Mathematics Colloquium

• Ethan Akin
• Gautam Chinta

The Mathematics Department Colloquium meets on Thursdays from 1-1:50pm in NAC 6/113, unless stated otherwise. The Colloquium is preceded by lunch in the Faculty Dining Room at 12pm.

All talks

• Thursday, November 12, 2009, 01:00PM, NAC 6/113

  Prof. Alex Kontorovich (Brown University and IAS), Counting Kissing Circles

  We will discuss recent progress on the Affine Linear Sieve, which aims to find primes in sets of integers generated by group actions. Applications include the Apollonian circle packing and prime entries in matrix groups. This is joint work with Hee Oh, Jean Bourgain, and Peter Sarnak.

  This talk will be suitable for undergraduates.

• Thursday, November 05, 2009, 01:00PM, NAC 6/113

  Prof. Józef Dodziuk (Queens College and CUNY GC), Combinatorial Laplacian on graphs

  I will talk about a certain difference operator acting on real-valued functions on vertices of a graph. I will try to motivate how "Combinatorial Laplacian" is a reasonable name for this operator by exploring its similarities with the Laplace operator in Euclidean spaces and Riemannian manifolds. We will consider, for example, the maximum principle, Harnack inequality, and isoperimetric inequalities.

  This talk will be suitable for undergraduates.

• Thursday, October 29, 2009, 01:00PM, NAC 6/113

  Prof. Bart Van Steirteghem (Medgar Evers College), The invariant Hilbert scheme of Alexeev and Brion

  This talk will be about two related objects introduced by V. Alexeev and M. Brion with a view to classifying affine algebraic varieties equipped with an action of a complex reductive group G.

  The objects bring geometry to the following natural question: to what extent does the G-module structure of the coordinate ring of an affine G-variety determine its algebra structure?

  I will introduce both objects with several elementary examples and will briefly mention a family of examples S. Papadakis and I recently obtained.

• Thursday, October 15, 2009, 01:00PM, NAC 6/113

  Karen Thompson (National Security Agency), Mathematicians at the National Security Agency and public key cryptography

  I will start with a brief history of NSA and talk about the varied things that mathematicians do there. I will talk a bit about the different kinds of mathematics that are important for solving our problems. I will give my background and experience over my now 24+ year career. Then I will talk about two different public key cryptography schemes, RSA and Diffie-Hellman, working through a basic example.

  Documents

  • Math 202 Course Information Sheet

• Thursday, October 08, 2009, 01:00PM, NAC 6/113

  Prof. Jay Jorgenson (CCNY), Zeta functions, heat kernels, and spectral asymptotics on degenerating families of discrete tori

  By a discrete torus we mean the Cayley graph associated to a finite abelian group with its canonical generators. A natural invariant associated to the graph is the set of eigenvalues of the adjacency matrix. In this talk, we will study results associated to the set of eigenvalues we the orders of the abelian groups tend to infinity. In particular, we will recover spectral theory on real tori as a limiting case of the discrete tori. Further problems and results will be discussed. (The research described in this talk is joint work with Gautam Chinta and Anders Karlsson.)