Excursion around the Mandelbrot set

Speaker: 

Mikhail Lyubich

Institution: 

Institute for Math Sciences at Stony Brook

Time: 

Tuesday, October 29, 2024 - 4:00pm to 5:00pm

Host: 

Location: 

ISEB 1010

The Mandelbrot set M is a fascinating fractal that encodes in one image the dynamical complexity of the quadratic family z^2 + c. We will wander around M, trying to make sense of its bubbles and their bifurcations, explain how baby Mandelbrot sets are born and where the herds of elephants march, along with various other observable features of M. Despite its enormous complexity, there is a good chance of obtaining a precise topological and geometric description of M. It depends, though, on confirming a long-standing “MLC Conjecture” (on the local connectivity of M) and building up several “Renormalization Theories” that control the small-scale structure of this set.

Random matrices and the Riemann zeta-function (Colloquium)

Speaker: 

Jon Keating

Institution: 

Oxford University

Time: 

Tuesday, January 9, 2024 - 4:00pm to 5:00pm

Host: 

Location: 

NS2 1201

I will review connections between random matrix theory and statistical properties of the Riemann zeta-function, including recent developments relating to extreme values of the zeta function on the critical line.

Nonlocal minimal surfaces

Speaker: 

Ovidiu Savin

Institution: 

Columbia University

Time: 

Tuesday, May 28, 2019 - 4:00pm to 5:00pm

Host: 

Location: 

NS2-3201

The theory of minimal surfaces in general Euclidean dimensions was developed in the 60's by De Giorgi, Reifenberg, Federer, Fleming, Almgren using measure theoretical methods. The approach due to De Giorgi is to interpret surfaces as boundaries of measurable sets E, and view the surface area as the perimeter of E which is defined as the BV norm of its characteristic function. A decade ago, we introduced with Caffarelli and Roquejoffre a nonlocal version of the perimeter functional which is relevant in the theory of phase-transitions with long-range interactions. In my lecture I will give an overview of the theory of the nonlocal minimal surfaces and discuss some of the more recent developments.

Public Lecture: Cryptography in the Vietnam War

Speaker: 

Neal Koblitz

Institution: 

University of Washington

Time: 

Tuesday, April 30, 2019 - 5:00pm to 6:00pm

Host: 

Location: 

ICS 174

One would assume that during the French and American wars in Vietnam, the impoverished guerrillas of the Viet Minh and NLF must have been badly outmatched on the purely technical side of warfare, including cryptography. However, the truth was more complex. In joint work with Phan Duong Hieu (of Limoges, France) we investigate the strengths and weaknesses of all sides in communications intelligence.

The Allen-Cahn equation and a conjecture of De Giorgi

Speaker: 

Ovidiu Savin

Institution: 

Columbia University

Time: 

Thursday, May 30, 2019 - 4:00pm to 5:00pm

Location: 

RH 306

The Allen-Cahn equation appears in the study of phase-transitions for a fluid with two-stable phases. It has been known from the work of Modica and Mortola that the level sets of the solution behave at large scales as minimal surfaces. This fact suggests that global solutions to the Allen-Cahn equation have the same rigidity properties as global minimal surfaces. In particular De Giorgi conjectured that the Bernstein theorem for minimal graphs is valid for the Allen-Cahn equation. I will discuss the history of this conjecture together with some of its nonlocal counterparts.

Colloquium: Non-uniform Complexity in Cryptography

Speaker: 

Neal Koblitz

Institution: 

University of Washington

Time: 

Thursday, May 2, 2019 - 4:00pm to 5:00pm

Host: 

Location: 

NS2-2201

Somewhat unexpectedly, a near consensus among theoreticians is that cryptographic theorems should be proved in the non-uniform model of complexity, rather than the standard uniform complexity model developed by Alan Turing, the “father of computer science.” In joint work with Alfred Menezes of the University of Waterloo, we have criticized the use of non-uniformity in cryptography, finding that even some of the most distinguished researchers have been led badly astray by their misplaced faith in non-uniformity

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