# The Abel Lectures

Avi Wigderson, Professor at the School of Mathematics, Institute for Advanced Study, Princeton will be delivering this year's Science Lecture at the University of Oslo, on May 23rd. The lecture is called *Randomness and pseudorandomness*, and is one of four lectures to be held this day in connection with the Abel Prize week. The other speakers are Abel Laureate Endre Szemerédi, László Lovász and Timothy Gowers.

**Avi Wigderson**: *Randomness and pseudorandomness:*

**Abstract**

Is the universe inherently deterministic or probabilistic? Perhaps more importantly - can we tell the difference between the two?

Humanity has pondered the meaning and utility of randomness for millennia.

There is a remarkable variety of ways in which we utilize perfect coin tosses to our advantage: in statistics, cryptography, game theory, algorithms, gambling... Indeed, randomness seems indispensable!

Which of these applications survive if the universe had no randomness in it at all? Which of them survive if only poor quality randomness is available, e.g. that arises from "unpredictable" phenomena like the weather or the stock market?

Pseudorandomness is the study, by mathematicians and computer scientists, of deterministic structures which share some properties of random ones.

Understanding pseudorandom objects and constructing them efficiently leads to a surprisingly positive answers to the questions above, namely that much can be done with poor quality randomness, of even without any randomness at all. I plan to explain key aspects of this theory, and mention some of Endre Szemeredi's contributions to pseudorandomness.

The talk is aimed at a general audience, and no particular background will be assumed.

**Endre Szemerédi:*** In every chaos there is an order*

**Abstract:**

The chaos and order will be defined relative to three problems.

1. Arithmetic progressions

This part is connected to a problem of Erdős and Turán from the 1930's. Related to the van der Waerden theorem, they asked if the density version of that result also holds:

Is it true that an infinite sequence of integers of positive (lower) density contains arbitrary long arithmetic progressions?

The first result in this direction was due to K. F. Roth, who proved that any sequence of integers of positive (lower) density contains a three-term arithmetic progression.

I will give a short history of the generalization of Roth's result and explain some ideas about the "easiest"" proof.

2. Long arithmetic progression in subset sums

I will give exact bound for the size of longest arithmetic progression in subset sums. In addition, I shall describe the structure of the subset sums, and give applications in number theory and probability theory.

3. Embedding sparse graphs into large graphs

**László Lovász:** The many facets of the Regularity Lemm

**Abstract:**

The Regularity Lemma of Szemeredi, first obtained in the context of his theorem on arithmetic progressions in dense seuqences, has become one of the most important and most powerful tools in graph theory. It is basic in

extremal graph theory and in the theory of property testing. Weaker versions with better bounds (Frieze and Kannan) and stronger versions (Alon, Fisher, Krivelevich and Szegedy) have been proved and used. However, the

significance of it goes way beyond graph theory: it can be viewed as statement in approximation theory, as a compactness result for the completion of the space of finite graphs, as a result about the dimensionality of a metric space associated with a graph, as a statement in information theory. It serves as the archetypal example of the dichotomy between structure and randomness as pointed out by Tao. Its extensions to hypergraphs, a difficult problem solved by Gowers and by Rodl, Skokan and Schacht, connects with higher order Fourier analysis.

**Timothy Gowers:** The afterlife of Szemerédi’s theorem

**Abstract:**

Szemerédi's theorem asserts that every set of integers of positive upper density contains arbitrarily long arithmetic progressions. This result has been extraordinarily influential, partly because of the tools that Szemerédi introduced in order to prove it, and partly because subsequent efforts to understand the result more fully have led to progress in many other areas of mathematics, including combinatorics, ergodic theory, harmonic analysis and number theory. I shall discuss some of these later developments, to which Szemerédi himself made several essential contributions.

### The Abel Lectures

**Program**

Location: Georg Sverdrups hus, Aud. 1, University of Oslo

23 May 2012 at 10:00 - 23 May 2012 at 15:15

10.00 Welome by Pro-Rector Inga Bostad, President of The Norwegian Academy of Science and Letters Nils Chr. Stenseth, and Chair of the Abel Committee Ragni Piene.**10.10 Professor Endre Szemerédi: **"In Every Chaos There is an Order"

*11.00 Coffee/tea***11.30 Professor László Lovász: **The many facets of the Regularity Lemma"12:30 Lunch (requires registration)

**13.30 Professor Timothy Gowers:**"The afterlife of Szemerédi's theorem"

14:15 Coffee/tea

**14:30 Science Lecture: Avi Wigderson, **"Randomness and Pseudorandomness"

15.15 Ending by Chair of the Abel Committee Ragni Piene

### President of the Academy announces Abel Prize winner

The President of the Norwegian Academy of Science and Letters, Hans Petter Graver (photo), will announce the winner of the 2019 Abel Prize at the Academy on March 19. The Academy's choice of laureate is based on the Abel Committee's recommendation. The chair of the Abel Committee, Hans Munthe-Kaas, will give the reasons for the awarding of the prize. The popular science presentation of the prize winner's work will be given by Jim Al-Khalili - a British physicist, author and broadcaster. He will also talk to the prize winner to get his/her immediate response to the news of being awarded the Abel Prize.

(08.03.2019) More### Sir Michael Atiyah, Abel Prize laureate, dies at 89

Atiyah was the recipient together with Isadore Singer of the Abel Prize in 2004, and he also received the Fields Medal, the American Philosophical Society’s Benjamin Franklin Medal, among many other honors. He was the former President of the Royal Society and of the Royal Society of Edinburgh. Atiyah was most recently an Honorary Professor in the School of Mathematics at the University of Edinburgh. Sir Michael, working at Cambridge University before he retired, made outstanding contributions to geometry and topology.

(14.01.2019) More### Yakov G. Sinai gives lecture at "Abel in Pittsburgh"

The Department of Mathematical Sciences at Carnegie Mellon University is hosting the "Abel in Pittsburgh" conference where Yakov G. Sinai who received the Abel Prize in 2014 is one of the speakers. The conference is organized by professor and member of the Abel commitee Irene Fonseca and will take place on the 11th of January 2019. "Abel in Pittsburgh" will be the 9th edition of a one-day conference with lectures aimed at a mathematically educated and interested audience, with the objective of increasing public awareness.

(05.11.2018) More### The Abel Symposium 2019

Abel Symposium 2019 will take place at Scandic Parken Hotel Ĺlesund, 23-29 June 2019. The title of the symposium is: Geometry, Lie Theory and Applications.

(02.11.2018) More### Who will be the next Abel Laureate?

The Abel Committee has embarked on the long journey in search of the next Abel Laureate. The committee which consists of five distinguished mathematicians has had its first meeting at the Norwegian Academy of Science and Letters in Oslo the 2nd and 3rd of October. The next meeting will take place in Pittsburgh, Pennsylvania early next year.

(03.10.2018) More