Cryptography and Counting Points on Elliptic Curves

Speaker: 

Nick Alexander

Institution: 

UCI

Time: 

Monday, November 8, 2010 - 5:30pm

Location: 

RH 306

In 2003, the National Security Agency (NSA) payed Certicom, a small Canadian security company, 25 million dollars for the right to use Certicom's elliptic curve cryptography technology. We will introduce elliptic curves and their applications to cryptography and computer security, and suggest why the NSA paid so much. Then we will describe the computationally important "point counting problem", which is necessary for efficient elliptic curve cryptography. We will survey some recent research that "counts points" on certain elliptic curves.

Ground States of the Two-Dimensional Spin Glass

Speaker: 

Professor Charles Newman

Institution: 

Courant Institute of Mathematical Sciences, NYU

Time: 

Friday, November 19, 2010 - 4:00pm

Location: 

RH 306

This is joint work with Louis-Pierre Arguin, Michael Damron and Dan Stein (arXiv:0911.4201). It is an open problem to determine the number of infinite-volume ground states in the Edwards-Anderson (nearest neighbor) spin glass modelon Z^d for d \geq 2 (with, say, mean zero Gaussian couplings). This is a limiting case of the problem of determining the number of extremal Gibbs states at low temperature. In both cases, there are competing conjectures for d \geq 3, but no complete results even for d=2. I report on new results which go some way toward proving that (with zero external field, so that ground states come in pairs, related by a global spin flip) there is only a single ground state pair (GSP). Our result is weaker in two ways: First, it applies not to the full plane Z^2, but to a half-plane. Second, rather than showing that a.s. (with respect to the quenched random coupling realization J) there is a single GSP, we show that there is a natural joint distribution on J and GSP's such that for a.e. J, the conditional distribution on GSP's given J is supported on only a single GSP. The methods used are a combination of percolation-like geometric arguments with translation invariance (in one of the two coordinate directions of the half-plane) and uses as a main tool the "excitation metastate" which is a probability measure on GSP's and on how they change as one or more individual couplings vary.

Critical Ising Models and (Conformal) Measure Ensembles

Speaker: 

Professor Charles Newman

Institution: 

Courant Institute of Mathematical Sciences, NYU

Time: 

Wednesday, November 17, 2010 - 4:00pm

Location: 

RH 306

I will discuss a representation for the magnetization field of the critical two-dimensional Ising model in the scaling limit as a random filed using an ensemble of measures on the plane associated with renormalized cluster areas.

The renormalized areas come from the scaling limit of critical FK (Fortuin-Kasteleyn) clusters and the random field is a convergent sum of the area measures with random signs. The representation is based on the interpretation of the lattice magnetization as the sum of the signed areas of clusters. If time permits, potential extensions, including to three dimensions, will also be discussed. The talk will be based on joint work with F. Camia (PNAS 106 (2009) 5457-5463) and on work in progress with F. Camia and C. Garban.

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