JHU Slow Pitch Seminars (2005-2006)

The Slow Pitch Seminars are arranged by graduate students for graduate students, and provide a forum for professors to present their work, interests and personal sides. Students are encouraged to use these seminars to gain a view of the current work in the department, get a closer look at potential advisors and to glimpse into the person behind the research.

Input from the graduate students of the math department is encouraged. We are constantly looking for suggestions about the format, questions for interviews and the line-up of professors. Please contact Hamid with any comments.


Schedule

Time & Date Location Speaker Topic
1 pm, Thursday, Nov. 17 Krieger 308 Chika Mese The Plateau Problem
1 pm, Thursday, Dec. 8 Krieger 308 Bernard Shiffman Complex Dynamics
1 pm, Thursday, April 6 Krieger 308 Florin Spinu The Selberg Trace Formula

Summary

Chika Mese

The Plateau Problem

The Plateau Problem is a famous problem in mathematics named after a Belgium physicist who studied soap films. Soap films are modeled mathematically by a minimal surface and the problem asks whether we can prove the existence a minimal surface spanning a given closed curve. Affirmative answer was given by J. Douglas in the early 1930's, and he was awarded the Fields Medal for his efforts. In this talk, we discuss Douglas' solution.

Interview with Chika

Bernard Shiffman

Complex Dynamics

Suppose that f(z) is a complex polynomial (or more generally a rational or meromorphic function). Start with a point z_0 in C. What is the behavior of the sequence of points z_1=f(z_0), z_2=f(z_1), ... z_{n+1}=f(z_n), ...? Sometimes the sequence will converge, sometimes it will approach a periodic orbit, and sometimes it will exhibit chaotic behavior. You may be familiar with the (usually) fractal "Julia sets" consisting of those points z_0 whose orbits z_1,z_2,z_3,... are chaotic. In fact, Montel's theorem was first discovered when he studied the sequence of iterates f(z), f(f(z)), f(f(f(z))), .... (It converges normally on the complement of the Julia set.)

This subject was first thoroughly investigated in the early 20th century by Fatou, Julia, Montel and others, and has had a recent renaissance. In this talk I will survey some of the classic results in complex dynamics, and indicate how some of these results extend to functions of several complex variables.

Here's a question to think about before the talk: A calculus student asked, "When I entered a number on my calculator and repeatedly hit the 'cosine' key, the result converged to .73908513. But when I entered a number and repeatedly hit the 'sine' key, the result didn't converge to 0. Why did this happen?" Were the student's conclusions correct? Can you answer the student's question?


Florin Spinu

The Selberg Trace Formula

Let $X=\GG\backslash\HH$ a compact Riemann surface of constant curvature. The trace formula is an identity relating the spectrum of the Laplace operator $\Delta$ to e length spectrum of closed geodesics in $X$. In particular this yields a Weyl asymptotic formula for the counting function $N(\lambda)=\sum_{\lam_j\leq \lam} 1$. The formula admits an immediate generalization higher dimensional $X=\GG\backslash\HH^n$. I will discuss the main ingredients involved in deriving the trace formula, Selberg's generalization to the non-compact case and the relation to Riemann $\zeta(s)$.