# 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

### "Abel in Barcelona" with lecture by Louis Nirenberg

Institut d'Estudis Catalans will host the Abel in Barcelona-event on Monday the 16th of January. In connection with the final meeting of the Abel committee, whose task it is to select the Abel Prize Laureate for 2017, there will be an afternoon of lectures aimed at a broad mathematical audience. Louis Nirenberg, who shared the Abel Prize 2015 with John Nash, will give the first lecture. There will also be lectures by two of the Abel committee members, Luigi Ambrosio and Ben Green.

(04.01.2017) More### Sir Andrew J. Wiles received the Abel Prize from H.R.H. Crown Prince Haakon

Andrew Wiles received the 2016 Abel Prize from Norway's Crown Prince Haakon at an award ceremony in Oslo today, on 24 May. He receives the prize "for his stunning proof of Fermat's Last Theorem by way of the modularity conjecture for semistable elliptic curves, opening a new era in number theory", to quote the Abel Committee. The Abel Prize carries a cash award of 6 million NOK (about EUR 700,000 or USD 750,000) and has been awarded annually since 2003 by the Norwegian Academy of Science and Letters.

(24.05.2016) More### The Abel lectures 2016

Abel Laureate Sir Andrew Wiles will give his prize lecture at the University of Oslo on the 25th of May, followed by two Abel Lectures by Henri Darmon and Manjul Bhargava. Simon Singh will then give the popular lecture *From Fermat's Last Theorem to Homer's Last Theorem.*

### Congratulations from the AMS President

Robert Bryant, President of the American Mathematical Society (AMS), congratulates Sir Andrew Wiles with the 2016 Abel Prize.

(15.03.2016) More### Martin Bridson, Head of the Mathematical Institute, University of Oxford, about Sir Andrew Wiles

“No individual exemplifies the relentless pursuit of mathematical understanding in the service of mankind better than Sir Andrew Wiles. His dedication to solving problems that have defied mankind for centuries, and the stunning beauty of his solutions to these problems, provide a beacon to inspire and sustain everyone who wrestles with the fundamental challenges of mathematics and the world around us. His work will inspire mathematicians and scientists for centuries to come. We are immensely proud to have Andrew as a colleague at the Mathematical Institute in Oxford.

(14.03.2016) More