Seminars

Nov
24
2015

Computer Science/Discrete Mathematics Seminar II

General systems of linear forms: equidistribution and true complexity
10:30am|S-101

Higher-order Fourier analysis is a powerful tool that can be used to analyse the densities of linear systems (such as arithmetic progressions) in subsets of Abelian groups. We are interested in the group $\mathbb{F}_p^n$, for fixed $p$ and large $n$...

Nov
23
2015

Computer Science/Discrete Mathematics Seminar I

Advances on Ramsey numbers
Jacob Fox
11:15am|S-101

Ramsey theory refers to a large body of deep results in mathematics whose underlying philosophy is captured succinctly by the statement that "Every very large system contains a large well-organized subsystem." Ramsey numbers capture how very large...

Nov
17
2015

Computer Science/Discrete Mathematics Seminar II

Cohomology for computer science
Alex Lubotzky
10:30am|S-101

We will start with presenting the basic notions of (co)homomology of simplical complexes (which requires only basic linear algebra over the field of order 2) and then we will indicate its relevance for several topics in computer science and...

Nov
16
2015

Computer Science/Discrete Mathematics Seminar I

How quaternion algebras over number fields are useful for creating compiler for a quantum computer?
Vadym Kliuchnikov
11:15am|S-101

Solving the following problem is crucial when compiling for a quantum computer: given a finite set $G$ of elements of $SU(2)$, target element $U$ from $SU(2)$ and real number $\epsilon$ find $g_1,\dotsc, g_N$ from $G$ such that $\| g_1 \dotsm g_N -...

Nov
10
2015

Computer Science/Discrete Mathematics Seminar II

Exponential separation of communication and external information
10:30am|S-101

We show an exponential gap between communication complexity and external information complexity, by analyzing a communication task suggested as a candidate by Braverman [Bra13]. Previously, only a separation of communication complexity and internal...

Nov
09
2015

Computer Science/Discrete Mathematics Seminar I

Cutting plane method: A faster algorithm for many (combinatorial) optimization problems
Yin Tat Lee
11:15am|S-101

Many polynomial-time solvable (combinatorial) optimization problems can be reduced to the feasibility problem and the intersection problem. In this talk, I will present the first nearly cubic time algorithm for both problems using a new cutting...

Nov
03
2015

Computer Science/Discrete Mathematics Seminar II

Two-source dispersers for polylogarithmic entropy and improved Ramsey graphs II
10:30am|S-101

In his 1947 paper that inaugurated the probabilistic method, Erdős proved the existence of $2 \log(n)$-Ramsey graphs on $n$ vertices. Matching Erdős' result with a constructive proof is a central problem in combinatorics that has gained a...

Nov
02
2015

Computer Science/Discrete Mathematics Seminar I

Two-source dispersers for polylogarithmic entropy and improved Ramsey graphs I
11:15am|S-101

In his 1947 paper that inaugurated the probabilistic method, Erdős proved the existence of $2 \log(n)$-Ramsey graphs on $n$ vertices. Matching Erdős' result with a constructive proof is a central problem in combinatorics that has gained a...

Oct
27
2015

Computer Science/Discrete Mathematics Seminar II

Algorithmic proof of the Lovasz Local Lemma via resampling oracles
10:30am|S-101

For a collection of events on a probability space with specified dependencies, the Lovasz Local Lemma ("LLL") gives a sufficient condition for the existence of a point avoiding all the events. Following Moser's discovery of an efficient algorithm...

Oct
26
2015

Computer Science/Discrete Mathematics Seminar I

Random words, longest increasing subsequences, and quantum PCA
John Wright
11:15am|S-101

Suppose you have access to iid samples from an unknown probability distribution $p = (p_1, \ldots, p_d)$ on $[d]$, and you want to learn or test something about it. For example, if one wants to estimate $p$ itself, then the empirical distribution...