance roughly means...

Erdős' unit distance problem and his related distinct distances problem are arguably the best known open problems in discrete geometry.

They ask for the maximum possible number of unit distances, and the minimum possible number of distinct...

Matrix powering, and more generally iterated matrix multiplication, is a fundamental linear algebraic primitive with myriad applications in computer science. Of particular interest is the problem’s space  complexity as it constitutes the main route...

A finite set system is union-closed if for every pair of sets in the system their union is also in the system.  Frankl in 1979 conjectured that for any such system there exists an element which is contained in ½ of the sets in that system (the only...

In a vertex expanding graph, every small subset of vertices neighbors many different vertices. Random graphs are near-optimal vertex expanders; however, it has proven difficult to create families of deterministic near-optimal vertex expanders, as...

It is widely believed that the physics of diffraction imposes certain fundamental limits on the resolution of an optical system. In this work we study the diffraction limit as a statistical inverse problem in increasingly more realistic mathematical...

In this talk, I will present the following two connections between private optimization and statistical physics, both via the problem of approximating a given covariance matrix with a low-rank matrix:

1. An efficient algorithm to privately compute a...

We will discuss a generalization of the celebrated Minimax Theorem (von Neumann, 1928) for binary zero-sum games. A simple game which fails to satisfy Minimax is Ephraim Kishon's “Jewish Poker” (see [1,2] below). In this game, each player picks a...

In 1948, Shannon used a probabilistic argument to show the existence of codes achieving channel capacity. In 1954, Muller and Reed introduced a simple deterministic code construction, conjectured shortly after to achieve channel capacity. Major...

In this work we prove a high dimensional analogue of the beloved Goldreich-Levin  theorem (STOC 1989), which is the first local list-decoding algorithm.  We consider the following algorithmic problem: given oracle access to a function $f: Z_q^m...

While the notion of spectral gap is a fundamental and very useful feature of reversible Markov chains, there is no standard analogue of this notion for nonreversible chains. In this talk, I will present a simple proposal for spectral gap of...

Strong spatial mixing (SSM) is an important and widely studied quantitative notion of "correlation decay" for a variety of natural distributions arising in statistical physics, probability theory, and theoretical computer science. One of the most...

Is randomness ever necessary for space-efficient computation? It is commonly conjectured that L = BPL, meaning that halting decision algorithms can always be derandomized without increasing their space complexity by more than a constant factor. In...

One of the major open problems in complexity theory is proving super-logarithmic lower bounds on the depth of circuits. Karchmer, Raz, and Wigderson (Computational Complexity 5(3/4), 1995) suggested approaching this problem by proving that depth...

A recent line of work has shown a surprising connection between multicalibration, a multi-group fairness notion, and omniprediction, a learning paradigm that provides simultaneous loss minimization guarantees for a large family of loss functions...

A function $f : \mathbb{F}_2^n \to \mathbb{F}_2^n$ is linear if $f(x+y)=f(x)+f(y)$ for all pairs $(x,y)$.

Suppose $f$ is "a bit linear" -- say, $f(x+y)=f(x)+f(y)$ for 1% of pairs $(x,y)$.  Must $f$ agree with a truly linear function a positive...

The Tree Evaluation Problem has emerged in the past decade as a leading candidate for separating logspace from polynomial time. In this talk we will introduce the problem, as well as the context behind its introduction and conjectured hardness. We...

In this talk, I will discuss progress on showing hardness of the Minimum Circuit Size Problem (MCSP). The computational complexity of MCSP is a longstanding mystery, dating back as far as Levin's seminal work on NP-completeness in 1973. Over the...

Consider an oracle which takes a point $x$ and returns the minimizer of a convex function $f$ in an $\ell_2$ ball of radius $r$ around $x$. While it is straightforward to show that $\approx r^{-1}$ queries to this oracle suffice to minimize $f$ to...

Over the last two decades we have developed good understanding how to quantify the impact of strategic user behavior on outcomes in many games (including traffic routing and online auctions) and showed that the resulting bounds extend to repeated...